Turn on macrocyclic chemosensor for Al3+ ion with facile synthesis and application in live cell imaging.

PubMed

Ezhumalai, Dhineshkumar; Mathivanan, Iyappan; Chinnadurai, Anbuselvan

2018-06-15

An effort of a new Schiff base macrocyclic chemosensor, 1 4 ‑methyl‑2,6,8,12,14,18‑hexaaza‑1,7,13(1,2),4,10,16(1,4)‑hexabenzenacyclooctadecaphane‑2,5,8,11,14,17‑hexaene (me1) and 1 4 ,7 4 ‑dimethyl‑2,6,8,12,14,18‑hexaaza‑1,7,13(1,2),4,10,16(1,4)‑hexabenzenacyclooctadecadecaphane‑2,5,8,11,14,17‑hexaene (dm2), which enables selective sensing of Al 3+ in aqueous DMF were synthesized by a simplistic one-step condensation reaction of macrocyclic compounds. The probe me1 and dm2 characterized by elemental analysis, FT-IR, 1 H and 13 C NMR, LC-MS spectral techniques. The compounds as mentioned above subjected to FE-SEM with EDS and elemental color mapping. On addition of Al 3+ , the fluorescent probe me1 and dm2 induces turn-on responses in both absorption and sensing spectra by a PET mechanism. The receptor me1 and dm2 serve highly selective, sensitive and turn-on detection of Al 3+ . Further, they did not interfere with other cations present in biological or environmental samples. The detection limit is found to be 3μM and 5μM. From the view of cytotoxic activity, the ability of these compounds me1 and dm2 to inhibit the growth of KB cell lines examined. The chelating functionality of compounds me1 and dm2 examined for their inhibitory properties of KB cell, live cell images. The compounds me1 and dm2 subjected to theoretical studies by DFT-B3LYP invoking the 6-31G level of theory. The energy of the HOMO and LUMO has been established. Copyright © 2018 Elsevier B.V. All rights reserved.

Trivalent Lewis Acidic Cations Govern the Electronic Properties and Stability of Heterobimetallic Complexes of Nickel.

PubMed

Kumar, Amit; Lionetti, Davide; Day, Victor W; Blakemore, James D

2018-01-02

Assembly of heterobimetallic complexes is synthetically challenging due to the propensity of ditopic ligands to bind metals unselectively. Here, we employ a novel divergent approach for selective preparation of a variety of bimetallic complexes within a ditopic macrocyclic ligand platform. In our approach, nickel is readily coordinated to a Schiff base cavity, and then a range of redox-inactive cations (M=Na + , Ca 2+ , Nd 3+ , and Y 3+ ) are installed in a pendant crown-ether-like site. This modular strategy allows access to complexes with the highly Lewis acidic trivalent cations Nd 3+ and Y 3+ , a class of compounds that were previously inaccessible. Spectroscopic and electrochemical studies reveal wide variations in properties that are governed most strongly by the trivalent cations. Exposure to dimethylformamide drives loss of Nd 3+ and Y 3+ from the pendant crown-ether site, suggesting solvent effects must be carefully considered in future applications involving use of highly Lewis acidic metals. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Schiff bases in medicinal chemistry: a patent review (2010-2015).

PubMed

Hameed, Abdul; Al-Rashida, Mariya; Uroos, Maliha; Abid Ali, Syed; Khan, Khalid Mohammed

2017-01-01

Schiff bases are synthetically accessible and structurally diverse compounds, typically obtained by facile condensation between an aldehyde, or a ketone with primary amines. Schiff bases contain an azomethine (-C = N-) linkage that stitches together two or more biologically active aromatic/heterocyclic scaffolds to form various molecular hybrids with interesting biological properties. Schiff bases are versatile metal complexing agents and have been known to coordinate all metals to form stable metal complexes with vast therapeutic applications. Areas covered: This review aims to provide a comprehensive overview of the various patented therapeutic applications of Schiff bases and their metal complexes from 2010 to 2015. Expert opinion: Schiff bases are a popular class of compounds with interesting biological properties. Schiff bases are also versatile metal complexing ligands and have been used to coordinate almost all d-block metals as well as lanthanides. Therapeutically, Schiff bases and their metal complexes have been reported to exhibit a wide range of biological activities such as antibacterial including antimycobacterial, antifungal, antiviral, antimalarial, antiinflammatory, antioxidant, pesticidal, cytotoxic, enzyme inhibitory, and anticancer including DNA damage.

Synthesis, characterization, spectroscopic and theoretical studies of new zinc(II), copper(II) and nickel(II) complexes based on imine ligand containing 2-aminothiophenol moiety

NASA Astrophysics Data System (ADS)

Shafaatian, Bita; Mousavi, S. Sedighe; Afshari, Sadegh

2016-11-01

New dimer complexes of zinc(II), copper(II) and nickel(II) were synthesized using the Schiff base ligand which was formed by the condensation of 2-aminothiophenol and 2-hydroxy-5-methyl benzaldehyde. This tridentate Schiff base ligand was coordinated to the metal ions through the NSO donor atoms. In order to prevent the oxidation of the thiole group during the formation of Schiff base and its complexes, all of the reactions were carried out under an inert atmosphere of argon. The X-ray structure of the Schiff base ligand showed that in the crystalline form the SH groups were oxidized to produce a disulfide Schiff base as a new double Schiff base ligand. The molar conductivity values of the complexes in dichloromethane implied the presence of non-electrolyte species. The fluorescence properties of the Schiff base ligand and its complexes were also studied in dichloromethane. The products were characterized by FT-IR, 1H NMR, UV/Vis spectroscopies, elemental analysis, and conductometry. The crystal structure of the double Schiff base was determined by single crystal X-ray diffraction. Furthermore, the density functional theory (DFT) calculations were performed at the B3LYP/6-31G(d,p) level of theory for the determination of the optimized structures of Schiff base complexes.

Syntheses, spectroscopic characterization, SOD-like properties and antibacterial activities of dimer copper (II) and nickel (II) complexes based on imine ligands containing 2-aminothiophenol moiety: X-ray crystal structure determination of disulfide Schiff bases

NASA Astrophysics Data System (ADS)

Bharti, Sulakshna; Choudhary, Mukesh; Mohan, Bharti; Rawat, S. P.; Sharma, S. R.; Ahmad, K.

2018-07-01

A series of new dimer complexes of copper (II) and nickel (II) were designed and synthesized using the Schiff base ligands which was formed by the condensation of 2-aminothiophenol with 2- methoxybenzaldehyde, 3-formylbenzonitrile and 3-bromo-2-hydroxy-5-nitrobenzaldehyde, respectively. The synthesized metallic complexes were characterized by using different physicochemical and spectroscopic methods. The most plausible geometry for the 1:2 complexes appeared to be distorted square-planar or tetrahedral environments. All the synthesized metal complexes are found to be binuclear and confirmed by elemental analyses, magnetic susceptibility measurements and ESR spectroscopy. The Schiff base ligands (HL1/HL2/H2L) were coordinated to the metal ions through the ONS/SNN and/or N, S donor atoms. In order to prevent the oxidation of the thiol group during the formation of Schiff bases and its complexes, all of the reactions were carried out under an inert atmosphere of argon. The X-ray structures of the Schiff base ligands showed that in the crystalline form the SH groups were oxidized to produce a disulfide Schiff bases as a new double Schiff base ligands (L1a/L2a/H2La). The L1b ligand is a bicyclic ring system of N, S-containing heterocyclic. The crystal structures of the double Schiff bases were determined by single crystal X-ray diffraction. The molar conductivity values of the complexes in DMSO implied the presence of non-electrolyte species. The SOD-like activity of Schiff bases and its complexes were investigated by NBT-DMSO assay and IC50 values were evaluated. Their biological properties have also been studied. These complexes were also tested for their in vitro antibacterial screening activities against three bacteria (Streptococcus aureus, Salmonella typhi, and Escherichia coli) comparing with the Schiff base ligands. Most of the complexes have higher antibacterial activities than those of the free Schiff bases, double Schiff bases and the control.

A heterobimetallic Ga/Yb-Schiff base complex for catalytic asymmetric alpha-addition of isocyanides to aldehydes.

PubMed

Mihara, Hisashi; Xu, Yingjie; Shepherd, Nicholas E; Matsunaga, Shigeki; Shibasaki, Masakatsu

2009-06-24

Development of a new heterobimetallic Ga(O-iPr)(3)/Yb(OTf)(3)/Schiff base 2d complex for catalytic asymmetric alpha-additions of isocyanides to aldehydes is described. Schiff base 2d derived from o-vanillin was suitable to utilize cationic rare earth metal triflates with good Lewis acidity in bimetallic Schiff base catalysis. The Ga(O-iPr)(3)/Yb(OTf)(3)/Schiff base 2d complex promoted asymmetric alpha-additions of alpha-isocyanoacetamides to aryl, heteroaryl, alkenyl, and alkyl aldehydes in good to excellent enantioselectivity (88-98% ee).

Gallium compounds for the design of (nano)radiophamarceuticals

NASA Astrophysics Data System (ADS)

Silva, Francisco Franca A. C.

The work presented in this thesis focus on the design of targeted nanosized and molecular tools, for the design of gallium radiopharmaceuticals with potential application in cancer theranostics. The first part describes gold nanoparticles (AuNPs) stabilized with thiolated derivatives of acyclic and macrocyclic chelators, and functionalized with bioactive peptides for specific targeting of Gastrin Releasing Peptide (GRP) and Epidermal Growth Factor (EGF) receptors. For GRPr targeting, the AuNPs were decorated with a bombesin (BBN) analog and stabilized with derivatives of diethylene triamine pentaacetic acid (DTPA) or 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelators for 67Ga complexation. From the evaluated radiolabeled nanoconstructs, the ones containing a dithioctic derivative of BBN and a thiolated DOTA chelator is the most promising one for the design of 67Ga (nano)radiopharmaceuticals, due to its high in vitro/in vivo stability, high cellular internalization in GRPr-positive PC3 cells, and significant tumor uptake in prostate cancer tumor xenografts. For EGFr targeting, the AuNPs were decorated with GE-11 peptide that was incorporated in a thiolated DOTA derivative. The resulting AuNPs were labeled with 67Ga using pre- and post-labeling approaches. Those obtained based on the pre-labeling approach showed an enhanced in vitro stability towards release of 67Ga while maintaining a high cellular internalization in A431 cells overexpressing EGFr. The second part describes new N4O2-donor acyclic chelators of the Schiff base type and the respective reduced amines, which contain pyridyl or pyrazolyl coordinating units at the central nitrogen atom of diethylenetriamine and phenol groups introduced at the terminal amines. The Schiff bases undergo decomposition reactions, while the corresponding amine derivatives give well defined monocationic Ga(III) complexes. However, only a pyridyl-containing amine derivative was able to effectively coordinate 67Ga. Biodistribution studies in mice showed that the corresponding radiocomplex displays a high in vivo stability and favourable pharmacokinetics, being a good candidate for further evaluation in radiopharmaceutical research.

Photostability and Performance of Polystyrene Films Containing 1,2,4-Triazole-3-thiol Ring System Schiff Bases.

PubMed

Ali, Gassan Q; El-Hiti, Gamal A; Tomi, Ivan Hameed R; Haddad, Raghad; Al-Qaisi, Alaa J; Yousif, Emad

2016-12-09

Series of 4-(4-substituted benzylideneamino)-5-(3,4,5-trimethoxyphenyl)-4 H -1,2,4-triazole-3-thiols were synthesized and their structures were confirmed. The synthesized Schiff bases were used as photostabilizers for polystyrene against photodegradation. Polystyrene polymeric films containing synthesized Schiff bases (0.5% by weight) were irradiated (λ max = 365 nm and light intensity = 6.43 × 10 -9 ein·dm -3 ·s -1 ) at room temperature. The photostabilization effect of 1,2,4-triazole-3-thiols Schiff bases was determined using various methods. All the additives used enhanced the photostability of polystyrene films against irradiation compared with the result obtained in the absence of Schiff base. The Schiff bases can act as photostabilizers for polystyrene through the direct absorption of UV radiation and/or radical scavengers.

Size-Selective Detection of Picric Acid by Fluorescent Palladium Macrocycles.

PubMed

Kumar, Sushil; Kishan, Ram; Kumar, Pramod; Pachisia, Sanya; Gupta, Rajeev

2018-02-19

This work presents the synthesis and characterization of two palladium-based fluorescent macrocycles offering hydrogen-bonding cavities of contrasting dimensions. Both palladium macrocycles function as chemosensors for the detection of nitroaromatics, whereas the larger macrocycle not only illustrates nanomolar detection of picric acid but also transports its significant amount from an aqueous to an organic phase.

Schiff base metal derivatives enhance the expression of HSP70 and suppress BAX proteins in prevention of acute gastric lesion.

PubMed

Golbabapour, Shahram; Gwaram, Nura Suleiman; Al-Obaidi, Mazen M Jamil; Soleimani, A F; Ali, Hapipah Mohd; Abdul Majid, Nazia

2013-01-01

Schiff base complexes have appeared to be promising in the treatment of different diseases and disorders and have drawn a lot of attention to their biological activities. This study was conducted to evaluate the regulatory effect of Schiff base metal derivatives on the expression of heat shock proteins (HSP) 70 and BAX in protection against acute haemorrhagic gastric ulcer in rats. Rats were assigned to 6 groups of 6 rats: the normal control (Tween 20 5% v/v, 5 mL/kg), the positive control (Tween 20 5% v/v, 5 mL/kg), and four Schiff base derivative groups named Schiff_1, Schiff_2, Schiff_3, and Schiff_4 (25 mg/kg). After 1 h, all of the groups received ethanol 95% (5 mL/kg) but the normal control received Tween 20 (Tween 20 5% v/v, 5 mL/kg). The animals were euthanized after 60 min and the stomachs were dissected for histology (H&E), immunohistochemistry, and western blot analysis against HSP70 and BAX proteins. The results showed that the Schiff base metal derivatives enhanced the expression of HSP70 and suppressed the expression of BAX proteins during their gastroprotection against ethanol-induced gastric lesion in rats.

Schiff Base Metal Derivatives Enhance the Expression of HSP70 and Suppress BAX Proteins in Prevention of Acute Gastric Lesion

PubMed Central

Gwaram, Nura Suleiman; Al-Obaidi, Mazen M. Jamil; Soleimani, A. F.; Ali, Hapipah Mohd; Abdul Majid, Nazia

2013-01-01

Schiff base complexes have appeared to be promising in the treatment of different diseases and disorders and have drawn a lot of attention to their biological activities. This study was conducted to evaluate the regulatory effect of Schiff base metal derivatives on the expression of heat shock proteins (HSP) 70 and BAX in protection against acute haemorrhagic gastric ulcer in rats. Rats were assigned to 6 groups of 6 rats: the normal control (Tween 20 5% v/v, 5 mL/kg), the positive control (Tween 20 5% v/v, 5 mL/kg), and four Schiff base derivative groups named Schiff_1, Schiff_2, Schiff_3, and Schiff_4 (25 mg/kg). After 1 h, all of the groups received ethanol 95% (5 mL/kg) but the normal control received Tween 20 (Tween 20 5% v/v, 5 mL/kg). The animals were euthanized after 60 min and the stomachs were dissected for histology (H&E), immunohistochemistry, and western blot analysis against HSP70 and BAX proteins. The results showed that the Schiff base metal derivatives enhanced the expression of HSP70 and suppressed the expression of BAX proteins during their gastroprotection against ethanol-induced gastric lesion in rats. PMID:24298554

Synthesis, spectroscopic properties and theoretical studies of bis-Schiff bases derived from polyamine and pyrazolones.

PubMed

Ren, Tiegang; Liu, Shuyun; Li, Guihui; Zhang, Jinglai; Guo, Jia; Li, Weijie; Yang, Lirong

2012-11-01

A series of novel bis-Schiff base were synthesized from 1-aryl-3-methyl-4-benzoyl-5-pyrazolones and diethylenetriamine (or triethylenetetramine) as the starting materials. All of these bis-Schiff bases were characterized by means of NMR, IR, and MS. The UV-vis absorption spectra and fluorescent spectra of these bis-Schiff bases were also measured. Moreover, the B3LYP/6-31G(d) method was used to optimize the ground state geometry of the bis-Schiff bases; and the UV-vis spectroscopic properties of the products were computed and compared with corresponding experimental data based on cc-pVDZ basis set of TD-B3LYP method. It has been found that all of these bis-Schiff bases show a remarkable absorption peak in a wavelength range of 270-340 nm; and their maximum emission peaks are around 348 nm. Copyright © 2012 Elsevier B.V. All rights reserved.

Microplate assay for screening the antibacterial activity of Schiff bases derived from substituted benzopyran-4-one.

PubMed

Amin, Rehab M; Abdel-Kader, Nora S; El-Ansary, Aida L

2012-09-01

Schiff bases (SB(1)-SB(3)) were synthesized from the condensation of 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one with 2-aminopyridine (SB(1)), p-phenylenediamine (SB(2)) and o-phenylenediamine (SB(3)), while Schiff bases (SB(4)-SB(6)) were synthesized by condensation of 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one with 2-aminopyridine (SB(4)), p-phenylenediamine (SB(5)) and o-phenylenediamine (SB(6)). Schiff bases were characterized using elemental analysis, IR, UV-Vis, (1)H NMR, (13)C NMR and mass spectroscopy. These compounds were screened for antibacterial activities by micro-plate assay technique. Escherichia coli and Staphylococcus capitis were exposed to different concentrations of the Schiff bases. Results showed that the antibacterial effect of these Schiff bases on Gram-negative bacteria were higher than that on Gram-positive bacteria moreover, the Schiff bases containing substituent OCH(3) on position five have higher antibacterial activity than that containing hydroxy group on the same position. Copyright © 2012 Elsevier B.V. All rights reserved.

Antimicrobial Activity and Urease Inhibition of Schiff Bases Derived from Isoniazid and Fluorinated Benzaldehydes and of Their Copper(II) Complexes.

PubMed

Habala, Ladislav; Varényi, Samuel; Bilková, Andrea; Herich, Peter; Valentová, Jindra; Kožíšek, Jozef; Devínsky, Ferdinand

2016-12-17

In order to evaluate the influence of substitution on biological properties of Schiff bases and their metal complexes, a series of differently substituted fluorine-containing Schiff bases starting from the drug isoniazid (isonicotinylhydrazide) were prepared and their structures were established by single-crystal X-ray diffraction. Also, four copper(II) complexes of these Schiff bases were synthesized. The prepared compounds were evaluated for their antimicrobial activity and urease inhibition. Two of the Schiff bases exerted activity against C. albicans . All copper(II) complexes showed excellent inhibitory properties against jack bean urease, considerably better than that of the standard inhibitor acetohydroxamic acid.

Benzaldehyde Schiff bases regulation to the metabolism, hemolysis, and virulence genes expression in vitro and their structure-microbicidal activity relationship.

PubMed

Xia, Lei; Xia, Yu-Fen; Huang, Li-Rong; Xiao, Xiao; Lou, Hua-Yong; Liu, Tang-Jingjun; Pan, Wei-Dong; Luo, Heng

2015-06-05

There is an urgent need to develop new antibacterial agents because of multidrug resistance by bacteria and fungi. Schiff bases (aldehyde or ketone-like compounds) exhibit intense antibacterial characteristics, and are therefore, promising candidates as antibacterial agents. To investigate the mechanism of action of newly designed benzaldehyde Schiff bases, a series of high-yielding benzaldehyde Schiff bases were synthesized, and their structures were determined by NMR and MS spectra data. The structure-microbicidal activity relationship of derivatives was investigated, and the antibacterial mechanisms were investigated by gene assays for the expression of functional genes in vitro using Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. The active compounds were selective for certain active groups. The polar substitution of the R2 group of the amino acids in the Schiff bases, affected the antibacterial activity against E. coli and S. aureus; specific active group at the R3 or R4 groups of the acylhydrazone Schiff bases could improve their inhibitory activity against these three tested organisms. The antibacterial mechanism of the active benzaldehyde Schiff bases appeared to regulate the expression of metabolism-associated genes in E. coli, hemolysis-associated genes in B. subtilis, and key virulence genes in S. aureus. Some benzaldehyde Schiff bases were bactericidal to all the three strains and appeared to regulate gene expression associated with metabolism, hemolysis, and virulence, in vitro. The newly designed benzaldehyde Schiff bases possessed unique antibacterial activity and might be potentially useful for prophylactic or therapeutic intervention of bacterial infections. Copyright © 2015. Published by Elsevier Masson SAS.

Mono-Schiff-base or di-Schiff-base? Synthesis, spectroscopic, X-ray structural and DFT study of a series of Schiff-bases derived from benzil dihydrazone

NASA Astrophysics Data System (ADS)

Tan, Xue-Jie; Hao, Xiu-Qi; Zhao, Qing-Zhe; Cheng, Shuang-Shuang; Xie, Wen-Long; Xing, Dian-Xiang; Liu, Yun; Song, Lai-Zhou

2015-11-01

A series of mono- and di-Schiff-bases based on Benzil Dihydrazone (BDH) were designed and synthesized to be set as the model compounds to explain which one should be the advanced product and which parameters will determine the end-product. As the first step of a series of investigations, this article presents the syntheses and characterization of five new Schiff-bases plus one preliminary reported Schiff-base, all derived from BDH. The compounds were characterized by single crystal (or conventional powder) X-ray diffractometry, elemental analysis, m.p., 1H NMR, 13C NMR, IR and UV-Vis. Structural features of the five new Schiff-bases are similar. For instance, all molecules are nonsymmetrical/symmetrical double helix with the torsion angle of two "half-parts" about 72-97°. The Ph-Cdbnd N-Ndbnd C-Ph moiety all exists in planar and anti form, indicating significant conjugation. The crystal structures appear to be stabilized by π-stacking between the aromatic rings, as well as by intermolecular hydrogen bonds and C-H … π stacking interactions. DFT calculations have been performed to explain the trend of the experimentally measured reaction yields. In the case of the studied systems by us, the type of Schiff-bases exhibits a clear dependence on the molar ratio of reactants if the products have similar stabilities. Otherwise the importance of reaction conditions will be weakened and the most stable product will be favored.

Macrocyclic fragrance materials--a screening-level environmental assessment using chemical categorization.

PubMed

Salvito, Daniel; Lapczynski, Aurelia; Sachse-Vasquez, Christen; McIntosh, Colin; Calow, Peter; Greim, Helmut; Escher, Beate

2011-09-01

A screening-level aquatic environmental risk assessment for macrocyclic fragrance materials using a "group approach" is presented using data for 30 macrocyclic fragrance ingredients. In this group approach, conservative estimates of environmental exposure and ecotoxicological effects thresholds for compounds within two subgroups (15 macrocyclic ketones and 15 macrocyclic lactones/lactides) were used to estimate the aquatic ecological risk potential for these subgroups. It is reasonable to separate these fragrance materials into the two subgroups based on the likely metabolic pathway required for biodegradation and on expected different ecotoxicological modes of action. The current volumes of use for the macrocyclic ketones in both Europe and North America ranges from <1 (low kg quantities) to no greater than 50 metric tonnes in either region and for macrocyclic lactones/lactides the volume of use range for both regions is <1 to no greater than 1000 metric tonnes in any one region. Based on these regional tonnages, biodegradability of these two subgroups of materials, and minimal in stream dilution (3:1), the conservatively predicted exposure concentrations for macrocyclic ketones would range from <0.01 to 0.05 μg/L in Europe and from <0.01 to 0.03 μg/L in North America. For macrocyclic lactones/lactides, the concentration within the mixing zone would range from <0.01 to 0.7 μg/L in Europe and from <0.01 to 1.0 μg/L in North America. The PNECs derived for the macrocyclic ketones is 0.22 μg/L and for macrocyclic lactones/lactides is 2.7 μg/L. The results of this screening-level aquatic ecological risk assessment indicate that at their current tonnage, often referred to as volumes of use, macrocyclic fragrance materials in Europe and North America, pose a negligible risk to aquatic biota; with no PEC/PNEC ratio exceeding 1 for any material in any subgroup. Copyright © 2011 Elsevier Inc. All rights reserved.

Poly(vinyl Chloride) Photostabilization in the Presence of Schiff Bases Containing a Thiadiazole Moiety.

PubMed

Shaalan, Naser; Laftah, Nawres; El-Hiti, Gamal A; Alotaibi, Mohammad Hayal; Muslih, Raad; Ahmed, Dina S; Yousif, Emad

2018-04-15

Five Schiff bases containing a thiadiazole moiety have been used as poly(vinyl chloride) photostabilizers at low concentrations. The efficiency of Schiff bases as photostabilizers was investigated using various techniques, for example, the changes in poly(vinyl chloride) infrared spectra, molecular weight, chain scission quantum yield, and surface morphology were monitored upon irradiation with an ultraviolet light. Evidently, all the additives used inhibited poly(vinyl chloride) photodegradation at a significant level. The most efficient Schiff base exhibited a high level of aromaticity and contained a hydroxyl group. It seems possible that such photostabilization could be due to the direct absorption of ultraviolet radiation by the additives. In addition, Schiff bases could act as radical scavengers and proton transfer facilitators to stabilize the polymeric materials.

Crystal structure characterization as well as theoretical study of spectroscopic properties of novel Schiff bases containing pyrazole group.

PubMed

Guo, Jia; Ren, Tiegang; Zhang, Jinglai; Li, Guihui; Li, Weijie; Yang, Lirong

2012-09-01

A series of novel Schiff bases containing pyrazole group were synthesized using 1-aryl-3-methyl-4-benzoyl-5-pyrazolone and phenylenediamine as the starting materials. All as-synthesized Schiff bases were characterized by means of NMR, FT-IR, and MS; and the molecular geometries of two Schiff bases as typical examples were determined by means of single crystal X-ray diffraction. In the meantime, the ultraviolet-visible light absorption spectra and fluorescent spectra of various as-synthesized products were also measured. Moreover, the B3LYP/6-1G(d,p) method was used for the optimization of the ground state geometry of the Schiff bases; and the spectroscopic properties of the products were computed and compared with corresponding experimental data based on cc-pVTZ basis set of TD-B3LYP method. It has been found that all as-synthesized Schiff bases show a remarkable absorption peak in a wavelength range of 270-370 nm; and their maximum emission peaks are around 344 nm and 332 nm, respectively. Copyright © 2012 Elsevier B.V. All rights reserved.

Comprehensive computational design of ordered peptide macrocycles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hosseinzadeh, Parisa; Bhardwaj, Gaurav; Mulligan, Vikram Khipple

Mixed chirality peptide macrocycles such as cyclosporine are among the most potent therapeutics identified to-date, but there is currently no way to systematically search through the structural space spanned by such compounds for new drug candidates. Natural proteins do not provide a useful guide: peptide macrocycles lack regular secondary structures and hydrophobic cores and have different backbone torsional constraints. Hence the development of new peptide macrocycles has been approached by modifying natural products or using library selection methods; the former is limited by the small number of known structures, and the latter by the limited size and diversity accessible throughmore » library-based methods. To overcome these limitations, here we enumerate the stable structures that can be adopted by macrocyclic peptides composed of L and D amino acids. We identify more than 200 designs predicted to fold into single stable structures, many times more than the number of currently available unbound peptide macrocycle structures. We synthesize and characterize by NMR twelve 7-10 residue macrocycles, 9 of which have structures very close to the design models in solution. NMR structures of three 11-14 residue bicyclic designs are also very close to the computational models. Our results provide a nearly complete coverage of the rich space of structures possible for short peptide based macrocycles unparalleled for other molecular systems, and vastly increase the available starting scaffolds for both rational drug design and library selection methods.« less

A Schiff base connectivity switch in sensory rhodopsin signaling

PubMed Central

Sineshchekov, Oleg A.; Sasaki, Jun; Phillips, Brian J.; Spudich, John L.

2008-01-01

Sensory rhodopsin I (SRI) in Halobacterium salinarum acts as a receptor for single-quantum attractant and two-quantum repellent phototaxis, transmitting light stimuli via its bound transducer HtrI. Signal-inverting mutations in the SRI–HtrI complex reverse the single-quantum response from attractant to repellent. Fast intramolecular charge movements reported here reveal that the unphotolyzed SRI–HtrI complex exists in two conformational states, which differ by their connection of the retinylidene Schiff base in the SRI photoactive site to inner or outer half-channels. In single-quantum photochemical reactions, the conformer with the Schiff base connected to the cytoplasmic (CP) half-channel generates an attractant signal, whereas the conformer with the Schiff base connected to the extracellular (EC) half-channel generates a repellent signal. In the wild-type complex the conformer equilibrium is poised strongly in favor of that with CP-accessible Schiff base. Signal-inverting mutations shift the equilibrium in favor of the EC-accessible Schiff base form, and suppressor mutations shift the equilibrium back toward the CP-accessible Schiff base form, restoring the wild-type phenotype. Our data show that the sign of the behavioral response directly correlates with the state of the connectivity switch, not with the direction of proton movements or changes in acceptor pKa. These findings identify a shared fundamental process in the mechanisms of transport and signaling by the rhodopsin family. Furthermore, the effects of mutations in the HtrI subunit of the complex on SRI Schiff base connectivity indicate that the two proteins are tightly coupled to form a single unit that undergoes a concerted conformational transition. PMID:18852467

A Schiff base connectivity switch in sensory rhodopsin signaling.

PubMed

Sineshchekov, Oleg A; Sasaki, Jun; Phillips, Brian J; Spudich, John L

2008-10-21

Sensory rhodopsin I (SRI) in Halobacterium salinarum acts as a receptor for single-quantum attractant and two-quantum repellent phototaxis, transmitting light stimuli via its bound transducer HtrI. Signal-inverting mutations in the SRI-HtrI complex reverse the single-quantum response from attractant to repellent. Fast intramolecular charge movements reported here reveal that the unphotolyzed SRI-HtrI complex exists in two conformational states, which differ by their connection of the retinylidene Schiff base in the SRI photoactive site to inner or outer half-channels. In single-quantum photochemical reactions, the conformer with the Schiff base connected to the cytoplasmic (CP) half-channel generates an attractant signal, whereas the conformer with the Schiff base connected to the extracellular (EC) half-channel generates a repellent signal. In the wild-type complex the conformer equilibrium is poised strongly in favor of that with CP-accessible Schiff base. Signal-inverting mutations shift the equilibrium in favor of the EC-accessible Schiff base form, and suppressor mutations shift the equilibrium back toward the CP-accessible Schiff base form, restoring the wild-type phenotype. Our data show that the sign of the behavioral response directly correlates with the state of the connectivity switch, not with the direction of proton movements or changes in acceptor pK(a). These findings identify a shared fundamental process in the mechanisms of transport and signaling by the rhodopsin family. Furthermore, the effects of mutations in the HtrI subunit of the complex on SRI Schiff base connectivity indicate that the two proteins are tightly coupled to form a single unit that undergoes a concerted conformational transition.

New Tetra-Schiff Bases as Efficient Photostabilizers for Poly(vinyl chloride).

PubMed

Ahmed, Dina S; El-Hiti, Gamal A; Hameed, Ayad S; Yousif, Emad; Ahmed, Ahmed

2017-09-09

Three new tetra-Schiff bases were synthesized and characterized to be used as photostabilizers for poly(vinyl chloride) (PVC) films. The photostability of PVC films (40 μm thickness) in the presence of Schiff bases (0.5 wt %) upon irradiation (300 h) with a UV light (λ max = 365 nm and light intensity = 6.43 × 10 -9 ein∙dm -3 ∙s -1 ) was examined using various spectroscopic measurements and surface morphology analysis. The changes in various functional groups' indices, weight and viscosity average molecular weight of PVC films were monitored against irradiation time. The additives used showed photostability for PVC films, with Schiff base 1 being the most effective additive upon irradiation, followed by 2 and 3 . The atomic force microscopy (AFM) images for the PVC surface containing Schiff base 1 after irradiation were found to be smooth, with a roughness factor ( R q) of 36.8, compared to 132.2 for the PVC (blank). Several possible mechanisms that explain PVC photostabilization upon irradiation in the presence of tetra-Schiff bases were proposed.

Advances in macrocyclic peptide-based antibiotics.

PubMed

Luther, Anatol; Bisang, Christian; Obrecht, Daniel

2018-06-01

Macrocyclic peptide-based natural products have provided powerful new antibiotic drugs, drug candidates, and scaffolds for medicinal chemists as a source of inspiration to design novel antibiotics. While most of those natural products are active mainly against Gram-positive pathogens, novel macrocyclic peptide-based compounds have recently been described, which exhibit potent and specific activity against some of the most problematic Gram-negative ESKAPE pathogens. This mini-review gives an up-date on recent developments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Progress of Chiral Schiff Bases with C1 Symmetry in Metal-Catalyzed Asymmetric Reactions.

PubMed

Hayashi, Masahiko

2016-12-01

In this Personal Account, various chiral Schiff base-metal-catalyzed enantioselective organic reactions are reported; the Schiff bases used were O,N,O- as well as N,N,P-tridentate ligands and N,N-bidentate ligands having C 1 symmetry. In particular, the enantioselective addition of trimethylsilyl cyanide, dialkylzinc, and organozinc halides to aldehydes, enantioselective 1,4-addition of dialkylzinc to cyclic and acyclic enones, and asymmetric allylic oxidation are reported. Typically, ketimine-type Schiff base-metal complexes exhibited higher reactivity and enantioselectivity compared with the corresponding aldimine-type Schiff base-metal complexes. Notably, remarkable ligand acceleration was observed for all reactions. The obtained products can be used as key intermediates for optically active natural products and pharmaceuticals. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photophysical properties of Schiff's bases from 3-(1,3-benzothiazol-2-yl)-2-hydroxy naphthalene-1-carbaldehyde.

PubMed

Satam, Manjaree A; Telore, Rahul D; Sekar, Nagaiyan

2014-11-11

A series of novel Schiff's bases have been synthesized from 3-(1,3-benzothiazol-2-yl)-2-hydroxynaphthalene-1-carbaldehyde. The presence of hydroxyl group ortho to the benzothiazolyl group as well as the imine linkage lead to the occurrence of excited state intramolecular proton transfer process. The computational strategy was used to study the ESIPT process of the synthesized Schiff's bases, which revealed surprisingly that the keto form predominantly exists in the ground state contradicting the ESIPT process. Density functional theory and time dependent density functional theory have been used to investigate the structural parameters and photophysical properties in different solvents of one of the Schiff's bases. The experimental results correlate well with the computed results. All Schiff's bases show good thermal stability. Copyright © 2014 Elsevier B.V. All rights reserved.

Silver(I) complexes of 2,4-dihydroxybenzaldehyde-amino acid Schiff bases-Novel noncompetitive α-glucosidase inhibitors.

PubMed

Zheng, Jingwei; Ma, Lin

2015-01-01

A series of silver(I) complexes of 2,4-dihydroxybenzaldehyde-amino acid Schiff bases were designed and tested for α-glucosidase inhibition. Our results indicate that all the silver complexes (4a-18a) possessed strong inhibitory activity at μmolL(-1) level, especially glutamine (12a) and histidine (18a) Schiff base silver(I) complexes exhibited an IC50 value of less than 0.01μmolL(-1). This series of compounds exhibited noncompetitive inhibition characteristics in kinetic studies. In addition, we investigated the mechanism of inhibition and the structure-activity relationships of the amino acid Schiff base silver complexes. Our results reveal that Schiff base silver complexes may be explored for their therapeutic potential as alternatives of α-glucosidase inhibitors. Copyright © 2015 Elsevier Ltd. All rights reserved.

Synthesis, characterization and antibacterial activity of biodegradable films prepared from Schiff bases of zein.

PubMed

Soliman, E A; Khalil, A A; Deraz, S F; El-Fawal, G; Elrahman, S Abd

2014-10-01

Pure zein is known to be very hydrophobic, but is still inappropriate for coating and film applications because of their brittle nature. In an attempt to improve the flexibility and the antimicrobial activity of these coatings and films, Chemical modification of zein through forming Schiff bases with different phenolic aldhydes was tried. Influence of this modifications on mechanical, topographical, wetting properties and antimicrobial activity of zein films were evaluated. The chemical structure of the Schiff bases films were characterized by ATR-FTIR spectroscopy. The results indicate an improvement in mechanical properties with chemically modification of zein to form Schiff bases leading to a reduction in the elastic modulus. An increase in the elongation at break has been observed, but with slight influence on tensile strength. Plasticized zein films have similar initial contact angle (∼40°). An increase in reaction temperature and time increases film's affinity towards water. As shown by contact angle measurements, a noticeable relation was found between film composition and the hydrophilicity. Surface topography also varied by forming Schiff bases, becoming rougher than zein-based films. The antibacterial activities of zein and Schiff bases of zein-based films were investigated against gram-positive bacteria (Listeria innocua, Listeria monocytogenes, Bacillus cereus and Clostridium sporogenes) and gram-negative bacteria (Escherichia coli, Yersinia enterocolitica and Salmonella enterica). It was found that the antibacterial activity of the Schiff bases-based films was more effective than that of zein-based films.

Heterocyclic Schiff bases as non toxic antioxidants: Solvent effect, structure activity relationship and mechanism of action

NASA Astrophysics Data System (ADS)

Shanty, Angamaly Antony; Mohanan, Puzhavoorparambil Velayudhan

2018-03-01

Phenolic heterocyclic imine based Schiff bases from Thiophene-2-carboxaldehyde and Pyrrole-2-carboxaldehyde were synthesized and characterized as novel antioxidants. The solvent effects of these Schiff bases were determined and compared with standard antioxidants, BHA employing DPPH assay and ABTS assay. Fixed reaction time and Steady state measurement were used for study. IC50 and EC50 were calculated. Structure-activity relationship revealed that the electron donating group in the phenolic ring increases the activity where as the electron withdrawing moiety decreases the activity. The Schiff base derivatives showed antioxidant property by two different pathways namely SPLET and HAT mechanisms in DPPH assay. While in ABTS method, the reaction between ABTS radical and Schiff bases involves electron transfer followed by proton transfer (ET-PT) mechanism. The cytotoxicity of these compounds has been evaluated by MTT assay. The results showed that all these compounds are non toxic in nature.

Design of cinnamaldehyde amino acid Schiff base compounds based on the quantitative structure–activity relationship

Treesearch

Hui Wang; Mingyue Jiang; Shujun Li; Chung-Yun Hse; Chunde Jin; Fangli Sun; Zhuo Li

2017-01-01

Cinnamaldehyde amino acid Schiff base (CAAS) is a new class of safe, bioactive compounds which could be developed as potential antifungal agents for fungal infections. To design new cinnamaldehyde amino acid Schiff base compounds with high bioactivity, the quantitative structure–activity relationships (QSARs) for CAAS compounds against Aspergillus niger (A. niger) and...

Synthesis, characterization and toxicity studies of pyridinecarboxaldehydes and L-tryptophan derived Schiff bases and corresponding copper (II) complexes.

PubMed

Malakyan, Margarita; Babayan, Nelly; Grigoryan, Ruzanna; Sarkisyan, Natalya; Tonoyan, Vahan; Tadevosyan, Davit; Matosyan, Vladimir; Aroutiounian, Rouben; Arakelyan, Arsen

2016-01-01

Schiff bases and their metal-complexes are versatile compounds exhibiting a broad range of biological activities and thus actively used in the drug development process. The aim of the present study was the synthesis and characterization of new Schiff bases and their copper (II) complexes, derived from L-tryptophan and isomeric (2-; 3-; 4-) pyridinecarboxaldehydes, as well as the assessment of their toxicity in vitro . The optimal conditions of the Schiff base synthesis resulting in up to 75-85% yield of target products were identified. The structure-activity relationship analysis indicated that the location of the carboxaldehyde group at 2-, 3- or 4-position with regard to nitrogen of the pyridine ring in aldehyde component of the L-tryptophan derivative Schiff bases and corresponding copper complexes essentially change the biological activity of the compounds. The carboxaldehyde group at 2- and 4-positions leads to the higher cytotoxic activity, than that of at 3-position, and the presence of the copper in the complexes increases the cytotoxicity. Based on toxicity classification data, the compounds with non-toxic profile were identified, which can be used as new entities in the drug development process using Schiff base scaffold.

Synthesis, characterization and biological activity of Schiff bases based on chitosan and arylpyrazole moiety.

PubMed

Salama, Hend E; Saad, Gamal R; Sabaa, Magdy W

2015-08-01

The Schiff bases of chitosan were synthesized by the reaction of chitosan with 3-(4-substituted-phenyl)-1-phenyl-1H-pyrazole-4-carbaldehyde. The structure of the prepared chitosan derivatives was characterized by FT-IR spectroscopy, elemental analysis, and X-ray diffraction studies and thermogravimetric analysis (TG). The results show that the specific properties of Schiff bases of chitosan can be altered by modifying the molecular structures with proper substituent groups.TG results reveal that the thermal stability of the prepared chitosan Schiff bases was lower than chitosan. The activation energy of decomposition was calculated using Coats-Redfern model. The antimicrobial activity of chitosan and Schiff bases of chitosan were investigated against Streptococcus pneumonia, Bacillis subtilis, Escherichia coli (as examples of bacteria) and Aspergillus fumigatus, Geotricum candidum and Syncephalastrum recemosum (as examples of fungi). The results indicated that the antimicrobial activity of the Schiff bases was stronger than that of chitosan and was dependent on the substituent group. The activity of un-substituted arylpyrazole chitosan derivative toward the investigated bacteria and fungi species was better than the other derivatives. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis, characterization and toxicity studies of pyridinecarboxaldehydes and L-tryptophan derived Schiff bases and corresponding copper (II) complexes

PubMed Central

Malakyan, Margarita; Babayan, Nelly; Grigoryan, Ruzanna; Sarkisyan, Natalya; Tonoyan, Vahan; Tadevosyan, Davit; Matosyan, Vladimir; Aroutiounian, Rouben; Arakelyan, Arsen

2016-01-01

Schiff bases and their metal-complexes are versatile compounds exhibiting a broad range of biological activities and thus actively used in the drug development process. The aim of the present study was the synthesis and characterization of new Schiff bases and their copper (II) complexes, derived from L-tryptophan and isomeric (2-; 3-; 4-) pyridinecarboxaldehydes, as well as the assessment of their toxicity in vitro. The optimal conditions of the Schiff base synthesis resulting in up to 75-85% yield of target products were identified. The structure-activity relationship analysis indicated that the location of the carboxaldehyde group at 2-, 3- or 4-position with regard to nitrogen of the pyridine ring in aldehyde component of the L-tryptophan derivative Schiff bases and corresponding copper complexes essentially change the biological activity of the compounds. The carboxaldehyde group at 2- and 4-positions leads to the higher cytotoxic activity, than that of at 3-position, and the presence of the copper in the complexes increases the cytotoxicity. Based on toxicity classification data, the compounds with non-toxic profile were identified, which can be used as new entities in the drug development process using Schiff base scaffold. PMID:28344771

FTIR Studies of Internal Water Molecules of Bacteriorhodopsin: Structural Analysis of Halide-bound D85S and D212N Mutants in the Schiff Base Region

NASA Astrophysics Data System (ADS)

Shibata, Mikihiro; Kandori, Hideki

2007-12-01

Bacteriorhodopsin (BR), a membrane protein found in Halobacterium salinarum, functions as a light-driven proton pump. The Schiff base region has a quadropolar structure with positive charges located at the protonated Schiff base and Arg82, and counterbalancing negative charges located at Asp85 and Asp212 (Figure 1A). It is known that BR lacks a proton-pumping activity if Asp85 or Asp212 is neutralized by mutation. On the other hand, binding of C1- brings different effects for pumping functions in mutants at D85 and D212 position. While C1--bound D85T and D85S pump C1-, photovoltage measurements suggested that C1--bound D212N pumps protons at low pH. In this study, we measured low-temperature FTIR spectra of D85S and D212N containing various halides to compare the halide binding site of both proteins. In the case of D85S, the N-D stretching vibrations of the Schiff base were halide-dependent. This result suggests that the halide is a hydrogen-bond acceptor of the Schiff base, being consistent with the X-ray crystal structure. On the other hand, no halide dependence was observed for vibrational bands of the retinal skeleton and the Schiff base in the D212N mutant. This result suggests that the halide does not form a hydrogen bond with the Schiff base directly, unlike the mutation at D85 position. Halide-dependent water bands in the Schiff base region also differ between D85S and D212N. From these results, halide binding site of both proteins and role of two negative charges in BR will be discussed.

Synthesis and antibacterial activity of Schiff bases and amines derived from alkyl 2-(2-formyl-4-nitrophenoxy)alkanoates.

PubMed

Goszczyńska, Agata; Kwiecień, Halina; Fijałkowski, Karol

A series of novel Schiff bases and secondary amines were obtained in good yields, as a result of the reductive amination of alkyl 2-(2-formyl-4-nitrophenoxy)alkanoates with both aniline and 4-methoxyaniline under established mild reaction conditions. Sodium triacetoxyborohydride as well as hydrogen in the presence of palladium on carbon were used as efficient reducing agents of the Schiff bases, in both direct and stepwise reductive amination processes. The Schiff bases, amines, and amine hydrochlorides were designed as potential antibacterial agents, and structure-activity relationship could be established following in vitro assays against Gram-positive and Gram-negative bacteria. The minimal inhibitory concentration and zone of inhibition were also determined. In these tests, some of Schiff bases and secondary amine hydrochlorides showed moderate-to-good activity against Gram-positive bacteria, including S. aureus , M. luteus , and S. mutans .

Amido-Schiff base derivatives as colorimetric fluoride sensor: Effect of nitro substitution on the sensitivity and color change.

PubMed

Ghosh, Soumen; Alam, Md Akhtarul; Ganguly, Aniruddha; Guchhait, Nikhil

2015-01-01

A series of Schiff bases synthesized by the condensation of benzohydrazide and -NO2 substituted benzaldehyde have been used as selective fluoride ion sensor. Test paper coated with these synthetic Schiff bases (test kits) can detect fluoride ion selectively with a drastic color change and detection can be achieved by just using the naked-eye without the help of any optical instrument. Interestingly, the position of -NO2 group in the amido Schiff bases has an effect on the sensitivity as well as on the change of color of species. Copyright © 2015 Elsevier B.V. All rights reserved.

Silica functionalized Cu(II) acetylacetonate Schiff base complex: An efficient catalyst for the oxidative condensation reaction of benzyl alcohol with amines

NASA Astrophysics Data System (ADS)

Anbarasu, G.; Malathy, M.; Karthikeyan, P.; Rajavel, R.

2017-09-01

Silica functionalized Cu(II) acetylacetonate Schiff base complex via the one pot reaction of silica functionalized 3-aminopropyltriethoxysilane with acetyl acetone and copper acetate has been reported. The synthesized material was well characterized by analytical techniques such as FT-IR, UV-DRS, XRD, SEM-EDX, HR-TEM, EPR, ICP-AES and BET analysis. The characterization results confirmed the grafting of Cu(II) Schiff base complex on the silica surface. The catalytic activity of synthesized silica functionalized Cu(II) acetylacetonate Schiff base complex was evaluated through the oxidative condensation reaction of benzyl alcohol to imine.

Synthesis and Evaluation of In Vitro Antibacterial and Antitumor Activities of Novel N,N-Disubstituted Schiff Bases

PubMed Central

Luo, Heng; Xia, Yu-fen; Sun, Bao-fei; Huang, Li-rong; Wang, Xing-hui; Lou, Hua-yong; Zhu, Xu-hui

2017-01-01

To get inside the properties of N,N-disubstituted Schiff bases, we synthesized three high-yielding benzaldehyde Schiff bases. We used the reaction between salicylaldehyde and different diamine compounds, including diamine, ethanediamine, and o-phenylenediamine, determining the structure of obtained molecules by nuclear magnetic resonance spectroscopy and electrospray ionization mass spectroscopy. We thus evaluated the microbicidal and antitumor activity of these compounds, showing that salicylaldehyde-hydrazine hydrate Schiff base (compound 1a) significantly inhibited the growth of S. aureus; salicylaldehyde-o-phenylenediamine Schiff base (compound 1c) displayed a strong capability to inhibit the proliferation of leukemia cell lines K562 and HEL. Moreover, we observed that the antibacterial action of 1a might be associated with the regulation of the expression of key virulence genes in S. aureus. Compound 1c resulted in a strong apoptotic activity against leukemia cells, also affecting the cell cycle distribution. Overall, our novel N,N-disubstituted Schiff bases possess unique antibacterial or antitumor activities that exhibit the potent application prospect in prophylactic or therapeutic interventions, providing new insights for developing new antibacterial and anticancer chemical agents. PMID:28713593

Synthesis of new 1,2,4-triazole compounds containing Schiff and Mannich bases (morpholine) with antioxidant and antimicrobial activities.

PubMed

Ünver, Yasemin; Deniz, Sadik; Çelik, Fatih; Akar, Zeynep; Küçük, Murat; Sancak, Kemal

2016-01-01

Compound 2 was synthesized by reacting CS 2 /KOH with compound 1. The treatment of compound 2 with hydrazine hydrate produced compound 3. Then, compound 3 was converted to Schiff bases (4a-d) by the handling with several aromatic aldehydes. The treatment of triazole compounds 4a-d containing Schiff base with morpholine gave compounds 5a-d. All compounds were tested for their antioxidant and antimicrobial activities. The antioxidant test results of DPPH• radical scavenging and ferric reducing/antioxidant power methods showed good antioxidant activity. The triazole-thiol (3) was the most active, and the effect of the substituent type of the thiophene ring on the activity was same for both Schiff bases (4a-d) and Mannich bases (5a-d). Among the newly synthesized triazole derivatives, the Schiff base 4d and the Mannich base 5d carrying nitro substituent on the thiophene ring showed promising antibacterial and antifungal activity, with lower MIC values than the standard antibacterial ampicillin.

A Multidimensional Diversity‐Oriented Synthesis Strategy for Structurally Diverse and Complex Macrocycles

PubMed Central

Nie, Feilin; Kunciw, Dominique L.; Wilcke, David; Stokes, Jamie E.; Galloway, Warren R. J. D.; Bartlett, Sean; Sore, Hannah F.

2016-01-01

Abstract Synthetic macrocycles are an attractive area in drug discovery. However, their use has been hindered by a lack of versatile platforms for the generation of structurally (and thus shape) diverse macrocycle libraries. Herein, we describe a new concept in library synthesis, termed multidimensional diversity‐oriented synthesis, and its application towards macrocycles. This enabled the step‐efficient generation of a library of 45 novel, structurally diverse, and highly‐functionalized macrocycles based around a broad range of scaffolds and incorporating a wide variety of biologically relevant structural motifs. The synthesis strategy exploited the diverse reactivity of aza‐ylides and imines, and featured eight different macrocyclization methods, two of which were novel. Computational analyses reveal a broad coverage of molecular shape space by the library and provides insight into how the various diversity‐generating steps of the synthesis strategy impact on molecular shape. PMID:27484830

Synthesis, spectroscopic, thermal and electrical conductivity studies of three charge transfer complexes formed between 1,3-di[( E)-1-(2-hydroxyphenyl)methylideneamino]-2-propanol Schiff base and different acceptors

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Ibrahim, Mohamed M.; Moussa, Mohamed A. A.

2012-01-01

Charge-transfer complexes (CTC) resulting from interactions of 1,3-di[( E)-1-(2-hydroxyphenyl) methylideneamino]-2-propanol Schiff base with some acceptors such as iodine (I2), bromine (Br2), and picric acid (PiA) have been isolated in the solid state in a chloroform solvent at room temperature. Based on elemental analysis, UV-Vis, infrared, and 1H NMR spectra, and thermogravimetric analysis (TG/DTG) of the solid CTC, [(Schiff)(I2)] (1), [(Schiff)(Br2)] complexes with a ratio of 1:1 and [(Schiff)(PiA)3] complexes with 1:3 have been prepared. In the picric acid complex, infrared and 1H NMR spectroscopic data indicate that the charge-transfer interaction is associated with a hydrogen bonding, whereas the iodine and bromine complexes were interpreted in terms of the formation of dative ion pairs [Schiff+, I{2/•-}] and [Schiff+, Br{2/•-}], respectively. Kinetic parameters were obtained for each stage of thermal degradation of the CT complexes using Coats-Redfern and Horowitz-Metzger methods. DC electrical properties as a function of temperature of these charge transfer complexes have been studied.

Accurate and Reliable Prediction of the Binding Affinities of Macrocycles to Their Protein Targets.

PubMed

Yu, Haoyu S; Deng, Yuqing; Wu, Yujie; Sindhikara, Dan; Rask, Amy R; Kimura, Takayuki; Abel, Robert; Wang, Lingle

2017-12-12

Macrocycles have been emerging as a very important drug class in the past few decades largely due to their expanded chemical diversity benefiting from advances in synthetic methods. Macrocyclization has been recognized as an effective way to restrict the conformational space of acyclic small molecule inhibitors with the hope of improving potency, selectivity, and metabolic stability. Because of their relatively larger size as compared to typical small molecule drugs and the complexity of the structures, efficient sampling of the accessible macrocycle conformational space and accurate prediction of their binding affinities to their target protein receptors poses a great challenge of central importance in computational macrocycle drug design. In this article, we present a novel method for relative binding free energy calculations between macrocycles with different ring sizes and between the macrocycles and their corresponding acyclic counterparts. We have applied the method to seven pharmaceutically interesting data sets taken from recent drug discovery projects including 33 macrocyclic ligands covering a diverse chemical space. The predicted binding free energies are in good agreement with experimental data with an overall root-mean-square error (RMSE) of 0.94 kcal/mol. This is to our knowledge the first time where the free energy of the macrocyclization of linear molecules has been directly calculated with rigorous physics-based free energy calculation methods, and we anticipate the outstanding accuracy demonstrated here across a broad range of target classes may have significant implications for macrocycle drug discovery.

A diversity-oriented synthesis strategy enabling the combinatorial-type variation of macrocyclic peptidomimetic scaffolds.

PubMed

Isidro-Llobet, Albert; Hadje Georgiou, Kathy; Galloway, Warren R J D; Giacomini, Elisa; Hansen, Mette R; Méndez-Abt, Gabriela; Tan, Yaw Sing; Carro, Laura; Sore, Hannah F; Spring, David R

2015-04-21

Macrocyclic peptidomimetics are associated with a broad range of biological activities. However, despite such potentially valuable properties, the macrocyclic peptidomimetic structural class is generally considered as being poorly explored within drug discovery. This has been attributed to the lack of general methods for producing collections of macrocyclic peptidomimetics with high levels of structural, and thus shape, diversity. In particular, there is a lack of scaffold diversity in current macrocyclic peptidomimetic libraries; indeed, the efficient construction of diverse molecular scaffolds presents a formidable general challenge to the synthetic chemist. Herein we describe a new, advanced strategy for the diversity-oriented synthesis (DOS) of macrocyclic peptidomimetics that enables the combinatorial variation of molecular scaffolds (core macrocyclic ring architectures). The generality and robustness of this DOS strategy is demonstrated by the step-efficient synthesis of a structurally diverse library of over 200 macrocyclic peptidomimetic compounds, each based around a distinct molecular scaffold and isolated in milligram quantities, from readily available building-blocks. To the best of our knowledge this represents an unprecedented level of scaffold diversity in a synthetically derived library of macrocyclic peptidomimetics. Cheminformatic analysis indicated that the library compounds access regions of chemical space that are distinct from those addressed by top-selling brand-name drugs and macrocyclic natural products, illustrating the value of our DOS approach to sample regions of chemical space underexploited in current drug discovery efforts. An analysis of three-dimensional molecular shapes illustrated that the DOS library has a relatively high level of shape diversity.

Modification in band gap of zirconium complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Mayank, E-mail: mayank30134@gmail.com; Singh, J.; Chouhan, S.

2016-05-06

The optical properties of zirconium complexes with amino acid based Schiff bases are reported here. The zirconium complexes show interesting stereo chemical features, which are applicable in organometallic and organic synthesis as well as in catalysis. The band gaps of both Schiff bases and zirconium complexes were obtained by UV-Visible spectroscopy. It was found that the band gap of zirconium complexes has been modified after adding zirconium compound to the Schiff bases.

Synthesis and photoluminescence properties of novel Schiff base type polymer-rare earth complexes containing furfural-based bidentate Schiff base ligands

NASA Astrophysics Data System (ADS)

Gao, Baojiao; Zhang, Dandan; Li, Yanbin

2018-03-01

Luminescent polymer-rare earth complexes are an important class of photoluminescence and electroluminescence materials. Via molecular design, two furfural-based bidentate Schiff base ligands, furfural-aniline (FA) type ligand and furfural-cyclohexylamine (FC) type ligand, were bonded on the side chains of polysulfone (PSF), respectively, forming two functionalized macromolecules, PSF-FA and PSF-FC. And then through respective coordination reactions of the two functionalized macromolecules with Eu(Ⅲ) ion and Tb(Ⅲ) ion, novel luminescent binary and ternary (with 1,10-phenanthroline as the second ligand) polymer-rare earth complexes were synthesized. For these complexes, on basis of the characterization of their chemical structures, they photoluminescence properties were main researched, and the relationship between their luminescent properties and structures was explored. The experimental results show that the complexes coming from PSF-FA and Eu(Ⅲ) ion including binary and ternary complexes emit strong red luminescence, indicating that the bonded bidentate Schiff base ligand FA can sensitize the fluorescence emission of Eu(III) ion. While the complexes coming from PSF-FC and Tb(Ⅲ) ion produce green luminescence, displaying that the bonded bidentate Schiff base ligand FC can sensitize the fluorescence emission of Tb(Ⅲ) ion. The fluorescence emission intensities of the ternary complexes were stronger than that of binary complexes, reflecting the important effect of the second ligand. The fluorescence emission of the solid film of complexes is much stronger than that of the solutions of complexes. Besides, by comparison, it is found that the furfural (as a heteroaromatic compound)-based Schiff base type polymer-rare earth complexes have stronger fluorescence emission and higher energy transfer efficiency than salicylaldehyde (as a common aromatic compound)-based Schiff base type polymer-rare earth complexes.

Structural and Biological Behaviour of Co(II), Cu(II) and Ni(II) Metal Complexes of Some Amino Acid Derived Schiff-Bases

PubMed Central

Chohan, Zahid H.; Praveen, M.; Ghaffar, A.

1997-01-01

Biologically active tridentate amino acid (Alanine, Glycine & Tyrosine) derived Schiff-bases and their Co(II), Cu(II) & Ni(II) complexes have been synthesised and characterised on the basis of their conductance and magnetic measurements, elemental analysis and 13C-NMR, 1H-NMR, IR and electronic spectral data. These Schiff-bases and their complexes have been evaluated for their antibacterial activity against bacterial species such as Staphylococcus aureus, Escherichia coli, Klebsiella pneumonae, Proteus vulgarus and Pseudomonas aeruginosa and this activity data show the metal complexes to be more antibacterial than the Schiff-bases against one or more bacterial species. PMID:18475798

In vitro antibacterial, antifungal and cytotoxic activities of some triazole Schiff bases and their oxovanadium(IV) complexes.

PubMed

Sumrra, Sajjad H; Chohan, Zahid H

2013-12-01

The condensation reaction of 3,5-diamino-1,2,4-triazole with methoxy-, chloro-, bromo-, iodo- and nitro-substituted 2-hydroxybenzaldehydes formed triazole Schiff bases (L(1))-(L(6)). The synthesized ligands have been characterized through physical, spectral and analytical data. Furthermore, the reaction of synthesized Schiff bases with the oxovanadium(IV) sulphate in (1:2) (metal:ligand) molar ratio afforded the oxovanadium(IV) complexes (1)-(6). All the complexes were non-electrolytic and showed a square-pyramidal geometry. The synthesized compounds have been screened for in-vitro antibacterial, antifungal and brine shrimp bioassay. The bioactivity data showed the complexes to be more active than the original Schiff bases.

Synthesis, characterization, spectroscopic studies and antimicrobial activity of three new Schiff bases derived from Heterocyclic moiety

NASA Astrophysics Data System (ADS)

Mesbah, Mounira; Douadi, Tahar; Sahli, Farida; Issaadi, Saifi; Boukazoula, Soraya; Chafaa, Salah

2018-01-01

Three new Schiff-bases compounds (I-III) were synthesized by a condensation reaction in 1:2 M ratios of 4,4‧-diaminodiphenyl sulfide and pyrrol/thiophene/furan-2-carboxaldehyde in ethanol. The structural determinations of the Schiff-bases were identified with the help of elemental analysis then confirmed by UV-Vis, FT-IR and 1H NMR. The products were obtained in excellent yields. On the other hand, the in vitro antibacterial and antifungal activities of the synthesized compounds were investigated using disc diffusion method. Schiff bases synthesized individually exhibited varying degrees of inhibitory effects on the growth of the tested microbial species.

DFT Analysis of Spin Crossover in Mn(III) Complexes: Is a Two-Electron S = 2 to S = 0 Spin Transition Feasible?

PubMed

Amabilino, Silvia; Deeth, Robert J

2017-03-06

Six-coordinate, rigorously octahedral d 4 Mn(III) spin crossover (SCO) complexes are limited by symmetry to an S = 1 (intermediate spin, IS) to S = 2 (high spin, HS) transition. In order to realize the potential S = 0 to S = 2 transition, a lower symmetry and/or change in coordination number is needed, which we explore here computationally. First, a number of complexes are analyzed to develop a reliable and relatively fast DFT protocol for reproducing known Mn(III) spin state energetics. The hybrid meta-GGA functional TPSSh with a modest split valence plus polarization basis set and an empirical dispersion correction is found to predict correctly the ground spin state of Mn(III) complexes, including true low-spin (LS) S = 0 systems, with a range of donor sets including the hexadentate [N 4 O 2 ] Schiff base ligands. The electronic structure design criteria necessary for realizing a ΔS = 2 SCO transition are described, and a number of model complexes are screened for potential SCO behavior. Five-coordinate trigonal-bipyramidal symmetry fails to yield any suitable systems. Seven-coordinate, approximately pentagonal bipyramidal symmetry is more favorable, and when a known pentadentate macrocyclic donor is combined with π-acceptor axial ligands, a novel Mn(III) complex, [Mn(PABODP)(PF 3 ) 2 ] 3+ (PABODP = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene), is predicted to have the right spin state energetics for an S = 0 to S = 2 transition. Successful synthesis of such a complex could provide the first example of a ΔS = 2 SCO transition for d 4 Mn(III). However, the combination of a rigid macrocycle and a high coordination number dilutes the stereochemical activity of the d electrons, leading to relatively small structural changes between HS and LS systems. It may therefore remain a challenge to realize strong cooperative effects in Mn(III) systems.

MacroEvoLution: A New Method for the Rapid Generation of Novel Scaffold-Diverse Macrocyclic Libraries.

PubMed

Saupe, Jörn; Kunz, Oliver; Haustedt, Lars Ole; Jakupovic, Sven; Mang, Christian

2017-09-04

Macrocycles are a structural class bearing great promise for future challenges in medicinal chemistry. Nevertheless, there are few flexible approaches for the rapid generation of structurally diverse macrocyclic compound collections. Here, an efficient method for the generation of novel macrocyclic peptide-based scaffolds is reported. The process, named here as "MacroEvoLution", is based on a cyclization screening approach that gives reliable access to novel macrocyclic architectures. Classification of building blocks into specific pools ensures that scaffolds with orthogonally addressable functionalities are generated, which can easily be used for the generation of structurally diverse compound libraries. The method grants rapid access to novel scaffolds with scalable synthesis (multi gram scale) and the introduction of further diversity at a late stage. Despite being developed for peptidic systems, the approach can easily be extended for the synthesis of systems with a decreased peptidic character. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Investigation of the antioxidant and radical scavenging activities of some phenolic Schiff bases with different free radicals.

PubMed

Marković, Zoran; Đorović, Jelena; Petrović, Zorica D; Petrović, Vladimir P; Simijonović, Dušica

2015-11-01

The antioxidant properties of some phenolic Schiff bases in the presence of different reactive particles such as (•)OH, (•)OOH, (CH2=CH-O-O(•)), and (-•)O2 were investigated. The thermodynamic values, ΔH BDE, ΔH IP, and ΔH PA, were used for this purpose. Three possible mechanisms for transfer of hydrogen atom, concerted proton-electron transfer (CPET), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) were considered. These mechanisms were tested in solvents of different polarity. On the basis of the obtained results it was shown that SET-PT antioxidant mechanism can be the dominant mechanism when Schiff bases react with radical cation, while SPLET and CPET are competitive mechanisms for radical scavenging of hydroxy radical in all solvents under investigation. Examined Schiff bases react with the peroxy radicals via SPLET mechanism in polar and nonpolar solvents. The superoxide radical anion reacts with these Schiff bases very slowly.

Charge transfer complexes of adenosine-5‧-monophosphate and cytidine-5‧-monophosphate with water-soluble cobalt(II) Schiff base complexes in aqueous solution

NASA Astrophysics Data System (ADS)

Boghaei, Davar M.; Gharagozlou, Mehrnaz

2006-01-01

Water-soluble cobalt(II) tetradentate Schiff base complexes have been shown to form charge transfer (CT) complexes with a series of nucleoside monophosphates including adenosine-5‧-monophosphate (AMP) and cytidine-5‧-monophosphate (CMP). The investigated water-soluble cobalt(II) Schiff base complexes are (i) disodium[{bis(5-sulfo-salicylaldehyde)-o-phenylenediiminato}cobalt(II)], Na2[Co(SO3-salophen)] (1); (ii) disodium[{bis(5-sulfo-salicylaldehyde)-4,5-dimethyl-o-phenylenediiminato}cobalt(II)], Na2[Co(SO3-sal-4,5-dmophen)] (2) and (iii) disodium[{bis(4-methoxy-5-sulfo-salicylaldehyde)-4,5-dimethyl-o-phenylenediiminato}cobalt(II)], Na2[Co(SO3-4-meosal-4,5-dmophen)] (3). The formation constant and thermodynamic parameters for charge transfer complex formation of water-soluble cobalt(II) Schiff base complexes with nucleoside monophosphates were determined spectrophotometrically in aqueous solution at constant ionic strength (I = 0.2 mol dm-3 KNO3) under physiological condition (pH 7.0) and at various temperatures between 288 and 308 K. The stoichiometry has been found to be 1:1 (water-soluble cobalt(II) Schiff base complex: nucleoside monophosphate) in each case. Our spectroscopic and thermodynamic results show that the interaction of water-soluble cobalt(II) Schiff base complexes with the investigated nucleoside monophosphates occurs mainly through the phosphate group. The trend of the interaction according to the cobalt(II) Schiff base complexes due to electronic and steric factors is as follows: Na2[Co(SO3-salophen)] > Na2[Co(SO3-sal-4,5-dmophen)] > Na2[Co(SO3-4-meosal-4,5-dmophen)]. Also the trend of the interaction of a given cobalt(II) Schiff base complex according to the nucleoside monophosphate is as follows: CMP > AMP.

One-pot microwave assisted synthesis under green chemistry conditions, antioxidant screening, and cytotoxicity assessments of benzimidazole Schiff bases and pyrimido[1,2-a]benzimidazol-3(4H)-ones.

PubMed

Neochoritis, Constantinos G; Zarganes-Tzitzikas, Tryfon; Tsoleridis, Constantinos A; Stephanidou-Stephanatou, Julia; Kontogiorgis, Christos A; Hadjipavlou-Litina, Dimitra J; Choli-Papadopoulou, Theodora

2011-01-01

The synthesis of a number of benzimidazole Schiff bases 3 and 3-oxo-pyrimido[1,2-a]benzimidazoles 4 in excellent yields by a one-step sequence from the reaction of 2-aminobenzimidazole under green chemistry conditions is described. Structural assignments of the new compounds as well as complete assignment of (1)H and (13)C NMR signals have been unambiguously achieved based on the analysis of their (1)H and (13)C NMR (1D and 2D), IR, MS and elemental analysis data. To the synthesized Schiff bases the E-configuration was assigned on the basis of comparison of experimental and calculated (DFT) (13)C NMR chemical shifts. Compounds 3 and 4 were evaluated as inhibitors of lipoxygenase (LOX) and of lipid peroxidation (LPO). All the tested derivatives showed inhibition of lipid peroxidation, whereas most of them were found to have higher activation than the reference compound trolox; The Schiff bases 3e, 3h, and 3i, and the pyrimidobenzimidazoles 4a, 4e and 4f were found to be the most potent. The most potent LOX inhibitor within the subset of Schiff bases was found compound 3i, followed by 3f, whereas compounds 4a and 4g were found the most potent of the 3-oxo-pyrimido[1,2-a]benzimidazole group. Moreover, some cytotoxicity assessments were undertaken, whereupon it was found that Schiff base 3i and pyrimidobenzimidazoles 4e and 4f did not exhibit cytotoxicity at similar concentrations resembling thus the inhibitory activity of lipid peroxidation. The most cytotoxic Schiff base and pyrimidobenzimidazole were found to be 3d and 4c, respectively. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

Metal based biologically active compounds: design, synthesis, and antibacterial/antifungal/cytotoxic properties of triazole-derived Schiff bases and their oxovanadium(IV) complexes.

PubMed

Chohan, Zahid H; Sumrra, Sajjad H; Youssoufi, Moulay H; Hadda, Taibi B

2010-07-01

A new series of oxovanadium(IV) complexes have been designed and synthesized with a new class of triazole Schiff bases derived from the reaction of 3,5-diamino-1,2,4-triazole with 2-hydroxy-1-naphthaldehyde, pyrrole-2-carboxaldehyde, pyridine-2-carboxaldehyde and acetyl pyridine-2-carboxaldehyde, respectively. Physical (magnetic susceptibility, molar conductance), spectral (IR, (1)H NMR, (13)C NMR, mass and electronic) and analytical data have established the structures of these synthesized Schiff bases and their oxovanadium(IV) complexes. The Schiff bases, predominantly act as bidentate and coordinate with the vanadium(IV) metal to give a stoichiometric ratio of 1:2 [M:L], forming a general formulae, [M(L-H)(2)] and [M(L)(2)]SO(4) where L = (L(1))-(L(4)) and M = VO(IV) of these complexes in a square-pyramidal geometry. In order to evaluate the biological activity of Schiff bases and to assess the role of vanadium(IV) metal on biological activity, the triazole Schiff bases and their oxovanadium(IV) complexes have been studied for in vitro antibacterial activity against four Gram-negative (Escherichia coli, Shigella flexenari, Pseudomonas aeruginosa, Salmonella typhi) and two Gram-positive (Staphylococcus aureus, Bacillus subtilis) bacterial strains, in vitro antifungal activity against Trichophyton longifucus, Candida albican, Aspergillus flavus, Microscopum canis, Fusarium solani and Candida glaberata. The simple Schiff bases showed weaker to significant activity against one or more bacterial and fungal strains. In most of the cases higher activity was exhibited upon coordination with vanadium(IV) metal. Brine shrimp bioassay was also carried out for in vitro cytotoxic properties against Artemia salina. Copyright (c) 2010 Elsevier Masson SAS. All rights reserved.

Three VO2+ complexes of the pyridoxal-derived Schiff bases: Synthesis, experimental and theoretical characterizations, and catalytic activity in a cyclocondensation reaction

NASA Astrophysics Data System (ADS)

Jafari-Moghaddam, Faezeh; Beyramabadi, S. Ali; Khashi, Maryam; Morsali, Ali

2018-02-01

Three oxovanadium(IV) complexes of the pyridoxal Schiff bases have been newly synthesized and characterized. The used Schiff bases were N,N‧-dipyridoxyl(ethylenediamine), N,N‧-dipyridoxyl(1,3-propanediamine) and N,N‧-dipyridoxyl(1,2-benzenediamine). Also, the optimized geometry, assignment of the IR bands and the Natural Bond Orbital (NBO) analysis of the complexes have been computed using the density functional theory (DFT) methods. Dianionic form of the Schiff bases (L2-) acts as a tetradentate N2O2 ligand. The coordinating atoms of the Schiff base are the phenolate oxygens and imine nitrogens, which occupy four base positions of the square-pyramidal geometry of the complexes. The oxo ligand occupies the apical position of the [VO(L)] complexes. In the optimized geometry of the complexes, the coordinated Schiff bases have more planar structure than their free form. Due to the high-energy gaps, all of the complexes are predicted to be stable. Good agreement between the experimental values and the DFT-computed results supports suitability of the optimized geometries for the complexes. The investigated complexes show high catalytic activities in synthesis of the tetrahydrobenzo[b]pyrans through a three-component cyclocondensation reaction of dimedone, malononitrile and some aromatic aldehydes. The complexes catalyzed the reaction in solvent free conditions and the catalysts were found to be reusable.

Theoretical study on the optical response behavior to hydrogen chloride gas of a series of Schiff-base-based star-shaped structures.

PubMed

Wang, Fei; Qi, Tianhong; Su, Zhongmin; Xie, Yuzhong

2018-02-17

Schiff-base compounds have many applications in the field of optoelectronic materials and chemical sensing because of their appealing coordination ability, and simple and easily accessible use in structural modification. Herein, five kinds of star-shaped Schiff-base compounds were designed and their optical response behavior to hydrogen chloride (HCl) gas was studied using dependent/time-dependent density functional theory (DFT/TDDFT). Moreover, the relationship between structures and properties was investigated upon changing the benzene group into N atom or triazine group at the core-position and introducing a methoxyl (-OCH 3 ) or nitro (-NO 2 ) group into the star-shaped Schiff-bases at the tail of the branches. The results show that all five Schiff-bases could be candidates for HCl gas sensing materials. Furthermore, introducing an electron-donating group at either the core or the tail forms a charge transfer channel with the electron deficient H-bonded imino group, which is convenient for charge transfer and subsequently promotes a red-shift in absorption spectra and fluorescence quenching.

High Affinity Macrocycle Threading by a Near-Infrared Croconaine Dye with Flanking Polymer Chains

PubMed Central

Liu, Wenqi; Peck, Evan M.; Smith, Bradley D.

2016-01-01

Croconaine dyes have narrow and intense absorption bands at ~800 nm, very weak fluorescence, and high photostabilities, which combine to make them very attractive chromophores for absorption-based imaging or laser heating technologies. The physical supramolecular properties of croconaine dyes have rarely been investigated, especially in water. This study focuses on a molecular threading process that encapsulates a croconaine dye inside a tetralactam macrocycle in organic or aqueous solvent. Macrocycle association and rate constant data are reported for a series of croconaine structures with different substituents attached to the ends of the dye. The association constants were highest in water (Ka ~109 M−1), and the threading rate constants (kon) increased in the solvent order H2O > MeOH > CHCl3. Systematic variation of croconaine substituents located just outside the croconaine/macrocycle complexation interface hardly changed Ka but had a strong influence on kon. A croconaine dye with N-propyl groups at each end of the structure exhibited a desirable mixture of macrocycle threading properties; that is, there was rapid and quantitative croconaine/macrocycle complexation at relatively high concentrations in water, and no dissociation of the pre-assembled complex when it was diluted into a solution of fetal bovine serum, even after laser induced photothermal heating of the solution. The combination of favorable near-infrared absorption properties and tunable mechanical stability makes threaded croconaine/macrocycle complexes very attractive as molecular probes or as supramolecular composites for various applications in absorption-based imaging or photothermal therapy. PMID:26807599

Synthesis, characterization, crystal structure and HSA binding of two new N,O,O-donor Schiff-base ligands derived from dihydroxybenzaldehyde and tert-butylamine

NASA Astrophysics Data System (ADS)

Khosravi, Iman; Hosseini, Farnaz; Khorshidifard, Mahsa; Sahihi, Mehdi; Rudbari, Hadi Amiri

2016-09-01

Two new o-hydroxy Schiff-bases compounds, L1 and L2, were derived from the 1:1 M condensation of 2,3-dihydroxybenzaldehyde and 2,4-dihydroxybenzaldehyde with tert-butylamine and were characterized by elemental analysis, FT-IR, 1H and 13C NMR spectroscopies. The crystal structure of L2 was also determined by single crystal X-ray analysis. The crystal structure of L2 showed that the compound exists as a zwitterionic form in the solid state, with the H atom of the phenol group being transferred to the imine N atom. It adopts an E configuration about the central Cdbnd N double bond. Furthermore, binding of these Schiff base ligands to Human Serum Albumin (HSA) was investigated by fluorescence quenching, absorption spectroscopy, molecular docking and molecular dynamics (MD) simulation methods. The fluorescence emission of HSA was quenched by ligands. Also, suitable models were used to analyze the UV-vis absorption spectroscopy data for titration of HSA solution by various amounts of Schiff bases. The spectroscopic studies revealed that these Schiff bases formed 1:1 complex with HSA. Energy transfer mechanism of quenching was discussed and the values of 3.35 and 1.57 nm as the mean distances between the bound ligands and the HSA were calculated for L1 and L2, respectively. Molecular docking results indicated that the main active binding site for these Schiff bases ligands is in subdomain IB. Moreover, MD simulation results suggested that this Schiff base complex can interact with HSA, with a slight modification of its tertiary structure.

Schiff Bases of Benzothiazol-2-ylamine and Thiazolo[5,4-b] pyridin-2-ylamine as Anticonvulsants: Synthesis, Characterization and Toxicity Profiling.

PubMed

Shukla, Rashmi; Singh, Ajeet P; Sonar, Pankaj K; Mishra, Mudita; Saraf, Shailendra K

2016-01-01

Schiff bases have a broad spectrum of biological activities like antiinflammatory, analgesic, antimicrobial, anticonvulsant, antitubercular, anticancer, antioxidant, anthelmintic and so forth. Thus, after a thorough perusal of literature, it was decided to conjugate benzothiazol-2-ylamine/thiazolo [5, 4-b] pyridin-2-ylamine with aromatic and heteroaromatic aldehydes to get a series of Schiff bases. Synthesis, characterization, in-silico toxicity profiling and anticonvulsant activity of the Schiff bases of Benzothiazol-2-ylamine and Thiazolo [5, 4-b] pyridin-2-ylamine. Aniline/4-aminopyridine was converted to the corresponding thiourea derivatives, which were cyclized to obtain benzothiazol-2-ylamine/thiazolo [5, 4-b] pyridin-2-ylamine. Finally, these were condensed with various aromatic and heteroaromatic aldehydes to obtain Schiff bases of benzothiazol-2-ylamine and thiazolo [5, 4-b] pyridin-2-ylamine. The synthesized compounds were characterized and screened for their anticonvulsant activity using maximal electroshock (MES) test and isoniazid (INH) induced convulsions test. In-silico toxicity profiling of all the synthesized compounds was done through "Lazar" and "Osiris" properties explorer. Majority of the compounds were more potent against MES induced convulsions than INH induced convulsions. Schiff bases of benzothiazol-2-ylamine were more effective than thiazolo [5, 4-b] pyridin-2-ylamine against MES induced convulsions. The compound benzothiazol-2-yl-(1H-indol-2-ylmethylene)-amine (VI) was the most potent member of the series against both types of convulsions. Compound VI exhibited the most significant activity profile in both the models. The compounds did not exhibit any carcinogenicity or acute toxicity in the in-silico studies. Thus, it may be concluded that the Schiff bases of benzothiazol-2-ylamine exhibit the potential to be promising and non-toxic anticonvulsant agents.

Langmuir-Blodgett Films of Aromatic Schiff’s Bases Functionalized in the Side Chains of Polymethacrylate

DTIC Science & Technology

1991-05-03

Report No. 21 - Latigmuir-Blodgett Films of Aromatic Schiffs Bases , K Fuctionalized in the Side Chains of Polymethacrylate by T. Takahashi, P. Miller...aromatic Schiff’s bases functionalized in the side chains of Polymethacrylate T. Takahashi**, P. Miller*, Y. M. Chen*, L. Samuelson***, D. Galotti, B...has been investigated for polymers in which nonlinear optical (NLO) moieties are attachcd i, the side chain of polymethacrylate (PMA) backbone. Polymer

Synthesis, spectroscopic characterization, DFT optimization and biological activities of Schiff bases and their metal (II) complexes

NASA Astrophysics Data System (ADS)

Rauf, Abdur; Shah, Afzal; Munawar, Khurram Shahzad; Khan, Abdul Aziz; Abbasi, Rashda; Yameen, Muhammad Arfat; Khan, Asad Muhammad; Khan, Abdur Rahman; Qureshi, Irfan Zia; Kraatz, Heinz-Bernhard; Zia-ur-Rehman

2017-10-01

A Novel Schiff base, 3-(((4-chlorophenyl)imino)methyl)benzene-1,2-diol (HL1) was successfully synthesized along with a structurally similar Schiff base 3-(((4-bromophenyl)imino)methyl)benzene-1,2-diol (HL2). Both the Schiff bases were used to synthesize their zinc (II) and cobalt (II) complexes. These compounds were characterized by FTIR, 1H NMR, 13C NMR and elemental analysis. Metal complexes were confirmed by TGA. Crystals of Schiff bases were also characterized by X-ray analysis and experimental parameters were found in line with the theoretical parameters. Quantum mechanical approach was also used to fine useful structural parameters and to ensure the geometry of metal complexes. The photometric behaviors of all the synthesized compounds were investigated in a wide pH range using BR buffers. The appearance of isosbestic points indicated the existence of Schiff bases in more than one isomeric form. Moreover, these compounds were screened for enzyme inhibition; antibacterial, cytotoxic and in vivo antidiabetic activities and compounds were found active against one or other activity. Results indicate that ZnL22 is a good inhibitor of alkaline phosphatase enzyme and possess highest potential against diabetes, blood cholesterol level and cancer cells. This effort just provides preliminary data for some biological properties. Further investigations are required to precisely determine mechanistic pathways of their use towards drug development.

A diversity-oriented synthesis strategy enabling the combinatorial-type variation of macrocyclic peptidomimetic scaffolds† †Electronic supplementary information (ESI) available: Experimental procedures, characterization data and details of the computational analyses. See DOI: 10.1039/c5ob00371g Click here for additional data file.

PubMed Central

Isidro-Llobet, Albert; Hadje Georgiou, Kathy; Galloway, Warren R. J. D.; Giacomini, Elisa; Hansen, Mette R.; Méndez-Abt, Gabriela; Tan, Yaw Sing; Carro, Laura; Sore, Hannah F.

2015-01-01

Macrocyclic peptidomimetics are associated with a broad range of biological activities. However, despite such potentially valuable properties, the macrocyclic peptidomimetic structural class is generally considered as being poorly explored within drug discovery. This has been attributed to the lack of general methods for producing collections of macrocyclic peptidomimetics with high levels of structural, and thus shape, diversity. In particular, there is a lack of scaffold diversity in current macrocyclic peptidomimetic libraries; indeed, the efficient construction of diverse molecular scaffolds presents a formidable general challenge to the synthetic chemist. Herein we describe a new, advanced strategy for the diversity-oriented synthesis (DOS) of macrocyclic peptidomimetics that enables the combinatorial variation of molecular scaffolds (core macrocyclic ring architectures). The generality and robustness of this DOS strategy is demonstrated by the step-efficient synthesis of a structurally diverse library of over 200 macrocyclic peptidomimetic compounds, each based around a distinct molecular scaffold and isolated in milligram quantities, from readily available building-blocks. To the best of our knowledge this represents an unprecedented level of scaffold diversity in a synthetically derived library of macrocyclic peptidomimetics. Cheminformatic analysis indicated that the library compounds access regions of chemical space that are distinct from those addressed by top-selling brand-name drugs and macrocyclic natural products, illustrating the value of our DOS approach to sample regions of chemical space underexploited in current drug discovery efforts. An analysis of three-dimensional molecular shapes illustrated that the DOS library has a relatively high level of shape diversity. PMID:25778821

Structural and molecular docking studies of biologically active mercaptopyrimidine Schiff bases

NASA Astrophysics Data System (ADS)

Kirubavathy, S. Jone; Velmurugan, R.; Karvembu, R.; Bhuvanesh, N. S. P.; Enoch, Israel V. M. V.; Selvakumar, P. Mosae; Premnath, D.; Chitra, S.

2017-01-01

Novel Schiff bases derived from the treatment of mercapto-diamino pyrimidine with two different aldehydes are characterized using elemental analysis, single crystal X-ray diffraction and 1H NMR spectroscopy. The pharmacological action of the synthesized compounds viz., antimicrobial, anticancer and antitubercular activities is studied. The Schiff bases show a very good activity against various test pathogens. DNA and β-CD binding interactions of the compounds are studied using UV-Visible absorption and fluorescence spectral measurements. The binding constants of the compounds towards β-CD are in the order of 103 to 104. Molecular docking is done using MOE program on the 3D structure of the enzymes, viz., human thymidylate synthase complexed with dump and raltitrex, candida albicans N-myristoyltransferasepeptidic inhibitor, catalytic domain of protein kinase pKnb from mycobacterium tuberculosis in complex with mitoxantrone, pare, topoisomerase atpase inhibitor, E. coli and lactobacillus casdihydrofolatereductase. The MIC/IC50 values of the Schiff bases are compared with the glide scores from the molecular docking studies. The number of hydrogen bonding interactions between the Schiff bases and amino acid residues are also reported.

Synthesis and spectral characterization of Schiff base complexes of Cu(II), Co(II), Zn(II) and VO(IV) containing 4-(4-aminophenyl)morpholine derivatives: Antimicrobial evaluation and anticancer studies

NASA Astrophysics Data System (ADS)

Dhahagani, K.; Mathan Kumar, S.; Chakkaravarthi, G.; Anitha, K.; Rajesh, J.; Ramu, A.; Rajagopal, G.

2014-01-01

Metal(II) chelates of Schiff bases derived from the condensation of 4-morpholinoaniline with substituted salicylaldehyde have been prepared and characterized by 1H NMR, IR, electronic, EPR, and magnetic measurement studies. The complexes are of the type M(X-MPMP)2 [where M = Cu(II), Co(II)), Zn(II), or VO(IV); MPMP = 2-[(4 morpholinophenyl imino) methyl] 4-X-phenol, X = Cl, (L1H), X = Br (L2H)]. Single crystal X-ray crystallography studies confirm the structure of newly synthesized Schiff bases. The Schiff bases act as bidentate monobasic ligands, coordinating through deprotonated phenolic oxygen and azomethine nitrogen atoms. The free ligands and metal complexes are screened for their biopotency. Metal complexes exhibit better activity than ligands. Anticancer activity of ligands and their metal complexes are evaluated in human heptocarcinoma(HepG2) cells. The preliminary bioassay indicates that the Schiff base and its zinc complex exhibit inhibitory activity against the human gastric cancer cell lines.

Ammonium chloride catalyzed synthesis of novel Schiff bases from spiro[indoline-3,4'-pyran]-3'-carbonitriles and evaluation of their antimicrobial and anti-breast cancer activities.

PubMed

Al-Shareef, Hossa F; Elhady, Heba A; Aboellil, Amany H; Hussein, Essam M

2016-01-01

Indolinone and spiro-indoline derivatives have been employed in the preparation of different important therapeutic compounds required for treatment of anticonvulsants, antibacterial, Antitubercular, and anticancer activities. Schiff bases have been found to possess various pharmacological activities such as antitubercular, plant growth inhibiting, insecticsidal, central nerve system depressant, antibacterial, anticancer, anti-inflammatory, and antimicrobial. Mannich bases have a variety of biological activities such as antibacterial and antifungal activities. In this study, a green, rapid and efficient protocol for the synthesis of a new series of Schiff bases from spiro[indoline-3,4'-pyran]-3'-carbonitrile derivatives using ammonium chloride as a very inexpensive and readily available reagent. The prepared compounds were assessed in vitro for their antimicrobial activity. Also, the cytotoxic activity of the prepared compounds was assessed in vitro against human cells line MCF7 breast cancer. Good activity was distinguished for Schiff bases from spiro[indoline-3,4'-pyran]-3'-carbonitriles, with some members recorded higher antimicrobial and anti-breast cancer activities.Graphical abstractNovel Schiff bases from spiro[indoline-3,4'-pyran]-3'-carbonitriles.

Recent Advances in Macrocyclic Fluorescent Probes for Ion Sensing.

PubMed

Wong, Joseph K-H; Todd, Matthew H; Rutledge, Peter J

2017-01-25

Small-molecule fluorescent probes play a myriad of important roles in chemical sensing. Many such systems incorporating a receptor component designed to recognise and bind a specific analyte, and a reporter or transducer component which signals the binding event with a change in fluorescence output have been developed. Fluorescent probes use a variety of mechanisms to transmit the binding event to the reporter unit, including photoinduced electron transfer (PET), charge transfer (CT), Förster resonance energy transfer (FRET), excimer formation, and aggregation induced emission (AIE) or aggregation caused quenching (ACQ). These systems respond to a wide array of potential analytes including protons, metal cations, anions, carbohydrates, and other biomolecules. This review surveys important new fluorescence-based probes for these and other analytes that have been reported over the past five years, focusing on the most widely exploited macrocyclic recognition components, those based on cyclam, calixarenes, cyclodextrins and crown ethers; other macrocyclic and non-macrocyclic receptors are also discussed.

Synthesis, crystal structure and biological activity of the Schiff base organotin(IV) complexes based on salicylaldehyde-o-aminophenol

NASA Astrophysics Data System (ADS)

Tan, Yu-Xing; Zhang, Zhi-Jian; Liu, Yang; Yu, Jiang-Xi; Zhu, Xiao-Ming; Kuang, Dai-Zhi; Jiang, Wu-Jiu

2017-12-01

Schiff base organotin(IV) complexes C1 ∼ C5b have been synthesized via the reaction of the substituted salicylaldehyde-o-aminophenol Schiff base ligands (L1 ∼ L3) with the dibenzyltin dichloride, n-butyltin trichloride or dibutyltin oxide, respectively. The complexes have been characterized by IR, UV-Vis, 1H NMR, 13C NMR spectra, elemental analysis and the crystal structures have been determined by X-ray diffraction. The anticancer activity of the Schiff base ligand and complexes C1 ∼ C5b against five species of cancer cell which are Hela, MCF7, HepG2, Colo205, NCIsbnd H460 were tested respectively, the tests showed that C1 ∼ C5b exhibited significant anticancer activity for the cancer cells in comparison with the ligand, and the activity was greater than carboplatin.

Electronic and vibrational exciton coupling in oxidized trianglimines.

PubMed

Szymkowiak, Joanna; Kwit, Marcin

2018-02-01

Readily available chiral trianglimine and their (poly)oxygenated congeners represent a unique class of macrocyclic rigid compounds optimal for testing electronic and vibrational circular dichroism exciton chirality methods. Electronic and vibrational circular dichroism spectra of such trianglimines are strongly affected by polar substituents in macrocycle skeletons. Double substitution by OH groups in each aromatic fragment of the macrocycle causes sign reversal of the exciton couplet in the region of the strongest UV absorption. On the other hand, electronic circular dichroism spectrum of the macrocycle having 2 methoxy groups shows 2 exciton couplets-the long-wavelength positive and the second of the negative sign, observed at the shorter wavelengths. VCD spectra of macrocyclic imines show vibrational exciton couplets in the region of strong C=N stretches. The signs of these couplets are positive and the opposite of the diamine chirality. For trianglimine macrocycles the interpretation of VCD spectra in terms of excitons is much more convincing than for electronic circular dichroism spectra. By contrast, trans-1,2-diaminocyclohexane-based vicinal diimines, being a one-third of the respective macrocycle, do not exhibit any vibrational exciton effect. Experimental data were confronted with DFT calculations. We observed good-to-excellent agreement between experimental and computed data. © 2017 Wiley Periodicals, Inc.

Synthesis, characterization and biological activity of C6-Schiff bases derivatives of chitosan.

PubMed

Xu, Ruibo; Aotegen, Bayaer; Zhong, Zhimei

2017-12-01

C 6 -Schiff bases derivatives of chitosan were synthesized for the first time. C 2 -amino groups and C 3 -hydroxy groups were firstly protected by CuSO 4 ·5H 2 O, and the C 6 -hydroxy was then transformed into aldehyde, which then reacted with anilines through nucleophilic addition to introduce the CN group at C 6 -position in chitosan chain. Finally, C 6 -Schiff bases derivatives of chitosan were got by the deprotection of C 2 -NH 2 with cation exchange resin. The structures and properties of the new synthesized products were characterized by Fourier transform infrared spectroscopy, 13 C NMR, SEM image, and elemental analysis. The antibacterial activities of derivatives were tested in the experiment, and the results showed that the prepared chitosan derivatives had significantly improved antibacterial activity toward Staphylococcus aureus and Escherichia coli. The Cytotoxicity test showed that the prepared chitosan derivatives had low Cytotoxicity, compared with chitosan and C 2 -benzaldehyde Schiff bases of chitosan. This paper allowed a new method for the synthesis of Schiff bases of chitosan, which was enlightening. Copyright © 2017 Elsevier B.V. All rights reserved.

Spectroscopic characterization, antimicrobial activity, DFT computation and docking studies of sulfonamide Schiff bases

NASA Astrophysics Data System (ADS)

Mondal, Sudipa; Mandal, Santi M.; Mondal, Tapan Kumar; Sinha, Chittaranjan

2017-01-01

Schiff bases synthesised from the condensation of 2-(hydroxy)naphthaldehyde and sulfonamides (sufathiazole (STZ), sulfapyridine (SPY), sulfadiazine (SDZ), sulfamerazine (SMZ) and sulfaguanidine (SGN)) are characterized by different spectroscopic data (FTIR, UV-Vis, Mass, NMR) and two of them, (E)-4-(((2-hydroxynaphthalen-1-yl)methylene)amino)-N-(thiazol-2-yl)benzenesulfonamide (1a) and (E)-N-(diaminomethylene)-4-(((2-hydroxynaphthalen-1-yl)methylene)amino)benzenesulfonamide (1e) have been confirmed by single crystal X-ray structure determination. Antimicrobial activities of the Schiff bases have been evaluated against certified and resistant Gram positive (Staphylococcus aureus, Enterococcus facelis) and Gram negative (Streptococcus pyogenes, Salmonella typhi, Shigella dysenteriae, Shigella flexneri, Klebsiella pneumonia) pathogens. Performance of Schiff base against the resistant pathogens are better than standard stain and MIC data lie 32-128 μg/ml while parent sulfonamides are effectively inactive (MIC >512 μg/ml). The DFT optimized structures of the Schiff bases have been used to accomplish molecular docking studies with DHPS (dihydropteroate synthase) protein structure (downloaded from Protein Data Bank) to establish the most preferred mode of interaction. ADMET filtration, Cytotoxicity (MTT assay) and haemolysis assay have been examined for evaluation of druglike character.

Synthesis, characterization and biological assay of Salicylaldehyde Schiff base Cu(II) complexes and their precursors

NASA Astrophysics Data System (ADS)

Iftikhar, Bushra; Javed, Kanwal; Khan, Muhammad Saif Ullah; Akhter, Zareen; Mirza, Bushra; Mckee, Vickie

2018-03-01

Three new Schiff base ligands were synthesized by the reaction of Salicylaldehyde with semi-aromatic diamines, prepared by the reduction of corresponding dinitro-compounds, and were further used for the formation of complexes with Cu(II) metal ion. The structural features of the synthesized compounds were confirmed by their physical properties and infrared, electronic and NMR spectroscopic techniques. The studies revealed that the synthesized Schiff bases existed as tetradentate ligands and bonded to the metal ion through the phenolic oxygen and azomethine nitrogen. One of the dinitro precursors was also analyzed by single crystal X-ray crystallography, which showed that it crystallizes in monoclinic system with space group P2/n. The thermal behavior of the Cu(II) complexes was determined by thermogravimetric analysis (TGA) and kinetic parameters were evaluated from the data. Schiff base ligands, their precursors and metal complexes were also screened for antibacterial, antifungal, antitumor, Brine shrimp lethality, DPPH free radical scavenging and DNA damage assays. The results of these analyses indicated the substantial potential of the synthesized Schiff bases, their precursors and Cu(II) complexes in biological field as future drugs.

The electric and thermoelectric properties of Cu(II)-Schiff base nano-complexes

NASA Astrophysics Data System (ADS)

Ibrahim, E. M. M.; Abdel-Rahman, Laila H.; Abu-Dief, Ahmed M.; Elshafaie, A.; Hamdan, Samar Kamel; Ahmed, A. M.

2018-05-01

The physical properties, such as electric and optical properties, of metal-Schiff base complexes have been widely investigated. However, their thermoelectric (TE) properties remain unreported. This work presents Cu(II)-Schiff base complexes as promising materials for TE power generation. Therefore, three Cu(II)-Schiff base complexes (namely, [Cu(C32H22N4O2)].3/2H2O, [Cu(C23H17N4O7Br)], and [Cu(C27H22N4O8)].H2O) have been synthesized in nanosized scale. The electric and TE properties have been studied and comprehensive discussions have been presented to promote the nano-complexes (NCs) practical applications in the field of TE power generation. The electrical measurements confirm that the NCs are semiconductors and the electrical conduction process is governed by intermolecular and intramolecular transfer of the charge carriers. The TE measurements reveal that the Cu(II)-Schiff base NCs are nondegenerate P-type semiconductors. The measured Seebeck coefficient values were higher compared to the values reported in previous works for other organic materials indicating that the complexes under study are promising candidates for theremoelectric applications if the electrical conductivity could be enhanced.

Mixed (phthalocyaninato)(Schiff-base) di-dysprosium sandwich complexes. Effect of magnetic coupling on the SMM behavior.

PubMed

Wang, Hailong; Liu, Chenxi; Liu, Tao; Zeng, Suyuan; Cao, Wei; Ma, Qi; Duan, Chunying; Dou, Jianmin; Jiang, Jianzhuang

2013-11-21

Reaction between Schiff-base ligand and half-sandwich complex M(Pc)(acac) led to the isolation of new sandwich-type mixed (phthalocyaninato)(Schiff-base) di-lanthanide compounds M2(Pc)2(L)H2O (M = Dy, Gd) (1, 2) [H2Pc = metal free phthalocyanine, Hacac = acetylacetone, H2L = N,N'-bis(3-methyloxysalicylidene)benzene-1,2-diamine] with the triple-decker molecular structure clearly revealed by single crystal X-ray diffraction analysis. For the comparative studies, sandwich triple-decker analogues with pure Schiff-base ligand M2(L)3H2O (M = Dy, Gd) (3, 4) were also prepared. Dynamic magnetic measurement result reveals the single-molecule magnet (SMM) nature of the di-dysprosium derivative 1, while the static magnetic investigation over both pure and the diamagnetic diluted samples of this compound discloses the interionic ferromagnetic coupling between the two dysprosium ions, which in turn effectively suppresses the QTM and enhances the energy barrier of this SMM. Nevertheless, comparative studies over the static magnetic properties of the di-dysprosium triple-decker complexes 1 and 3 indicate the stronger magnetic coupling between the two lanthanide ions in mixed (phthalocyaninato)(Schiff-base) species than in the pure Schiff-base triple-decker analogue, suggesting the special coordination sphere around the dysprosium ions in the former compound over the latter one on the more intense inter-ionic ferromagnetic coupling. As a very small step towards understanding the structure-property relationship, the present result will be surely helpful for the design and synthesis of the multinuclear lanthanide-based SMMs with good properties.

ForceGen 3D structure and conformer generation: from small lead-like molecules to macrocyclic drugs

NASA Astrophysics Data System (ADS)

Cleves, Ann E.; Jain, Ajay N.

2017-05-01

We introduce the ForceGen method for 3D structure generation and conformer elaboration of drug-like small molecules. ForceGen is novel, avoiding use of distance geometry, molecular templates, or simulation-oriented stochastic sampling. The method is primarily driven by the molecular force field, implemented using an extension of MMFF94s and a partial charge estimator based on electronegativity-equalization. The force field is coupled to algorithms for direct sampling of realistic physical movements made by small molecules. Results are presented on a standard benchmark from the Cambridge Crystallographic Database of 480 drug-like small molecules, including full structure generation from SMILES strings. Reproduction of protein-bound crystallographic ligand poses is demonstrated on four carefully curated data sets: the ConfGen Set (667 ligands), the PINC cross-docking benchmark (1062 ligands), a large set of macrocyclic ligands (182 total with typical ring sizes of 12-23 atoms), and a commonly used benchmark for evaluating macrocycle conformer generation (30 ligands total). Results compare favorably to alternative methods, and performance on macrocyclic compounds approaches that observed on non-macrocycles while yielding a roughly 100-fold speed improvement over alternative MD-based methods with comparable performance.

Macrocyclic drugs and synthetic methodologies toward macrocycles

PubMed Central

Yu, Xufen; Sun, Dianqing

2015-01-01

Macrocyclic scaffolds are commonly found in bioactive natural products and pharmaceutical molecules. So far, a large number of macrocyclic natural products have been isolated and synthesized. The construction of macrocycles is generally considered as a crucial and challenging step in the synthesis of macrocyclic natural products. Over the last several decades, numerous efforts have been undertaken toward the synthesis of complex naturally occurring macrocycles and great progresses have been made to advance the field of total synthesis. The commonly used synthetic methodologies toward macrocyclization include macrolactonization, macrolactamization, transition metal-catalyzed cross coupling, ring-closing metathesis, and click reaction, among others. Selected recent examples of macrocyclic synthesis of natural products and druglike macrocycles with significant biological relevance are highlighted in each class. The primary goal of this review is to summarize currently used macrocyclic drugs, highlight the therapeutic potential of this underexplored drug class and outline the general synthetic methodologies for the synthesis of macrocycles. PMID:23708234

Fluorescence Turn-on Enantioselective Recognition of both Chiral Acidic Compounds and α-Amino Acids by a Chiral Tetraphenylethylene Macrocycle Amine.

PubMed

Feng, Hai-Tao; Zhang, Xing; Zheng, Yan-Song

2015-08-21

New chiral tetraphenylethylene (TPE) macrocycles bearing optically pure amine groups were synthesized and found to have a discriminating ability between the two enantiomers of not only chiral acidic compounds but also α-amino acids by enantioselective aggregation and aggregation-induced emission (AIE) effects. NMR spectra, including 2D-NOESY, disclosed that the host-guest interaction of the macrocycle receptor played a key role in addition to the acid-base interactions.

Antibacterial and antifungal metal based triazole Schiff bases.

PubMed

Chohan, Zahid H; Hanif, Muhammad

2013-10-01

A new series of four biologically active triazole derived Schiff base ligands (L(1)-L(4)) and their cobalt(II), nickel(II), copper(II) and zinc(II) complexes (1-16) have been synthesized and characterized. The ligands were prepared by the condensation reaction of 3-amino-5-methylthio-1H-1,2,4-triazole with chloro-, bromo- and nitro-substituted 2-hydroxybenzaldehyde in an equimolar ratio. The antibacterial and antifungal bioactivity data showed the metal(II) complexes to be more potent antibacterial and antifungal than the parent Schiff bases against one or more bacterial and fungal species.

Constitutive signaling by the phototaxis receptor sensory rhodopsin II from disruption of its protonated Schiff base–Asp-73 interhelical salt bridge

PubMed Central

Spudich, Elena N.; Zhang, Weisheng; Alam, Maqsudul; Spudich, John L.

1997-01-01

Sensory rhodopsin II (SRII) is a repellent phototaxis receptor in the archaeon Halobacterium salinarum, similar to visual pigments in its seven-helix structure and linkage of retinal to the protein by a protonated Schiff base in helix G. Asp-73 in helix C is shown by spectroscopic analysis to be a counterion to the protonated Schiff base in the unphotolyzed SRII and to be the proton acceptor from the Schiff base during photoconversion to the receptor signaling state. Coexpression of the genes encoding mutated SRII with Asn substituted for Asp-73 (D73N) and the SRII transducer HtrII in H. salinarum cells results in a 3-fold higher swimming reversal frequency accompanied by demethylation of HtrII in the dark, showing that D73N SRII produces repellent signals in its unphotostimulated state. Analogous constitutive signaling has been shown to be produced by the similar neutral residue substitution of the Schiff base counterion and proton acceptor Glu-113 in human rod rhodopsin. The interpretation for both seven-helix receptors is that light activation of the wild-type protein is caused primarily by photoisomerization-induced transfer of the Schiff base proton on helix G to its primary carboxylate counterion on helix C. Therefore receptor activation by helix C–G salt-bridge disruption in the photoactive site is a general mechanism in retinylidene proteins spanning the vast evolutionary distance between archaea and humans. PMID:9144172

Tackling the conformational sampling of larger flexible compounds and macrocycles in pharmacology and drug discovery.

PubMed

Chen, I-Jen; Foloppe, Nicolas

2013-12-15

Computational conformational sampling underpins much of molecular modeling and design in pharmaceutical work. The sampling of smaller drug-like compounds has been an active area of research. However, few studies have tested in details the sampling of larger more flexible compounds, which are also relevant to drug discovery, including therapeutic peptides, macrocycles, and inhibitors of protein-protein interactions. Here, we investigate extensively mainstream conformational sampling methods on three carefully curated compound sets, namely the 'Drug-like', larger 'Flexible', and 'Macrocycle' compounds. These test molecules are chemically diverse with reliable X-ray protein-bound bioactive structures. The compared sampling methods include Stochastic Search and the recent LowModeMD from MOE, all the low-mode based approaches from MacroModel, and MD/LLMOD recently developed for macrocycles. In addition to default settings, key parameters of the sampling protocols were explored. The performance of the computational protocols was assessed via (i) the reproduction of the X-ray bioactive structures, (ii) the size, coverage and diversity of the output conformational ensembles, (iii) the compactness/extendedness of the conformers, and (iv) the ability to locate the global energy minimum. The influence of the stochastic nature of the searches on the results was also examined. Much better results were obtained by adopting search parameters enhanced over the default settings, while maintaining computational tractability. In MOE, the recent LowModeMD emerged as the method of choice. Mixed torsional/low-mode from MacroModel performed as well as LowModeMD, and MD/LLMOD performed well for macrocycles. The low-mode based approaches yielded very encouraging results with the flexible and macrocycle sets. Thus, one can productively tackle the computational conformational search of larger flexible compounds for drug discovery, including macrocycles. Copyright © 2013 Elsevier Ltd. All rights reserved.

Host-guest capability of a three-dimensional heterometallic macrocycle.

PubMed

Fan, Qi-Jia; Lin, Yue-Jian; Hahn, F Ekkehardt; Jin, Guo-Xin

2018-02-13

A three-dimensional heterometallic coordination macrocycle is found to be capable of encapsulating planar pyrene (G1), coronene (G4) and non-planar corannulene (G2) guest molecules in high yields, giving rise to 1 : 1 host-guest complexes. The bowl-shaped guest corannulene is found to be significantly flattened upon inclusion within the cavity. However, macrocyclic compounds with larger cavity sizes, which form 1 : 1 stoichiometry assemblies with a naphthalene bisimide planar molecule (G3), are more inclined to form infinite sandwich structures. Furthermore, these heterometallic coordination macrocycles can be destroyed in the presence of a soft base to form hexanuclear triangular prism complexes. These structures are unambiguously revealed by single-crystal X-ray analysis.

Physicochemical characterization of novel Schiff bases derived from developed bacterial cellulose 2,3-dialdehyde.

PubMed

Keshk, Sherif M A S; Ramadan, Ahmed M; Bondock, Samir

2015-08-20

The synthesis of two novel Schiff's bases (cellulose-2,3-bis-[(4-methylene-amino)-benzene-sulfonamide] (5) & cellulose-2,3-bis-[(4-methylene-amino)-N-(thiazol-2-yl)-benzenesulfonamide] (6) via condensation reactions of periodate oxidized developed bacterial cellulose ODBC (2) with sulfa drugs [sulfanilamide (3) & sulfathiazole (4)] was reported. The physicochemical characterization of the condensation products was performed using FTIR, (1)H NMR, (13)C NMR spectral analyses, X-ray diffraction and DTA. The ODBC exhibited the highest degree of oxidation based on the aldehyde group number percentage (82.9%), which confirms the highest reactivity of developed bacterial cellulose [DBC (1)]. The X-ray diffractograms indicated an increase in the interplanar distance of the cellulose Schiff base (6) compared to ODBC (2) due to sulfathiazole (4) inclusion between ODBC (2) sheets corresponding to the 1 1 0 plane. In addition, the aldehyde content of Schiff base (6) was (20.8%) much lower than that of Schiff base (5) (41.5%). These results confirmed the high affinity of sulfathiazole (4) to the ODBC (2) chain, and the substantial changes in the original properties of ODBC were due to these chemical modifications rather than the sulfanilamide (3). Copyright © 2015 Elsevier Ltd. All rights reserved.

New Inducible Nitric Oxide Synthase and Cyclooxygenase-2 Inhibitors, Nalidixic Acid Linked to Isatin Schiff Bases via Certain l-Amino Acid Bridges.

PubMed

Naglah, Ahmed M; Ahmed, Atallah F; Wen, Zhi-Hong; Al-Omar, Mohamed A; Amr, Abd El-Galil E; Kalmouch, Atef

2016-04-15

A series of new Schiff bases were synthesized by condensation of isatins with the nalidixic acid-l-amino acid hydrazides. Prior to hydrazide formation, a peptide linkage has been prepared via coupling of nalidixic acid with appropriate l-amino acid methyl esters to yield 3a-c. The chemical structures of the new Schiff bases (5b and 5d-h) were confirmed by means of IR, NMR, mass spectroscopic, and elemental analyses. The anti-inflammatory activity of these Schiff bases was evaluated via measurement of the expressed inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in the lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells model. The Schiff bases exhibited significant dual inhibitory effect against the induction of the pro-inflammatory iNOS and COX-2 proteins with variable potencies. However, they strongly down-regulated the iNOS expression to the level of 16.5% ± 7.4%-42.2% ± 19.6% compared to the effect on COX-2 expression (<56.4% ± 3.1% inhibition) at the same concentration (10 μM). The higher iNOS inhibition activity of the tested Schiff bases, relative to that of COX-2, seems to be a reflection of the combined suppressive effects exerted by their nalidixic acid, isatins (4a-c), and l-amino acid moieties against iNOS expression. These synthesized nalidixic acid-l-amino acid-isatin conjugates can be regarded as a novel class of anti-inflammatory antibacterial agents.

Binary and ternary copper(II) complexes of a new Schiff base ligand derived from 4-acetyl-5,6-diphenyl-3(2H)-pyridazinone: Synthesis, spectral, thermal, antimicrobial and antitumor studies

NASA Astrophysics Data System (ADS)

Shebl, Magdy; Adly, Omima M. I.; Abdelrhman, Ebtesam M.; El-Shetary, B. A.

2017-10-01

A new Schiff base ligand was synthesized by the reaction of 4-acetyl-5,6-diphenyl-3(2H)-pyridazinone with ethylenediamine. A series of binary copper(II) Schiff base complexes have been synthesized by using various copper(II) salts; AcO-, NO3-, ClO4-, Cl- and Br-. Ternary complexes were synthesized by using auxiliary ligands (L‧) [N,O-donor; 8-hydroxyquinoline and glycine or N,N-donor; 1,10-phenanthroline, bipyridyl and 2-aminopyridine]. The structures of the Schiff base and its complexes were characterized by elemental and thermal analyses, IR, electronic, mass, 1H NMR and ESR spectra in addition to conductivity and magnetic susceptibility measurements. The obtained complexes include neutral binuclear complexes as well as neutral and cationic mononuclear complexes according to the anion used and the experimental conditions. The ESR spin Hamiltonian parameters of some complexes were calculated and discussed. The metal complexes exhibited octahedral and square planar geometrical arrangements depending on the nature of the anion. Kinetic parameters (Ea, A, ΔH, ΔS and ΔG) of the thermal decomposition stages were evaluated using Coats-Redfern equations. The antimicrobial activity of the Schiff base and its complexes was screened against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram-negative bacteria (Salmonella typhimurium and Escherichia coli), yeast (Candida albicans) and fungus (Aspergillus fumigatus). The antitumor activity of the Schiff base and some of its Cu(II) complexes was investigated against HepG-2 cell line.

Distinguishing Two Ammonium and Triazolium Sites of Interaction in a Three-Station [2]Rotaxane Molecular Shuttle.

PubMed

Waelès, Philip; Fournel-Marotte, Karine; Coutrot, Frédéric

2017-08-25

This paper reports on the synthesis of a tri-stable [2]rotaxane molecular shuttle, in which the motion of the macrocycle is triggered by either selective protonation/deprotonation or specific carbamoylation/decarbamoylation of an alkylbenzylamine. The threaded axle is surrounded by a dibenzo[24]crown[8] (DB24C8) macrocycle and contains three sites of different binding affinities towards the macrocycle. An N-methyltriazolium moiety acts as a molecular station that has weak affinity for the DB24C8 macrocycle and is located in the centre of the molecular axle. Two other molecular stations, arylammonium and alkylbenzylammonium moieties, sit on either side of the triazolium moiety along the molecular axle and have stronger affinities for the DB24C8 macrocycle. These two ammonium moieties are covalently linked to two different stopper groups at each extremity of the thread: a tert-butylphenyl group and a substituted DB24C8 unit. Owing to steric hindrance, the former does not allow any π-π stacking interactions with the encircling DB24C8 macrocycle, whereas the latter residue does; therefore, this allows the discrimination of the two ammonium stations by the surrounding DB24C8 macrocycle in the fully protonated state. In the deprotonated state, the contrasting reactivity of the amine functional groups, as either a base or a nucleophile, allows for selective reactions that trigger the controlled shuttling of the macrocycle around the three molecular stations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Schiff bases of putrescine with methylglyoxal protect from cellular damage caused by accumulation of methylglyoxal and reactive oxygen species in Dictyostelium discoideum.

PubMed

Park, Seong-Jun; Kwak, Min-Kyu; Kang, Sa-Ouk

2017-05-01

Polyamines protect protein glycation in cells against the advanced glycation end product precursor methylglyoxal, which is inevitably produced during glycolysis, and the enzymes that detoxify this α-ketoaldehyde have been widely studied. Nonetheless, nonenzymatic methylglyoxal-scavenging molecules have not been sufficiently studied either in vitro or in vivo. Here, we hypothesized reciprocal regulation between polyamines and methylglyoxal modeled in Dictyostelium grown in a high-glucose medium. We based our hypothesis on the reaction between putrescine and methylglyoxal in putrescine-deficient (odc - ) or putrescine-overexpressing (odc oe ) cells. In these strains, growth and cell cycle were found to be dependent on cellular methylglyoxal and putrescine contents. The odc - cells showed growth defects and underwent G1 phase cell cycle arrest, which was efficiently reversed by exogenous putrescine. Cellular methylglyoxal, reactive oxygen species (ROS), and glutathione levels were remarkably changed in odc oe cells and odc̄ cells. These results revealed that putrescine may act as an intracellular scavenger of methylglyoxal and ROS. Herein, we observed interactions of putrescine and methylglyoxal via formation of a Schiff base complex, by UV-vis spectroscopy, and confirmed this adduct by liquid chromatography with mass spectrometry via electrospray ionization. Schiff bases were isolated, analyzed, and predicted to have molecular masses ranging from 124 to 130. We showed that cellular putrescine-methylglyoxal Schiff bases were downregulated in proportion to the levels of endogenous or exogenous putrescine and glutathione in the odc mutants. The putrescine-methylglyoxal Schiff base affected endogenous metabolite levels. This is the first report showing that cellular methylglyoxal functions as a signaling molecule through reciprocal interactions with polyamines by forming Schiff bases. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis, characterization and biological studies of Schiff bases derived from heterocyclic moiety.

PubMed

Shanty, Angamaly Antony; Philip, Jessica Elizabeth; Sneha, Eeettinilkunnathil Jose; Prathapachandra Kurup, Maliyeckal R; Balachandran, Sreedharannair; Mohanan, Puzhavoorparambil Velayudhan

2017-02-01

Some new Schiff bases (H 1 -H 7 ) have been synthesized by the condensation of 2-aminophenol, 2-amino-4-nitrophenol, 2-amino-4-methylphenol, 2-amino benzimidazole with thiophene-2-carboxaldehyde and pyrrole-2-carboxaldehyde. The structures of newly synthesized compounds were characterized by elemental analysis, FT-IR, 1 H NMR, UV-VIS, and single crystal X-ray crystallography. The in vitro antibacterial activity of the synthesized compounds has been tested against Salmonella typhi, Bacillus coagulans, Bacillus pumills, Escherichia coli, Bacillus circulans, Pseudomonas, Clostridium and Klebsilla pneumonia by disk diffusion method. The quantitative antimicrobial activity of the test compounds was evaluated using Resazurin based Microtiter Dilution Assay. Ampicillin was used as standard antibiotics. Schiff bases individually exhibited varying degrees of inhibitory effects on the growth of the tested bacterial species. The antioxidant activity of the synthesized compounds was determined by the 1,1-diphenyl-2-picrylhydrazyl(DPPH) method. IC 50 value of synthesized Schiff bases were calculated and compared with standard BHA. Copyright © 2016 Elsevier Inc. All rights reserved.

Protein changes associated with reprotonation of the Schiff base in the photocycle of Asp96-->Asn bacteriorhodopsin. The MN intermediate with unprotonated Schiff base but N-like protein structure

NASA Technical Reports Server (NTRS)

Sasaki, J.; Shichida, Y.; Lanyi, J. K.; Maeda, A.

1992-01-01

The difference Fourier transform infrared spectrum for the N intermediate in the photoreaction of the light-adapted form of bacteriorhodopsin can be recorded at pH 10 at 274 K (Pfefferle, J.-M., Maeda, A., Sasaki, J., and Yoshizawa, T. (1991) Biochemistry 30, 6548-6556). Under these conditions, Asp96-->Asn bacteriorhodopsin gives a photoproduct which shows changes in protein structure similar to those observed in N of wild-type bacteriorhodopsin. However, decreased intensity of the chromophore bands and the single absorbance maximum at about 400 nm indicate that the Schiff base is unprotonated, as in the M intermediate. This photoproduct was named MN. At pH 7, where the supply of proton is not as restricted as at pH 10, Asp96-->Asn bacteriorhodopsin yields N with a protonated Schiff base. The Asn96 residue, which cannot deprotonate as Asp96 in wild-type bacteriorhodopsin, is perturbed upon formation of both MN at pH 10 and N at pH 7. We suggest that the reprotonation of the Schiff base is preceded by a large change in the protein structure including perturbation of the residue at position 96.

Synthesis and spectral characterization of Zn(II) microsphere series for antimicrobial application

NASA Astrophysics Data System (ADS)

Singh, Ajay K.; Pandey, Sarvesh K.; Pandey, O. P.; Sengupta, S. K.

2014-09-01

Microsphere series have been synthesized by reacting zinc(II) acetate dihydrate with Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-thiadiazole/oxadiazole/triazole with salicylaldehyde. Elemental analysis suggests that the complexes have 1:2 and 1:1 stoichiometry of the type [Zn(L)2(H2O)2] and [Zn(L‧)(H2O)2]; LH = Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-thia/oxadiazole with salicylaldehyde; L‧H2 = Schiff bases derived from 3-(substituted phenyl)-4-amino-5-hydrazino-1,2,4-triazole and salicylaldehyde and were characterized by elemental analyses, IR, 1H NMR and 13C NMR spectral data. Scanning electron microscopy (SEM) showed that synthesized materials have microsphere like structure and there EDX analysis comparably matches with elemental analysis. For the antimicrobial application Schiff bases and their zinc(II) complexes were screened for four bacteria e.g. Bacillus subtilis, Pseudomonas aeruginosa, Salmonella typhi, Streptococcus pyogenes and four fungi e.g. Cyrtomium falcatum, Aspergillus niger, Fusarium oxysporium and Curvularia pallescence by the reported method. Schiff base and Zn(II) compounds showed significant antimicrobial activities. However, activities increase upon chelation. Thermal analysis (TGA) data of compound (10) showed its stability up to 300 °C.

Synthesis and spectroscopic properties of novel asymmetric Schiff bases.

PubMed

Güngör, Ozlem; Gürkan, Perihan

2010-09-15

Three novel diimine Schiff bases including two asymmetric imines (2-OH)R-CHN-C(6)H(4)-CHN-R'(2-OH) type [where R=R'=phenyl for H(2)L(1); R=naphthyl, R'=phenyl for H(2)L(2) and R=R'=naphthyl for H(2)L(3)] have been synthesized with a new two step method. For this purpose, the starting Schiff bases 4-nitrobenzylidene-2-hydroxyaniline (SB(1)-NO(2)) and 4-nitrobenzylidene-2-hydroxy-3-naphthylamine (SB(2)-NO(2)) have been synthesized, previously. Nitro groups of them have been reduced into their amino derivatives (SB(1)-NH(2) and SB(2)-NH(2)) with sodium dithionite as selective reductant and the other imino groups have been formed by adding salicylaldehyde or 2-hydroxy-1-naphthaldehyde to the same solutions. The structures of the diimine Schiff bases were confirmed by elemental analyses, ESI-MS, FT-IR, (1)H NMR and (13)C NMR spectroscopy. The phenol-imine and keto-amine tautomerism of the Schiff bases were investigated by FT-IR, (1)H NMR, (13)C NMR techniques and UV-vis spectra in different solvents (DMSO, methanol, chloroform, toluene and cyclohexane). The effects of acidic and basic media on the tautomeric equilibria were discussed. Copyright 2010 Elsevier B.V. All rights reserved.

Synthesis, crystal structure, fluorescence and electrochemical studies of a new tridentate Schiff base ligand and its nickel(II) and palladium(II) complexes

NASA Astrophysics Data System (ADS)

Shafaatian, Bita; Soleymanpour, Ahmad; Kholghi Oskouei, Nasim; Notash, Behrouz; Rezvani, Seyyed Ahmad

2014-07-01

A new unsymmetrical tridentate Schiff base ligand was derived from the 1:1 M condensation of ortho-vanillin with 2-mercaptoethylamine. Nickel and palladium complexes were obtained by the reaction of the tridentate Schiff base ligand with nickel(II) acetate tetrahydrate and palladium(II) acetate in 2:1 M ratio. In nickel and palladium complexes the ligand was coordinated to metals via the imine N and enolic O atoms. The S groups of Schiff bases were not coordinated to the metals and S-S coupling was occured. The complexes have been found to possess 1:2 Metal:Ligand stoichiometry and the molar conductance data revealed that the metal complexes were non-electrolytes. The complexes exhibited octahedral coordination geometry. The emission spectra of the ligand and its complexes were studied in methanol. Electrochemical properties of the ligand and its metal complexes were investigated in the CH3CN solvent at the 100 mV s-1 scan rate. The ligand and metal complexes showed both reversible and quasi-reversible processes at this scan rate. The Schiff base and its complexes have been characterized by IR, 1H NMR, UV/Vis, elemental analyses and conductometry. The crystal structure of nickel complex has been determined by single crystal X-ray diffraction.

Schiff base-Poloxamer P85 combination demonstrates chemotherapeutic effect on prostate cancer cells in vitro.

PubMed

Demirci, Selami; Doğan, Ayşegül; Türkmen, Neşe Başak; Telci, Dilek; Rizvanov, Albert A; Şahin, Fikrettin

2017-02-01

Prostate cancer is a multistep and complicated cancer type that is regulated by androgens at the cellular level and remains the second commonest cause of death among men. Discovery and development of novel chemotherapeutic agents enabling rapid tumor cell death with minimal toxic effects to healthy tissues might greatly improve the safety of chemotherapy. The present study evaluates the anti-cancer activity of a novel heterodinuclear copper(II)Mn(II) complex (Schiff base) in combination with poly(ethylene oxide) and poly(propylene oxide) block copolymer (Pluronic) P85. We used assays for cell proliferation, apoptosis, cell migration and invasion, DNA binding and cleavage to elucidate the molecular mechanisms of action, in addition to the anti-inflammatory potency of the new combination. The combined treatment of Schiff base and P85 lead to a remarkable anti-cancer effect on prostate cancer cell lines. Cell proliferation was inhibited in Schiff base-P85 treatment. The activity of this formulation is on DNA binding and cleavage and prevents inflammation in in vitro conditions. This is the first study presenting the anti-cancer activity of the present Schiff base derivative and its combination with P85 to treat prostate cancer in vitro. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Peptidic Macrocycles - Conformational Sampling and Thermodynamic Characterization

PubMed Central

2018-01-01

Macrocycles are of considerable interest as highly specific drug candidates, yet they challenge standard conformer generators with their large number of rotatable bonds and conformational restrictions. Here, we present a molecular dynamics-based routine that bypasses current limitations in conformational sampling and extensively profiles the free energy landscape of peptidic macrocycles in solution. We perform accelerated molecular dynamics simulations to capture a diverse conformational ensemble. By applying an energetic cutoff, followed by geometric clustering, we demonstrate the striking robustness and efficiency of the approach in identifying highly populated conformational states of cyclic peptides. The resulting structural and thermodynamic information is benchmarked against interproton distances from NMR experiments and conformational states identified by X-ray crystallography. Using three different model systems of varying size and flexibility, we show that the method reliably reproduces experimentally determined structural ensembles and is capable of identifying key conformational states that include the bioactive conformation. Thus, the described approach is a robust method to generate conformations of peptidic macrocycles and holds promise for structure-based drug design. PMID:29652495

Peptidic Macrocycles - Conformational Sampling and Thermodynamic Characterization.

PubMed

Kamenik, Anna S; Lessel, Uta; Fuchs, Julian E; Fox, Thomas; Liedl, Klaus R

2018-05-29

Macrocycles are of considerable interest as highly specific drug candidates, yet they challenge standard conformer generators with their large number of rotatable bonds and conformational restrictions. Here, we present a molecular dynamics-based routine that bypasses current limitations in conformational sampling and extensively profiles the free energy landscape of peptidic macrocycles in solution. We perform accelerated molecular dynamics simulations to capture a diverse conformational ensemble. By applying an energetic cutoff, followed by geometric clustering, we demonstrate the striking robustness and efficiency of the approach in identifying highly populated conformational states of cyclic peptides. The resulting structural and thermodynamic information is benchmarked against interproton distances from NMR experiments and conformational states identified by X-ray crystallography. Using three different model systems of varying size and flexibility, we show that the method reliably reproduces experimentally determined structural ensembles and is capable of identifying key conformational states that include the bioactive conformation. Thus, the described approach is a robust method to generate conformations of peptidic macrocycles and holds promise for structure-based drug design.

Design of metal cofactors activated by a protein–protein electron transfer system

PubMed Central

Ueno, Takafumi; Yokoi, Norihiko; Unno, Masaki; Matsui, Toshitaka; Tokita, Yuichi; Yamada, Masako; Ikeda-Saito, Masao; Nakajima, Hiroshi; Watanabe, Yoshihito

2006-01-01

Protein-to-protein electron transfer (ET) is a critical process in biological chemistry for which fundamental understanding is expected to provide a wealth of applications in biotechnology. Investigations of protein–protein ET systems in reductive activation of artificial cofactors introduced into proteins remains particularly challenging because of the complexity of interactions between the cofactor and the system contributing to ET. In this work, we construct an artificial protein–protein ET system, using heme oxygenase (HO), which is known to catalyze the conversion of heme to biliverdin. HO uses electrons provided from NADPH/cytochrome P450 reductase (CPR) through protein–protein complex formation during the enzymatic reaction. We report that a FeIII(Schiff-base), in the place of the active-site heme prosthetic group of HO, can be reduced by NADPH/CPR. The crystal structure of the Fe(10-CH2CH2COOH-Schiff-base)·HO composite indicates the presence of a hydrogen bond between the propionic acid carboxyl group and Arg-177 of HO. Furthermore, the ET rate from NADPH/CPR to the composite is 3.5-fold faster than that of Fe(Schiff-base)·HO, although the redox potential of Fe(10-CH2CH2COOH-Schiff-base)·HO (−79 mV vs. NHE) is lower than that of Fe(Schiff-base)·HO (+15 mV vs. NHE), where NHE is normal hydrogen electrode. This work describes a synthetic metal complex activated by means of a protein–protein ET system, which has not previously been reported. Moreover, the result suggests the importance of the hydrogen bond for the ET reaction of HO. Our Fe(Schiff-base)·HO composite model system may provide insights with regard to design of ET biosystems for sensors, catalysts, and electronics devices. PMID:16769893

Studies on free radical scavenging, cancer cell antiproliferation, and calf thymus DNA interaction of Schiff bases.

PubMed

da Silva, Cleiton M; Silva, Marina M; Reis, Fabiano S; Ruiz, Ana Lúcia T G; de Carvalho, João E; Santos, Josué C C; Figueiredo, Isis M; Alves, Rosemeire B; Modolo, Luzia V; de Fátima, Ângelo

2017-07-01

Thirty-nine Schiff bases were synthesized by performing microwave-assisted condensation of the corresponding aldehydes and aromatic amines. Their reactive nitrogen species (RNS) scavenging activity and inhibitory effects against cancer cell growth were then subsequently investigated. Additionally, the interaction between the calf thymus DNA (ctDNA) and selected Schiff bases was evaluated using fluorescence spectroscopy, and their binding parameters were determined. The yields of the various compounds ranged from moderate to excellent (43-99%) after only a 2-min reaction. The hydroxylated Schiff bases 2, 8, 15, 16, 18, 20, 29, 32, 34, and 37 were found to be potent scavengers of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals with half-maximal scavenging concentration (SC 50 ) values lower than that of the positive control, resveratrol. The presence of hydroxyl substituents on the aromatic rings also proved essential to the cytotoxicity of the compounds. The binding constants (K b ) obtained using fluorescence spectroscopy ranged from 0.37 to 3.07×10 5 Lmol -1 , and were strongly influenced by the structure and hydroxylation degree. Schiff bases 3 and 8 showed promising cytotoxic activity, with half-maximal growth inhibitory (GI 50 ) values in the same order of magnitude as those exhibited by the reference drug, doxorubicin against various cell lines. Interestingly, these compounds also showed the highest K b , suggesting that the cytotoxic activity could be related to their interaction with the DNA of the tumor cells. The results of this study highlighted some Schiff bases as potential lead compounds for the design of new free radical scavengers and anticancer agents. Copyright © 2017 Elsevier B.V. All rights reserved.

Experimental and theoretical studies of the products of addition-elimination reactions between benzil dihydrazone and three isomeric chlorobenzaldehydes.

PubMed

Liu, Yun-Na; Cheng, Shuang-Shuang; Wang, Chao; Xing, Dian-Xiang; Liu, Yun; Tan, Xue-Jie

2015-07-01

A series of mono- and di-Schiff bases formed between benzil dihydrazone {BDH; systematic name: (1Z)-[(2E)-2-hydrazinylidene-1,2-diphenylethylidene]hydrazine} and three isomeric chlorobenzaldehydes were designed and synthesized to be used as model compounds to help to explain the reaction mechanisms for the formation of Schiff bases. These compounds are 1-(2-chlorobenzylidene)-2-{2-[2-(2-chlorobenzylidene)hydrazin-1-ylidene]-1,2-diphenylethylidene}hydrazine (BDHOCB), and the 3-chloro (BDHMCB) and 4-chloro (BDHPCB) analogues, all having the formula C28H20Cl2N4. Surprisingly, only di-Schiff bases were obtained; our attempts to push the reaction in favour of the mono-Schiff bases all failed. Density functional theory (DFT) calculations were performed to explain the trend in the experimental results. In the case of the systems studied, the type of Schiff base produced exhibits a clear dependence on the HOMO-LUMO energy gaps (ΔE(HOMO-LUMO)), i.e. the product is mainly governed by its stability. The compounds were characterized by single-crystal X-ray diffractometry, elemental analysis, melting point, (1)H NMR and (13)C NMR spectroscopy. The structural features of the three new Schiff bases are similar. For instance, they have the same chemical formula, all the molecules have a symmetrical double helix structure, with each Ph-C=N-N=C-Ph arm exhibiting an anti conformation, and their supramolecular interactions include intermolecular π-π and weak C-H...π stacking interactions. The crystal systems are different, however, viz. triclinic (space group P1¯) for BDHPCB, monoclinic (space group P2(1)/n) for BDHOCB and orthorhombic (space group Pnna) for BDHMCB.

Ion Sensor Properties of Fluorescent Schiff Bases Carrying Dipicolylamine Groups. A Simple Spectrofluorimetric Method to Determine Cu (II) in Water Samples.

PubMed

Vanlı, Elvan; Mısır, Miraç Nedim; Alp, Hakan; Ak, Tuğba; Özbek, Nurhayat; Ocak, Ümmühan; Ocak, Miraç

2017-09-01

Four fluorescent Schiff bases carrying dipicolylamine groups were designed and synthesized to determine their ion sensor properties in partial aqueous solution. The corresponding amine compound and the aldehyde compounds such as 1-naphthaldehyde, 9-anthraldehyde, phenanthrene-9-carboxaldehyde and 1-pyrenecarboxaldehyde were used to prepare the new Schiff bases. The influence of many metal cations and anions on the spectroscopic properties of the ligands was investigated in ethanol-water (1:1) by means of emission spectrometry. From the spectrofluorimetric titrations, the complexation stoichiometry and complex stability constants of the ligands with Cd 2+ , Zn 2+ , Cu 2+ and Hg 2+ ions were determined. The ligands did not interact with the anions. However, the Schiff base derived from phenanthrene-9-carboxaldehyde showed sensitivity for Cu 2+ among the tested metal ions. The phenanthrene-based Schiff base was used as analytical ligand for the simple and fast determination of Cu 2+ ion in water samples. A modified standard addition method was used to eliminate matrix effect. The linear range was from 0.3 mg/L to 3.8 μg/L. Detection and quantification limits were 0.14 and 0.43 mg/L, respectively. Maximum contaminant level goal (MCLG) for copper in drinking water according to EPA is 1.3 mg/L. The proposed method has high sensitivity to determine copper in drinking waters.

Schiff and pseudo-Schiff reagents: the reactions and reagents of Hugo Schiff, including a classification of various kinds of histochemical reagents used to detect aldehydes.

PubMed

Dapson, R W

2016-11-01

During the 1860's, Hugo Schiff studied many reactions between amines and aldehydes, some of which have been used in histochemistry, at times without credit to Schiff. Much controversy has surrounded the chemical structures and reaction mechanisms of the compounds involved, but modern analytical techniques have clarified the picture. I review these reactions here. I used molecular modeling software to investigate dyes that contain primary amines representing eight chemical families. All dyes were known to perform satisfactorily for detecting aldehydes in tissue sections. The models verified the correct chemical structures at various points in their reactions and also determined how decolorization occurred in those with "leuco" forms. Decolorization in the presence of sulfurous acid can occur by either adduction or reduction depending on the dye. The final condensation product with aldehyde was determined to be either a C-sulfonic acid adduct on the carbonyl carbon atom or an aminal at the same atom. Based on the various outcomes, I have placed the dyes and their reactions into five categories. Because Hugo Schiff studied the reactions between aldehydes and amines with and without various acids or alcohol, it is only proper to call each of them Schiff reactions that used various types of Schiff reagents.

One-step electrochemical deposition of Schiff base cobalt complex as effective water oxidation catalyst

NASA Astrophysics Data System (ADS)

Huang, Binbin; Wang, Yan; Zhan, Shuzhong; Ye, Jianshan

2017-02-01

Schiff base metal complexes have been applied in many fields, especially, a potential homogeneous catalyst for water splitting. However, the high overpotential, time consumed synthesis process and complicated working condition largely limit their application. In the present work, a one-step approach to fabricate Schiff base cobalt complex modified electrode is developed. Microrod clusters (MRC) and rough spherical particles (RSP) can be obtained on the ITO electrode through different electrochemical deposition condition. Both of the MRC and RSP present favorable activity for oxygen evolution reaction (OER) compared to the commercial Co3O4, taking an overpotential of 650 mV and 450 mV to drive appreciable catalytic current respectively. The highly active and stable RSP shows a Tafel plot of 84 mV dec-1 and negligible decrease of the current density for 12 h bulk electrolysis. The synthesis strategy of effective and stable catalyst in this work provide a simple method to fabricate heterogeneous OER catalyst with Schiff base metal complex.

A new chitosan Schiff base supported Pd(II) complex for microwave-assisted synthesis of biaryls compounds

NASA Astrophysics Data System (ADS)

Baran, Talat

2017-08-01

In this study, a new heterogeneous palladium (II) catalyst that contains O-carboxymethyl chitosan Schiff base has been designed for Suzuki coupling reactions. The chemical structures of the synthesized catalyst were characterized with the FTIR, TG/DTG, ICP-OES, SEM/EDAX, 1H NMR, 13C NMR, GC/MS, XRD, and magnetic moment techniques. The reusability and catalytic behavior of heterogeneous catalyst was tested towards Suzuki reactions. As a result of the tests, excellent selectivity was obtained, and by-products of homo coupling were not seen in the spectra. The biaryls products were identified on a GC/MS. In addition, it was determined in the reusability tests that the catalysts could be used several times (seven runs). More importantly, with very low catalyst loading (6 × 10-3 mol %) in very short reaction time (5 min), chitosan Schiff base supported Pd(II) complex gave high TON and TOF values. These findings showed that Schiff base supported Pd(II) catalyst is suitable for Suzuki cross coupling reactions.

Keto-enol tautomerism in asymmetric Schiff bases derived from p-phenylenediamine

NASA Astrophysics Data System (ADS)

Užarević, Krunoslav; Rubčić, Mirta; Stilinović, Vladimir; Kaitner, Branko; Cindrić, Marina

2010-12-01

Reaction of dehydroacetic acid and p-phenylenediamine afforded a monosubstituted Schiff base, I, with the other amino group free. In further reactions with various salicylaldehyde derivatives, I served as a precursor for synthesis of asymmetric bis-Schiff bases. The synthesized compounds are thus comprised of two subunits, dehydroacetic ( dha) and salicylidene ( sal), which are bridged by the phenylene linker. All products were investigated by means of elemental analysis, FT-IR and NMR spectroscopy, thermal methods, powder X-ray diffraction and, when possible, by single crystal X-ray crystallography. Structural and spectroscopic studies revealed that in the bis-products, the dha subunit adopts the keto-amino tautomeric form, while the sal subunit adopts the enol-imino form. Tautomeric forms were not affected if a methoxo group was introduced on the salicylidene ring. Both tautomeric subunits are stabilized by strong resonance-assisted hydrogen bonds, RAHB. The two subunits of the prepared bis-Schiff bases predominantly retain in solution the same tautomeric forms as found in the solid state.

New Thiazolyl-triazole Schiff Bases: Synthesis and Evaluation of the Anti-Candida Potential.

PubMed

Stana, Anca; Enache, Alexandra; Vodnar, Dan Cristian; Nastasă, Cristina; Benedec, Daniela; Ionuț, Ioana; Login, Cezar; Marc, Gabriel; Oniga, Ovidiu; Tiperciuc, Brîndușa

2016-11-22

In the context of the dangerous phenomenon of fungal resistance to the available therapies, we present here the chemical synthesis of a new series of thiazolyl-triazole Schiff bases B1 - B15 , which were in vitro assessed for their anti- Candida potential. Compound B10 was found to be more potent against Candida spp. when compared with the reference drugs Fluconazole and Ketoconazole. A docking study of the newly synthesized Schiff bases was performed, and results showed good binding affinity in the active site of co-crystallized Itraconazole-lanosterol 14α-demethylase isolated from Saccharomyces cerevisiae . An in silico ADMET (absorption, distribution, metabolism, excretion, toxicity) study was done in order to predict some pharmacokinetic and pharmacotoxicological properties. The Schiff bases showed good drug-like properties. The results of in vitro anti- Candida activity, a docking study and ADMET prediction revealed that the newly synthesized compounds have potential anti- Candida activity and evidenced the most active derivative, B10 , which can be further optimized as a lead compound.

Oxidative peptide /and amide/ formation from Schiff base complexes

NASA Technical Reports Server (NTRS)

Strehler, B. L.; Li, M. P.; Martin, K.; Fliss, H.; Schmid, P.

1982-01-01

One hypothesis of the origin of pre-modern forms of life is that the original replicating molecules were specific polypeptides which acted as templates for the assembly of poly-Schiff bases complementary to the template, and that these polymers were then oxidized to peptide linkages, probably by photo-produced oxidants. A double cycle of such anti-parallel complementary replication would yield the original peptide polymer. If this model were valid, the Schiff base between an N-acyl alpha mino aldehyde and an amino acid should yield a dipeptide in aqueous solution in the presence of an appropriate oxidant. In the present study it is shown that the substituted dipeptide, N-acetyl-tyrosyl-tyrosine, is produced in high yield in aqueous solution at pH 9 through the action of H2O2 on the Schiff-base complex between N-acetyl-tyrosinal and tyrosine and that a great variety of N-acyl amino acids are formed from amino acids and aliphatic aldehydes under similar conditions.

Schiff's Bases and Crown Ethers as Supramolecular Sensing Materials in the Construction of Potentiometric Membrane Sensors

PubMed Central

Faridbod, Farnoush; Ganjali, Mohammad Reza; Dinarvand, Rassoul; Norouzi, Parviz; Riahi, Siavash

2008-01-01

Ionophore incorporated PVC membrane sensors are well-established analytical tools routinely used for the selective and direct measurement of a wide variety of different ions in complex biological and environmental samples. Potentiometric sensors have some outstanding advantages including simple design and operation, wide linear dynamic range, relatively fast response and rational selectivity. The vital component of such plasticized PVC members is the ionophore involved, defining the selectivity of the electrodes' complex formation. Molecular recognition causes the formation of many different supramolecules. Different types of supramolecules, like calixarenes, cyclodextrins and podands, have been used as a sensing material in the construction of ion selective sensors. Schiff's bases and crown ethers, which feature prominently in supramolecular chemistry, can be used as sensing materials in the construction of potentiometric ion selective electrodes. Up to now, more than 200 potentiometric membrane sensors for cations and anions based on Schiff's bases and crown ethers have been reported. In this review cation binding and anion complexes will be described. Liquid membrane sensors based on Schiff's bases and crown ethers will then be discussed. PMID:27879786

Cytotoxic effects of new synthesis heterocyclic derivatives of Amoxicillin on some cancer cell lines

NASA Astrophysics Data System (ADS)

Al-Rawi, M. S.; Hussei, D. F.; Al-Taie, A. F.; Al-Halbosiy, M. M.; Hameed, B. A.

2018-05-01

A new Schiff base [I] was prepared by refluxing Amoxicillin trihydrate and 4-Hydroxy- 3,5-dimethoxybenzaldehyde in aqueous methanol solution using glacial acetic acid as a catalyst. The new 1,3-oxazepine derivative [II] was obtained by Diels- Alder reaction of Schiff base [I] with phthalic anhydride in dry benzene. The reaction of Schiff base [I] with thioglycolic acid in dry benzene led to the formation of thiazolidin-4-one derivative [III]. While the imidazolidin-4-one [IV] derivative was produced by reacting the mentioned Schiff base [I] with glycine and triethylamine in ethanol for 9 hrs. Tetrazole derivative [V] was synthesized by refluxing Schiff base [I] with sodium azide in dimethylformamid DMF. The structure of synthesized compounds[I-V] was characterized by their melting points, elemental analysis CHN-S and by their spectral data; FTIR and 1H NMR spectroscopy. Two cancer cell lines include: (RD) human pelvic rhabdomyosarcoma and (L20B) the mice intestines carcinoma cell line (which expresses the genes for human cellular receptor for Polio viruses) were used in this study. The cytotoxic effect of different concentrations of all the synthesized compounds for 48 hrs was examined. All compounds except [IV] and [V] showed less than 50% inhibition for (L20B), while these compounds exhibit inhibition more than 50% inhibition for (RD).

Synthesis, spectral and antimicrobial activity of Zn(II) complexes with Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-thiadiazole and benzaldehyde/2-hydroxyacetophenone/indoline-2,3-dione

NASA Astrophysics Data System (ADS)

Singh, Ajay K.; Pandey, O. P.; Sengupta, S. K.

2013-09-01

Zn(II) complexes have been synthesized by reacting zinc acetate with Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-thiadiazole and 2-hydroxyacetophenone/benzaldehyde/indoline-2,3-dione. All these complexes are soluble in DMF and DMSO; low molar conductance values indicate that they are non electrolytes. Elemental analyses suggest that the complexes have 1:2 metal to ligands stoichiometry of the types [ZnL2(H2O)2](L = monoanionic Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-thiadiazole and 2-hydroxyacetophenone/indoline-2,3-dione) [ZnL2‧(OOCCH3)2(H2O)2](L‧ = neutral Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-thiadiazole and benzaldehyde), and they were characterized by IR, 1H NMR, and 13C NMR. Particle sizes of synthesized compounds were measured with dynamic light scattering (DLS) analyser which indicates that particle diameter are of the range ca. 100-200 nm. All these Schiff bases and their complexes have also been screened for their antibacterial (Bacillus subtilis (B. subtilis), Escherichia coli (E. coli) and antifungal activities (Colletotrichum falcatum (C. falcatum), Aspergillus niger (A. niger), Fusarium oxysporium (F. oxysporium) Curvularia pallescence (C. pallescence). The antimicrobial activities have shown that upon complexation the activity increases.

Adaptive self-assembly and induced-fit transformations of anion-binding metal-organic macrocycles

NASA Astrophysics Data System (ADS)

Zhang, Ting; Zhou, Li-Peng; Guo, Xiao-Qing; Cai, Li-Xuan; Sun, Qing-Fu

2017-06-01

Container-molecules are attractive to chemists due to their unique structural characteristics comparable to enzymes and receptors in nature. We report here a family of artificial self-assembled macrocyclic containers that feature induced-fit transformations in response to different anionic guests. Five metal-organic macrocycles with empirical formula of MnL2n (M=Metal L=Ligand n=3, 4, 5, 6, 7) are selectively obtained starting from one simple benzimidazole-based ligand and square-planar palladium(II) ions, either by direct anion-adaptive self-assembly or induced-fit transformations. Hydrogen-bonding interactions between the inner surface of the macrocycles and the anionic guests dictate the shape and size of the product. A comprehensive induced-fit transformation map across all the MnL2n species is drawn, with a representative reconstitution process from Pd7L14 to Pd3L6 traced in detail, revealing a gradual ring-shrinking mechanism. We envisage that these macrocyclic molecules with adjustable well-defined hydrogen-bonding pockets will find wide applications in molecular sensing or catalysis.

Development of inexpensive metal macrocyclic complexes for use in fuel cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doddapaneni, N.; Ingersoll, D.; Kosek, J.A.

Several metal macrocyclic complexes were synthesized for use as catalysts in fuel cells. An initial evaluation of their ability to catalyze the fuel cell reactions were completed. Based on this initial evaluation, one metal macrocyclic catalyst was selected and long-term stability testing in a fuel cell was initiated. The fuel cell employing this catalyst was operated continuously for one year with little signs of catalyst degradation. The effect of synthetic reformates on the performance of the catalyst in the fuel cell environment also demonstrated high tolerance of this catalyst for common contaminants and poisons.

Two-Dimensional Nanoporous Networks Formed by Liquid-to-Solid Transfer of Hydrogen-Bonded Macrocycles Built from DNA Bases.

PubMed

Bilbao, Nerea; Destoop, Iris; De Feyter, Steven; González-Rodríguez, David

2016-01-11

We present an approach that makes use of DNA base pairing to produce hydrogen-bonded macrocycles whose supramolecular structure can be transferred from solution to a solid substrate. A hierarchical assembly process ultimately leads to two-dimensional nanostructured porous networks that are able to host size-complementary guests. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemopreventive evaluation of a Schiff base derived copper (II) complex against azoxymethane-induced colorectal cancer in rats.

PubMed

Hajrezaie, Maryam; Hassandarvish, Pouya; Moghadamtousi, Soheil Zorofchian; Gwaram, Nura Suleiman; Golbabapour, Shahram; Najihussien, Abdrabuh; Almagrami, Amel Abdullah; Zahedifard, Maryam; Rouhollahi, Elham; Karimian, Hamed; Fani, Somaye; Kamalidehghan, Behnam; Majid, Nazia Abdul; Ali, Hapipah Mohd; Abdulla, Mahmood Ameen

2014-01-01

Based on the potential of Schiff base compounds to act as sources for the development of cancer chemotherapeutic agents, this in vivo study was performed to investigate the inhibitory properties of the synthetic Schiff base compound Cu(BrHAP)2 on colonic aberrant crypt foci (ACF). This study involved five groups of male rats. The negative control group was injected with normal saline once a week for 2 weeks and fed 10% Tween 20 for 10 weeks, the cancer control group was subcutaneously injected with 15 mg/kg azoxymethane once per week for two consecutive weeks, the positive control group was injected with 15 mg/kg azoxymethane once per week for two consecutive weeks and 35 mg/kg 5-fluorouracil (injected intra-peritoneally) for 4 weeks, and the experimental groups were first injected with 15 mg/kg azoxymethane once per week for two consecutive weeks and then fed 2.5 or 5 mg/kg of the Schiff base compound once a day for 10 weeks. Application of the Schiff base compound suppressed total colonic ACF formation by up to 72% to 74% (P<0.05) when compared with the cancer control group. Analysis of colorectal specimens revealed that treatments with the Schiff base compound decreased the mean crypt scores in azoxymethane-treated rats. Significant elevations of superoxide dismutase, glutathione peroxidase and catalase activities and a reduction in the level of malondialdehyde were also observed. Histologically, all treatment groups exhibited significant decreases in dysplasia compared to the cancer control group (P<0.05). Immunohistochemical staining demonstrated down-regulation of the PCNA protein. Comparative western blot analysis revealed that COX-2 and Bcl2 were up-regulated and Bax was down-regulated compared with the AOM control group. The current study demonstrated that the Cu(BrHAP)2 compound has promising chemoprotective activities that are evidenced by significant decreases in the numbers of ACFs in azoxymethane-induced colon cancer.

Chemopreventive Evaluation of a Schiff Base Derived Copper (II) Complex against Azoxymethane-Induced Colorectal Cancer in Rats

PubMed Central

Hajrezaie, Maryam; Hassandarvish, Pouya; Moghadamtousi, Soheil Zorofchian; Gwaram, Nura Suleiman; Golbabapour, Shahram; NajiHussien, Abdrabuh; Almagrami, Amel Abdullah; Zahedifard, Maryam; Rouhollahi, Elham; Karimian, Hamed; Fani, Somaye; Kamalidehghan, Behnam; Majid, Nazia Abdul; Ali, Hapipah Mohd; Abdulla, Mahmood Ameen

2014-01-01

Background Based on the potential of Schiff base compounds to act as sources for the development of cancer chemotherapeutic agents, this in vivo study was performed to investigate the inhibitory properties of the synthetic Schiff base compound Cu(BrHAP)2 on colonic aberrant crypt foci (ACF). Methodology This study involved five groups of male rats. The negative control group was injected with normal saline once a week for 2 weeks and fed 10% Tween 20 for 10 weeks, the cancer control group was subcutaneously injected with 15 mg/kg azoxymethane once per week for two consecutive weeks, the positive control group was injected with 15 mg/kg azoxymethane once per week for two consecutive weeks and 35 mg/kg 5-fluorouracil (injected intra-peritoneally) for 4 weeks, and the experimental groups were first injected with 15 mg/kg azoxymethane once per week for two consecutive weeks and then fed 2.5 or 5 mg/kg of the Schiff base compound once a day for 10 weeks. Application of the Schiff base compound suppressed total colonic ACF formation by up to 72% to 74% (P<0.05) when compared with the cancer control group. Analysis of colorectal specimens revealed that treatments with the Schiff base compound decreased the mean crypt scores in azoxymethane-treated rats. Significant elevations of superoxide dismutase, glutathione peroxidase and catalase activities and a reduction in the level of malondialdehyde were also observed. Histologically, all treatment groups exhibited significant decreases in dysplasia compared to the cancer control group (P<0.05). Immunohistochemical staining demonstrated down-regulation of the PCNA protein. Comparative western blot analysis revealed that COX-2 and Bcl2 were up-regulated and Bax was down-regulated compared with the AOM control group. Conclusion The current study demonstrated that the Cu(BrHAP)2 compound has promising chemoprotective activities that are evidenced by significant decreases in the numbers of ACFs in azoxymethane-induced colon cancer. PMID:24618844

Deuterium isotope effect on 13C chemical shifts of tetrabutylammonium salts of Schiff bases amino acids.

PubMed

Rozwadowski, Z

2006-09-01

Deuterium isotope effects on 13C chemical shift of tetrabutylammonium salts of Schiff bases, derivatives of amino acids (glycine, L-alanine, L-phenylalanine, L-valine, L-leucine, L-isoleucine and L-methionine) and various ortho-hydroxyaldehydes in CDCl3 have been measured. The results have shown that the tetrabutylammonium salts of the Schiff bases amino acids, being derivatives of 2-hydroxynaphthaldehyde and 3,5-dibromosalicylaldehyde, exist in the NH-form, while in the derivatives of salicylaldehyde and 5-bromosalicylaldehyde a proton transfer takes place. The interactions between COO- and NH groups stabilize the proton-transferred form through a bifurcated intramolecular hydrogen bond. Copyright (c) 2006 John Wiley & Sons, Ltd.

Synthesis, spectroscopic characterization and antimicrobial studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes with Schiff bases derived from 5-bromo-salicylaldehyde

NASA Astrophysics Data System (ADS)

Kursunlu, Ahmed Nuri; Guler, Ersin; Sevgi, Fatih; Ozkalp, Birol

2013-09-01

In this study, the new Schiff base ligands derived from condensation of amine and 5-bromo-salicylaldehyde were characterized. All compounds, the Schiff bases and the metal complexes, were characterized by elemental analyzes, FT-IR, 1H NMR, 13C NMR and magnetic susceptibility measurements. The synthesized ligands, along with their metal (II) complexes, were screened for their in vitro antibacterial activity against four Gram-negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Salmonella enteritidis) and four Gram-positive (Streptococcus pyogones, Bacillus cereus, Staphylococcus aureus and Methicillin-resistant S. aureus) bacterial strains by using disc diffusion and broth microdilution techniques.

In vivo three-dimensional molecular imaging with Biosensor Imaging of Redundant Deviation in Shifts (BIRDS) at high spatiotemporal resolution.

PubMed

Coman, Daniel; de Graaf, Robin A; Rothman, Douglas L; Hyder, Fahmeed

2013-11-01

Spectroscopic signals which emanate from complexes between paramagnetic lanthanide (III) ions (e.g. Tm(3+)) and macrocyclic chelates (e.g. 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate, or DOTMA(4-)) are sensitive to physiology (e.g. temperature). Because nonexchanging protons from these lanthanide-based macrocyclic agents have relaxation times on the order of a few milliseconds, rapid data acquisition is possible with chemical shift imaging (CSI). Thus, Biosensor Imaging of Redundant Deviation in Shifts (BIRDS) which originate from nonexchanging protons of these paramagnetic agents, but exclude water proton detection, can allow molecular imaging. Previous two-dimensional CSI experiments with such lanthanide-based macrocyclics allowed acquisition from ~12-μL voxels in rat brain within 5 min using rectangular encoding of k space. Because cubical encoding of k space in three dimensions for whole-brain coverage increases the CSI acquisition time to several tens of minutes or more, a faster CSI technique is required for BIRDS to be of practical use. Here, we demonstrate a CSI acquisition method to improve three-dimensional molecular imaging capabilities with lanthanide-based macrocyclics. Using TmDOTMA(-), we show datasets from a 20 × 20 × 20-mm(3) field of view with voxels of ~1 μL effective volume acquired within 5 min (at 11.7 T) for temperature mapping. By employing reduced spherical encoding with Gaussian weighting (RESEGAW) instead of cubical encoding of k space, a significant increase in CSI signal is obtained. In vitro and in vivo three-dimensional CSI data with TmDOTMA(-), and presumably similar lanthanide-based macrocyclics, suggest that acquisition using RESEGAW can be used for high spatiotemporal resolution molecular mapping with BIRDS. Copyright © 2013 John Wiley & Sons, Ltd.

Self-Assembling Organic Nanopores as Synthetic Transmembrane Channels with Tunable Functions

NASA Astrophysics Data System (ADS)

Wei, Xiaoxi

A long-standing goal in the area of supramolecular self-assembly involves the development of synthetic ion/water channels capable of mimicking the mass-transport characteristics of biological channels and pores. Few examples of artificial transmembrane channels with large lumen, high conductivity and selectivity are known. A review of pronounced biological transmembrane protein channels and some representative synthetic models have been provided in Chapter 1, followed by our discovery and initial investigation of shape-persistent oligoamide and phenylene ethynylene macrocycles as synthetic ion/water channels. In Chapter 2, the systematic structural modification of oligoamide macrocycles 1, the so-called first-generation of these shape-persistent macrocycles, has led to third-generation macrocycles 3. The third generation was found to exhibit unprecedented, strong intermolecular association in both the solid state and solution via multiple techniques including X-ray diffraction (XRD), SEM, and 1H NMR. Fluorescence spectroscopy paired with dynamic light scattering (DLS) revealed that macrocycles 3 can assemble into a singly dispersed nanotubular structure in solution. The resultant self-assembling pores consisting of 3 were examined by HPTS-LUVs assays and BLM studies (Chapter 3) and found to form cation-selective (PK+/PCl- = 69:1) transmembrane ion channels with large conductance (200 ˜ 2000 pS for alkali cations) and high stability with open times reaching to 103 seconds. Tuning the aggregation state of macrocycles by choosing an appropriate polar solvent mixture (i.e., 3:1, THF:DMF, v/v) and concentration led to the formation of ion channels with well-defined square top behavior. A parallel study using DLS to examine the size of aggregates was used in conjunction with channel activity assays (LUVs/BLM) to reveal the effects of the aggregation state on channel activity. Empirical evidence now clearly indicates that a preassembled state, perhaps that of a nanotubular assembly, rather than the individual molecules of 3, is required to partition into the lipid bilayer in order for these macrocycles to act as channels. Further structural modification has led to fourth-generation macrocycles 4 having readily-tunable cavities (Chapter 4). Macrocycles 4 , with a hybrid backbone composed half of the oligoamide and half of the phenylene ethynylene moieties, exhibits similar self-assembling behavior by forming nanotubular stacks. The results of a preliminary study based on LUVs-assays and BLM single channel recording experiments are summarized and clearly indicate that ion channels formed by this fourth-generation exhibit high stability and differing ion selectivity largely consistent with the corresponding structural modification of the interior cavity. Especially, the increased anion conductance observed for 4d indicates that our strategy of tuning supramolecular function based on synthetic modification of the backbone and pore is effective. In Chapter 5, our four-residue tetraurea macrocycles 5 have shown significant potency to selectively interact with the G-quadruplex, leading to a strong stabilization effect for G-quadruplex without binding to duplex DNA as observed by UV-melt assays. The ready synthetic availability of these macrocycles makes them amenable to future chemical modification, which allows systematic improvement of binding affinity and specificity. Moreover, it has been discovered that these macrocycles can partition into lipid bilayers and form very stable transmembrane ion channels with a pore size of ˜5 A. Preliminary data shows that this smaller ion channel may lead to exceptional ion conducting selectivity, which is rarely seen in the field of synthetic ion pores. These molecules may serve as a unique platform for the rational development of potent and versatile therapeutic agents. The exceptional ion conducting properties of these channels place aromatic oligoamide macrocycles 3 and 4 at a unique position with both high conductance and long channel-opening duration. These results demonstrate that oligoamide macrocycles provide us a reliable platform based on which further development of highly conducting and selective synthetic mass-transporting channels, with functions that are comparable to or even rival those of natural channels and pores, may be developed. Further improvement of these synthetic channels could lead to numerous applications, such as those for complementing ion channel deficiency in clinical medicine, designing biosensors, and the development of new materials, as well as their use in separation and purifications.

Fluorescent chemosensor based on sensitive Schiff base for selective detection of Zn2+

NASA Astrophysics Data System (ADS)

Singh, T. Sanjoy; Paul, Pradip C.; Pramanik, Harun A. R.

2014-03-01

A Schiff-base fluorescent compound - N, N‧-bis(salicylidene)-1,2 - phenylenediamine (LH2) was synthesized and evaluated as a chemoselective Zn2+ sensor. Addition of Zn2+ to ethanol solution of LH2 resulted in a red shift with a pronounced enhancement in the fluorescence intensity. Moreover, other common alkali, alkaline earth and transition metal ions failed to induce response or minimal spectral changes. Notably, this chemosensor could distinguish clearly Zn2+ from Cd2+. Fluorescence studies on free Schiff base ligand LH2 and LH2 - Zn2+ complex reveal that the quantum yield strongly increases upon coordination. The stoichiometric ratio and association constant were evaluated using Benesi - Hildebrand relation giving 1:1 stoichiometry. This further corroborated 1:1 complex formation based on Job's plot analyses.

Synthesis and Characterization of Metal Complexes with Schiff Base Ligands

ERIC Educational Resources Information Center

Wilkinson, Shane M.; Sheedy, Timothy M.; New, Elizabeth J.

2016-01-01

In order for undergraduate laboratory experiments to reflect modern research practice, it is essential that they include a range of elements, and that synthetic tasks are accompanied by characterization and analysis. This intermediate general chemistry laboratory exercise runs over 2 weeks, and involves the preparation of a Schiff base ligand and…

Synthesis, characterization and catalytic activity of nanosized Ni complexed aminoclay

NASA Astrophysics Data System (ADS)

Ranchani, A. Amala Jeya; Parthasarathy, V.; Devi, A. Anitha; Meenarathi, B.; Anbarasan, R.

2017-11-01

A novel Ni complexed aminoclay (AC) catalyst was prepared by complexation method followed by reduction reaction. Various analytical techniques such as FTIR spectroscopy, UV-visible spectroscopy, DSC, TGA, SEM, HRTEM, EDX, XPS and WCA measurement are used to characterize the synthesized material. The AC-Ni catalyst system exhibited improved thermal stability and fiber-like morphology. The XPS results declared the formation of Ni nanoparticles. Thus, synthesized catalyst was tested towards the Schiff base formation reaction between various bio-medical polymers and aniline under air atmosphere at 85 °C for 24 h. The catalytic activity of the catalyst was studied by varying the % weight loading of the AC-Ni system towards the Schiff base formation. The Schiff base formation was quantitatively calculated by the 1H-NMR spectroscopy. While increasing the % weight loading of the AC-Ni catalyst, the % yield of Schiff base was also increased. The k app and Ti values were determined for the reduction of indole and α-terpineol in the presence of AC-Ni catalyst system. The experimental results were compared with the literature report.

Synthesis, spectroscopic, thermal and antimicrobial studies of neodymium(III) and samarium(III) complexes derived from tetradentate ligands containing N and S donor atoms

NASA Astrophysics Data System (ADS)

Ain, Qurratul; Pandey, S. K.; Pandey, O. P.; Sengupta, S. K.

2015-04-01

Trivalent lanthanide complexes of the type [Ln(L)Cl(H2O)2] (where Ln = Nd(III) or Sm(III) and LH2 = Schiff bases derived by the condensation of 3-(phenyl/substitutedphenyl)-4-amino-5-mercapto-1,2,4-triazole with diacetyl/benzil) have been synthesized by the reactions of anhydrous lanthanide(III) chloride with Schiff bases in methanol. The structures of the complexes have been proposed on the basis of elemental analysis, electrical conductance, magnetic moment, spectroscopic measurements (IR, 1H, 13C NMR and UV-vis spectra) and X-ray diffraction studies. The spectral data reveal that the Schiff base ligands behave as dibasic tetradentate chelating agents having coordination sites at two thiol sulfur atoms and two azomethine nitrogen atoms. The presence of coordinated water in metal complexes was confirmed by thermal and IR data of the complexes. All the Schiff bases and their metal complexes have also been screened for their antibacterial activity against Bacillus subtilis, Staphylococcus aureus and antifungal activities against Aspergillus niger, Curvularia pallescens and Colletotrichum capsici.

Synthesis, spectral characterization and DNA binding of Schiff-base metal complexes derived from 2-amino-3-hydroxyprobanoic acid and acetylacetone

NASA Astrophysics Data System (ADS)

Hosny, Nasser Mohammed; Hussien, Mostafa A.; Radwan, Fatima M.; Nawar, Nagwa

2014-11-01

Four new metal complexes derived from the reaction of Cu(II), Co(II), Ni(II) and Zn(II) acetates with the Schiff-base ligand (H3L) resulted from the condensation of the amino acid 2-amino-3-hydroxyprobanoic acid (serine) and acetylacetone have been synthesized and characterized by, elemental analyses, ES-MS, IR, UV-Vis., 1H NMR, 13C NMR, ESR, thermal analyses (TGA and DTG) and magnetic measurements. The results showed that the Schiff-base ligand acts as bi-negative tridentate through the azomethine nitrogen, the deprotonated carboxylate oxygen and the enolic carbonyl oxygen. The optical band gaps measurements indicated the semi-conducting nature of these complexes. Molecular docking was used to predict the binding between the Schiff base ligand with the receptor of prostate cancer mutant H874Y. The interactions between the Cu(II) complex and calf thymus DNA (CT-DNA) have been studied by UV spectra. The results confirm that the Cu(II) complex binds to CT-DNA in an intercalative mode.

A Quantum Chemical and Statistical Study of Phenolic Schiff Bases with Antioxidant Activity against DPPH Free Radical

PubMed Central

Anouar, El Hassane

2014-01-01

Phenolic Schiff bases are known as powerful antioxidants. To select the electronic, 2D and 3D descriptors responsible for the free radical scavenging ability of a series of 30 phenolic Schiff bases, a set of molecular descriptors were calculated by using B3P86 (Becke’s three parameter hybrid functional with Perdew 86 correlation functional) combined with 6-31 + G(d,p) basis set (i.e., at the B3P86/6-31 + G(d,p) level of theory). The chemometric methods, simple and multiple linear regressions (SLR and MLR), principal component analysis (PCA) and hierarchical cluster analysis (HCA) were employed to reduce the dimensionality and to investigate the relationship between the calculated descriptors and the antioxidant activity. The results showed that the antioxidant activity mainly depends on the first and second bond dissociation enthalpies of phenolic hydroxyl groups, the dipole moment and the hydrophobicity descriptors. The antioxidant activity is inversely proportional to the main descriptors. The selected descriptors discriminate the Schiff bases into active and inactive antioxidants. PMID:26784873

GIAO-DFT calculation of 15 N NMR chemical shifts of Schiff bases: Accuracy factors and protonation effects.

PubMed

Semenov, Valentin A; Samultsev, Dmitry O; Krivdin, Leonid B

2018-02-09

15 N NMR chemical shifts in the representative series of Schiff bases together with their protonated forms have been calculated at the density functional theory level in comparison with available experiment. A number of functionals and basis sets have been tested in terms of a better agreement with experiment. Complimentary to gas phase results, 2 solvation models, namely, a classical Tomasi's polarizable continuum model (PCM) and that in combination with an explicit inclusion of one molecule of solvent into calculation space to form supermolecule 1:1 (SM + PCM), were examined. Best results are achieved with PCM and SM + PCM models resulting in mean absolute errors of calculated 15 N NMR chemical shifts in the whole series of neutral and protonated Schiff bases of accordingly 5.2 and 5.8 ppm as compared with 15.2 ppm in gas phase for the range of about 200 ppm. Noticeable protonation effects (exceeding 100 ppm) in protonated Schiff bases are rationalized in terms of a general natural bond orbital approach. Copyright © 2018 John Wiley & Sons, Ltd.

Solute-solvent interactions in chloroform solutions of halogenated symmetric double Schiff bases of 1,1'-bis(4-aminophenyl)cyclohexane at 308.15 K according to ultrasonic and viscosity data

NASA Astrophysics Data System (ADS)

Gangani, B. J.; Patel, J. P.; Parsania, P. H.

2015-12-01

The density, viscosity and ultrasonic speed (2 MHz) of chloroform solutions of halogenated symmetric double Schiff bases of 1,1'-bis(4-aminophenyl)cyclohexane were investigated at 308.15 K. Various acoustical parameters such as specific acoustical impedance ( Z), adiabatic compressibility ( Ka), Rao's molar sound function ( R m), van der Waals constant ( b), internal pressure (π), free volume ( V f), intermolecular free path length ( L f), classical absorption coefficient (α/ f 2)Cl) and viscous relaxation time (τ) were determine using ultrasonic speed ( U), viscosity (η) and density (ρ) data of Schiff bases solutions and correlated with concentration. Linear increase of Z, b, R, τ, and (α/ f 2)Cl except π (nonlinear) and linear decrease of Ka and L f except V f (nonlinear) with increasing concentration of Schiff bases suggested presence of strong molecular interactions in the solutions. The positive values of solvation number further supported strong molecular interactions in the solutions. The nature and position of halogen substituent also affected the strength of molecular interactions.

Synthetic bioactive novel ether based Schiff bases and their copper(II) complexes

NASA Astrophysics Data System (ADS)

Shabbir, Muhammad; Akhter, Zareen; Ismail, Hammad; Mirza, Bushra

2017-10-01

Novel ether based Schiff bases (HL1- HL4) were synthesized from 5-chloro-2-hydroxy benzaldehyde and primary amines (1-amino-4-phenoxybenzene, 4-(4-aminophenyloxy) biphenyl, 1-(4-aminophenoxy) naphthalene and 2-(4-aminophenoxy) naphthalene). From these Schiff bases copper(II) complexes (Cu(L1)2-Cu(L4)2)) were synthesized and characterized by elemental analysis and spectroscopic (FTIR, NMR) techniques. The synthesized Schiff bases and copper(II) complexes were further assessed for various biological studies. In brine shrimp assay the copper(II) complexes revealed 4-fold higher activity (LD50 3.8 μg/ml) as compared with simple ligands (LD50 12.4 μg/ml). Similar findings were observed in potato disc antitumor assay with higher activities for copper(II) complexes (IC50 range 20.4-24.1 μg/ml) than ligands (IC50 range 40.5-48.3 μg/ml). DPPH assay was performed to determine the antioxidant potential of the compounds. Significant antioxidant activity was shown by the copper(II) complexes whereas simple ligands have shown no activity. In DNA protection assay significant protection behavior was exhibited by simple ligand molecules while copper(II) complexes showed neutral behavior (neither protective nor damaging).

Exploring DNA binding and nucleolytic activity of few 4-aminoantipyrine based amino acid Schiff base complexes: A comparative approach

NASA Astrophysics Data System (ADS)

Raman, N.; Sakthivel, A.; Pravin, N.

A series of novel Co(II), Cu(II), Ni(II) and Zn(II) complexes were synthesized from Schiff base(s), obtained by the condensation of 4-aminoantipyrine with furfural and amino acid (glycine(L1)/alanine(L2)/valine(L3)) and respective metal(II) chloride. Their structural features and other properties were explored from the analytical and spectral methods. The binding behaviors of the complexes to calf thymus DNA were investigated by absorption spectra, viscosity measurements and cyclic voltammetry. The intrinsic binding constants for the above synthesized complexes are found to be in the order of 102 to 105 indicating that most of the synthesized complexes are good intercalators. The binding constant values (Kb) clearly indicate that valine Schiff-base complexes have more intercalating ability than alanine and glycine Schiff-base complexes. The results indicate that the complexes bind to DNA through intercalation and act as efficient cleaving agents. The in vitro antibacterial and antifungal assay indicates that these complexes are good antimicrobial agents against various pathogens. The IC50 values of [Ni(L1)2] and [Zn(L1)2] complexes imply that these complexes have preferable ability to scavenge hydroxyl radical.

Synthesis, spectroscopic, coordination and biological activities of some organometallic complexes derived from thio-Schiff base ligands

NASA Astrophysics Data System (ADS)

Abou-Hussein, Azza A.; Linert, Wolfgang

2014-01-01

Two series of mono- and binuclear complexes cyclic or acyclic thio-ferocine Schiff base ligands, derived from the condensation of 2-aminobenzenthiol (L) with monoacetyl ferrocene in the molar ratio 1:1 or in the molar ratio 1:2 for diacetyl ferocine have been prepared. The condensation reactions yield the corresponding Schiff Base ligands, HLa-Maf and H2Lb-Daf. The chelation of the ligands to metal ions occurs through the sulfur of the thiol group as well as the nitrogen atoms of the azomethine group of the ligands. HLa-Maf acts as monobasic bidentate or dibasic tetradentate, while H2Lb-Daf behaves as twice negatively cargend tetradentate ligand. The structures of these ligands were elucidated by elemental analysis, infrared, ultraviolet-visible spectra, as well as 1H NMR spectra. Reactions of the Schiff bases ligands with ruthenium(III), oxovanadium(IV) and dioxouranium(VI) afforded the corresponding transition metal complexes. The properties of the newly prepared complexes were analyse by elemental analyses, infrared, electronic spectra, 1H NMR as well as the magnetic susceptibility and conductivity measurement. The metal complexes exhibits different geometrical arrangements such as octahedral and square pyramidal coordination. Schiff base ligands and their metal complexes were tested against two pathogenic bacteria as Gram-positive and Gram-negative bacteria as well as one kind of fungi to study their biological activity. All the complexes exhibit antibacterial and antifungal activities against these organisms.

Synthesis, characterization of 1,2,4-triazole Schiff base derived 3d-metal complexes: Induces cytotoxicity in HepG2, MCF-7 cell line, BSA binding fluorescence and DFT study

NASA Astrophysics Data System (ADS)

Tyagi, Prateek; Tyagi, Monika; Agrawal, Swati; Chandra, Sulekh; Ojha, Himanshu; Pathak, Mallika

2017-01-01

Two novel Schiff base ligands H2L1 and H2L2 have been synthesized by condensation reaction of amine derivative of 1,2,4-triazole moiety with 2-hydroxy-4-methoxybenzaldehyde. Co(II), Ni(II), Cu(II) and Zn(II) of the synthesized Schiff bases were prepared by using a molar ratio of ligand:metal as 1:1. The structure of the Schiff bases and synthesized metal complexes were established by 1H NMR, UV-Vis, IR, Mass spectrometry and molar conductivity. The thermal stability of the complexes was study by TGA. Fluorescence quenching mechanism of metal complexes 1-4 show that Zn(II) and Cu(II) complex binds more strongly to BSA. In DFT studies the geometries of Schiff bases and metal complexes were fully optimized with respect to the energy using the 6-31 + g(d,p) basis set. The spectral data shows that the ligands behaves as binegative tridentate. On the basis of the spectral studies, TGA and DFT data an octahedral geometry has been assigned for Co(II), Ni(II), square planar for Cu(II) and tetrahedral for Zn(II) complexes. The anticancer activity were screened against human breast cancer cell line (MCF-7) and human hepatocellular liver carcinoma cell line (Hep-G2). Result indicates that metal complexes shows increase cytotoxicity in proliferation to cell lines as compared to free ligand.

Synthesis, spectral and antimicrobial activity of Zn(II) complexes with Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-thiadiazole and benzaldehyde/2-hydroxyacetophenone/indoline-2,3-dione.

PubMed

Singh, Ajay K; Pandey, O P; Sengupta, S K

2013-09-01

Zn(II) complexes have been synthesized by reacting zinc acetate with Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-thiadiazole and 2-hydroxyacetophenone/benzaldehyde/indoline-2,3-dione. All these complexes are soluble in DMF and DMSO; low molar conductance values indicate that they are non electrolytes. Elemental analyses suggest that the complexes have 1:2 metal to ligands stoichiometry of the types [ZnL2(H2O)2](L=monoanionic Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-thiadiazole and 2-hydroxyacetophenone/indoline-2,3-dione) [ZnL2(')(OOCCH3)2(H2O)2](L'=neutral Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-thiadiazole and benzaldehyde), and they were characterized by IR, (1)H NMR, and (13)C NMR. Particle sizes of synthesized compounds were measured with dynamic light scattering (DLS) analyser which indicates that particle diameter are of the range ca. 100-200nm. All these Schiff bases and their complexes have also been screened for their antibacterial (Bacillus subtilis (B. subtilis), Escherichia coli (E. coli) and antifungal activities (Colletotrichum falcatum (C. falcatum), Aspergillus niger (A. niger), Fusarium oxysporium (F. oxysporium) Curvularia pallescence (C. pallescence). The antimicrobial activities have shown that upon complexation the activity increases. Copyright © 2013 Elsevier B.V. All rights reserved.

Design, spectral characterization, thermal, DFT studies and anticancer cell line activities of Co(II), Ni(II) and Cu(II) complexes of Schiff bases derived from 4-amino-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol.

PubMed

Tyagi, Prateek; Chandra, Sulekh; Saraswat, B S; Yadav, Deepak

2015-06-15

A series of two biologically active Schiff base ligands L(1), L(2) have been synthesized in equimolar reaction of 4-amino-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol with thiophene-2-carbaldehyde and furan-2-carbaldehyde. The synthesized Schiff bases were used for complexation with different metal ions like Co(II), Ni(II) and Cu(II) by using a molar ratio of ligand: metal as 1:1 and 2:1. The characterization of Schiff bases and metal complexes was done by (1)H NMR, UV-Vis, TGA, IR, mass spectrometry and molar conductivity studies. The in DFT studies the geometries of Schiff bases and metal complexes were fully optimized with respect to the energy using the 6-31+g(d,p) basis set. On the basis of the spectral studies an octahedral geometry has been assigned for Co(II), Ni(II) and Cu(II) complexes. The effect of these complexes on proliferation of human breast cancer cell line (MCF-7) and human hepatocellular liver carcinoma cell line (Hep-G2) were studied and compared with those of free ligand. The anticancer cell line results reveal that all metal complexes show moderate to significant % cytotoxicity on cell line HepG2 and MCF-7. Copyright © 2015 Elsevier B.V. All rights reserved.

Biologically active Schiff bases containing thiophene/furan ring and their copper(II) complexes: Synthesis, spectral, nonlinear optical and density functional studies

NASA Astrophysics Data System (ADS)

Gündüzalp, Ayla Balaban; Özsen, İffet; Alyar, Hamit; Alyar, Saliha; Özbek, Neslihan

2016-09-01

Schiff bases; 1,8-bis(thiophene-2-carboxaldimine)-p-menthane (L1) and 1,8-bis(furan-2-carboxaldimine)-p-menthane (L2) have been synthesized and characterized by elemental analysis, 1Hsbnd 13C NMR, UV-vis, FT-IR and LC-MS methods. 1H and 13C shielding tensors for L1 and L2 were calculated with GIAO/DFT/B3LYP/6-311++G(d,p) methods in CDCl3. The vibrational band assignments, nonlinear optical (NLO) activities, frontier molecular orbitals (FMOs) and absorption spectrum have been investigated by the same basis set. Schiff base-copper(II) complexes have been synthesized and structurally characterized with spectroscopic methods, magnetic and conductivity measurements. The spectroscopic data suggest that Schiff base ligands coordinate through azomethine-N and thiophene-S/furan-O donors (as SNNS and ONNO chelating systems) to give a tetragonal geometry around the copper(II) ions. Schiff bases and Cu(II) complexes have been screened for their biological activities on different species of pathogenic bacteria, those are, Gram positive bacteria: Bacillus subtitilus, Yersinia enterotica, Bacillus cereus, Listeria monocytogenes, Micrococcus luteus and Gram negative bacteria: Escherichia coli, Pseudomonas aeroginosa, Shigella dysenteriae, Salmonella typhi, Klebsiella pseudomonas by using microdilution technique (MIC values in mM). Biological activity results show that Cu(II) complexes have higher activities than parent ligands and metal chelation may affect significantly the antibacterial behavior of the organic ligands.

Organic Materials as Electrodes for Li-ion Batteries

DTIC Science & Technology

2015-09-04

Various macrocycles, their synthesis, characterization and subsequent use in lithium - ion batteries were attempted. Ellagic acid, alizarin and...Various macrocycles, their synthesis, characterization and subsequent use in lithium - ion batteries were attempted. Ellagic acid, alizarin and...characterization and subsequent use in lithium - ion batteries have been attempted to. Lithium -based batteries are at the forefront of battery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richter, H.T.; Brown, L.S.; Lanyi, J.K.

Because asp-85 is the acceptor of the retinal Schiff base proton during light-driven proton transport by bacteriorhodopsin, modulation of its pK{sub a} in the photocycle is to be expected. The complex titration of asp-85 in the unphotolyzed protein was suggested to reflect the dependence of this residue on the protonation state of another, unidentified group. from the pH dependencies of the rate constant for the thermal equilibration of retinal isomeric states (dark adaptation) and the deprotonation kinetics of the Schiff base during the photocycle in the E204Q and E204D mutants, we identify the residue as glu-204. The nature of itsmore » interaction with our recent finding that glu-204 is the origin of the proton released to the extracellular surface upon protonation of asp-85 during that transport. We propose, therefore, that the following series of events occur in the photocycle. Protonation of asp-85 in the proton equilibrium with the Schiff base of the photoisomerized retinal results in the dissociation of glu-204 and proton release to the extracellular surface upon protonation of asp-85 during the transport. We propose, therefore, that the following series of events occur in the photocycle. Protonation of asp-85 in the proton equilibrium with the Schiff base shifts toward complete proton transfer. This constitutes the first phase of the reprotonation switch because it excludes asp-85 as a donor in the reprotonation of the Schiff base that follows. The sequential structural changes of the protein that ensue, detected earlier by diffraction, are suggested to facilitate the change of the access of the Schiff base toward the cytoplasmic side at the second phase of the switch, and the lowering the pK{sub a} of asp-96, so as to make it a proton donor, as the third phase. 77 refs., 6 figs.« less

FTIR study of the photoreaction of bovine rhodopsin in the presence of hydroxylamine.

PubMed

Katayama, Kota; Furutani, Yuji; Kandori, Hideki

2010-07-15

In bovine rhodopsin, 11-cis-retinal forms a Schiff base linkage with Lys296. The Schiff base is not reactive to hydroxylamine in the dark, which is consistent with the well-protected retinal binding site. In contrast, under illumination it easily forms all-trans retinal oxime, resulting in the loss of color. This suggests that activation of rhodopsin creates a specific reaction channel for hydroxylamine or loosens the chromophore binding pocket. In the present study, to extract structural information on the Schiff base vicinity and to understand the changes upon activation of rhodopsin, we compared light-induced FTIR difference spectra of bovine rhodopsin in the presence and absence of hydroxylamine under physiological pH (approximately 7). Although the previous FTIR study did not observe the complex formation between rhodopsin and G-protein transducin in hydrated films, the present study clearly shows that hydrated films can be used for studies of the interaction between rhodopsin and hydroxylamine. Hydroxylamine does not react with the Schiff base of Meta-I intermediate trapped at 240 K, possibly because of decreased conformational motions under the frozen environment, while FTIR spectroscopy showed that hydroxylamine affects the hydrogen bonds of the Schiff base and water molecules in Meta-I. In contrast, formation of the retinal oxime was clearly observed at 280 K, the characteristic temperature of Meta-II accumulation in the absence of hydroxylamine, and time-dependent formation of retinal oxime was observed from Meta-II at 265 K as well. The obtained difference FTIR spectra of retinal oxime and opsin are different from that of Meta-II. It is likely that the antiparallel beta-sheet constituting a part of the retinal binding pocket at the extracellular surface is structurally disrupted in the presence of hydroxylamine, which allows the hydrolysis of the Schiff base into retinal oxime.

Synthesis of novel macrocycles carrying pincer-type ligands as future candidates for potential applications in size-selective, stereochemical and recyclable catalysts

NASA Astrophysics Data System (ADS)

Khan, Burhan; Shah, Muhammad Raza; Rabnawaz, Muhammad

2018-03-01

Macrocycles with ultra dense functionalities are very useful but are difficult to synthesize. In this study, we report six novel macrocycles bearing a pincer ligand alone or a combination of pincer-calixarenes, and pincer-fluorene moieties. Click chemistry was utilized to synthesize the desired macrocycles in good yields. These macrocycles were fully characterized using mass spectrometry (EI-MS, ESI-MS, and MALDI-TOF MS), and NMR spectroscopy. These macrocycles are under investigations as size-selective and recyclable catalysts for various chemical transformations.

Enhanced liquid-liquid anion exchange using macrocyclic anion receptors: effect of receptor structure on sulphate-nitrate exchange selectivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moyer, Bruce A; Sloop Jr, Frederick; Fowler, Christopher J

2010-01-01

When certain macrocyclic anion receptors are added to a chloroform solution of the nitrate form of a lipophilic quaternary ammonium salt (methyltri-C8,10-ammonium nitrate, Aliquat 336N), the extraction of sulphate from an aqueous sodium nitrate solution via exchange with the organic-phase nitrate is significantly enhanced. Eight macrocycles were surveyed, including two derivatives of a tetraamide macrocycle, five derivatives of calix[4]pyrrole and -decafluorocalix[5]pyrrole. Under the hypothesis that the enhancement originates from sulphate binding by the anion receptors in the chloroform phase, it was possible to obtain reasonable fits to the sulphate distribution survey data based on the formation of 1:1 and 2:1more » receptor:sulphate complexes in the chloroform phase. Apparent 1:1 sulphate-binding constants obtained from the model in this system fell in the range . Comparison of the results for the various anion receptors included in this study reveals that sulphate binding is sensitive to the nature of the substituents on the parent macrocycle scaffolds in a way that does not follow straightforwardly from simple chemical expectations, such as electron-withdrawing effects on hydrogen-bond donor strength.« less

Synthesis, characterization and biological activity of some platinum(II) complexes with Schiff bases derived from salicylaldehyde, 2-furaldehyde and phenylenediamine.

PubMed

Gaballa, Akmal S; Asker, Mohsen S; Barakat, Atiat S; Teleb, Said M

2007-05-01

Four platinum(II) complexes of Schiff bases derived from salicylaldehyde and 2-furaldehyde with o- and p-phenylenediamine were reported and characterized based on their elemental analyses, IR and UV-vis spectroscopy and thermal analyses (TGA). The complexes were found to have the general formula [Pt(L)(H(2)O)(2)]Cl(2) x nH(2)O (where n=0 for complexes 1, 3, 4; n=1 for complex 2. The data obtained show that Schiff bases were interacted with Pt(II) ions in the neutral form as a bidentate ligand and the oxygens rather than the nitrogens are the most probable coordination sites. Square planar geometrical structure with two coordinated water molecules were proposed for all complexes The free ligands, and their metal complexes were screened for their antimicrobial activities against the following bacterial species: E. coli, B. subtilis, P. aereuguinosa, S. aureus; fungus A. niger, A. fluves; and the yeasts C. albican, S. cervisiea. The activity data show that the platinum(II) complexes are more potent antimicrobials than the parent Schiff base ligands against one or more microorganisms.

Synthesis and biological evaluation of histamine Schiff bases as carbonic anhydrase I, II, IV, VII, and IX activators.

PubMed

Akocak, Suleyman; Lolak, Nabih; Vullo, Daniela; Durgun, Mustafa; Supuran, Claudiu T

2017-12-01

A series of 20 histamine Schiff base was synthesised by reaction of histamine, a well known carbonic anhydrase (CA, E.C 4.2.2.1.) activator pharmacophore, with substituted aldehydes. The obtained histamine Schiff bases were assayed as activators of five selected human (h) CA isozymes, the cytosolic hCA I, hCA II, and hCA VII, the membrane-anchored hCA IV and transmembrane hCA IX. Some of these compounds showed efficient activity (in the nanomolar range) against the cytosolic isoform hCA VII, which is a key CA enzyme involved in brain metabolism. Moderate activity was observed against hCA I and hCA IV (in the nanomolar to low micromolar range). The structure-activity relationship for activation of these isoforms with the new histamine Schiff bases is discussed in detail based on the nature of the aliphatic, aromatic, or heterocyclic moiety present in the aldehyde fragment of the molecule, which may participate in diverse interactions with amino acid residues at the entrance of the active site, where activators bind, and which is the most variable part among the different CA isoforms.

Coordination behavior of new bis Schiff base ligand derived from 2-furan carboxaldehyde and propane-1,3-diamine. Spectroscopic, thermal, anticancer and antibacterial activity studies

NASA Astrophysics Data System (ADS)

Mohamed, Gehad G.; Zayed, Ehab M.; Hindy, Ahmed M. M.

2015-06-01

Novel bis Schiff base ligand, [N1,N3-bis(furan-2-ylmethylene)propane-1,3-diamine], was prepared by the condensation of furan-2-carboxaldehyde with propane-1,3-diamine. Its conformational changes on complexation with transition metal ions [Co(II), Ni(II), Cu(II), Mn(II), Cd(II), Zn(II) and Fe(III)] have been studied on the basis of elemental analysis, conductivity measurements, spectral (infrared, 1H NMR, electronic), magnetic and thermogravimetric studies. The conductance data of the complexes revealed their electrolytic nature suggesting them as 1:2 (for bivalent metal ions) and 1:3 (for Fe(III) ion) electrolytes. The complexes were found to have octahedral geometry based on magnetic moment and solid reflectance measurements. Thermal analysis data revealed the decomposition of the complexes in successive steps with the removal of anions, coordinated water and bis Schiff base ligand. The thermodynamic parameters were calculated using Coats-Redfern equation. The Anticancer screening studies were performed on human colorectal cancer (HCT), hepatic cancer (HepG2) and breast cancer (MCF-7) cell lines. The antimicrobial activity of all the compounds was studied against Gram negative (Escherichia coli and Proteus vulgaris) and Gram positive (Bacillus vulgaris and Staphylococcus pyogones) bacteria. It was observed that the coordination of metal ion has a pronounced effect on the microbial activities of the bis Schiff base ligand. All the metal complexes have shown higher antimicrobial effect than the free bis Schiff base ligand.

How Proteins Bind Macrocycles

PubMed Central

Villar, Elizabeth A.; Beglov, Dmitri; Chennamadhavuni, Spandan; Porco, John A.; Kozakov, Dima; Vajda, Sandor; Whitty, Adrian

2014-01-01

The potential utility of synthetic macrocycles as drugs, particularly against low druggability targets such as protein-protein interactions, has been widely discussed. There is little information, however, to guide the design of macrocycles for good target protein-binding activity or bioavailability. To address this knowledge gap we analyze the binding modes of a representative set of macrocycle-protein complexes. The results, combined with consideration of the physicochemical properties of approved macrocyclic drugs, allow us to propose specific guidelines for the design of synthetic macrocycles libraries possessing structural and physicochemical features likely to favor strong binding to protein targets and also good bioavailability. We additionally provide evidence that large, natural product derived macrocycles can bind to targets that are not druggable by conventional, drug-like compounds, supporting the notion that natural product inspired synthetic macrocycles can expand the number of proteins that are druggable by synthetic small molecules. PMID:25038790

Synthesis, X-ray crystallography, thermal studies, spectroscopic and electrochemistry investigations of uranyl Schiff base complexes.

PubMed

Asadi, Zahra; Shorkaei, Mohammad Ranjkesh

2013-03-15

Some tetradentate salen type Schiff bases and their uranyl complexes were synthesized and characterized by UV-Vis, NMR, IR, TG, C.H.N. and X-ray crystallographic studies. From these investigations it is confirmed that a solvent molecule occupied the fifth position of the equatorial plane of the distorted pentagonal bipyramidal structure. Also, the kinetics of complex decomposition by using thermo gravimetric methods (TG) was studied. The thermal decomposition reactions are first order for the studied complexes. To examine the properties of uranyl complexes according to the substitutional groups, we have carried out the electrochemical studies. The electrochemical reactions of uranyl Schiff base complexes in acetonitrile were reversible. Copyright © 2012 Elsevier B.V. All rights reserved.

Two novel macroacyclic schiff bases containing bis-N 2O 2 donor set and their binuclear complexes: synthesis, spectroscopic and magnetic properties

NASA Astrophysics Data System (ADS)

Karaoglu, Kaan; Baran, Talat; Serbest, Kerim; Er, Mustafa; Degirmencioglu, Ismail

2009-03-01

Herein, we report two novel macroacyclic Schiff bases derived from tetranaphthaldehyde derivative compound and their binuclear Mn(II), Ni(II), Cu(II) and Zn(II) complexes. The structures of the compounds have been proposed by elemental analyses, spectroscopic data i.e. IR, 1H and 13C NMR, UV-Vis, electrospray ionisation mass spectra, molar conductivities and magnetic susceptibility measurements. The stoichiometries of the complexes derived from mass and elemental analysis correspond to the general formula [M 2L(ClO 4) n](ClO 4) 4-n, (where M is Mn(II), Ni(II), Cu(II), Zn(II) and L represents the Schiff base ligands).

Antiaflatoxigenic and Antimicrobial Activities of Schiff Bases of 2-Hydroxy-4-methoxybenzaldehyde, Cinnamaldehyde, and Similar Aldehydes.

PubMed

Harohally, Nanishankar V; Cherita, Chris; Bhatt, Praveena; Anu Appaiah, K A

2017-10-11

2-Hydroxy-4-methoxybenzaldehyde (HMBA) is a nontoxic phenolic flavor from dietary source Decalipus hamiltonii and Hemidesmus indicus. HMBA is an excellent antimicrobial agent with additional antiaflatoxigenic potency. On the other hand, cinnamaldehyde from cinnamon is a widely employed flavor with significant antiaflatoxigenic activity. We have attempted the enhancement of antiaflatoxigenic and antimicrobial properties of HMBA, cinnamaldehyde, and similar molecules via Schiff base formation accomplished from condensation reaction with amino sugar (d-glucamine). HMBA derived Schiff bases exhibited commendable antiaflatoxigenic activity at the concentration 0.1 mg/mL resulting in 9.6 ± 1.9% growth of Aspergillus flavus and subsequent 91.4 ± 3.9% reduction of aflatoxin B 1 with respect to control.

Design of cinnamaldehyde amino acid Schiff base compounds based on the quantitative structure-activity relationship.

PubMed

Wang, Hui; Jiang, Mingyue; Li, Shujun; Hse, Chung-Yun; Jin, Chunde; Sun, Fangli; Li, Zhuo

2017-09-01

Cinnamaldehyde amino acid Schiff base (CAAS) is a new class of safe, bioactive compounds which could be developed as potential antifungal agents for fungal infections. To design new cinnamaldehyde amino acid Schiff base compounds with high bioactivity, the quantitative structure-activity relationships (QSARs) for CAAS compounds against Aspergillus niger ( A. niger ) and Penicillium citrinum (P. citrinum) were analysed. The QSAR models ( R 2  = 0.9346 for A. niger , R 2  = 0.9590 for P. citrinum, ) were constructed and validated. The models indicated that the molecular polarity and the Max atomic orbital electronic population had a significant effect on antifungal activity. Based on the best QSAR models, two new compounds were designed and synthesized. Antifungal activity tests proved that both of them have great bioactivity against the selected fungi.

Design of cinnamaldehyde amino acid Schiff base compounds based on the quantitative structure–activity relationship

PubMed Central

Wang, Hui; Jiang, Mingyue; Hse, Chung-Yun; Jin, Chunde; Sun, Fangli; Li, Zhuo

2017-01-01

Cinnamaldehyde amino acid Schiff base (CAAS) is a new class of safe, bioactive compounds which could be developed as potential antifungal agents for fungal infections. To design new cinnamaldehyde amino acid Schiff base compounds with high bioactivity, the quantitative structure–activity relationships (QSARs) for CAAS compounds against Aspergillus niger (A. niger) and Penicillium citrinum (P. citrinum) were analysed. The QSAR models (R2 = 0.9346 for A. niger, R2 = 0.9590 for P. citrinum,) were constructed and validated. The models indicated that the molecular polarity and the Max atomic orbital electronic population had a significant effect on antifungal activity. Based on the best QSAR models, two new compounds were designed and synthesized. Antifungal activity tests proved that both of them have great bioactivity against the selected fungi. PMID:28989758

Resonance raman spectroscopy of an ultraviolet-sensitive insect rhodopsin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pande, C.; Deng, H.; Rath, P.

1987-11-17

The authors present the first visual pigment resonance Raman spectra from the UV-sensitive eyes of an insect, Ascalaphus macaronius (owlfly). This pigment contains 11-cis-retinal as the chromophore. Raman data have been obtained for the acid metarhodopsin at 10/sup 0/C in both H/sub 2/O and D/sub 2/O. The C=N stretching mode at 1660 cm/sup -1/ in H/sub 2/O shifts to 1631 cm/sup -1/ upon deuteriation of the sample, clearly showing a protonated Schiff base linkage between the chromophore and the protein. The structure-sensitive fingerprint region shows similarities to the all-trans-protonated Schiff base of model retinal chromophores, as well as to themore » octopus acid metarhodopsin and bovine metarhodopsin I. Although spectra measured at -100/sup 0/C with 406.7-nm excitation, to enhance scattering from rhodopsin (lambda/sub max/ 345 nm), contain a significant contribution from a small amount of contaminants (cytochrome(s) and/or accessory pigment) in the sample, the C=N stretch at 1664 cm/sup -1/ suggests a protonated Schiff base linkage between the chromophore and the protein in rhodopsin as well. For comparison, this mode also appears at approx. 1660 cm/sup -1/ in both the vertebrate (bovine) and the invertebrate (octopus) rhodopsins. These data are particularly interesting since the absorption maximum of 345 nm for rhodopsin might be expected to originate from an unprotonated Schiff base linkage. That the Schiff base linkage in the owlfly rhodopsin, like in bovine and in octopus, is protonated suggests that a charged chromophore is essential to visual transduction.« less

Steric effects in the design of Co-Schiff base complexes for the catalytic oxidation of lignin models to para-benzoquinones

Treesearch

Berenger Biannic; Joseph J. Bozell; Thomas Elder

2014-01-01

New Co-Schiff base complexes that incorporate a sterically hindered ligand and an intramolecular bulky piperazine base in close proximity to the Co center are synthesized. Their utility as catalysts for the oxidation of para-substituted lignin model phenols with molecular oxygen is examined. Syringyl and guaiacyl alcohol, as models of S and G units in lignin, are...

Preparation of new Schiff bases derived from beta-enaminonitriles and hetarylcarboxaldehydes. Anti-inflammatory and ulcerogenic activities.

PubMed

Atta, S M; Ameen, A

1993-12-01

Schiff bases 3a-j were prepared by reacting the beta-enaminonitriles (1a,b) with the appropriate hetarylcarboxaldehyde, in boiling ethanol. Structural elucidations for the new compounds (3a-j) were based upon compatible analytical and spectroscopic results. Compounds 1a, 1b, 3a, 3c, 3d and 3i were tested for their anti-inflammatory and ulcerogenic activities.

The mechanism of the formation of the hemiaminal and Schiff base from the benzaldehyde and triazole studied by means of the topological analysis of electron localisation function and catastrophe theory

NASA Astrophysics Data System (ADS)

Berski, Slawomir; Zbigniew Ciunik, Leszek

2015-04-01

The mechanisms of reaction of benzaldehyde (ald) with 4-amine-4H-1,2,4-triazole (4at), leading to Schiff base (Sch) and water, were investigated using topological analysis of the electron localisation function and catastrophe theory. Two reactions (synthesis of hemiaminal and synthesis of Schiff base) are represented by one catastrophe sequence: ald+4at: 1-14-[FF†F†FFTS1FF†F†FF†F†CF†]-2-9-[C†FFTS3F†F†FFF]-0:Sch+H2O with only fold (F) and cusp (C) catastrophes. The first reaction, in which a molecule of the hemiaminal is formed, consists of 14 steps separated by 13 catastrophes. The mechanism is non-concerted. The covalent bond C-N is formed after the formation of the O-H bond is terminated. The Schiff base formation through the water molecule elimination in the second reaction requires nine steps with eight catastrophes. The mechanism is non-concerted because first the C-O bond is broken and then the proton transfer occurs that results in the O-H bond creation.

Synthesis and biological evaluation of novel aromatic and heterocyclic bis-sulfonamide Schiff bases as carbonic anhydrase I, II, VII and IX inhibitors.

PubMed

Akocak, Suleyman; Lolak, Nabih; Nocentini, Alessio; Karakoc, Gulcin; Tufan, Anzel; Supuran, Claudiu T

2017-06-15

A series of sixteen novel aromatic and heterocyclic bis-sulfonamide Schiff bases were prepared by conjugation of well known aromatic and heterocyclic aminosulfonamide carbonic anhydrase (CA, EC 4.2.1.1) inhibitor pharmacophores with aromatic and heterocyclic bis-aldehydes. The obtained bis-sulfonamide Schiff bases were investigated as inhibitors of four selected human (h) CA isoforms, hCA I, hCA II, hCA VII and hCA IX. Most of the newly synthesized compounds showed a good inhibitory profile against isoforms hCA II and hCA IX, also showing moderate selectivity against hCA I and VII. Several efficient lead compounds were identified among this bis-sulfonamide Schiff bases with low nanomolar to sub-nanomolar activity against hCA II (K i s ranging between 0.4 and 861.1nM) and IX (K i s between 0.5 and 933.6nM). Since hCA II and hCA IX are important drug targets (antiglaucoma and anti-tumor agents), these isoform-selective inhibitors may be considered of interest for various biomedical applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis and biological evaluation of novel 6-hydroxy-benzo[d][1,3]oxathiol-2-one Schiff bases as potential anticancer agents.

PubMed

Chazin, Eliza de Lucas; Sanches, Paola de Souza; Lindgren, Eric Brazil; Vellasco Júnior, Walcimar Trindade; Pinto, Laine Celestino; Burbano, Rommel Mario Rodríguez; Yoneda, Julliane Diniz; Leal, Kátia Zaccur; Gomes, Claudia Regina Brandão; Wardell, James Lewis; Wardell, Solange Maria Silva Veloso; Montenegro, Raquel Carvalho; Vasconcelos, Thatyana Rocha Alves

2015-01-27

With the aim of discovering new anticancer agents, we have designed and synthesized novel 6-hydroxy-benzo[d][1,3]oxathiol-2-one Schiff bases. The synthesis started with the selective nitration at 5-position of 6-hydroxybenzo[d][1,3]oxathiol-2-one (1) leading to the nitro derivative 2. The nitro group of 2 was reduced to give the amino intermediate 3. Schiff bases 4a-r were obtained from coupling reactions between 3 and various benzaldehydes and heteroaromatic aldehydes. All the new compounds were fully identified and characterized by NMR (1H and 13C) and specifically for 4q by X-ray crystallography. The in vitro cytotoxicity of the compounds was evaluated against cancer cell lines (ACP-03, SKMEL-19 and HCT-116) by using MTT assay. Schiff bases 4b and 4o exhibited promising cytotoxicity against ACP-03 and SKMEL-19, respectively, with IC50 values lower than 5 μM. This class of compounds can be considered as a good starting point for the development of new lead molecules in the fight against cancer.

Carbonic anhydrase inhibitors. Inhibition of human cytosolic isoforms I and II with (reduced) Schiff's bases incorporating sulfonamide, carboxylate and carboxymethyl moieties.

PubMed

Nasr, Gihane; Cristian, Alina; Barboiu, Mihail; Vullo, Daniella; Winum, Jean-Yves; Supuran, Claudiu T

2014-05-15

A library of Schiff bases was synthesized by condensation of aromatic amines incorporating sulfonamide, carboxylic acid or carboxymethyl functionalities as Zn(2+)-binding groups, with aromatic aldehydes incorporating tert-butyl, hydroxy and/or methoxy groups. The corresponding amines were thereafter obtained by reduction of the imines. These compounds were assayed for the inhibition of two cytosolic human carbonic anhydrase (hCA, EC 4.2.1.1) isoenzymes, hCA I and II. The Ki values of the Schiff bases were in the range of 7.0-21,400nM against hCA II and of 52-8600nM against hCA I, respectively. The corresponding amines showed Ki values in the range of 8.6nM-5.3μM against hCA II, and of 18.7-251nM against hCA I, respectively. Unlike the imines, the reduced Schiff bases are stable to hydrolysis and several low-nanomolar inhibitors were detected, most of them incorporating sulfonamide groups. Some carboxylates also showed interesting CA inhibitory properties. Such hydrosoluble derivatives may show pharmacologic applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

Strained Cyclophane Macrocycles: Impact of Progressive Ring Size Reduction on Synthesis and Structure

PubMed Central

Bogdan, Andrew R.; Jerome, Steven V.; Houk, K. N.; James, Keith

2012-01-01

The synthesis, X-ray crystal structures, and calculated strain energies are reported for a homologous series of 11- to 14-membered drug-like cyclophane macrocycles, representing an unusual region of chemical space that can be difficult to access synthetically. The ratio of macrocycle to dimer, generated via a copper catalyzed azide-alkyne cycloaddition macrocyclization in flow at elevated temperature, could be rationalized in terms of the strain energy in the macrocyclic product. The progressive increase in strain resulting from reduction in macrocycle ring size, or the introduction of additional conformational constraints, results in marked deviations from typical geometries. These strained cyclophane macrocyclic systems provide access to spatial orientations of functionality that would not be readily available in unstrained or acyclic analogs. The most strained system prepared represents the first report of an 11-membered cyclophane containing a 1,4-disubstituted 1,2,3-triazole ring, and establishes a limit to the ring strain that can be generated using this macrocycle synthesis methodology. PMID:22133103

Spectroscopic studies on two mono nuclear iron (III) complexes derived from a schiff base and an azodye

NASA Astrophysics Data System (ADS)

Mini, S.; Sadasivan, V.; Meena, S. S.; Bhatt, Pramod

2014-10-01

Two new mono nuclear Fe(III) complexes of an azodye (ANSN) and a Schiff base (FAHP) are reported. The azodye is prepared by coupling diazotized 1-amino-2-naphthol-4-sulphonicacid with 2-naphthol and the Schiff base is prepared by condensing 2-amino-3-hydroxy pyridine with furfural. The complexes were synthesized by the reaction of FeCl3˙2H2O with respective ligands. They were characterized on the basis of elemental analysis and spectral studies like IR, NMR, Electronic and M.ssbauer. Magnetic susceptibility and Molar conductance of complexes at room temperature were studied. Based on the spectroscopic evidences and other analytical data the complexes are formulated as[Fe(ANSN)Cl(H2O)2] and [Fe(FAHP)Cl2(H2O)2].

Development of a chemical strategy to produce rare aldohexoses from ketohexoses using 2-aminopyridine.

PubMed

Hasehira, Kayo; Miyanishi, Nobumitsu; Sumiyoshi, Wataru; Hirabayashi, Jun; Nakakita, Shin-ichi

2011-12-13

Rare sugars are monosaccharides that are found in relatively low abundance in nature. Herein, we describe a strategy for producing rare aldohexoses from ketohexoses using the classical Lobry de Bruyn-Alberda van Ekenstein transformation. Upon Schiff-base formation of keto sugars, a fluorescence-labeling reagent, 2-aminopyridine (2-AP), was used. While acting as a base catalyst, 2-AP efficiently promoted the ketose-to-aldose transformation, and acting as a Schiff-base reagent, it effectively froze the ketose-aldose equilibrium. We could also separate a mixture of Sor, Gul, and Ido in their Schiff-base forms using a normal-phase HPLC separation system. Although Gul and Ido represent the most unstable aldohexoses, our method provides a practical way to rapidly obtain these rare aldohexoses as needed. Copyright © 2011 Elsevier Ltd. All rights reserved.

One-Bead-Two-Compound Thioether Bridged Macrocyclic γ-AApeptide Screening Library against EphA2.

PubMed

Shi, Yan; Challa, Sridevi; Sang, Peng; She, Fengyu; Li, Chunpu; Gray, Geoffrey M; Nimmagadda, Alekhya; Teng, Peng; Odom, Timothy; Wang, Yan; van der Vaart, Arjan; Li, Qi; Cai, Jianfeng

2017-11-22

Identification of molecular ligands that recognize peptides or proteins is significant but poses a fundamental challenge in chemical biology and biomedical sciences. Development of cyclic peptidomimetic library is scarce, and thus discovery of cyclic peptidomimetic ligands for protein targets is rare. Herein we report the unprecedented one-bead-two-compound (OBTC) combinatorial library based on a novel class of the macrocyclic peptidomimetics γ-AApeptides. In the library, we utilized the coding peptide tags synthesized with Dde-protected α-amino acids, which were orthogonal to solid phase synthesis of γ-AApeptides. Employing the thioether linkage, the desired macrocyclic γ-AApeptides were found to be effective for ligand identification. Screening the library against the receptor tyrosine kinase EphA2 led to the discovery of one lead compound that tightly bound to EphA2 (K d = 81 nM) and potently antagonized EphA2-mediated signaling. This new approach of macrocyclic peptidomimetic library may lead to a novel platform for biomacromolecular surface recognition and function modulation.

Templated bilayer self-assembly of fully conjugated π-expanded macrocyclic oligothiophenes complexed with fullerenes

PubMed Central

Cojal González, José D.; Iyoda, Masahiko; Rabe, Jürgen P.

2017-01-01

Fully conjugated macrocyclic oligothiophenes exhibit a combination of highly attractive structural, optical and electronic properties, and multifunctional molecular thin film architectures thereof are envisioned. However, control over the self-assembly of such systems becomes increasingly challenging, the more complex the target structures are. Here we show a robust self-assembly based on hierarchical non-covalent interactions. A self-assembled monolayer of hydrogen-bonded trimesic acid at the interface between an organic solution and graphite provides host-sites for the epitaxial ordering of Saturn-like complexes of fullerenes with oligothiophene macrocycles in mono- and bilayers. STM tomography verifies the formation of the templated layers. Molecular dynamics simulations corroborate the conformational stability and assign the adsorption sites of the adlayers. Scanning tunnelling spectroscopy determines their rectification characteristics. Current–voltage characteristics reveal the modification of the rectifying properties of the macrocycles by the formation of donor–acceptor complexes in a densely packed all-self-assembled supramolecular nanostructure. PMID:28281557

Templated bilayer self-assembly of fully conjugated π-expanded macrocyclic oligothiophenes complexed with fullerenes

NASA Astrophysics Data System (ADS)

Cojal González, José D.; Iyoda, Masahiko; Rabe, Jürgen P.

2017-03-01

Fully conjugated macrocyclic oligothiophenes exhibit a combination of highly attractive structural, optical and electronic properties, and multifunctional molecular thin film architectures thereof are envisioned. However, control over the self-assembly of such systems becomes increasingly challenging, the more complex the target structures are. Here we show a robust self-assembly based on hierarchical non-covalent interactions. A self-assembled monolayer of hydrogen-bonded trimesic acid at the interface between an organic solution and graphite provides host-sites for the epitaxial ordering of Saturn-like complexes of fullerenes with oligothiophene macrocycles in mono- and bilayers. STM tomography verifies the formation of the templated layers. Molecular dynamics simulations corroborate the conformational stability and assign the adsorption sites of the adlayers. Scanning tunnelling spectroscopy determines their rectification characteristics. Current-voltage characteristics reveal the modification of the rectifying properties of the macrocycles by the formation of donor-acceptor complexes in a densely packed all-self-assembled supramolecular nanostructure.

A general strategy for synthesis of cyclophane-braced peptide macrocycles via palladium-catalysed intramolecular sp3 C-H arylation

NASA Astrophysics Data System (ADS)

Zhang, Xuekai; Lu, Gang; Sun, Meng; Mahankali, Madhu; Ma, Yanfei; Zhang, Mingming; Hua, Wangde; Hu, Yuting; Wang, Qingbing; Chen, Jinghuo; He, Gang; Qi, Xiangbing; Shen, Weijun; Liu, Peng; Chen, Gong

2018-05-01

New methods capable of effecting cyclization, and forming novel three-dimensional structures while maintaining favourable physicochemical properties are needed to facilitate the development of cyclic peptide-based drugs that can engage challenging biological targets, such as protein-protein interactions. Here, we report a highly efficient and generally applicable strategy for constructing new types of peptide macrocycles using palladium-catalysed intramolecular C(sp3)-H arylation reactions. Easily accessible linear peptide precursors of simple and versatile design can be selectively cyclized at the side chains of either aromatic or modified non-aromatic amino acid units to form various cyclophane-braced peptide cycles. This strategy provides a powerful tool to address the long-standing challenge of size- and composition-dependence in peptide macrocyclization, and generates novel peptide macrocycles with uniquely buttressed backbones and distinct loop-type three-dimensional structures. Preliminary cell proliferation screening of the pilot library revealed a potent lead compound with selective cytotoxicity toward proliferative Myc-dependent cancer cell lines.

Prolinimines: N-Amino-l-Pro-methyl Ester (Hydrazine) Schiff Bases from a Fish Gastrointestinal Tract-Derived Fungus, Trichoderma sp. CMB-F563.

PubMed

Mohamed, Osama G; Khalil, Zeinab G; Capon, Robert J

2018-01-19

A rice cultivation of a fish gastrointestinal tract-derived fungus, Trichoderma sp. CMB-F563, yielded natural products incorporating a rare hydrazine moiety, embedded within a Schiff base. Structures inclusive of absolute configurations were assigned to prolinimines A-D (1-4) on the basis of detailed spectroscopic and C 3 Marfey's analysis, as well as biosynthetic considerations, biomimetic total synthesis, and chemical transformations. Of note, monomeric 1 proved to be acid labile and, during isolation, underwent quantitative transformation to dimeric 3 and trimeric 4. Prolinimines are only the second reported natural products incorporating an N-amino-Pro residue, the first to include l-Pro, the first to occur as Schiff bases, and the first to be isolated from a microorganism.

Synthesis and characterization of a novel schiff base of 1,2-diaminopropane with substituted salicyaldehyde and its transition metal complexes: Single crystal structures and biological activities

NASA Astrophysics Data System (ADS)

Tadavi, Samina K.; Yadav, Abhijit A.; Bendre, Ratnamala S.

2018-01-01

A novel schiff base H2L derived from simple condensation of 2-hydroxy-6-isopropyl-3-methyl benzaldehyde and 1,2-diaminopropane in 2:1 M ratio and its [MnL], [CoL] and [NiL]2 complexes have been prepared and characterized by spectroscopic technique, elemental analysis, SEM-EDX analysis, and cyclic voltammetry. Additionally, single crystal X-ray diffraction technique has been applied to the schiff base ligand H2L and its nickel complex. The structure of nickel complex exhibited dimeric form with formula [NiL]2 with distorted square planar geometry around each nickel center. Furthermore, all the synthesized compounds were screened for their antimicrobial and antioxidant and DNA cleavage activities.

Synthesis, characterization and biological properties of thienyl derived triazole Schiff bases and their oxovanadium(IV) complexes.

PubMed

Chohan, Zahid H; Sumrra, Sajjad H

2012-04-01

A new series of biologically active thienyl derived triazole Schiff bases and their oxovanadium(IV) complexes have been synthesized and characterized on the basis of physical (m.p., magnetic susceptibility and conductivity), spectral (IR, ¹H and ¹³C NMR, electronic and mass spectrometry) and microanalytical data. All the Schiff base ligands and their oxovanadium(IV) complexes have been subjected to in vitro antibacterial activity against four Gram-negative (Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa, Salmonella enterica serover typhi) and two Gram-positive (Staphylococcus aureus and Bacillus subtilis) bacterial strains and, for in vitro antifungal activity against Trichophyton longifucus, Candida albican, Aspergillus flavus, Microscopum canis, Fusarium solani and Candida glabrata. Brine shrimp bioassay was also carried out to check the cytotoxic nature of these compounds.

Novel polymer anchored Cr(III) Schiff base complexes: Synthesis, characterization and antimicrobial properties

NASA Astrophysics Data System (ADS)

Selvi, Canan; Nartop, Dilek

2012-09-01

New polymer-bound Schiff bases and Cr(III) complexes have been synthesized by the reaction of 4-benzyloxybenzaldehyde, polymer-bound with 2-aminophenol, 2-amino-4-chlorophenol and 2-amino-4-methylphenol. The structure of polymeric-Schiff bases and their Cr(III) complexes have been characterized by elemental analyses, magnetic measurements, IR, UV-Vis, TG-DTA and 1H-NMR. All these compounds have also been investigated for antibacterial activity by the well-diffusion method against Staphylococcus aureus (RSKK-07035), Shigella dysenteria type 10 (RSKK 1036), Listeria monocytogenes 4b(ATCC 19115, Escherichia coli (ATCC 1230), Salmonella typhi H (NCTC 901.8394), Staphylococcus epidermis (ATCC 12228), Brucella abortus (RSKK-03026), Micrococcs luteus (ATCC 93419, Bacillus cereus sp., Pseudomonas putida sp. and for antifungal activity against Candida albicans (Y-1200-NIH).

Synthesis, spectroscopic characterization and pH dependent photometric and electrochemical fate of Schiff bases.

PubMed

Rauf, Abdur; Shah, Afzal; Abbas, Saghir; Rana, Usman Ali; Khan, Salah Ud-Din; Ali, Saqib; Zia-Ur-Rehman; Qureshi, Rumana; Kraatz, Heinz-Bernhard; Belanger-Gariepy, Francine

2015-03-05

A new Schiff base, 1-((4-bromophenylimino) methyl) naphthalen-2-ol (BPIMN) was successfully synthesized and characterized by (1)H NMR, (13)C NMR, FTIR and UV-Vis spectroscopy. The results were compared with a structurally related Schiff base, 1-((4-chlorophenylimino) methyl) naphthalen-2-ol (CPIMN). The photometric and electrochemical fate of BPIMN and CPIMN was investigated in a wide pH range. The experimental findings were supported by quantum mechanical approach. The redox mechanistic pathways were proposed on the basis of results obtained electrochemical techniques. Moreover, pH dependent UV-Vis spectroscopy of BPIMN and CPIMN was carried out and the appearance of isosbestic points indicated the existence of these compounds in different tautomeric forms. Copyright © 2014 Elsevier B.V. All rights reserved.

Specific Inhibition of the transcription factor Ci by a Cobalt(III)-Schiff base-DNA conjugate

PubMed Central

Hurtado, Ryan R.; Harney, Allison S.; Heffern, Marie C.; Holbrook, Robert J.; Holmgren, Robert A.; Meade, Thomas J.

2012-01-01

We describe the use of Co(III) Schiff base-DNA conjugates, a versatile class of research tools that target C2H2 transcription factors, to inhibit the Hedgehog (Hh) pathway. In developing mammalian embryos, Hh signaling is critical for the formation and development of many tissues and organs. Inappropriate activation of the Hedgehog (Hh) pathway has been implicated in a variety of cancers including medulloblastomas and basal cell carcinomas. It is well known that Hh regulates the activity of the Gli family of C2H2 zinc finger transcription factors in mammals. In Drosophila the function of the Gli proteins is performed by a single transcription factor with an identical DNA binding consensus sequence, Cubitus Interruptus (Ci). We have demonstrated previously that conjugation of a specific 17 base-pair oligonucleotide to a Co(III) Schiff base complex results in a targeted inhibitor of the Snail family C2H2 zinc finger transcription factors. Modification of the oligonucleotide sequence in the Co(III) Schiff base-DNA conjugate to that of Ci’s consensus sequence (Co(III)-Ci) generates an equally selective inhibitor of Ci. Co(III)-Ci irreversibly binds the Ci zinc finger domain and prevents it from binding DNA in vitro. In a Ci responsive tissue culture reporter gene assay, Co(III)-Ci reduces the transcriptional activity of Ci in a concentration dependent manner. In addition, injection of wild-type Drosophila embryos with Co(III)-Ci phenocopies a Ci loss of function phenotype, demonstrating effectiveness in vivo. This study provides evidence that Co(III) Schiff base-DNA conjugates are a versatile class of specific and potent tools for studying zinc finger domain proteins and have potential applications as customizable anti-cancer therapeutics. PMID:22214326

Microscale Synthesis, Reactions, and (Super 1)H NMR Spectroscopic Investigations of Square Planar Macrocyclic, Tetramido-N Co(III) Complexes Relevant to Green Chemistry

ERIC Educational Resources Information Center

Watson, Tanya T.; Uffelman, Erich S.; Lee, Daniel W., III; Doherty, Jonathan R.; Schulze, Carl; Burke, Amy L.; Bonnema, Kristen, R.

2004-01-01

The microscale preparation, characterization, and reactivity of a square planar Co(III) complex that has grown out of a program to introduce experiments of relevance to green chemistry into the undergraduate curriculum is presented. The given experiments illustrate the remarkable redox and aqueous acid-base stability that make the macrocycles very…

Organic Materials as Electrodes for Li-ion Batteries

DTIC Science & Technology

2015-09-04

given for each class of materials. Various macrocycles, their synthesis, characterization and subsequent use in lithium - ion batteries were attempted...macrocycles, their synthesis, characterization and subsequent use in lithium - ion batteries have been attempted to. Lithium -based batteries are at the...organic dye can be used for storing reversibly, both lithium and sodium ions for rechargeable battery applications. In the present study, we have

Biodegradable polyester-based eco-composites containing hemp fibers modified with macrocyclic oligomers

NASA Astrophysics Data System (ADS)

Conzatti, Lucia; Utzeri, Roberto; Hodge, Philip; Stagnaro, Paola

2016-05-01

An original compatibilizing pathway for hemp fibers/poly(1,4-butylene adipate-co-terephtalate) (PBAT) eco-composites was explored exploiting the capability of macrocyclic oligomers (MCOs), obtained by cyclodepolymerization (CDP) of PBAT at high dilution, of being re-converted into linear chains by entropically-driven ring-opening polymerization (ED-ROP) that occurs simply heating the MCOS in the bulk. CDP reaction of PBAT was carried out varying solvent, catalyst and reaction time. Selected MCOs were used to adjust the conditions of the ED-ROP reaction. The best experimental conditions were then adopted to modify hemp fibers. Eco-composites based on PBAT and hemp fibers as obtained or modified with PBAT macrocyclics or oligomers were prepared by different process strategies. The best fiber-PBAT compatibility was observed when the fibers were modified with PBAT oligomers before incorporation in the polyester matrix.

Solar Thermal Energy Storage in a Photochromic Macrocycle.

PubMed

Vlasceanu, Alexandru; Broman, Søren L; Hansen, Anne S; Skov, Anders B; Cacciarini, Martina; Kadziola, Anders; Kjaergaard, Henrik G; Mikkelsen, Kurt V; Nielsen, Mogens Brøndsted

2016-07-25

The conversion and efficient storage of solar energy is recognized to hold significant potential with regard to future energy solutions. Molecular solar thermal batteries based on photochromic systems exemplify one possible technology able to harness and apply this potential. Herein is described the synthesis of a macrocycle based on a dimer of the dihydroazulene/vinylheptafulvene (DHA/VHF) photo/thermal couple. By taking advantage of conformational strain, this DHA-DHA macrocycle presents an improved ability to absorb and store incident light energy in chemical bonds (VHF-VHF). A stepwise energy release over two sequential ring-closing reactions (VHF→DHA) combines the advantages of an initially fast discharge, hypothetically addressing immediate energy consumption needs, followed by a slow process for consistent, long-term use. This exemplifies another step forward in the molecular engineering and design of functional organic materials towards solar thermal energy storage and release. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis, structure elucidation, biological screening, molecular modeling and DNA binding of some Cu(II) chelates incorporating imines derived from amino acids

NASA Astrophysics Data System (ADS)

Abdel-Rahman, Laila H.; Abu-Dief, Ahmed M.; Ismael, Mohammed; Mohamed, Mounir A. A.; Hashem, Nahla Ali

2016-01-01

Three tridentate Schiff bases amino acids were prepared by direct condensation of 3-methoxysalicylaldehyde (MS) or 4-diethylaminosalicylaldehyde (DS) with α-amino acid ligands [L-phenylalanine (P), L-histidine (H) and DL-tryptophan (T)]. The prepared Schiff bases amino acids were investigated by melting points, elemental analysis, 1HNMR and 13CNMR, IR, UV-Vis spectra, conductivity and magnetic measurements analyses. Subsequently, copper was introduced and Cu(II) complexes formed. These complexes were analyzed by thermal and elemental analyses and further investigated by FT-IR and UV/Vis spectroscopies. The experimental results indicating that all Cu(II) complexes contain hydrated water molecules (except DSPCu complex) and don't contain coordinated water molecules. The kinetic and thermal parameters were extracted from the thermal data using Coast and Redfern method. The molar conductance values of the Schiff base amino acid ligands and their Cu(II) complexes were relatively low, showing that these compounds have non-electrolytic nature. Magnetic susceptibility measurements showed the diamagnetic nature of the Schiff base amino acid ligands and paramagnetic nature of their complexes. Additionally, a spectrophotometric method was determined to extract their stability constants. It was found that the complexes possess 1:2 (M:L) stoichiometry. The results suggested that 3-methoxysalicylaldehyde and 4-diethylaminosalicylaldehyde amino acid Schiff bases behave as monobasic tridentate ONO ligands and coordinate Cu(II) ions in octahedral geometry according to the general formula [Cu(HL)2]·nH2O. To further understanding the structural and electronic properties of these complexes, Density Functional Theory (DFT) calculations were employed and provided a satisfactory description. The optimized structures of MST Schiff base ligand and its complex were calculated using DFT. The antimicrobial activity of the Schiff base ligands and their complexes were screened against some types of bacteria such as Bacillus subtilis (+ve), Escherichia coli (-ve) and Micrococcus luteus (+ve) and some types of fungi such as Asperagillus niger, Candida glabrata and Saccharomyces cerevisiae. The results of these studies indicated that the metal complexes exhibit a stronger antibacterial and antifungal efficiency compared to their corresponding ligands. The complexes were screened for antiviral activity against a panel of DNA and RNA viruses. Minimum cytotoxic and minimum virus inhibitory concentrations of these complexes were determined. The mode of interaction between complexes and CT-DNA was monitored using absorption spectra, viscosity measurements and gel electrophoreses.

Intraindividual Analysis of Signal Intensity Changes in the Dentate Nucleus After Consecutive Serial Applications of Linear and Macrocyclic Gadolinium-Based Contrast Agents.

PubMed

Radbruch, Alexander; Weberling, Lukas D; Kieslich, Pascal J; Hepp, Johanna; Kickingereder, Philipp; Wick, Wolfgang; Schlemmer, Heinz-Peter; Bendszus, Martin

2016-11-01

Recent studies reported an increase in the dentate nucleus (DN)-to-pons signal intensity (SI) ratio (DN-pons SI ratio) on unenhanced T1-weighted images in patients who received consecutive serial injections of linear gadolinium-based contrast agents (GBCAs). In contrast, most studies found no increase in the DN-pons SI ratio when patients were treated with consecutive serial injections of macrocyclic GBCAs. However, the potential difference between macrocyclic and linear GBCAs has never been assessed in individuals who received subsequent applications of both contrast agents. In this retrospective study, we assessed the evolution of the DN-pons SI ratio change in patients that were treated with a comparable number of serial consecutive injections of the linear GBCA gadopentetate dimeglumine and subsequent serial injections of the macrocyclic GBCAs gadobutrol and gadoterate meglumine. Data of 36 patients was analyzed. All patients underwent at least 5 consecutive administrations of the linear GBCA gadopentetate dimeglumine followed by an equal number of consecutive administrations of the macrocyclic GBCA gadobutrol. In 12 of the 36 patients, 5 or more final consecutive injections of the macrocyclic GBCA gadoterate meglumine were analyzed additionally. The difference of DN-pons SI ratios on unenhanced T1-weighted images was calculated by subtracting the ratio at the first examination from the ratio at the last examination in each of the 3 periods. The mean DN-pons SI ratio difference in the gadopentetate dimeglumine period was significantly greater than 0 (mean ± SD, 0.0448 ± 0.0345; P < 0.001), whereas the mean DN-pons SI ratio difference in the subsequent gadobutrol and gadoterate meglumine period was significantly smaller than 0 (gadobutrol: -0.0178 ± 0.0459, P = 0.026; gadoterate meglumine: -0.0250 ± 0.0284, P = 0.011). In this observational study, the application of the linear GBCA gadopentetate dimeglumine was associated with a DN-pons SI ratio increase, whereas subsequent applications of the macrocyclic GBCAs gadobutrol or gadoterate meglumine in the same patients were not. Rather, the current data tentatively suggest a decrease in preexisting hyperintensities over time when linear GBCAs are changed to macrocyclic GBCAs, potentially indicating a washout effect or precipitation of gadolinium. Future patient studies need to include control groups to replicate the present results, and additional animal studies should be conducted to clarify the underlying mechanism of the proposed SI decrease.

Bambus[n]urils: a new family of macrocyclic anion receptors.

PubMed

Havel, Vaclav; Svec, Jan; Wimmerova, Michaela; Dusek, Michal; Pojarova, Michaela; Sindelar, Vladimir

2011-08-05

A recently discovered anion receptor is jointed by three related macrocycles differing in the number of glycoluril units and type of substitution. The synthesis is carried out in nonpolar solvents compared to aqueous media used in the case of the original macrocycle. The size of macrocycle is controlled by a template. A hexameric macrocycle with benzyl substitution binds halide anions with an affinity exceeding 10(9) M(-1) while a tetrameric analog does not bind any of the investigated anions. © 2011 American Chemical Society

Synthesis and Degradation of Schiff Bases Containing Heterocyclic Pharmacophore

PubMed Central

Ledeţi, Ionuţ; Alexa, Anda; Bercean, Vasile; Vlase, Gabriela; Vlase, Titus; Şuta, Lenuţa-Maria; Fuliaş, Adriana

2015-01-01

This paper reports on the synthesis and characterization of two Schiff bases bearing 1,2,4-triazolic moieties, namely 4H-4-(2-hydroxy-benzylidene-amino)-5-benzyl-3-mercapto-1,2,4-triazole and 4H-4-(4-nitro-benzylidene-amino)-5-benzyl-3-mercapto-1,2,4-triazole using thin layer chromatography, melting interval, elemental analysis, spectroscopy and thermal stability studies. PMID:25590299

Origin of SMM behaviour in an asymmetric Er(III) Schiff base complex: a combined experimental and theoretical study.

PubMed

Das, Chinmoy; Upadhyay, Apoorva; Vaidya, Shefali; Singh, Saurabh Kumar; Rajaraman, Gopalan; Shanmugam, Maheswaran

2015-04-11

An asymmetric erbium(III) Schiff base complex [Er(HL)2(NO3)3] was synthesized which shows SMM behaviour with an Ueff of 5.2 K. Dipolar interaction in 1 significantly reduced upon dilution which increases the barrier height to 51.5 K. Ab initio calculations were performed to shed light on the mechanism of magnetization relaxation.

Preparation of macrocycles with high carbon content: Toward the synthesis of endohedral metal fullerene complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, T.C.; Rubin, Y.

1995-12-31

This research is focused on the synthesis of macrocycles with high carbon content for the purpose of total synthesis of fullerenes or fullerene-like structures with the ultimate goal of obtaining endohedral metal complexes of fullerene C{sub 60}. Toward this goal, the authors have utilized organometallic chemistry to synthesize novel cyclophanes such as 1 which are constituted primarily of acetylenic units. The authors believe such macrocycles may be C{sub 60} precursors since studies have shown that acetylenic macrocycles form fullerenes in the gas phase. The authors have synthesized macrocycle 1 using a highly convergent route from commercially available starting materials. Themore » macrocycle 1 is produced from copper (I) catalyzed coupling of 2 which is obtained in turn by the coupling of the copper acetylide 3 with 4. The suitability of macrocycles such as 1 for fullerene precursors is currently under investigation.« less

Topical cream-based dosage forms of the macrocyclic drug delivery vehicle cucurbit[6]uril.

PubMed

Seif, Marian; Impelido, Michael L; Apps, Michael G; Wheate, Nial J

2014-01-01

The macrocycle family of molecules called cucurbit[n]urils are potential drug delivery vehicles as they are able to form host-guest complexes with many different classes of drugs. This study aimed to examine the utility of Cucurbit[6]uril (CB[6]) in topical cream-based formulations for either localised treatment or for transdermal delivery. Cucurbit[6]uril was formulated into both buffered cream aqueous- and oily cream-based dosage forms. The solid state interaction of CB[6] with other excipients was studied by differential scanning calorimetry and the macrocycle's transdermal permeability was determined using rat skin. Significant solid state interactions were observed between CB[6] and the other dosage form excipients. At concentrations up to 32% w/w the buffered aqueous cream maintained its normal consistency and could be effectively applied to skin, but the oily cream was too stiff and is not suitable as a dosage form. Cucurbit[6]uril does not permeate through skin; as such, the results imply that cucurbituril-based topical creams may potentially only have applications for localised skin treatment and not for transdermal drug delivery.

Topical Cream-Based Dosage Forms of the Macrocyclic Drug Delivery Vehicle Cucurbit[6]uril

PubMed Central

Seif, Marian; Impelido, Michael L.; Apps, Michael G.; Wheate, Nial J.

2014-01-01

The macrocycle family of molecules called cucurbit[n]urils are potential drug delivery vehicles as they are able to form host-guest complexes with many different classes of drugs. This study aimed to examine the utility of Cucurbit[6]uril (CB[6]) in topical cream-based formulations for either localised treatment or for transdermal delivery. Cucurbit[6]uril was formulated into both buffered cream aqueous- and oily cream-based dosage forms. The solid state interaction of CB[6] with other excipients was studied by differential scanning calorimetry and the macrocycle's transdermal permeability was determined using rat skin. Significant solid state interactions were observed between CB[6] and the other dosage form excipients. At concentrations up to 32% w/w the buffered aqueous cream maintained its normal consistency and could be effectively applied to skin, but the oily cream was too stiff and is not suitable as a dosage form. Cucurbit[6]uril does not permeate through skin; as such, the results imply that cucurbituril-based topical creams may potentially only have applications for localised skin treatment and not for transdermal drug delivery. PMID:24454850

Synthesis, Spectral, and In Vitro Antibacterial Studies of Organosilicon(IV) Complexes with Schiff Bases Derived from Amino Acids.

PubMed

Singh, Har Lal; Singh, Jangbhadur; Mukherjee, A

2013-01-01

The present work stems from our interest in the synthesis, characterization, and antibacterial evaluation of organosilicon(IV) complexes of a class of amino-acid-based Schiff base which have been prepared by the interaction of ethoxytrimethylsilane with the Schiff bases (N OH) in 1 : 1 molar ratio. These complexes have been characterized by elemental analysis, molar conductance, and spectroscopic studies including electronic IR and NMR ((1)H, (13)C, and (29)Si) spectroscopy. The analytical and spectral data suggest trigonal bipyramidal geometry around the silicon atom in the resulting complexes. The ligands and their organosilicon complexes have also been evaluated for in vitro antimicrobial activity against bacteria (Bacillus cereus, Nocardia spp., E. aerogenes, Escherichia coli, Klebsiella spp., and Staphylococcus spp.). The complexes were found to be more potent as compared to the ligands.

Unusual saccharin-N,O (carbonyl) coordination in mixed-ligand copper(II) complexes: Synthesis, X-ray crystallography and biological activity

NASA Astrophysics Data System (ADS)

Mokhtaruddin, Nur Shuhada Mohd; Yusof, Enis Nadia Md; Ravoof, Thahira B. S. A.; Tiekink, Edward R. T.; Veerakumarasivam, Abhi; Tahir, Mohamed Ibrahim Mohamed

2017-07-01

Three tridentate Schiff bases containing N and S donor atoms were synthesized via the condensation reaction between S-2-methylbenzyldithiocarbazate with 2-acetyl-4-methylpyridine (S2APH); 4-methyl-3-thiosemicarbazide with 2-acetylpyridine (MT2APH) and 4-ethyl-3-thiosemicarbazide with 2-acetylpyridine (ET2APH). Three new, binuclear and mixed-ligand copper(II) complexes with the general formula, [Cu(sac)(L)]2 (sac = saccharinate anion; L = anion of the Schiff base) were then synthesized, and subsequently characterized by IR and UV/Vis spectroscopy as well as by molar conductivity and magnetic susceptibility measurements. The Schiff bases were also spectroscopically characterized using NMR and MS to further confirm their structures. The spectroscopic data indicated that the Schiff bases behaved as a tridentate NNS donor ligands coordinating via the pyridyl-nitrogen, azomethine-nitrogen and thiolate-sulphur atoms. Magnetic data indicated a square pyramidal environment for the complexes and the conductivity values showed that the complexes were essentially non-electrolytes in DMSO. The X-ray crystallographic analysis of one complex, [Cu(sac)(S2AP)]2 showed that the Cu(II) atom was coordinated to the thiolate-S, azomethine-N and pyridyl-N donors of the S2AP Schiff base and to the saccharinate-N from one anion, as well as to the carbonyl-O atom from a symmetry related saccharinate anion yielding a centrosymmetric binuclear complex with a penta-coordinate, square pyramidal geometry. All the copper(II) saccharinate complexes were found to display strong cytotoxic activity against the MCF-7 and MDA-MB-231 human breast cancer cell lines.

Sensitized terbium(III) macrocyclic-phthalimide complexes as luminescent pH switches.

PubMed

Chen, Gaoyun; Wardle, Nicholas J; Sarris, Jason; Chatterton, Nicholas P; Bligh, S W Annie

2013-10-21

Four new macrocyclic-phthalimide ligands were synthesised via the coupling of N-(3-bromopropyl)phthalimide either to cyclen (1,4,7,10-tetraazacyclododecane) itself or its carboxylate-functionalized analogues, and photophysical studies were carried out on their corresponding Tb(III) complexes in aqueous media as a function of pH. Luminescence intensities of Tb·L1a–Tb·L3a were in ‘switched off’ mode under acidic conditions (pH < 4), and were activated on progression to basic conditions as the phthalimido functions therein were hydrolysed to their corresponding phthalamates Tb·L1b–Tb·L3b. Emission of phthalamate-based macrocyclic Tb(III) complexes Tb·L1b–Tb·L3b was in ‘switched on’ mode between pH 4 and 11, exhibiting high quantum yields (Φ) and long lifetimes (τ) of the order of milliseconds at pH ~ 6. Tb(III) emissions were found to decline with increasing number of chromophores. The values of Φ and τ were 46% and 2.4 ms respectively for Tb·L1b at pH ~ 6 when activated. This is the best pH-dependent sensor based on a Tb(III) complex reported to date, benefiting from the macrocyclic architecture of the ligand.

Discovery of (10 R )-7-Amino-12-fluoro-2,10,16-trimethyl-15-oxo-10,15,16,17-tetrahydro- 2H -8,4-(metheno)pyrazolo[4,3- h ][2,5,11]-benzoxadiazacyclotetradecine-3-carbonitrile (PF-06463922), a Macrocyclic Inhibitor of Anaplastic Lymphoma Kinase (ALK) and c-ros Oncogene 1 (ROS1) with Preclinical Brain Exposure and Broad-Spectrum Potency against ALK-Resistant Mutations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Ted W.; Richardson, Paul F.; Bailey, Simon

2014-06-12

Although crizotinib demonstrates robust efficacy in anaplastic lymphoma kinase (ALK)-positive non-small-cell lung carcinoma patients, progression during treatment eventually develops. Resistant patient samples revealed a variety of point mutations in the kinase domain of ALK, including the L1196M gatekeeper mutation. In addition, some patients progress due to cancer metastasis in the brain. Using structure-based drug design, lipophilic efficiency, and physical-property-based optimization, highly potent macrocyclic ALK inhibitors were prepared with good absorption, distribution, metabolism, and excretion (ADME), low propensity for p-glycoprotein 1-mediated efflux, and good passive permeability. These structurally unusual macrocyclic inhibitors were potent against wild-type ALK and clinically reported ALK kinasemore » domain mutations. Significant synthetic challenges were overcome, utilizing novel transformations to enable the use of these macrocycles in drug discovery paradigms. This work led to the discovery of 8k (PF-06463922), combining broad-spectrum potency, central nervous system ADME, and a high degree of kinase selectivity.« less

How vertebrate and invertebrate visual pigments differ in their mechanism of photoactivation

PubMed Central

Nakagawa, Masashi; Iwasa, Tatsuo; Kikkawa, Satoshi; Tsuda, Motoyuki; Ebrey, Thomas G.

1999-01-01

In vertebrate visual pigments, a glutamic acid serves as a negative counterion to the positively charged chromophore, a protonated Schiff base of retinal. When photoisomerization leads to the Schiff base deprotonating, the anionic glutamic acid becomes protonated, forming a neutral species that activates the visual cascade. We show that in octopus rhodopsin, the glutamic acid has no anionic counterpart. Thus, the “counterion” is already neutral, so no protonated form of an initially anionic group needs to be created to activate. This helps to explain another observation—that the active photoproduct of octopus rhodopsin can be formed without its Schiff base deprotonating. In this sense, the mechanism of light activation of octopus rhodopsin is simpler than for vertebrates, because it eliminates one of the steps required for vertebrate rhodopsins to achieve their activating state. PMID:10339563

Synthesis and antimicrobial activities of new higher amino acid Schiff base derivatives of 6-aminopenicillanic acid and 7-aminocephalosporanic acid

NASA Astrophysics Data System (ADS)

Özdemir (nee Güngör), Özlem; Gürkan, Perihan; Özçelik, Berrin; Oyardı, Özlem

2016-02-01

Novel β-lactam derivatives (1c-3c) (1d-3d) were produced by using 6-aminopenicillanic acid (6-APA), 7-aminocephalosporanic acid (7-ACA) and the higher amino acid Schiff bases. The synthesized compounds were characterized by elemental analysis, IR, 1H/13C NMR and UV-vis spectra. Antibacterial activities of all the higher amino acid Schiff bases (1a-3a) (1b-3b) and β-lactam derivatives were screened against three gram negative bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Acinetobacter baumannii RSKK 02026), three gram positive bacteria (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 07005, Bacillus subtilis ATCC 6633) and their drug-resistant isolates by using broth microdilution method. Two fungi (Candida albicans and Candida krusei) were used for antifungal activity.

Diorganotin(IV) complexes of biologically potent 4(3H)-quinazolinone derived Schiff bases: synthesis, spectroscopic characterization, DNA interaction studies and antimicrobial activity.

PubMed

Prasad, Kollur Shiva; Kumar, Linganna Shiva; Chandan, Shivamallu; Jayalakshmi, Basvegowda; Revanasiddappa, Hosakere D

2011-10-15

Four Schiff base ligands and their corresponding organotin(IV) complexes have been synthesized and characterized by elemental analyses, IR, (1)H NMR, MS and thermal studies. The Schiff bases are obtained by the condensation of 3-amino-2-methyl-4(3H)-quinazolinone with different substituted aldehydes. The elemental analysis data suggest the stoichiometry to be 1:1 ratio formation. Infrared spectral data agreed with the coordination to the central metal ion through imine nitrogen, lactam oxygen and deprotonated phenolic oxygen atoms. All the synthesized compounds have been evaluated for antimicrobial activity against selected species of microorganisms. In addition, DNA binding/cleavage capacity of the compounds was analyzed by absorption spectroscopy, viscosity measurements and gel electrophoresis methods. Copyright © 2011 Elsevier B.V. All rights reserved.

Effects of Schiff Base Formation and Aldol Condensation on the Determination of Aldehydes in Rice Wine Using GC-MS.

PubMed

Han, Ji Hye; Lee, Sang Mi; Kim, Young-Suk

2017-04-11

The Schiff base reaction and aldol condensation that occur during sample preparation can lead to the reduction of aldehyde content in the analysis of traditional Korean rice wine, makgeolli. The contents of aldehydes were decreased, whereas those of hydroxy carbonyl compounds were increased by increasing the pH. In the presence of added amino acids, the levels of aldehydes in makgeolli were reduced as the amount of the amino acid alanine increased. Also, the contents of hydroxyl carbonyl compounds were reduced by alanine addition as compared to the control. Therefore, the determination of aldehydes can be affected by pH and the amount of amino acids, which can vary during fermentation and storage of alcoholic beverages because pH and amino acids affect Schiff base formation and aldol condensation.

Design and Synthesis of Novel Arylketo-containing P1-P3 Linked Macro-cyclic BACE-1 Inhibitors

PubMed Central

Sandgren, Veronica; Belda, Oscar; Kvarnström, Ingemar; Lindberg, Jimmy; Samuelsson, Bertil; Dahlgren, Anders

2015-01-01

A series of arylketo-containing P1-P3 linked macrocyclic BACE-1 inhibitors were designed, synthesized, and compared with compounds with a previously known and extensively studied corresponding P2 isophthalamide moiety with the aim to improve on permeability whilst retaining the enzyme- and cell-based activities. Several inhibitors displayed substantial increases in Caco-2 cell-based permeability compared to earlier synthesized inhibitors and notably also with retained activities, showing that this approach might yield BACE-1 inhibitors with improved properties. PMID:25937848

Tetradentate Schiff base platinum(II) complexes as new class of phosphorescent materials for high-efficiency and white-light electroluminescent devices.

PubMed

Che, Chi-Ming; Chan, Siu-Chung; Xiang, Hai-Feng; Chan, Michael C W; Liu, Yu; Wang, Yue

2004-07-07

The capabilities of readily prepared and sublimable Pt(II) Schiff base triplet emitters as OLED dopants have been examined; maximum luminous and power efficiencies and luminance of 31 cd A(-1), 14 lm W(-1), and 23,000 cd m(-2), respectively, and white EL (CIE: 0.33, 0.35) by simultaneous host/dopant emission, have been achieved.

Synthesis, characterization, and biological evaluation of Schiff base-platinum(II) complexes

NASA Astrophysics Data System (ADS)

Shiju, C.; Arish, D.; Bhuvanesh, N.; Kumaresan, S.

2015-06-01

The platinum complexes of Schiff base ligands derived from 4-aminoantipyrine and a few substituted aldehydes were synthesized and characterized by elemental analysis, mass, 1H NMR, IR, electronic spectra, molar conductance, and powder XRD. The structure of one of the ligands L5 was confirmed by a single crystal XRD analysis. The Schiff base ligand crystallized in the triclinic, space group P-1 with a = 7.032(2) Ǻ, b = 9.479(3) Ǻ, c = 12.425(4) Ǻ, α = 101.636(3)°, β = 99.633(3)°, γ = 94.040(3)°, V = 795.0(4) Ǻ3, Z = 2, F(0 0 0) = 352, Dc = 1.405 mg/m3, μ = 0.099 mm-1, R = 0.0378, and wR = 0.0967. The spectral results show that the Schiff base ligand acts as a bidentate donor coordinating through the azomethine nitrogen and the carbonyl oxygen atoms. The geometrical structures of these complexes are found to be square planar. Antimicrobial studies indicate that these complexes exhibit better activity than the ligand. The anticancer activities of the complexes have also been studied towards human cervical cancer cell line (HeLa), Colon Cancer Cells (HCT116) and Epidermoid Carcinoma Cells (A431) and it was found that the [Pt(L3)Cl2] complex is more active.

Isotope effect studies of the pyruvate-dependent histidine decarboxylase from Lactobacillus 30a

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abell, L.M.; O'Leary, M.H.

1988-08-09

The decarboxylation of histidine by the pyruvate-dependent histidine decarboxylase of Lactobacillus 30 a shows a carbon isotope effect k/sup 12//k/sup 13/ = 1.0334 +/- 0.0005 and a nitrogen isotope effect k/sup 14//k/sup 15/ = 0.9799 +/- 0.0006 at pH 4.8, 37/sup 0/C. The carbon isotope effect is slightly increased by deuteriation of the substrate and slightly decreased in D/sub 2/O. The observed nitrogen isotope effect indicates that the imine nitrogen in the substrate-Schiff base intermediate complex is ordinarily protonated, and the pH dependence of the carbon isotope effect indicates that both protonated and unprotonated forms of this intermediate are capablemore » of undergoing decarboxylation. As with the pyridoxal 5'-phosphate dependent enzyme, Schiff base formation and decarboxylation are jointly rate-limiting, with the intermediate histidine-pyruvate Schiff base showing a decarboxylation/Schiff base hydrolysis ratio of 0.5-1.0 at pH 4.8. The decarboxylation transition state is more reactant-like for the pyruvate-dependent enzyme than for the pyridoxal 5'-phosphate dependent enzyme. These studies find no particular energetic or catalytic advantage to the use of pyridoxal 5'-phosphate over covalently bound pyruvate in catalysis of the decarboxylation of histidine.« less

Kinetics and thermodynamics of irreversible inhibition of matrix metalloproteinase 2 by a Co(III) Schiff base complex

PubMed Central

Harney, Allison S.; Sole, Laura B.

2012-01-01

Cobalt(III) Schiff base complexes have been used as potent inhibitors of protein function through the coordination to histidine residues essential for activity. The kinetics and thermodynamics of the binding mechanism of Co(acacen)(NH3)2Cl [Co(acacen); where H2acacen is bis(acetylacetone)ethylenediimine] enzyme inhibition has been examined through the inactivation of matrix metalloproteinase 2 (MMP-2) protease activity. Co(acacen) is an irreversible inhibitor that exhibits time- and concentration-dependent inactivation of MMP-2. Co(acacen) inhibition of MMP-2 is temperature-dependent, with the inactivation increasing with temperature. Examination of the formation of the transition state for the MMP-2/Co(acacen) complex was determined to have a positive entropy component indicative of greater disorder in the MMP-2/Co(acacen) complex than in the reactants. With further insight into the mechanism of Co(acacen) complexes, Co(III) Schiff base complex protein inactivators can be designed to include features regulating activity and protein specificity. This approach is widely applicable to protein targets that have been identified to have clinical significance, including matrix metalloproteinases. The mechanistic information elucidated here further emphasizes the versatility and utility of Co(III) Schiff base complexes as customizable protein inhibitors. PMID:22729838

Synthesis and optical characterization of novel carbazole Schiff bases

NASA Astrophysics Data System (ADS)

Çiçek, Baki; Çalışır, Ümit; Tavaslı, Mustafa; Tülek, Remziye; Teke, Ali

2018-02-01

In this study, newly substituted carbazole derivatives of S1; (Z)-4-((9-isobutyl-9H-carbazol-3-ylimino)methyl)phenol, S2; (Z)-9-butyl- N-(2,3,4-trimethoxybenzylidine)-9H-carbazol-3-amine, S3; (Z)-4-((9-octyl-9H-carbazol-3-ylimino)methyl)benzene-1,2-diol and S4; (Z)-3-((9-octyl-9H-carbazol-3-ylimino)methyl)benzene-1,2-diol compounds are synthesized by using condensation reaction between carbazole amines and aromatic aldehydes. All synthesized carbazole Schiff bases are purified by crystallizing from chloroform. The structural and optical characterizations of synthesized compounds are investigated by FT-IR (Fourier Transform-Infrared Spectroscopy), 1H NMR (Proton Nuclear Magnetic Resonance), 13C NMR (Carbon Nuclear Magnetic Resonance), LC-MS (Liquid Chromatography-Mass Spectrometry) and temperature dependent PL (Photoluminescence) measurements. The formations of synthesized Schiff bases were confirmed by FT-IR, NMR and microanalysis. Due to stronger π-conjugation and efficient charge transfer from host material, the broad and complex bands centered at about ∼2.16 and ∼1.76 eV are observed in PL spectra for all samples. Their relative intensities depend on functional groups associated with the carbazole. These newly synthesized Schiff bases could be considered as an active emissive layer for organic light emitting diodes.

Trimodal Control of Ion-Transport Activity on Cyclo-oligo-(1→6)-β-D-glucosamine-Based Artificial Ion-Transport Systems.

PubMed

Roy, Arundhati; Saha, Tanmoy; Gening, Marina L; Titov, Denis V; Gerbst, Alexey G; Tsvetkov, Yury E; Nifantiev, Nikolay E; Talukdar, Pinaki

2015-11-23

Cyclo-oligo-(1→6)-β-D-glucosamines functionalized with hydrophobic tails are reported as a new class of transmembrane ion-transport system. These macrocycles with hydrophilic cavities were introduced as an alternative to cyclodextrins, which are supramolecular systems with hydrophobic cavities. The transport activities of these glycoconjugates were manipulated by altering the oligomericity of the macrocycles, as well as the length and number of attached tails. Hydrophobic tails of 3 different sizes were synthesized and coupled with each glucosamine scaffold through the amide linkage to obtain 18 derivatives. The ion-transport activity increased from di- to tetrameric glucosamine macrocycles, but decreased further when flexible pentameric glucosamine was introduced. The ion-transport activity also increased with increasing length of attached linkers. For a fixed length of linkers, the transport activity decreased when the number of such tails was reduced. All glycoconjugates displayed a uniform anion-selectivity sequence: Cl(-) >Br(-) >I(-) . From theoretical studies, hydrogen bonding between the macrocycle backbone and the anion bridged through water molecules was observed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure-based design of oxygen-linked macrocyclic kinase inhibitors: discovery of SB1518 and SB1578, potent inhibitors of Janus kinase 2 (JAK2) and Fms-like tyrosine kinase-3 (FLT3)

NASA Astrophysics Data System (ADS)

Poulsen, Anders; William, Anthony; Blanchard, Stéphanie; Lee, Angeline; Nagaraj, Harish; Wang, Haishan; Teo, Eeling; Tan, Evelyn; Goh, Kee Chuan; Dymock, Brian

2012-04-01

Macrocycles from our Aurora project were screened in a kinase panel and were found to be active on other kinase targets, mainly JAKs, FLT3 and CDKs. Subsequently these compounds became leads in our JAK2 project. Macrocycles with a basic nitrogen in the linker form a salt bridge with Asp86 in CDK2 and Asp698 in FLT3. This residue is conserved in most CDKs resulting in potent pan CDK inhibition. One of the main project objectives was to achieve JAK2 potency with 100-fold selectivity against CDKs. Macrocycles with an ether linker have potent JAK2 activity with the ether oxygen forming a hydrogen bond to Ser936. A hydrogen bond to the equivalent residues of JAK3 and most CDKs cannot be formed resulting in good selectivity for JAK2 over JAK3 and CDKs. Further optimization of the macrocyclic linker and side chain increased JAK2 and FLT3 activity as well as improving DMPK properties. The selective JAK2/FLT3 inhibitor 11 (Pacritinib, SB1518) has successfully finished phase 2 clinical trials for myelofibrosis and lymphoma. Another selective JAK2/FLT3 inhibitor, 33 (SB1578), has entered phase 1 clinical development for the non-oncology indication rheumatoid arthritis.

Lead Diversification through a Prins-Driven Macrocyclization Strategy: Application to C13-Diversified Bryostatin Analogues.

PubMed

Wender, Paul A; Billingsley, Kelvin L

2013-01-01

The design, synthesis, and biological evaluation of a novel class of C13-diversified bryostatin analogues are described. An innovative and general strategy based on a Prins macrocyclization-nucleophilic trapping cascade was used to achieve late-stage diversification. In vitro analysis of selected library members revealed that modification at the C13 position of the bryostatin scaffold can be used as a diversification handle to regulate biological activity.

Ultrasensitive and highly selective detection of Cu2 + ions based on a new carbazole-Schiff

NASA Astrophysics Data System (ADS)

Yin, Jun; Bing, Qijing; Wang, Lin; Wang, Guang

2018-01-01

A new chemosensor for Cu2 + based on Schiff base with high sensitivity and selectivity was designed and synthesized. The fluorescence intensity of the chemosensor in CH3CN solution was enhanced 160-fold after the addition of 10 equiv. Cu2 + over other metal ions. In addition, it also facilitates colorimetric detection for Cu2 + in CH3CN solution. The chemosensor displayed low detection limit and fast response time to Cu2 +.

In vitro anticancer activities of Schiff base and its lanthanum complex

NASA Astrophysics Data System (ADS)

Neelima; Poonia, Kavita; Siddiqui, Sahabjada; Arshad, Md; Kumar, Dinesh

2016-02-01

Schiff base metal complexes are well-known to intercalate DNA. The La(III) complexes have been synthesized such that they hinder with the role of the topoisomerases, which control the topology of DNA during the cell-division cycle. Although several promising chemotherapeutics have been developed, on the basis of Schiff base metal complex DNA intercalating system they did not proceed past clinical trials due to their dose-limiting toxicity. Herein, we discuss an alternative compound, the La(III) complex, [La(L1)2Cl3]·7H2O based on a Schiff base ligand 2,3-dihydro-1H-indolo-[2,3-b]-phenazin-4(5H)-ylidene)benzothiazole-2-amine (L1), and report in vitro cell studies. Results of antitumor activity using cell viability assay, reactive oxygen species (ROS) generation and nuclear condensation in PC-3 (Human, prostate carcinoma) cells show that the metal complex is more potent than ligand. La(III) complexes have been synthesized by reaction of lanthanum(III) salt in 1:2 M ratio with ligands L1 and 3-(ethoxymethylene)-2,3-dihydro-1H-indolo[2,3-b]-phenazin-4(5H)-ylidene)benzathiazole-2-amine (L2) in methanol. The ligands and their La(III) complexes were characterized by molar conductance, magnetic susceptibility, elemental analyses, FT-IR, UV-Vis, 1H/13C NMR, thermogravimetric, XRD, and SEM analysis.

Synthesis and Biological Evaluation of Macrocyclized Betulin Derivatives as a Novel Class of Anti-HIV-1 Maturation Inhibitors.

PubMed

Tang, Jun; Jones, Stacey A; Jeffery, Jerry L; Miranda, Sonia R; Galardi, Cristin M; Irlbeck, David M; Brown, Kevin W; McDanal, Charlene B; Han, Nianhe; Gao, Daxin; Wu, Yongyong; Shen, Bin; Liu, Chunyu; Xi, Caiming; Yang, Heping; Li, Rui; Yu, Yajun; Sun, Yufei; Jin, Zhimin; Wang, Erjuan; Johns, Brian A

2014-01-01

A macrocycle provides diverse functionality and stereochemical complexity in a conformationally preorganized ring structure, and it occupies a unique chemical space in drug discovery. However, the synthetic challenge to access this structural class is high and hinders the exploration of macrocycles. In this study, efficient synthetic routes to macrocyclized betulin derivatives have been established. The macrocycle containing compounds showed equal potency compared to bevirimat in multiple HIV-1 antiviral assays. The synthesis and biological evaluation of this novel series of HIV-1 maturation inhibitors will be discussed.

An azine based sensor for selective detection of Cu2 + ions and its copper complex for sensing of phosphate ions in physiological conditions and in living cells

NASA Astrophysics Data System (ADS)

Tiwari, Karishma; Kumar, Sumit; Kumar, Vipan; Kaur, Jeevanjot; Arora, Saroj; Mahajan, Rakesh Kumar

2018-02-01

A simple and cost effective unsymmetrical azine based Schiff base, 5-diethylamino-2-[(2-hydroxy-benzylidene)hydrazonomethyl]-phenol (1) was synthesized which selectively detect Cu2 + ions in the presence of other competitive ions through ;naked eye; in physiological conditions (EtOH-buffer (1:1, v/v, HEPES 10 mM, pH = 7.4)). The presence of Cu2 + induce color change from light yellow green to yellow with the appearance of a new band at 450 nm in UV-Vis spectra of Schiff base 1. The fluorescence of Schiff base 1 (10 μM) was quenched completely in the presence of 2.7 equiv. of Cu2 + ions. Sub-micromolar limit of detection (LOD = 3.4 × 10- 7 M), efficient Stern-Volmer quenching constant (KSV = 1.8 × 105 L mol- 1) and strong binding constant (log Kb = 5.92) has been determined with the help of fluorescence titration profile. Further, 1 - Cu2 + complex was employed for the detection of phosphate ions (PO43 -, HPO42 - and H2PO4-) at micromolar concentrations in EtOH-buffer of pH 7.4 based on fluorescence recovery due to the binding of Cu2 + with phosphate ions. Solubility at low concentration in aqueous medium, longer excitation (406 nm) and emission wavelength (537 nm), and biocompatibility of Schiff base 1 formulates its use in live cell imaging.

Synthesis, spectroscopic characterization, and antibacterial evaluation of new Schiff bases bearing benzimidazole moiety

NASA Astrophysics Data System (ADS)

Redayan, Muayed Ahmed; Salih Hussein, Maha; Tark lafta, Ashraf

2018-05-01

The present work comprise synthesis of new derivatives for Schiff bases bearing benzimidazole ring. Compounds 1(a-d) were prepared by reaction of o-pheneylenediamine with a various of amino acids (glycine, alanine, phenyl alanine and tyrosine) in the presence 6N HCl to yielded derivatives of benzimidazole compounds containing free –NH2 group. Then these compounds used to prepare different Schiff bases through reaction with various of aromatic aldehydes. The chemical structure of synthesized compounds were confirmed by FTIR,1H,13C-NMR, and 13C-NMR dept135 spectroscopy. Some selected compounds were evaluated in vitro for their antibacterial activity against two types of Gram-positive bacteria namely (Staphylococcous aureus, Bacillus subtilis) and Gram-negative bacteria namely (Pseudomonas aeruginosa, Escherichia coli). Most of the results of the antibacterial activity of these compounds were good when compared with the standard antibiotic ampicillin and ciprofloxacin.

Development and cytotoxicity of Schiff base derivative as a fluorescence probe for the detection of L-Arginine

NASA Astrophysics Data System (ADS)

Shang, Xuefang; Li, Jie; Guo, Kerong; Ti, Tongyu; Wang, Tianyun; Zhang, Jinlian

2017-04-01

Inspired from biological counter parts, chemical modification of Schiff base derivatives with function groups may provide a highly efficient method to detect amino acids. Therefore, a fluorescent probe involving Schiff base and hydroxyl group has been designed and prepared, which showed high response and specificity for Arginine (Arg) among normal eighteen standard kinds of amino acids (Alanine, Valine, Leucine, Isoleucine, Methionine, Asparticacid, Glutamicacid, Arginine, Glycine, Serine, Threonine, Asparagine, Phenylalanine, Histidine, Tryptophan, Proline, Lysine, Glutamine, Tyrosine and Cysteine). Furthermore, theoretical investigation further illustrated the possible binding mode in the host-guest interaction and the roles of molecular frontier orbitals in molecular interplay. In addition, the synthesized fluorescent probe exhibited high binding ability for Arg and low cytotoxicity to MCF-7 cells over a concentration range of 0-200 μg mL-1 which can be also used as a biosensor for the Arg detection in vivo.

A novel Schiff-base as a Cu(II) ion fluorescent sensor in aqueous solution

NASA Astrophysics Data System (ADS)

Gündüz, Z. Yurtman; Gündüz, C.; Özpınar, C.; Urucu, O. Aydın

2015-02-01

A new fluorescent Cu(II) sensor (L) obtained from the Schiff base of 5,5‧-methylene-bis-salicylaldehyde with amidol (2,4-diaminophenol) was synthesized and characterized by FT-IR, MS, 1H NMR, 13C NMR techniques. In the presence of pH 6.5 (KHPO4-Na2HPO4) buffer solutions, copper reacted with L to form a stable 2:1 complex. Fluorescence spectroscopic study showed that Schiff base is highly sensitive towards Cu(II) over other metal ions (K+, Na+, Al3+, Ni2+, Co2+, Fe3+, Zn2+, Pb2+) in DMSO/H2O (30%, v/v). The sensor L was successfully applied to the determination of copper in standard reference material. The structural properties and molecular orbitals of the complex formed between L and Cu2+ ions were also investigated using quantum chemical computations.

Structural and cytotoxic studies of cationic thiosemicarbazones

NASA Astrophysics Data System (ADS)

Sinniah, Saravana Kumar; Sim, Kae Shin; Ng, Seik Weng; Tan, Kong Wai

2017-06-01

Schiff bases from the thiosemicarbazones family with variable N4 substituents are known to show enhanced growth inhibitory properties. In view of these facts and as a part of our continuous interest in cationic Schiff bases, we have developed several Schiff base ligands from (3-formyl-4-hydroxyphenyl)methyltriphenylphosphonium (T) in present study. The compounds were characterized by various spectroscopic methods (infrared spectra, 1H NMR, 13C NMR, HRESIMS and X-ray crystallography). Three of the N4 substituents, namely P(tsc)T, FP(tsc)T and EP(tsc)T exerted strong growth inhibitory properties by inhibiting the highly metastasis prostate cancer growth (PC-3). The thiosemicarbazone with ethylphenyl (EP) moiety displayed most potent activity against all cell lines tested. The MTT data obtained from analysis establishes that phenyl substituent enhances the growth inhibitory properties of the compound. The result affirms that EP(tsc)T would serve as a lead scaffold for rational anticancer agent development.

Improvement in Titanium Complexes Bearing Schiff Base Ligands in the Ring-Opening Polymerization of L-Lactide: A Dinuclear System with Hydrazine-Bridging Schiff Base Ligands.

PubMed

Tseng, Hsi-Ching; Chen, Hsing-Yin; Huang, Yen-Tzu; Lu, Wei-Yi; Chang, Yu-Lun; Chiang, Michael Y; Lai, Yi-Chun; Chen, Hsuan-Ying

2016-02-15

A series of titanium (Ti) complexes bearing hydrazine-bridging Schiff base ligands were synthesized and investigated as catalysts for the ring-opening polymerization (ROP) of L-lactide (LA). Complexes with electron withdrawing or steric bulky groups reduced the catalytic activity. In addition, the steric bulky substituent on the imine groups reduced the space around the Ti atom and then reduced LA coordination with Ti atom, thereby reducing catalytic activity. All the dinuclear Ti complexes exhibited higher catalytic activity (approximately 10-60-fold) than mononuclear L(Cl-H)-TiOPr2 did. The strategy of bridging dinuclear Ti complexes with isopropoxide groups in the ROP of LA was successful, and adjusting the crowded heptacoordinated transition state by the bridging isopropoxide groups may be the key to our successful strategy.

Efficient alkene epoxidation catalyzed by molybdenyl acetylacetonate supported on aminated UiO-66 metal-organic framework

NASA Astrophysics Data System (ADS)

Kardanpour, Reihaneh; Tangestaninejad, Shahram; Mirkhani, Valiollah; Moghadam, Majid; Mohammadpoor-Baltork, Iraj; Zadehahmadi, Farnaz

2015-03-01

Metal-organic frameworks (MOFs) containing Mo Schiff base complexes were prepared by post-synthesis method and applied as efficient catalysts in the epoxidation of alkenes with tert-BuOOH. In this manner, UiO-66-NH2 (UiO=University of Oslo) MOF was reacted with salicylaldehyde and thiophene-2-carbaldehyde to produce bidentate Schiff bases. Then, the Schiff base ligands were used for immobilization of molybdenyl acetylacetonate. These new catalysts were characterized by FT-IR, UV-vis spectroscopic techniques, X-ray diffraction (XRD), BET, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and field emission scanning electron microscopy (FE-SEM). These catalytic systems showed excellent activity in the epoxidation of alkenes such as cyclic and linear ones with tert-butyl hydroperoxide (TBHP) in 1,2-dichloroethane, and reused several times without any appreciable loss of their activity.

Synthesis and structural features of U VI and V IV chelate complexes with (hhmmbH)Cl·H 2O [hhmmb = {3-hydroxyl-5-(hydroxymethyl)-2-methylpyridine-4-yl-methylene}benzohydrazide], a new Schiff base ligand derived from vitamin B6

NASA Astrophysics Data System (ADS)

Back, Davi Fernando; Ballin, Marco Aurélio; de Oliveira, Gelson Manzoni

2009-10-01

The Schiff base ligand {3-hydroxyl-5-(hydroxymethyl)-2-methylpyridine-4-yl-methylene}benzohydrazide hydrochloride monohydrated {(hhmmbH)Cl·H 2O} ( 1) was prepared by reaction of pyridoxine hydrochloride with benzoic acid hydrazide. The reaction of 1 with [VO(acac) 2] and triethylamine yields the neutral vanadium IV complex [VO 2(hhmmb)]·Py ( 2), with a distorted quadratic pyramidal configuration. The Schiff base 1 reacts also with UO 2(NO 3) 2·6H 2O and triethylamine under deprotonation giving the uranium VI cationic complexes [UO 2(hhmmb)(H 2O)Cl] + ( 3) and [UO 2(hhmmb)(CH 3OH)Cl] + ( 4), both showing the classical pentagonal bipyrimidal geometry of UO22+ complexes. The structural features of all compounds are discussed.

Asymmetric synthesis of α-amino acids via homologation of Ni(II) complexes of glycine Schiff bases. Part 2: aldol, Mannich addition reactions, deracemization and (S) to (R) interconversion of α-amino acids.

PubMed

Sorochinsky, Alexander E; Aceña, José Luis; Moriwaki, Hiroki; Sato, Tatsunori; Soloshonok, Vadim

2013-11-01

This review provides a comprehensive treatment of literature data dealing with asymmetric synthesis of α-amino-β-hydroxy and α,β-diamino acids via homologation of chiral Ni(II) complexes of glycine Schiff bases using aldol and Mannich-type reactions. These reactions proceed with synthetically useful chemical yields and thermodynamically controlled stereoselectivity and allow direct introduction of two stereogenic centers in a single operation with predictable stereochemical outcome. Furthermore, new application of Ni(II) complexes of α-amino acids Schiff bases for deracemization of racemic α-amino acids and (S) to (R) interconversion providing additional synthetic opportunities for preparation of enantiomerically pure α-amino acids, is also reviewed. Origin of observed diastereo-/enantioselectivity in the aldol, Mannich-type and deracemization reactions, generality and limitations of these methodologies are critically discussed.

Can a proton be encapsulated in tetraamido/diamino quaternized macrocycles in aqueous solution and electric field?

PubMed

Jiang, Nan; Ma, Jing

2011-09-12

The proton-binding behavior of solvated tetraamido/diamino quaternized macrocyclic compounds with rigid phenyl and flexible phenyl bridges in the absence or presence of an external electric field is investigated by molecular dynamics simulation. The proton can be held through H-bonding interactions with the two carbonyl oxygen atoms in macrocycles containing rigid (phenyl) and flexible (propyl) bridges. The solute-solvent H-bonding interactions cause the macrocyclic backbones to twist to different extents, depending on the different bridges. The macrocycle with the rigid phenyl linkages folds into a cuplike shape due to π-π interaction, while the propyl analogue still maintains the ellipsoidal ringlike shape with just a slight distortion. The potential energy required for proton transfer is larger in the phenyl-containing macrocycle than in the compound with propyl units. When an external electric field with a strength of 2.5 V nm(-1) is exerted along the carbonyl oxygen atoms, a difference in proton encircling is exhibited for macrocycles with rigid and flexible bridges. In contrast to encapsulation of a proton in the propyl analogue, the intermolecular solute-solvent H-bonding and intramolecular π-π stacking between the two rigid phenyl spacers leads to loss of the proton from the highly distorted cuplike macrocycle with phenyl bridges. The competition between intra- and intermolecular interactions governs the behavior of proton encircling in macrocycles. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Oxidation of benzoin catalyzed by oxovanadium(IV) schiff base complexes

PubMed Central

2013-01-01

Background The oxidative transformation of benzoin to benzil has been accomplished by the use of a wide variety of reagents or catalysts and different reaction procedures. The conventional oxidizing agents yielded mainly benzaldehyde or/and benzoic acid and only a trace amount of benzil. The limits of practical utilization of these reagents involves the use of stoichiometric amounts of corrosive acids or toxic metallic reagents, which in turn produce undesirable waste materials and required high reaction temperatures. In recent years, vanadium complexes have attracted much attention for their potential utility as catalysts for various types of reactions. Results Active and selective catalytic systems of new unsymmetrical oxovanadium(IV) Schiff base complexes for the oxidation of benzoin is reported. The Schiff base ligands are derived between 2-aminoethanol and 2-hydroxy-1-naphthaldehyde (H2L1) or 3-ethoxy salicylaldehyde (H2L3); and 2-aminophenol and 3-ethoxysalicylaldehyde (H2L2) or 2-hydroxy-1-naphthaldehyde (H2L4). The unsymmetrical Schiff bases behave as tridentate dibasic ONO donor ligands. Reaction of these Schiff base ligands with oxovanadyl sulphate afforded the mononuclear oxovanadium(IV) complexes (VIVOLx.H2O), which are characterized by various physico-chemical techniques. The catalytic oxidation activities of these complexes for benzoin were evaluated using H2O2 as an oxidant. The best reaction conditions are obtained by considering the effect of solvent, reaction time and temperature. Under the optimized reaction conditions, VOL4 catalyst showed high conversion (>99%) with excellent selectivity to benzil (~100%) in a shorter reaction time compared to the other catalysts considered. Conclusion Four tridentate ONO type Schiff base ligands were synthesized. Complexation of these ligands with vanadyl(IV) sulphate leads to the formation of new oxovanadium(IV) complexes of type VIVOL.H2O. Elemental analyses and spectral data of the free ligands and their oxovanadium(IV) complexes were found to be in good agreement with their structures, indicating high purity of all the compounds. Oxovanadium complexes were screened for the oxidation of benzoin to benzil using H2O2 as oxidant. The effect of time, solvent and temperature were optimized to obtain maximum yield. The catalytic activity results demonstrate that these catalytic systems are both highly active and selective for the oxidation of benzoin under mild reaction conditions. PMID:23294561

Oxidation of benzoin catalyzed by oxovanadium(IV) schiff base complexes.

PubMed

Alsalim, Tahseen A; Hadi, Jabbar S; Ali, Omar N; Abbo, Hanna S; Titinchi, Salam Jj

2013-01-07

The oxidative transformation of benzoin to benzil has been accomplished by the use of a wide variety of reagents or catalysts and different reaction procedures. The conventional oxidizing agents yielded mainly benzaldehyde or/and benzoic acid and only a trace amount of benzil. The limits of practical utilization of these reagents involves the use of stoichiometric amounts of corrosive acids or toxic metallic reagents, which in turn produce undesirable waste materials and required high reaction temperatures.In recent years, vanadium complexes have attracted much attention for their potential utility as catalysts for various types of reactions. Active and selective catalytic systems of new unsymmetrical oxovanadium(IV) Schiff base complexes for the oxidation of benzoin is reported. The Schiff base ligands are derived between 2-aminoethanol and 2-hydroxy-1-naphthaldehyde (H2L1) or 3-ethoxy salicylaldehyde (H2L3); and 2-aminophenol and 3-ethoxysalicylaldehyde (H2L2) or 2-hydroxy-1-naphthaldehyde (H2L4). The unsymmetrical Schiff bases behave as tridentate dibasic ONO donor ligands. Reaction of these Schiff base ligands with oxovanadyl sulphate afforded the mononuclear oxovanadium(IV) complexes (VIVOLx.H2O), which are characterized by various physico-chemical techniques.The catalytic oxidation activities of these complexes for benzoin were evaluated using H2O2 as an oxidant. The best reaction conditions are obtained by considering the effect of solvent, reaction time and temperature. Under the optimized reaction conditions, VOL4 catalyst showed high conversion (>99%) with excellent selectivity to benzil (~100%) in a shorter reaction time compared to the other catalysts considered. Four tridentate ONO type Schiff base ligands were synthesized. Complexation of these ligands with vanadyl(IV) sulphate leads to the formation of new oxovanadium(IV) complexes of type VIVOL.H2O.Elemental analyses and spectral data of the free ligands and their oxovanadium(IV) complexes were found to be in good agreement with their structures, indicating high purity of all the compounds.Oxovanadium complexes were screened for the oxidation of benzoin to benzil using H2O2 as oxidant. The effect of time, solvent and temperature were optimized to obtain maximum yield. The catalytic activity results demonstrate that these catalytic systems are both highly active and selective for the oxidation of benzoin under mild reaction conditions.

Comprehensive computational design of ordered peptide macrocycles

PubMed Central

Hosseinzadeh, Parisa; Bhardwaj, Gaurav; Mulligan, Vikram Khipple; Shortridge, Matthew D.; Craven, Timothy W.; Pardo-Avila, Fátima; Rettie, Stephen A.; Kim, David E.; Silva, Daniel-Adriano; Ibrahim, Yehia M.; Webb, Ian K.; Cort, John R.; Adkins, Joshua N.; Varani, Gabriele; Baker, David

2018-01-01

Mixed-chirality peptide macrocycles such as cyclosporine are among the most potent therapeutics identified to date, but there is currently no way to systematically search the structural space spanned by such compounds. Natural proteins do not provide a useful guide: Peptide macrocycles lack regular secondary structures and hydrophobic cores, and can contain local structures not accessible with L-amino acids. Here, we enumerate the stable structures that can be adopted by macrocyclic peptides composed of L- and D-amino acids by near-exhaustive backbone sampling followed by sequence design and energy landscape calculations. We identify more than 200 designs predicted to fold into single stable structures, many times more than the number of currently available unbound peptide macrocycle structures. Nuclear magnetic resonance structures of 9 of 12 designed 7- to 10-residue macrocycles, and three 11- to 14-residue bicyclic designs, are close to the computational models. Our results provide a nearly complete coverage of the rich space of structures possible for short peptide macrocycles and vastly increase the available starting scaffolds for both rational drug design and library selection methods. PMID:29242347

Experimental and theoretical studies of Schiff bases as corrosion inhibitors.

PubMed

Jamil, Dalia M; Al-Okbi, Ahmed K; Al-Baghdadi, Shaimaa B; Al-Amiery, Ahmed A; Kadhim, Abdulhadi; Gaaz, Tayser Sumer; Kadhum, Abdul Amir H; Mohamad, Abu Bakar

2018-02-05

Relatively inexpensive, stable Schiff bases, namely 3-((4-hydroxybenzylidene)amino)-2-methylquinazolin-4(3H)-one (BZ3) and 3-((4-(dimethylamino)benzylidene)amino)-2-methylquinazolin-4(3H)-one (BZ4), were employed as highly efficient inhibitors of mild steel corrosion by corrosive acid. The inhibition efficiencies were estimated based on weight loss method. Moreover, scanning electron microscopy was used to investigate the inhibition mechanism. The synthesized Schiff bases were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and micro-elemental analysis. The inhibition efficiency depends on three factors: the amount of nitrogen in the inhibitor, the inhibitor concentration and the inhibitor molecular weight. Inhibition efficiencies of 96 and 92% were achieved with BZ4 and BZ3, respectively, at the maximum tested concentration. Density functional theory calculations of BZ3 and BZ4 were performed to compare the effects of hydroxyl and N,N-dimethylamino substituents on the inhibition efficiency, providing insight for designing new molecular structures that exhibit enhanced inhibition efficiencies.

Synthesis, spectroscopic, DFT studies and biological activity of some ruthenium carbonyl derivatives of bis-(salicylaldehyde)phenylenediimine Schiff base ligand

NASA Astrophysics Data System (ADS)

Ramadan, Ramadan M.; Abu Al-Nasr, Ahmad K.; Ali, Omayma A. M.

2018-06-01

Bis-(salicylaldehyde)phenylenediimine Schiff base (H2salphen) reacted oxidatively with the triruthenium dodecacarbonyl complex, [Ru3(CO)12] to give the dicarbonyl derivative [Ru(CO)2(salphen)], 1. In presence of a secondary ligand L (L = pyridine, triphenyl phosphine, 2-aminobenzimidazole or thiourea), the monocarbonyl derivatives [Ru(CO)(salphen)L], 2-5, were isolated. When the bipyridine (bpy) ligand was used as a secondary ligand, the dicarbonyl complex [Ru(CO)2(Hsalphen)(bpy)], 6, was obtained. In complexes 1-5, the Schiff base ligand acted as a tetradentate, while it coordinated as a bidentate in complex 6. The structure and stoichiometry of the complexes were investigated by the conventional analytical and spectroscopic techniques, which revealed that they have several structural arrangements. The structures of ligand and complexes were verified by theoretical calculations based on accurate DFT approximations. The relative reactivities were estimated using chemical descriptors analysis. Biological activities of the complexes against the Escherchia coli and Staphylococcus aureus bacteria were screened.

Hyperpolarization of Nitrogen-15 Schiff Bases by Reversible Exchange Catalysis with para-Hydrogen.

PubMed

Logan, Angus W J; Theis, Thomas; Colell, Johannes F P; Warren, Warren S; Malcolmson, Steven J

2016-07-25

NMR with thermal polarization requires relatively concentrated samples, particularly for nuclei with low abundance and low gyromagnetic ratios, such as (15) N. We expand the substrate scope of SABRE, a recently introduced hyperpolarization method, to allow access to (15) N-enriched Schiff bases. These substrates show fractional (15) N polarization levels of up to 2 % while having only minimal (1) H enhancements. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stereoselective synthesis of unsaturated α-amino acids.

PubMed

Fanelli, Roberto; Jeanne-Julien, Louis; René, Adeline; Martinez, Jean; Cavelier, Florine

2015-06-01

Stereoselective synthesis of unsaturated α-amino acids was performed by asymmetric alkylation. Two methods were investigated and their enantiomeric excess measured and compared. The first route consisted of an enantioselective approach induced by the Corey-Lygo catalyst under chiral phase transfer conditions while the second one involved the hydroxypinanone chiral auxiliary, both implicating Schiff bases as substrate. In all cases, the use of a prochiral Schiff base gave higher enantiomeric excess and yield in the final desired amino acid.

Electrochemical investigation on the corrosion inhibition of mild steel by Quinazoline Schiff base compounds in hydrochloric acid solution.

PubMed

Khan, Ghulamullah; Basirun, Wan Jeffrey; Kazi, Salim Newaz; Ahmed, Pervaiz; Magaji, Ladan; Ahmed, Syed Muzamil; Khan, Ghulam Mustafa; Rehman, Muhammad Abdur; Badry, Ahmad Badarudin Bin Mohamad

2017-09-15

The inhibitory effect of two Schiff bases 3-(5-methoxy-2-hydroxybenzylideneamino)-2-(-5-methoxy-2-hydroxyphenyl)-2,3-dihydroquinazoline-4(1H)-one (MMDQ), and 3-(5-nitro-2-hydroxybenzylideneamino)-2(5-nitro-2-hydroxyphenyl)-2,3-dihydroquinazoline-4(1H)-one (NNDQ) on the corrosion of mild steel in 1M hydrochloric acid were studied using mass loss, potentiodynamic polarization technique and electrochemical impedance spectroscopy measurements at ambient temperature. The investigation results indicate that the Schiff Bases compounds with an average efficiency of 92% at 1.0mM of additive concentration have fairly effective inhibiting properties for mild steel in hydrochloric acid, and acts as mixed type inhibitor character. The inhibition efficiencies measured by all measurements show that the inhibition efficiencies increase with increase in inhibitor concentration. This reveals that the inhibitive mechanism of inhibitors were primarily due to adsorption on mild steel surface, and follow Langmuir adsorption isotherm. The temperature effect on the inhibition process in 1MHCl with the addition of investigated Schiff bases was studied at a temperature range of 30-60°C, and the activation parameters (Ea, ΔH and ΔS) were calculated to elaborate the corrosion mechanism. The differences in efficiency for two investigated inhibitors are associated with their chemical structures. Copyright © 2017 Elsevier Inc. All rights reserved.

Newer mixed ligand Schiff base complexes from aquo-N-(2‧-hydroxy acetophenone) glycinatocopper(II) as synthon: DFT, antimicrobial activity and molecular docking study

NASA Astrophysics Data System (ADS)

Pramanik, Harun A. R.; Das, Dharitri; Paul, Pradip C.; Mondal, Paritosh; Bhattacharjee, Chira R.

2014-02-01

Synthesis of a series of newer mixed ligand copper(II) complexes of aminoacid Schiff base of the type [CuL(X)] (L = N-(2‧-hydroxy acetophenone) glycinate, X = imidazole (im) 2, benzimidazole (benz) 3, pyridine (py) 4, hydrazine (hz) 5,8-hydroxyquinoline (8-hq) 6, pyrrolidine (pyrr) 7, piperidine (pip) 8, and nicotinamide (nic) 9) have been accomplished from the interaction of an aquated Schiff base complex, [CuL(H2O)]·H2O, 1 with some selected neutral nitrogen-donor ligands. The copper(II) Schiff base complex, [CuL(H2O)]·H2O, L = N-(2‧-hydroxy acetophenone) glycinate was synthesized from the reaction of glycine and 2‧ hydroxy acetophenone and copper(II) acetate. The compounds were characterised by elemental analysis, spectral, magnetic and thermal studies. The density functional theory calculations were performed using LANL2DZ and 6-311 G(d, p) basis sets with B3LYP correlation functional to ascertain the stable electronic structure, HOMO-LUMO energy gap, chemical hardness and dipole moment of the mixed ligand complexes. A distorted square planar geometry has been conjectured for the complexes. Antibacterial activities of the ligand and its metal complexes have been tested against selected gram-positive and gram-negative strains and correlated with computational docking scores.

Structural characterization of new Schiff bases of sulfamethoxazole and sulfathiazole, their antibacterial activity and docking computation with DHPS protein structure.

PubMed

Mondal, Sudipa; Mandal, Santi M; Mondal, Tapan Kumar; Sinha, Chittaranjan

2015-01-01

New Schiff bases (1, 2) of substituted salicylaldehydes and sulfamethoxazole (SMX)/sulfathiazole (STZ) are synthesized and characterized by elemental analysis and spectroscopic data. Single crystal X-ray structure of one of the compounds (E)-4-((3,5-dichloro-2-hydroxybenzylidene)amino)-N-(5-methylisoxazol-3-yl)benzenesulfonamide (1c) has been determined. Antimicrobial activities of the Schiff bases and parent sulfonamides (SMX, STZ) have been examined against several Gram-positive and Gram-negative bacteria and sulfonamide resistant pathogens; the lowest MIC is observed for (E)-4-((3,5-dichloro-2-hydroxybenzylidene)amino)-N-(thiazol-2-yl)benzene sulfonamide (2c) (8.0 μg mL(-1)) and (E)-4-((3,5-dichloro-2-hydroxybenzylidene)amino)-N-(5-methylisoxazol-3-yl)benzene sulfonamide (1c) (16.0 μg mL(-1)) against sulfonamide resistant pathogens. DFT optimized structures of the Schiff bases have been used to carry out molecular docking studies with DHPS (dihydropteroate synthase) protein structure (downloaded from Protein Data Bank) using Discovery Studio 3.5 to find the most preferred binding mode of the ligand inside the protein cavity. The theoretical data have been well correlated with the experimental results. Cell viability assay and ADMET studies predict that 1c and 2c have good drug like characters. Copyright © 2015 Elsevier B.V. All rights reserved.

Transient Resonance Raman Spectroscopy of a Light-Driven Sodium-Ion-Pump Rhodopsin from Indibacter alkaliphilus.

PubMed

Kajimoto, Kousuke; Kikukawa, Takashi; Nakashima, Hiroki; Yamaryo, Haruki; Saito, Yuta; Fujisawa, Tomotsumi; Demura, Makoto; Unno, Masashi

2017-05-04

Sodium-ion-pump rhodopsin (NaR) is a microbial rhodopsin that transports Na + during its photocycle. Here we explore the photocycle mechanism of NaR from Indibacter alkaliphilus with transient absorption and transient resonance Raman spectroscopy. The transient absorption data indicate that the photocycle of NaR is K (545 nm) → L (490 nm)/M (420 nm) → O 1 (590 nm) → O 2 (560 nm) → NaR, where the L and M are formed as equilibrium states. The presence of K, L, M, and O intermediates was confirmed by the resonance Raman spectra with 442 and 532 nm excitation. The main component of the transient resonance Raman spectra was due to L which contains a 13-cis retinal protonated Schiff base. The presence of an enhanced hydrogen out-of-plane band as well as its sensitivity to the H/D exchange indicate that the retinal chromophore is distorted near the Schiff base region in L. Moreover, the retinal Schiff base of the L state forms a hydrogen bond that is stronger than that of the dark state. These observations are consistent with a Na + pumping mechanism that involves a proton transfer from the retinal Schiff base to a key aspartate residue (Asp116 in Krokinobacter eikastus rhodopsin 2) in the L/M states.

Computational studies on nonlinear optical property of novel Wittig-based Schiff-base ligands and copper(II) complex

NASA Astrophysics Data System (ADS)

Rajasekhar, Bathula; Patowary, Nidarshana; K. Z., Danish; Swu, Toka

2018-07-01

Hundred and forty-five novel molecules of Wittig-based Schiff-base (WSB), including copper(II) complex and precursors, were computationally screened for nonlinear optical (NLO) properties. WSB ligands were derived from various categories of amines and aldehydes. Wittig-based precursor aldehydes, (E)-2-hydroxy-5-(4-nitrostyryl)benzaldehyde (f) and 2-hydroxy-5-((1Z,3E)-4-phenylbuta-1,3-dien-1-yl) benzaldehyde (g) were synthesised and spectroscopically confirmed. Schiff-base ligands and copper(II) complex were designed, optimised and their NLO property was studied using GAUSSIAN09 computer program. For both optimisation and hyperpolarisability (finite-field approach) calculations, Density Functional Theory (DFT)-based B3LYP method was applied with LANL2DZ basis set for metal ion and 6-31G* basis set for C, H, N, O and Cl atoms. This is the first report to present the structure-activity relationship between hyperpolarisability (β) and WSB ligands containing mono imine group. The study reveals that Schiff-base ligands of the category N-2, which are the ones derived from the precursor aldehyde, 2-hydroxy-5-(4nitro-styryl)benzaldehyde and pre-polarised WSB coordinated with Cu(II), encoded as Complex-1 (β = 14.671 × 10-30 e.s.u) showed higher β values over other categories, N-1 and N-3, i.e. WSB derived from precursor aldehydes, 2-hydroxy-5-styrylbenzaldehyde and 2-hydroxy-5-((1Z,3E)-4-phenylbuta-1,3-dien-1-yl)benzaldehyde, respectively. For the first time here we report the geometrical isomeric effect on β value.

Synthesis of highly functionalized macrocycles by the peripheral functionalization of macrocyclic diimines.

PubMed

Sierra, Miguel A; Pellico, Daniel; Gómez-Gallego, Mar; Mancheño, María José; Torres, Rosario

2006-11-10

The easily available macrocyclic diimines 4-7 can be stereoselectively transformed to macrocyclic bis-beta-amino acids 13-17, macrocyclic bisazetidines 18-20, and macrocyclic bisamides 21 and 22 by means of the corresponding bis-beta-lactam scaffolds 8-12. These key intermediates are available through standard Staudinger reaction and obtained as the cis-cis diastereomers, exclusively. An interesting relation between the proximity of the reactive C=N bonds and the selectivity in the formation of the bis-beta-lactams 8-12 is observed. Thus, diimine 4 leads to low selectivities, producing a 1:1 mixture of cis-syn-cis and cis-anti-cis diastereomers, while diimines 5-7 having the diimine sites more separated lead almost exclusively to the cis-anti-cis diastereomers. The stereochemistry of all the products was unambiguously assigned by X-ray diffraction analysis of compounds cis-syn-cis 8 and cis-anti-cis 12-Co2CO6 complex.

Structural and conformational determinants of macrocycle cell permeability.

PubMed

Over, Björn; Matsson, Pär; Tyrchan, Christian; Artursson, Per; Doak, Bradley C; Foley, Michael A; Hilgendorf, Constanze; Johnston, Stephen E; Lee, Maurice D; Lewis, Richard J; McCarren, Patrick; Muncipinto, Giovanni; Norinder, Ulf; Perry, Matthew W D; Duvall, Jeremy R; Kihlberg, Jan

2016-12-01

Macrocycles are of increasing interest as chemical probes and drugs for intractable targets like protein-protein interactions, but the determinants of their cell permeability and oral absorption are poorly understood. To enable rational design of cell-permeable macrocycles, we generated an extensive data set under consistent experimental conditions for more than 200 non-peptidic, de novo-designed macrocycles from the Broad Institute's diversity-oriented screening collection. This revealed how specific functional groups, substituents and molecular properties impact cell permeability. Analysis of energy-minimized structures for stereo- and regioisomeric sets provided fundamental insight into how dynamic, intramolecular interactions in the 3D conformations of macrocycles may be linked to physicochemical properties and permeability. Combined use of quantitative structure-permeability modeling and the procedure for conformational analysis now, for the first time, provides chemists with a rational approach to design cell-permeable non-peptidic macrocycles with potential for oral absorption.

Anti-MRSA activity of isoplagiochin-type macrocyclic bis(bibenzyl)s is mediated through cell membrane damage.

PubMed

Onoda, Kenji; Sawada, Hiromi; Morita, Daichi; Fujii, Kana; Tokiwa, Hiroaki; Kuroda, Teruo; Miyachi, Hiroyuki

2015-07-01

We synthesized three geometrical isomers of a macrocyclic bis(bibenzyl) based on isoplagiochin, a natural product isolated from bryophytes, and evaluated their antibacterial activity towards methicillin-resistant Staphylococcus aureus (anti-MRSA activity). The isomer containing a 1,4-linked ring (5) showed only weak activity, whereas the isomers containing a 1,3-linked (6) or 1,2-linked (7) C ring showed potent anti-MRSA activity. Molecular dynamics calculations indicated that these differences are probably due to differences in the conformational flexibility of the macrocyclic ring; the active compounds 6 and 7 were more rigid than 5. In order to understand the action mechanism of anti-MRSA activity, we investigated the cellular flux of a fluorescent DNA-binder, ethidium bromide (EtBr), in the presence and absence of these macrocycles. The active compound 6 increased the levels of EtBr inflow and outflow in S. aureus cells, as did our potent anti-MRSA riccardin derivative (4), indicating that these compounds increased the permeability of the cytoplasmic membrane. Inactive 5 had no effect on EtBr inflow or outflow. Furthermore, compound 6 abrogated the normal intracellular concentration gradients of Na(+) and K(+) in S. aureus cells, increasing the intracellular Na(+) concentration and decreasing the K(+) concentration, while 5 had no such effect. These results indicate that anti-MRSA-active macrocyclic bis(bibenzyl) derivatives directly damage the gram-positive bacterial membrane, resulting in increased permeability. Copyright © 2015 Elsevier Ltd. All rights reserved.

A novel complexity-to-diversity strategy for the diversity-oriented synthesis of structurally diverse and complex macrocycles from quinine.

PubMed

Ciardiello, J J; Stewart, H L; Sore, H F; Galloway, W R J D; Spring, D R

2017-06-01

Recent years have witnessed a global decline in the productivity and advancement of the pharmaceutical industry. A major contributing factor to this is the downturn in drug discovery successes. This can be attributed to the lack of structural (particularly scaffold) diversity and structural complexity exhibited by current small molecule screening collections. Macrocycles have been shown to exhibit a diverse range of biological properties, with over 100 natural product-derived examples currently marketed as FDA-approved drugs. Despite this, synthetic macrocycles are widely considered to be a poorly explored structural class within drug discovery, which can be attributed to their synthetic intractability. Herein we describe a novel complexity-to-diversity strategy for the diversity-oriented synthesis of novel, structurally complex and diverse macrocyclic scaffolds from natural product starting materials. This approach exploits the inherent structural (including functional) and stereochemical complexity of natural products in order to rapidly generate diversity and complexity. Readily-accessible natural product-derived intermediates serve as structural templates which can be divergently functionalized with different building blocks to generate a diverse range of acyclic precursors. Subsequent macrocyclisation then furnishes compounds that are each based around a distinct molecular scaffold. Thus, high levels of library scaffold diversity can be rapidly achieved. In this proof-of-concept study, the natural product quinine was used as the foundation for library synthesis, and six novel structurally diverse, highly complex and functionalized macrocycles were generated. Copyright © 2017 Elsevier Ltd. All rights reserved.

Studies on DNA binding behaviour of biologically active transition metal complexes of new tetradentate N2O2 donor Schiff bases: inhibitory activity against bacteria.

PubMed

Sobha, S; Mahalakshmi, R; Raman, N

2012-06-15

A series of Cu(II), Ni(II) and Zn(II) complexes of the type ML have been synthesized with Schiff bases derived from o-acetoacetotoluidide, 2-hydroxybenzaldehyde and o-phenylenediamine/1,4-diaminobutane. The complexes are insoluble in common organic solvents but soluble in DMF and DMSO. The measured molar conductance values in DMSO indicate that the complexes are non-electrolytic in nature. All the six metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic data. The analytical data helped to elucidate the structure of the metal complexes. The Schiff bases are found to act as tetradentate ligands using N(2)O(2) donor set of atoms leading to a square-planar geometry for the complexes around all the metal ions. The binding properties of metal complexes with DNA were investigated by absorption spectra, viscosity measurements and cyclic voltammetry. Detailed analysis reveals that the metal complexes intercalate into the DNA base stack as intercalators. All the metal complexes cleave the pUC19 DNA in presence of H(2)O(2.) The Schiff bases and their complexes have been screened for their antibacterial activity against five bacterial strains (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, Klebsiella pneumoniae) by disk diffusion method. All the metal complexes have potent biocidal activity than the free ligands. Copyright © 2012 Elsevier B.V. All rights reserved.

Final Technical Report: Targeting DOE-Relevant Ions with Supramolecular Strategies, DE-SC0010555

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowman-James, Kristin

The effectiveness of three popular supramolecular strategies to selectively target negatively charged ions (anions) was evaluated. Ions of interest included oxo anions, particularly sulfate, that hamper nuclear waste remediation. Three objectives were pursued using a simple building block strategies and by strategically placing anion-binding sites at appropriate positions on organic host molecules. The goal of the first objective was to assess the influence of secondary, tertiary and quaternized amines on binding tetrahedral anions using mixed amide/amine macrocyclic and urea/amine hosts containing aromatic or heteroaromatic spacers. Objective 2 focused on the design of ion pair hosts, using mixed macrocyclic anion hostsmore » joined through polyether linkages. Objective 3 was to explore the synthesis of new metal-linked extended macrocyclic frameworks to leverage anion binding. Key findings were that smaller 24-membered macrocycles provided the most complementary binding for sulfate ion and mixed urea/amine chelates showed enhanced binding over amide corollaries in addition to being highly selective for SO 4 2- in the presence of small quantities of water. In addition to obtaining prototype metal-linked macrocyclic anion hosts, a new dipincer ligand was designed that can be used to link macrocyclic or other supramolecular hosts in extended frameworks. When the tetraamide-based pincers are bound to two metal ions, an interesting phenomenon occurs. Upon deprotonation of the amides, two new protons appear between adjacent carbonyl pairs on the ligand, which may modify the chemistry, and metal-metal interactions in the complexes. Gel formation occurred for some of these extended hosts, and the physical properties are currently under investigation. The new tetracarboxamide-based pincers can also provide basic frameworks for double macrocycles capable of binding ion pairs as well as for binding metal ions and exploring intermetallic interactions through the pyrazine π system. Additionally appendages capable of influencing solvation effects can be introduced, and a number of other potential applications can be realized in areas such as soft materials chemistry, catalysis, sensing, and proton switches, the latter for binding and release of targeted guests. These findings provide a better foundation for understanding the selective binding of anions by targeted placement of hydrogen binding sites, and the strengths and weaknesses of various functional groups, that will allow for more the design of more effective anion sequestering agents. Our design strategy also used simple, cost-effective building blocks for host synthesis to allow for scale-up should real-world applications be forthcoming.« less

Synthesis of Strained 1,3-Diene Macrocycles via Copper-Mediated Castro-Stephens Coupling/Alkyne Reduction Tandem Reactions.

PubMed

Li, Wei; Schneider, Christopher M; Georg, Gunda I

2015-08-07

A copper-mediated macrocyclization involving the reaction of a vinyl iodide and a terminal alkyne followed by an in situ reduction of the enyne intermediate is reported. The reaction generates a conjugated Z-double bond within a strained medium-size lactone, lactam, or ether macrocycle. A variety of macrocyclic compounds bearing different ring sizes and functionalities were synthesized. A complementary stepwise procedure was also developed for less strained ring systems.

Synthesis of 5-iodo-1,2,3-triazole-containing macrocycles using copper flow reactor technology.

PubMed

Bogdan, Andrew R; James, Keith

2011-08-05

A new macrocyclization strategy to synthesize 12- to 31-membered 5-iodo-1,2,3-triazole-containing macrocycles is described. The macrocycles have been generated using a simple and efficient copper-catalyzed cycloaddition in flow under environmentally friendly conditions. This methodology also permits the facile, regioselective synthesis of 1,4,5-trisubstituted-1,2,3-triazole-containing macrocyles using palladium-catalyzed cross-coupling reactions. © 2011 American Chemical Society

Predicting bioactive conformations and binding modes of macrocycles

NASA Astrophysics Data System (ADS)

Anighoro, Andrew; de la Vega de León, Antonio; Bajorath, Jürgen

2016-10-01

Macrocyclic compounds experience increasing interest in drug discovery. It is often thought that these large and chemically complex molecules provide promising candidates to address difficult targets and interfere with protein-protein interactions. From a computational viewpoint, these molecules are difficult to treat. For example, flexible docking of macrocyclic compounds is hindered by the limited ability of current docking approaches to optimize conformations of extended ring systems for pose prediction. Herein, we report predictions of bioactive conformations of macrocycles using conformational search and binding modes using docking. Conformational ensembles generated using specialized search technique of about 70 % of the tested macrocycles contained accurate bioactive conformations. However, these conformations were difficult to identify on the basis of conformational energies. Moreover, docking calculations with limited ligand flexibility starting from individual low energy conformations rarely yielded highly accurate binding modes. In about 40 % of the test cases, binding modes were approximated with reasonable accuracy. However, when conformational ensembles were subjected to rigid body docking, an increase in meaningful binding mode predictions to more than 50 % of the test cases was observed. Electrostatic effects did not contribute to these predictions in a positive or negative manner. Rather, achieving shape complementarity at macrocycle-target interfaces was a decisive factor. In summary, a combined computational protocol using pre-computed conformational ensembles of macrocycles as a starting point for docking shows promise in modeling binding modes of macrocyclic compounds.

An azine based sensor for selective detection of Cu2+ ions and its copper complex for sensing of phosphate ions in physiological conditions and in living cells.

PubMed

Tiwari, Karishma; Kumar, Sumit; Kumar, Vipan; Kaur, Jeevanjot; Arora, Saroj; Mahajan, Rakesh Kumar

2018-02-15

A simple and cost effective unsymmetrical azine based Schiff base, 5-diethylamino-2-[(2-hydroxy-benzylidene)hydrazonomethyl]-phenol (1) was synthesized which selectively detect Cu 2+ ions in the presence of other competitive ions through "naked eye" in physiological conditions (EtOH-buffer (1:1, v/v, HEPES 10mM, pH=7.4)). The presence of Cu 2+ induce color change from light yellow green to yellow with the appearance of a new band at 450nm in UV-Vis spectra of Schiff base 1. The fluorescence of Schiff base 1 (10μM) was quenched completely in the presence of 2.7 equiv. of Cu 2+ ions. Sub-micromolar limit of detection (LOD=3.4×10 -7 M), efficient Stern-Volmer quenching constant (K SV =1.8×10 5 Lmol -1 ) and strong binding constant (log K b =5.92) has been determined with the help of fluorescence titration profile. Further, 1-Cu 2+ complex was employed for the detection of phosphate ions (PO 4 3- , HPO 4 2- and H 2 PO 4 - ) at micromolar concentrations in EtOH-buffer of pH7.4 based on fluorescence recovery due to the binding of Cu 2+ with phosphate ions. Solubility at low concentration in aqueous medium, longer excitation (406nm) and emission wavelength (537nm), and biocompatibility of Schiff base 1 formulates its use in live cell imaging. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis and evaluation of nanoglobular macrocyclic Mn(II) chelate conjugates as non-gadolinium(III) MRI contrast agents.

PubMed

Tan, Mingqian; Ye, Zhen; Jeong, Eun-Kee; Wu, Xueming; Parker, Dennis L; Lu, Zheng-Rong

2011-05-18

Because of the recent observation of the toxic side effects of Gd(III) based MRI contrast agents in patients with impaired renal function, there is strong interest on developing alternative contrast agents for MRI. In this study, macrocyclic Mn(II) chelates were conjugated to nanoglobular carriers, lysine dendrimers with a silsesquioxane core, to synthesize non-Gd(III) based MRI contrast agents. A generation 3 nanoglobular conjugate of Mn(II)-1,4,7-triaazacyclononane-1,4,7-triacetate-GA amide (G3-NOTA-Mn) was also synthesized and evaluated. The per ion T(1) and T(2) relaxivities of G2, G3, G4 nanoglobular Mn(II)-DOTA monoamide conjugates decreased with increasing generation of the carriers. The T(1) relaxivities of G2, G3, and G4 nanoglobular Mn(II)-DOTA conjugates were 3.3, 2.8, and 2.4 mM(-1) s(-1) per Mn(II) chelate at 3 T, respectively. The T(1) relaxivity of G3-NOTA-Mn was 3.80 mM(-1) s(-1) per Mn(II) chelate at 3 T. The nanoglobular macrocyclic Mn(II) chelate conjugates showed good in vivo stability and were readily excreted via renal filtration. The conjugates resulted in much less nonspecific liver enhancement than MnCl(2) and were effective for contrast-enhanced tumor imaging in nude mice bearing MDA-MB-231 breast tumor xenografts at a dose of 0.03 mmol Mn/kg. The nanoglobular macrocyclic Mn(II) chelate conjugates are promising nongadolinium based MRI contrast agents.

Metal based pharmacologically active agents: Synthesis, structural characterization, molecular modeling, CT-DNA binding studies and in vitro antimicrobial screening of iron(II) bromosalicylidene amino acid chelates

NASA Astrophysics Data System (ADS)

Abdel-Rahman, Laila H.; El-Khatib, Rafat M.; Nassr, Lobna A. E.; Abu-Dief, Ahmed M.; Ismael, Mohamed; Seleem, Amin Abdou

2014-01-01

In recent years, great interest has been focused on Fe(II) Schiff base amino acid complexes as cytotoxic and antitumor drugs. Thus a series of new iron(II) complexes based on Schiff bases amino acids ligands have been designed and synthesized from condensation of 5-bromosalicylaldehyde (bs) and α-amino acids (L-alanine (ala), L-phenylalanine (phala), L-aspartic acid (aspa), L-histidine (his) and L-arginine (arg)). The structure of the investigated iron(II) complexes was elucidated using elemental analyses, infrared, ultraviolet-visible, thermogravimetric analysis, as well as conductivity and magnetic susceptibility measurements. Moreover, the stoichiometry and the stability constants of the prepared complexes have been determined spectrophotometrically. The results suggest that 5-bromosalicylaldehyde amino acid Schiff bases (bs:aa) behave as dibasic tridentate ONO ligands and coordinate to Fe(II) in octahedral geometry according to the general formula [Fe(bs:aa)2]ṡnH2O. The conductivity values between 37 and 64 ohm-1 mol-1 cm2 in ethanol imply the presence of nonelectrolyte species. The structure of the complexes was validated using quantum mechanics calculations based on accurate DFT methods. Geometry optimization of the Fe-Schiff base amino acid complexes showed that all complexes had octahedral coordination. In addition, the interaction of these complexes with (CT-DNA) was investigated at pH = 7.2, by using UV-vis absorption, viscosity and agarose gel electrophoresis measurements. Results indicated that the investigated complexes strongly bind to calf thymus DNA via intercalative mode and showed a different DNA binding according to the sequence: bsari > bshi > bsali > bsasi > bsphali. Moreover, the prepared compounds are screened for their in vitro antibacterial and antifungal activity against three types of bacteria, Escherichia coli, Pseudomonas aeruginosa and Bacillus cereus and three types of anti fungal cultures, Penicillium purpurogenium, Aspergillus flavus and Trichotheium rosium. The results of these studies indicated that the metal complexes exhibit a stronger antibacterial and antifungal efficiency than their corresponding Schiff base amino acid ligands.

The chemical mechanism of sheep liver 6-phosphogluconate dehydrogenase. A Schiff-base intermediate is not involved.

PubMed Central

Topham, C M; Dalziel, K

1986-01-01

[2-18O]Ribulose 5-phosphate was prepared and shown to be converted enzymically by 6-phosphogluconate dehydrogenase from sheep liver into 6-phosphogluconate with complete retention of the heavy isotope. This finding unequivocally excludes the possibility of a Schiff-base mechanism for the enzyme. The involvement of metal ions has already been excluded, and other possible mechanisms are discussed. The enzyme was purified by an improved large-scale procedure, which is briefly described. PMID:3718491

Synthesis of Two Coumarin-Derived Schiff Bases and Investigation of theirs Selectivity for Zn2.

PubMed

Fan, Long

2017-07-01

In this study, the coumarin-derived schiff bases (HL 1 and HL 2 ) have been designed and synthesized. Upon the addition of Zn 2+ , both of them show significant fluorescence enhancement owing to inhibits PET and ESIPT process respectively. However, the receptor HL 2 response toward Cd 2+ , Mg 2+ , Ba 2+ , Ca 2+ besides Zn 2+ and exhibits fluorescence enhancement but not enough to detection of the concentration levels of Zn 2+ .

Concurrent treatment with a macrocyclic lactone and benzimidazole provides season long performance advantages in grazing cattle harboring macrocyclic lactone resistant nematodes.

PubMed

Edmonds, M D; Vatta, A F; Marchiondo, A A; Vanimisetti, H B; Edmonds, J D

2018-03-15

In 2013, a 118-day study was initiated to investigate the efficacy of concurrent treatment at pasture turnout with an injectable macrocyclic lactone with activity up to 28 days and an oral benzimidazole, referred to as "conventional" anthelmintics, when compared to treatment with conventional macrocyclic lactone alone or an injectable macrocyclic lactone with extended activity of 100 days or longer. A group of 210 steers were obtained from a ranch in California and transported to Idaho, USA. A total of 176 steers with the highest fecal egg counts were blocked by pre-treatment body weights and pasture location. A total of 44 pasture paddocks were assigned with 4 steers per paddock with 12 paddocks per therapeutic treatment group and 8 paddocks per controls. The four treatments were injectable doramectin (Dectomax ® , Zoetis Inc., 0.2 mg kg -1 BW, SC), injectable doramectin concurrently with oral albendazole (Valbazen ® , Zoetis Inc., 10 mg kg -1 BW, PO), extended release injectable eprinomectin (LongRange™, Merial Limited, 1 mg kg -1 BW, SC) or saline. Cattle were individually weighed and sampled for fecal egg count on Days 0, 31/32, 61, 88, and 117/118 with an additional fecal sample on Day 14. At conclusion, one steer per paddock was euthanized for nematode recovery. The results from the first 32 days found evidence of macrocyclic lactone resistance against injectable doramectin and extended release eprinomectin. During this period the concurrent therapy provided nearly 100% efficacy based on fecal egg count reduction and a 19.98% improvement in total weight gain compared to controls (P = 0.039). At the conclusion of the 118-day study and past the approved efficacy for the conventional anthelmintics, the concurrent therapy with conventional anthelmintics provided a 22.98% improvement in total weight gain compared to controls (P = 0.004). The 118-day improvement in weight gain for the extended release eprinomectin group (29.06% compared to control) was not statistically different from the concurrent therapy with conventional anthelmintics. The results indicate that concurrent treatment with a conventional macrocyclic lactone and benzimidazole may provide production benefits early in the grazing period that continue throughout the entire period for cattle harboring macrocyclic lactone resistant nematodes. By using two different anthelmintic classes together, macrocyclic lactone resistant parasites were effectively controlled early in the period. Furthermore, the use of an effective conventional anthelmintic treatment regimen without an extended period of drug release may help to promote refugia and decrease the further selection for anthelmintic resistant parasites. Copyright © 2018 Elsevier B.V. All rights reserved.

Structure-Activity Relationship and Molecular Mechanics Reveal the Importance of Ring Entropy in the Biosynthesis and Activity of a Natural Product.

PubMed

Tran, Hai L; Lexa, Katrina W; Julien, Olivier; Young, Travis S; Walsh, Christopher T; Jacobson, Matthew P; Wells, James A

2017-02-22

Macrocycles are appealing drug candidates due to their high affinity, specificity, and favorable pharmacological properties. In this study, we explored the effects of chemical modifications to a natural product macrocycle upon its activity, 3D geometry, and conformational entropy. We chose thiocillin as a model system, a thiopeptide in the ribosomally encoded family of natural products that exhibits potent antimicrobial effects against Gram-positive bacteria. Since thiocillin is derived from a genetically encoded peptide scaffold, site-directed mutagenesis allows for rapid generation of analogues. To understand thiocillin's structure-activity relationship, we generated a site-saturation mutagenesis library covering each position along thiocillin's macrocyclic ring. We report the identification of eight unique compounds more potent than wild-type thiocillin, the best having an 8-fold improvement in potency. Computational modeling of thiocillin's macrocyclic structure revealed a striking requirement for a low-entropy macrocycle for activity. The populated ensembles of the active mutants showed a rigid structure with few adoptable conformations while inactive mutants showed a more flexible macrocycle which is unfavorable for binding. This finding highlights the importance of macrocyclization in combination with rigidifying post-translational modifications to achieve high-potency binding.

Correlation between oxygen adsorption energy and electronic structure of transition metal macrocyclic complexes.

PubMed

Liu, Kexi; Lei, Yinkai; Wang, Guofeng

2013-11-28

Oxygen adsorption energy is directly relevant to the catalytic activity of electrocatalysts for oxygen reduction reaction (ORR). In this study, we established the correlation between the O2 adsorption energy and the electronic structure of transition metal macrocyclic complexes which exhibit activity for ORR. To this end, we have predicted the molecular and electronic structures of a series of transition metal macrocyclic complexes with planar N4 chelation, as well as the molecular and electronic structures for the O2 adsorption on these macrocyclic molecules, using the density functional theory calculation method. We found that the calculated adsorption energy of O2 on the transition metal macrocyclic complexes was linearly related to the average position (relative to the lowest unoccupied molecular orbital of the macrocyclic complexes) of the non-bonding d orbitals (d(z(2)), d(xy), d(xz), and d(yz)) which belong to the central transition metal atom. Importantly, our results suggest that varying the energy level of the non-bonding d orbitals through changing the central transition metal atom and/or peripheral ligand groups could be an effective way to tuning their O2 adsorption energy for enhancing the ORR activity of transition metal macrocyclic complex catalysts.

Synthesis, characterization, DFT calculations and biological studies of Mn(II), Fe(II), Co(II) and Cd(II) complexes based on a tetradentate ONNO donor Schiff base ligand

NASA Astrophysics Data System (ADS)

Abdel-Rahman, Laila H.; Ismail, Nabawia M.; Ismael, Mohamed; Abu-Dief, Ahmed M.; Ahmed, Ebtehal Abdel-Hameed

2017-04-01

This study highlights synthesis and characterization of a tetradentate ONNO Schiff base ligand namely (1, 1‧- (pyridine-2, 3-dimethyliminomethyl) naphthalene-2, 2‧-diol) and hereafter denotes as "HNDAP″ and selected metal complexes including Mn(II), Fe(II), Co(II) and Cd(II) as a central metal. HNDAP was synthesized from 1:2 M ratio condensation of 2, 3-diaminopyridine and 2- hydroxy-1-naphthaldhyde, respectively. The stoichiometric ratios of the prepared complexes were estimated using complementary techniques such as; elemental analyses (-C, H, N), FT-IR, magnetic measurements and molar conductivity. Furthermore, their physicochemical studies were carried out using thermal TGA, DTA and kinetic-thermodynamic studies along with DFT calculations. The results of elemental analyses showed that these complexes are present in a 1:1 metal-to- ligand molar ratio. Moreover, the magnetic susceptibilities values at room temperature revealed that Mn(II), Fe(II) and Co(II) complexes are paramagnetic in nature and have an octahedral (Oh) geometry. In contrast, Cd(II) is diamagnetic and stabilizes in square planar sites. The molar conductivity measurements indicated that all complexes are nonelectrolytes in dimethyl formamide. Spectral data suggested that the ligand is as tetradentate and coordinated with Co(II) ion through two phenolic OH and two azomethine nitrogen. However, for Mn(II), Fe(II) and Cd(II) complexes, the coordination occurred through two phenolic oxygen and two azomethine nitrogen with deprotonation of OH groups. The proposed chemical structures have been validated by quantum mechanics calculations. Antimicrobial activities of both the HNDAP Schiff base ligand and its metal complexes were tested against strains of Gram (-ve) E. coli and Gram (+ve) B. subtilis and S. aureus bacteria and C. albicans, A. flavus and T. rubrum fungi. All the prepared compounds showed good results of inhibition against the selected pathogenic microorganisms. The investigated HNDAP Schiff base complexes showed higher activity and stability than their corresponding HNDAP Schiff base ligand and the highest activity observed for Cd(II) complex. Moreover, the prepared Schiff base ligand and its Mn(II) and Co(II) complexes have been evaluated for their anticancer activities against two cancer cell lines namely; colon carcinoma cells (HCT-116 cell line) and hepatocellular carcinoma (Hep-G2) cell lines The interaction of Mn(II) and Co(II) complexes with calf thymus DNA (CT-DNA) was studied by absorption spectroscopic technique and viscosity measurements. Both complexes showed a successful interaction with CT-DNA via intercalation mode.

Design, synthesis, X-ray studies, and biological evaluation of novel macrocyclic HIV-1 protease inhibitors involving the P1'-P2' ligands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Arun K.; Sean Fyvie, W.; Brindisi, Margherita

Design, synthesis, and evaluation of a new class of HIV-1 protease inhibitors containing diverse flexible macrocyclic P1'-P2' tethers are reported. Inhibitor 5a with a pyrrolidinone-derived macrocycle exhibited favorable enzyme inhibitory and antiviral activity (Ki = 13.2 nM, IC50 = 22 nM). Further incorporation of heteroatoms in the macrocyclic skeleton provided macrocyclic inhibitors 5m and 5o. These compounds showed excellent HIV-1 protease inhibitory (Ki = 62 pM and 14 pM, respectively) and antiviral activity (IC50 = 5.3 nM and 2.0 nM, respectively). Inhibitor 5o also remained highly potent against a DRV-resistant HIV-1 variant.

Zn(II), Ni(II), Cu(II) and Pb(II) complexes of tridentate asymmetrical Schiff base ligands: Synthesis, characterization, properties and biological activity

NASA Astrophysics Data System (ADS)

Şahin, Mustafa; Koçak, Nuriye; Erdenay, Damla; Arslan, Uğur

2013-02-01

New asymmetrical tridentate Schiff base ligands were synthesized using 1,2-phenylenediamine, 4-methyl-1,2-phenylenediamine, 2-hydroxy-1-napthaldehyde, 9-anthracenecarboxaldehyde. Schiff base ligands and their metal complexes were synthesised and characterized by using FT-IR, 1H NMR, 13C NMR, UV-Vis, XRD, ESR, elemental analysis and fluorescence studies. The antimicrobial activity of the ligands and their metal complexes were studied against Staphylococcus aureus ATCC 29213, S. aureus ATCC 25923, Streptococcus mutans RSHM 676, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853. The determination of the antibacterial activity was done using the broth microdilution methods. In general, it has been determined that the studied compounds have MIC values similar to Gram-positive and Gram-negative bacteria. It has been found that Ni, Pb, Zn derivatives of HL1A and ZnL2A has lower MIC values than ampicillin for P. aeruginosa ATCC 27853 strain.

A gallium(III) Schiff base-curcumin complex that binds to amyloid-β plaques.

PubMed

Lange, Jaclyn L; Hayne, David J; Roselt, Peter; McLean, Catriona A; White, Jonathan M; Donnelly, Paul S

2016-09-01

Gallium-68 is a positron-emitting isotope that can be used in positron-emission tomography imaging agents. Alzheimer's disease is associated with the formation of plaques in the brain primarily comprised of aggregates of a 42 amino acid protein called amyloid-β. With the goal of synthesising charge neutral, low molecular weight, lipophilic gallium complexes with the potential to cross the blood-brain barrier and bind to Aβ plaques we have used an ancillary tetradentate N 2 O 2 Schiff base ligand and the β-diketone curcumin as a bidentate ligand to give a six-coordinate Ga 3+ complex. The tetradentate Schiff base ligand adopts the cis-β configuration with deprotonated curcumin acting as a bidentate ligand. The complex binds to amyloid-β plaques in human brain tissue and it is possible that extension of this chemistry to positron-emitting gallium-68 could provide useful imaging agents for Alzheimer's disease. Copyright © 2016 Elsevier Inc. All rights reserved.

Ultrasonic promoted synthesis of novel s-triazine-Schiff base derivatives; molecular structure, spectroscopic studies and their preliminary anti-proliferative activities

NASA Astrophysics Data System (ADS)

El-Faham, Ayman; Soliman, Saied M.; Ghabbour, Hazem A.; Elnakady, Yasser A.; Mohaya, Talal A.; Siddiqui, Mohammed R. H.; Albericio, Fernando

2016-12-01

Novel series of s-triazine-Schiff base derivatives were synthesized employing ultrasonic irradiation and characterized by NMR (1H and 13C), FT-IR, and elemental analysis. The use of ultrasonic irradiation has allowed the preparation of the target products with better yields in shorter reaction time and excellent purities compared to the conventional heating. X-ray single crystal diffraction experiments verified the molecular structure of four from the new prepared s-triaizne-Schiff base derivatives. The molecular structures of the studied compounds are computerized using DFT/B3LYP method. The effects of substituent at the triazine and phenyl ring on the electronic and spectroscopic properties of the studied compounds were also investigated. The natural atomic charges showed that pipridino-s-triazine derivatives are richer in electrons than those having morpholino derivatives. The anti-proliferative effects for the prepared compounds were tested against three different cancer cell lines.

The Zinc-Schiff Base-Novicidin Complex as a Potential Prostate Cancer Therapy

PubMed Central

Milosavljevic, Vedran; Haddad, Yazan; Merlos Rodrigo, Miguel Angel; Moulick, Amitava; Polanska, Hana; Hynek, David; Heger, Zbynek; Kopel, Pavel; Adam, Vojtech

2016-01-01

Prostate cancer cells control energy metabolism by chelating intracellular zinc. Thus, zinc delivery has been a popular therapeutic approach for prostate cancer. Here, we propose the use of the membrane-penetrating peptide Novicidin connected to zinc-Schiff base as a carrier vehicle for the delivery of zinc to prostate cells. Mass spectrometry, electrochemistry and spectrophotometry confirmed the formation/stability of this complex and provided insight regarding the availability of zinc for complex interactions. This delivery system showed minor toxicity in normal PNT1A cells and high potency towards PC3 tumor cells. The complex preferentially penetrated PC3 tumor cells in contrast to confinement to the membranes of PNT1A. Furthermore, zinc uptake was confirmed in both cell lines. Molecular analysis was used to confirm the activation of zinc stress (e.g., ZnT-1) and apoptosis (e.g., CASP-1). Our results strongly suggest that the zinc-Schiff base-Novicidin complex has great potential as a novel anticancer drug. PMID:27727290

Two different forms of metarhodopsin II: Schiff base deprotonation precedes proton uptake and signaling state.

PubMed

Arnis, S; Hofmann, K P

1993-08-15

Rhodopsin is a retinal protein and a G-protein-coupled receptor; it shares with both of these families the seven helix structure. To generate the G-interacting helix-loop conformation, generally identified with the 380-nm absorbing metarhodopsin II (MII) photoproduct, the retinal Schiff base bond to the apoprotein must be deprotonated. This occurs as a key event also in the related retinal proteins, sensory rhodopsins, and the proton pump bacteriorhodopsin. In MII, proton uptake from the aqueous phase must be involved as well, since its formation increases the pH of the aqueous medium and is accelerated under acidic conditions. In the native membrane, the pH effect matches MII formation kinetically, suggesting that intramolecular and aqueous protonation changes contribute in concert to the protein transformation. We show here, however, that proton uptake, as indicated by bromocresol purple, and Schiff base deprotonation (380-nm absorption change) show different kinetics when the protein is solubilized in suitable detergents. Our data are consistent with a two-step reaction:

Antioxidant, electrochemical, thermal, antimicrobial and alkane oxidation properties of tridentate Schiff base ligands and their metal complexes

NASA Astrophysics Data System (ADS)

Ceyhan, Gökhan; Çelik, Cumali; Uruş, Serhan; Demirtaş, İbrahim; Elmastaş, Mahfuz; Tümer, Mehmet

2011-10-01

In this study, two Schiff base ligands (HL 1 and HL 2) and their Cu(II), Co(II), Ni(II), Pd(II) and Ru(III) metal complexes were synthesized and characterized by the analytical and spectroscopic methods. Alkane oxidation activities of the metal complexes were studied on cyclohexane as substrate. The ligands and their metal complexes were evaluated for their antimicrobial activity against Corynebacterium xerosis, Bacillus brevis, Bacillus megaterium, Bacillus cereus, Mycobacterium smegmatis, Staphylococcus aureus, Micrococcus luteus and Enterococcus faecalis (as Gram-positive bacteria) and Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Yersinia enterocolitica, Klebsiella fragilis, Saccharomyces cerevisiae, and Candida albicans (as Gram-negative bacteria). The antioxidant properties of the Schiff base ligands were evaluated in a series of in vitro tests: 1,1-diphenyl-2-picrylhydrazyl (DPPH rad ) free radical scavenging and reducing power activity of superoxide anion radical generated non-enzymatic systems. Electrochemical and thermal properties of the compounds were investigated.

Self-Assembly of a [1+1] Ionic Hexagonal Macrocycle and its Antiproliferative Activity

NASA Astrophysics Data System (ADS)

Singh, Khushwant; Gangrade, Ankit; Bhowmick, Sourav; Jana, Achintya; Mandal, Biman B.; Das, Neeladri

2018-04-01

A unique irregular hexagon was self-assembled using an organic donor clip (bearing terminal pyridyl units) and a complementary organometallic acceptor clip. The resulting metallamacrocycle was characterized by multinuclear NMR, mass spectrometry, and elemental analyses. Molecular modeling confirmed hexagonal shaped cavity for this metallamacrocycle which is a unique example of a discrete hexagonal framework self-assembled from only two building blocks. Cytotoxicity of the Pt-based acceptor tecton and the self-assembled PtII-based macrocycle was evaluated using three cancer cell lines and results were compared with cisplatin. Results confirmed a positive effect of the metallamacrocycle formation on cell growth inhibition.

Comparison of MRI properties between derivatized DTPA and DOTA gadolinium-dendrimer conjugates.

PubMed

Nwe, K; Bernardo, M; Regino, C A S; Williams, M; Brechbiel, M W

2010-08-15

In this report we directly compare the in vivo and in vitro MRI properties of gadolinium-dendrimer conjugates of derivatized acyclic diethylenetriamine-N,N',N',N'',N''-pentaacetic acid (1B4M-DTPA) and macrocyclic 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (C-DOTA). The metal-ligand chelates were pre-formed in alcohol prior to conjugation to the generation 4 PAMAM dendrimer (G4D), and the dendrimer-based agents were purified by Sephadex(R) G-25 column. The analysis and SE-HPLC data indicated chelate to dendrimer ratios of 30:1 and 28:1, respectively. Molar relaxivity measured at pH 7.4, 22 degrees C, and 3T are comparable (29.5 vs 26.9 mM(-1)s(-1)), and both conjugates are equally viable as MRI contrast agents based on the images obtained. The macrocyclic agent however exhibits a faster rate of clearance in vivo (t(1/2)=16 vs 29 min). Our conclusion is that the macrocyclic-based agent is the more suitable agent for in vivo use for these reasons combined with kinetic inertness associated with the Gd(III) DOTA complex stability properties. Published by Elsevier Ltd.

Comparison of MRI properties between derivatized DTPA and DOTA gadolinium-dendrimer conjugates

PubMed Central

Nwe, K.; Bernardo, M; Regino, C. A. S.; Williams, M; Brechbiel, M. W.

2010-01-01

In this report we directly compare the in vivo and in vitro MRI properties of gadolinium-dendrimer conjugates of derivatized acyclic diethylenetriamine-N,N’,N’,N’’, N’’-pentaacetic acid (1B4M-DTPA) and macrocyclic 1,4,7,10-tetraazacyclododecane-N,N’,N’’,N’’’-tetraacetic acid (C-DOTA). The metal-ligand chelates were pre-formed in alcohol prior to conjugation to the generation 4 PAMAM dendrimer (G4D), and the dendrimer-based agents were purified by Sephadex® G-25 column. The analysis and SE-HPLC data indicated chelate to dendrimer ratios of 30:1 and 28:1 respectively. Molar relaxivity measured at pH 7.4, 22°C, and 3T are comparable (29.5 vs. 26.9 mM−1s−1), and both conjugates are equally viable as MRI contrast agents based on the images obtained. The macrocyclic agent however exhibits a faster rate of clearance in vivo (t1/2 = 16 vs. 29 min.). Our conclusion is that the macrocyclic-based agent is the more suitable agent for in vivo use for these reasons combined with kinetic inertness associated with the Gd(III) DOTA complex stability properties. PMID:20663676

Antimicrobial salicylaldehyde Schiff bases: synthesis, characterization and evaluation.

PubMed

Adeel-Sharif, Hafiz Muhammad; Ahmed, Dildar; Mir, Hira

2015-03-01

As the pathogens soon develop resistance to the existing antibiotics, the demand for new and more effective anti-microbial agents is a continuous phenomenon. In this paper we are reporting synthesis and spectral data of eight Schiff bases of salicylaldehyde with different amines, and evaluation of their anti-microbial activities against different bacterial strains. The bases were synthesized by reflux method, and their structures were determined based FT-IR, (1)H-NMR, (13)C-NMR and Mass spectrometric data. The Schiff bases synthesized included 2-{[(Z)-(2-hydroxyphenyl) methylidene] amino}benzoicacid (SB1), 4-{[(Z)-(2-hydroxyphenyl) methylidene] amino} benzoic acid (SB2),2-[(naphthalene-2-ylimino)methyl] phenol(SB3),2-2'-[benzene-1,4-diylbis(nitrilomethylylidene)]diphenol (SB4), 2-2'-[benzene-1,2-diylbis (nitrile-(E)-methylylidene)]diphenol (SB5), 2-[(2-phenylhydrazineylidene)methyl]phenol (SB6), 2-2'-[ethene-1,2-diylbis(iminomethanediyl)]diphenol (SB7) and 2-[(Z)-(phenylimino)methyl]phenol (SB8). The anti-microbial activities of synthesized Schiff bases were determined in terms of zones of inhibition and minimum inhibitory concentrations (MICs). All the bases showed moderate to good activities against all the tested microorganisms. The MICs of most compounds were 100-200βg/mL against different microorganisms. However, it was 50βg/mL for SB1 against P. aeruginosa (1), SB3 against P. aurantiaca, P. aeruginosa (1), E. coli (2), S. typhi (2) and C. freundii, SB4against E. coli (2), S. typhi (1) and S. maltophilia, SB5 against K. pneumoniae and S. typhi (2), SB6 against P. aeruginosa (3) and C. freundii, SB7 against E. cloacae and A. lipoferum, and SB8 against E. coli (2). Considerably active bases may prove to be potential candidates for future antibiotic drugs.

The two consecutive M substates in the photocycle of bacteriorhodopsin are affected specifically by the D85N and D96N residue replacements

NASA Technical Reports Server (NTRS)

Zimanyi, L.; Cao, Y.; Chang, M.; Ni, B.; Needleman, R.; Lanyi, J. K.

1992-01-01

The photocycle of the proton pump bacteriorhodopsin contains two consecutive intermediates in which the retinal Schiff base is unprotonated; the reaction between these states, termed M1 and M2, was suggested to be the switch in the proton transport which reorients the Schiff base from D85 on the extracellular side to D96 on the cytoplasmic side (Varo and Lanyi, Biochemistry 30, 5016-5022, 1991). At pH 10 the absorption maxima of both M1 and M2 could be determined in the recombinant D96N protein. We find that M1 absorbs at 411 nm as do M1 and M2 in wild-type bacteriorhodopsin, but M2 absorbs at 404 nm. Thus, in M2 but not M1 the unprotonated Schiff base is affected by the D96N residue replacement. The connectivity of the Schiff base to D96 in the detected M2 state, but not in M1, is thereby established. On the other hand, the photostationary state which develops during illumination of D85N bacteriorhodopsin contains an M state corresponding to M1 with an absorption maximum shifted to 400 nm, suggesting that this species in turn is affected by D85. These results are consistent with the suggestion that M1 and M2 are pre-switch and post-switch states, respectively.

DNA Cleavage, Cytotoxic Activities, and Antimicrobial Studies of Ternary Copper(II) Complexes of Isoxazole Schiff Base and Heterocyclic Compounds

PubMed Central

Chityala, Vijay Kumar; Sathish Kumar, K.; Macha, Ramesh; Tigulla, Parthasarathy; Shivaraj

2014-01-01

Novel mixed ligand bivalent copper complexes [Cu. L. A. ClO 4] and [Cu. L. A] where “L” is Schiff bases, namely 2-((3,4-dimethylisoxazol-5-ylimino)methyl)-4-bromophenol (DMIIMBP)/2-((3,4-dimethylisoxazol-5-ylimino)methyl)-4-chlorophenol (DMIIMCP), and “A” is heterocyclic compound, such as 1,10-phenanthroline (phen)/2,21-bipyridyl (bipy)/8-hydroxyquinoline (oxine)/5-chloro-8-hydroxyquinoline (5-Cl-oxine), have been synthesized. These complexes have been characterized by IR, UV-Vis, ESR, elemental analysis, magnetic moments, TG, and DTA. On the basis of spectral studies and analytical data, five-coordinated square pyramidal/four-coordinated square planar geometry is assigned to all complexes. The ligands and their ternary complexes with Cu(II) have been screened for antimicrobial activity against bacteria and fungi by paper disc method. The antimicrobial studies of Schiff bases and their metal complexes showed significant activity and further it is observed that the metal complexes showed more activity than corresponding Schiff bases. In vitro antitumor activity of Cu(II) complexes was assayed against human cervical carcinoma (HeLa) cancer cells and it was observed that few complexes exhibit good antitumor activity on HeLa cell lines. The DNA cleavage studies have also been carried out on pBR 322 and it is observed that these Cu(II) complexes are capable of cleaving supercoiled plasmid DNA in the presence of H2O2 and UV light. PMID:24895493

Metal (II) Complexes Derived from Naphthofuran-2-carbohydrazide and Diacetylmonoxime Schiff Base: Synthesis, Spectroscopic, Electrochemical, and Biological Investigation

PubMed Central

Sumathi, R. B.; Halli, M. B.

2014-01-01

A new Schiff base and a new series of Co(II), Ni(II), Cu(II), Cd(II), and Hg(II) complexes were synthesized by the condensation of naphthofuran-2-carbohydrazide and diacetylmonoxime. Metal complexes of the Schiff base were prepared from their chloride salts of Co(II), Ni(II), Cu(II), Cd(II), and Hg(II) in ethanol. The ligand along with its metal complexes have been characterized on the basis of analytical data, IR, electronic, mass, 1HNMR, ESR spectral data, thermal studies, magnetic susceptibility, and molar conductance measurements. The nonelectrolytic behaviour of the complexes was assessed from the measured low conductance data. The elemental analysis of the complexes confirm the stoichiometry of the type CuL2Cl2 and MLCl2 where M = Ni(II), Co(II), Cd(II), and Hg(II) and L = Schiff base. The redox property of the Cu(II) complex was investigated by electrochemical method using cyclic voltammetry. In the light of these results, Co(II), Ni(II), and Cu(II) complexes are assigned octahedral geometry, Cd(II), and Hg(II) complexes tetrahedral geometry. In order to evaluate the effect of metal ions upon chelation, both the ligand and its metal complexes were screened for their antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The DNA cleaving capacity of all the complexes was analysed by agarose gel electrophoresis method. PMID:24592203

Cr(III), Fe(III) and Co(III) complexes of tetradentate (ONNO) Schiff base ligands: Synthesis, characterization, properties and biological activity

NASA Astrophysics Data System (ADS)

Keskioğlu, Eren; Gündüzalp, Ayla Balaban; Çete, Servet; Hamurcu, Fatma; Erk, Birgül

2008-08-01

A series of metal complexes were synthesized from equimolar amounts of Schiff bases: 1,4-bis[3-(2-hydroxy-1-naphthaldimine)propyl]piperazine (bappnaf) and 1,8-bis[3-(2-hydroxy-1-naphthaldimine)- p-menthane (damnaf) with metal chlorides. All of synthesized compounds were characterized by elemental analyses, spectral (UV-vis, IR, 1H- 13C NMR, LC-MS) and thermal (TGA-DTA) methods, magnetic and conductance measurements. Schiff base complexes supposed in tetragonal geometry have the general formula [M(bappnaf or damnaf)]Cl· nH 2O, where M = Cr(III), Co(III) and n = 2, 3. But also Fe(III) complexes have octahedral geometry by the coordination of two water molecules and the formula is [Fe(bappnaf or damnaf)(H 2O) 2]Cl. The changes in the selected vibration bands in FT-IR indicate that Schiff bases behave as (ONNO) tetradentate ligands and coordinate to metal ions from two phenolic oxygen atoms and two azomethine nitrogen atoms. Conductance measurements suggest 1:1 electrolytic nature of the metal complexes. The synthesized compounds except bappnaf ligand have the antimicrobial activity against the bacteria: Escherichia coli (ATCC 11230), Yersinia enterocolitica (ATCC 1501), Bacillus magaterium (RSKK 5117), Bacillus subtilis (RSKK 244), Bacillus cereus (RSKK 863) and the fungi: Candida albicans (ATCC 10239). These results have been considerably interest in piperazine derivatives due to their significant applications in antimicrobial studies.

Synthesis and spectral characterization of trinuclear, oxo-centered, carboxylate-bridged, mixed-valence iron complexes with Schiff bases.

PubMed

Singh, Atresh Kumar; Singh, Alok Kumar

2012-10-01

Some novel trinuclear, oxo-centered, carboxylate-bridged, mixed-valence iron complexes of the general formula [Fe(3)O(OOCR)(3)(SB)(3)L(3)] (where R=C(13)H(27), C(15)H(31) or C(17)H(35,) HSB=Schiff bases and L=Ethanol) have been synthesized by the stepwise substitutions of acetate ions from μ(3)-oxo-hexa(acetato)tri(aqua)iron(II)diiron(III), first with straight chain carboxylic acids and then with Schiff bases. The complexes were characterized by elemental analyses, molecular weight determinations and spectral (electronic, infrared, FAB mass, Mössbauer and powder XRD) studies. Molar conductance measurements indicated the complexes to be non-electrolytes in nitrobenzene. Bridging nature of carboxylate and Schiff base anions in the complexes was established by their infrared spectra. Mössbauer spectroscopic studies indicated two quadrupole-split doublets due to Fe(II) and Fe(III) ions at 80, 200 and 295K, confirming the complexes are mixed-valence species. This was also supported by the observed electronic spectra of the complexes. Magnetic susceptibility measurements displayed octahedral geometry around iron in mixed-valence state and a net antiferromagnetic exchange coupling via μ-oxo atom. Trinuclear nature of the complexes was confirmed by their molecular weight determination and FAB mass spectra. A plausible structure for these complexes has been established on the basis of spectral and magnetic moment data. Copyright © 2012 Elsevier B.V. All rights reserved.

Synthesis and in vitro acetylcholinesterase and butyrylcholinesterase inhibitory potential of hydrazide based Schiff bases.

PubMed

Rahim, Fazal; Ullah, Hayat; Taha, Muhammad; Wadood, Abdul; Javed, Muhammad Tariq; Rehman, Wajid; Nawaz, Mohsan; Ashraf, Muhammad; Ali, Muhammad; Sajid, Muhammad; Ali, Farman; Khan, Muhammad Naseem; Khan, Khalid Mohammed

2016-10-01

To discover multifunctional agents for the treatment of Alzheimer's disease, a series of hydrazide based Schiff bases were designed and synthesized based on multitarget-directed strategy. We have synthesized twenty-eight analogs of hydrazide based Schiff bases, characterized by various spectroscopic techniques and evaluated in vitro for acetylcholinesterase and butyrylcholinesterase inhibition. All compounds showed varied degree of acetylcholinesterase and butyrylcholinesterase inhibition when compared with standard Eserine. Among the series, compounds 10, 3 and 24 having IC50 values 4.12±0.01, 8.12±0.01 and 8.41±0.06μM respectively showed potent acetylcholinesterase inhibition when compared with Eserine (IC50=0.85±0.0001μM). Three compounds 13, 24 and 3 having IC50 values 6.51±0.01, 9.22±0.07 and 37.82±0.14μM respectively showed potent butyrylcholinesterase inhibition by comparing with eserine (IC50=0.04±0.0001μM). The remaining compounds also exhibited moderate to weak inhibitory potential. Structure activity relationship has been established. Through molecular docking studies the binding interaction was confirmed. Copyright © 2016 Elsevier Inc. All rights reserved.

Syntheses, characterization, superoxide dismutase, antimicrobial, crystal structure and molecular studies of copper (II) and nickel (II) complexes with 2-((E)-(2, 4-dibromophenylimino) methyl)-4-bromophenol as Schiff base ligand

NASA Astrophysics Data System (ADS)

Bharti, Sulakshna; Choudhary, Mukesh; Mohan, Bharti; Rawat, S. P.; Sharma, S. R.; Ahmad, Khursheed

2017-12-01

Three new copper (II) and nickel (II) complexes viz. [Cu(L)2](1a), [Cu(L)2](1b) and [Ni(L)2].DMF(2), where HL = 2-((E)-(2, 4-dibromophenylimino) methyl)-4-bromophenol, have been synthesized and characterized by using various physico-chemical and spectroscopic techniques. The crystal structures of Schiff base (HL) and their metal complexes (1a), (1b) and (2) were determined by single crystal X-ray diffraction. IR and UV-Vis spectra and magnetic susceptibility measurements agree with the observed crystal structures. The crystallographic and spectroscopic studies confirmed four coordinate environments around the metal (II) ions. The synthesized Schiff base ligand (HL) crystallizes in the orthorhombic system of the space group Pbca. Complex (1a) of HL was crystallized in the monoclinic system of the space group P21/c, a = 10.1712(9) Å, b = 10.9299(10) Å,c = 12.7684(11) Å,α = 90̊,β = 104.649(2)̊, γ = 90̊ and Z = 2 whereas complex (1b) and (2) crystallized in the triclinic system of the space group P-1, a = 11.499(5)Å, b = 11.598(5)Å, c = 12.211(5)Å, α = 98.860(5), β = 115.653(5),γ = 100.906(5) and Z = 2 for (1b), a = 9.080(6) Å, b = 9.545(8)Å, c = 9.545(8)Å, α = 101.43(4)º,β = 99.63(3)̊, γ = 117.71(2)º and Z = 1 for (2). The synthesized ligand (HL) was behaved as monobasic bidentate Schiff base ligand having N and O donor sites. The electron paramagnetic resonance spectra indicate a dx2-y2ground state (g|| > g⊥> 2.0023) for (1a) and (1b). Copper (II) complexes display X-band EPR spectra in 100% DMSO and 77 K, giving indicating dx2-y2ground state. Superoxide dismutase-like activities of HL and its complexes were investigated by nitrobluetetrazolium chloride-DMSO assay and IC50 values were evaluated. These complexes were also tested for their in vitro antimicrobial activities against two bacteria (E. coli and Salmonella typhi) and two fungi (Pencillium, Aspergillus sp.) comparing with the Schiff base. The antimicrobial results showed that the complexes were more biologically active compounds to the Schiff base (HL).

Improving the reactivity of phenylacetylene macrocycles toward topochemical polymerization by side chains modification

PubMed Central

Daigle, Maxime; Cantin, Katy

2014-01-01

Summary The synthesis and self-assembly of two new phenylacetylene macrocycle (PAM) organogelators were performed. Polar 2-hydroxyethoxy side chains were incorporated in the inner part of the macrocycles to modify the assembly mode in the gel state. With this modification, it was possible to increase the reactivity of the macrocycles in the xerogel state to form polydiacetylenes (PDAs), leading to a significant enhancement of the polymerization yields. The organogels and the PDAs were characterized using Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). PMID:25161718

The addition of a second lanthanide ion to increase the luminescence of europium(III) macrocyclic complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bromm, A.J. Jr.; Vallarino, L.M.; Leif, R.C.

At present, the microscopic visualization of luminescent labels containing lanthanide(III) ions, primarily europium(III), as light-emitting centers is best performed with time-gated instrumentation, which by virtually eliminating the background fluorescence results in an improved signal to noise ratio. However, the use of the europium(III) macrocycle, Quantum Dye{trademark}, in conjunction with the strong luminescence enhancing effect (cofluorescence) of yttrium(III) or gadolinium(III), can eliminate the need for such specialized instrumentation. In the presence of Gd(III), the luminescence of the Eu(III)-macrocycles can be conveniently observed with conventional fluorescence instrumentation at previously unattainable low levels. The Eu(III) {sup 5}D{sub 0} {r_arrow} {sup 7}F{sub 2} emissionmore » of the Eu(III)-macrocycles was observed as an extremely sharp band with a maximum at 619 nm and a clearly resolved characteristic pattern. At very low Eu(III)-macrocycle concentrations, another sharp emission was detected at 614 nm, arising from traces of Eu(III) present in even the purest commercially available gadolinium products. Discrimination of the resolved emissions of the Eu(III)-macrocycle and Eu(III) contaminant should provide a means to further lower the limit of detection of the Eu(III)-macrocycle.« less

Development and Evaluation of Cefadroxil Drug Loaded Biopolymeric Films Based on Chitosan-Furfural Schiff Base

PubMed Central

Dixit, Ritu B.; Uplana, Rahul A.; Patel, Vishnu A.; Dixit, Bharat C.; Patel, Tarosh S.

2010-01-01

Cefadroxil drug loaded biopolymeric films of chitosan-furfural schiff base were prepared by reacting chitosan with furfural in presence of acetic acid and perchloric acid respectively for the external use. Prepared films were evaluated for their strength, swelling index, thickness, drug content, uniformity, tensile strength, percent elongation, FTIR spectral analysis and SEM. The results of in vitro diffusion studies revealed that the films exhibited enhanced drug diffusion as compared to the films prepared using untreated chitosan. The films also demonstrated good to moderate antibacterial activities against selective gram positive and gram negative bacteria. PMID:21179325

Exploration of cellular DNA lesion, DNA-binding and biocidal ordeal of novel curcumin based Knoevenagel Schiff base complexes incorporating tryptophan: Synthesis and structural validation

NASA Astrophysics Data System (ADS)

Chandrasekar, Thiravidamani; Raman, Natarajan

2016-07-01

A few novel Schiff base transition metal complexes of general formula [MLCl] (where, L = Schiff base, obtained by the condensation reaction of Knoevenagel condensate of curcumin, L-tryptophan and M = Cu(II), Ni(II), Co(II), and Zn(II)), were prepared by stencil synthesis. They were typified using UV-vis, IR, EPR spectral techniques, micro analytical techniques, magnetic susceptibility and molar conductivity. Geometry of the metal complexes was examined and recognized as square planar. DNA binding and viscosity studies revealed that the metal(II) complexes powerfully bound via an intercalation mechanism with the calf thymus DNA. Gel-electrophoresis technique was used to investigate the DNA cleavage competence of the complexes and they establish to approve the cleavage of pBR322 DNA in presence of oxidant H2O2. This outcome inferred that the synthesized complexes showed better nuclease activity. Moreover, the complexes were monitored for antimicrobial activities. The results exposed that the synthesized compounds were forceful against all the microbes under exploration.

From Mesocates to Helicates: Structural, Magnetic and Chiro-Optical Studies on Nickel(II) Supramolecular Assemblies Derived from Tetradentate Schiff Bases.

PubMed

Mayans, Júlia; Font-Bardia, Mercè; Di Bari, Lorenzo; Arrico, Lorenzo; Zinna, Francesco; Pescitelli, Gennaro; Escuer, Albert

2018-05-28

The systematic reactions of a family of tetradentate pyridyl/imine and quinolyl/imine racemic or enantiopure Schiff bases with Ni(NO 3 ) 2 or Ni(ClO 4 ) 2 in the presence of sodium azide yielded, as a function of the starting racemic, chiral or achiral base, a set of chiral, meso or achiral complexes. In all cases, the compounds consist of two Ni II cations linked by a double azido bridge in its end-on coordination mode. All the dimers exhibit a mesocate supramolecular structure and one of them, the unprecedented mix of helicate and mesocate in 2:1 ratio. The transition from mesocate to helicate conformation has been reached by tuning the flexibility of the central spacers of the Schiff bases and the size of the substituents. Electronic circular dichroism (ECD) studies have been performed for two pairs of enantiomers and interpreted by means of DFT calculations. Susceptibility measurements show a ferromagnetic coupling between the Ni II cations mediated by the end-on azido bridges. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis, solvatochromaticity and bioactivities of some transition metal complexes with 2-(R-benzylideneamino)-pyridin-3-ol Schiff base derivatives

NASA Astrophysics Data System (ADS)

Ahmed, I. S.; Kassem, M. A.

2010-10-01

New four Schiff bases are prepared by condensation of 2-amino-pyridin-3-ol with 3, 4-dihydroxy-benzaldehyde (I), 2-hydroxybenzaldehyde (II), 5-bromo-2-hydroxybenzaldehyde (III), and 4-dimethylaminobenzaldehyde (IV). The structures of these compounds are characterized based on elemental analyses (C. H. N), IR and 1H NMR. Also, the electronic absorption spectra are recorded in organic solvents of different polarity. The solvents are selected to be covered a wide range of parameters (refractive index, dielectric constant and hydrogen bonding capacity). The UV-vis absorption spectra of Schiff base compounds are investigated in aqueous buffer solutions of varying pH and utilized for the determination of ionization constant, p Ka and activation free energy, Δ G* of the ionization process. The biological activity against bacterial species and fungi as microorganisms representing different microbial categories such as (two Gram-negative bacteria, Eschericha coli and Agrobacterium sp.),three Gram-positive bacteria ( Staphylococcus aureus, Bacillus subtlus and Bacillus megatherium), yeast ( Candida albicans), and fungi ( Aspergillus niger) were studied.

Synthesis, SAR Study and Evaluation of Mannich and Schiff Bases of Pyrazol-5(4H)-one Moiety Containing 3-(Hydrazinyl)-2-phenylquinazolin-4(3H)-one

PubMed Central

Sivakumar, K. K.; Rajasekharan, A.; Rao, R.; Narasimhan, B.

2013-01-01

In the present investigation, a series of 12 Mannich bases (QP1-12) and 5 Schiff bases (QSP1-5) of pyrazol-5(4H)-one moiety containing 3-(hydrazinyl)-2-phenylquinazolin-4(3H)-one has been synthesized and characterized by physicochemical as well as spectral means. The synthesized Mannich and Schiff bases were screened for their preliminary antimicrobial activity against Gram-positive and Gram-negative bacterial as well as fungal strains by the determination of zone of inhibition. Mannich bases (QP1-12) were found to be more potent antibacterial agents against Gram-positive bacteria, whereas Schiff bases (QSP1-5) were more potent against Gram-negative bacteria and fungi. Minimum inhibitory concentration result demonstrated that Mannich base compound (QP7) having ortho -OH and para -COOH group showed some improvement in antibacterial activity (minimum inhibitory concentration of 48.88×10−3 μM/ml) among the tested Gram-positive organisms and it also exhibit minimum inhibitory concentration of value of 12.22×10−3 μM/ml for Klebsiella pneumoniae. The antitubercular activity of synthesized compounds against Mycobacterium tuberculosis (H37Rv) was determined using microplate alamar blue assay. Compound QP11 showed appreciable antitubercular activity (minimum inhibitory concentration of 6.49×10−3 μM/ml) which was more active than the standard drugs, ethambutol (minimum inhibitory concentration of 7.60×10−3 μM/ml) and ciprofloxacin (9.4×10−3 μM/ml). Compounds QP11, QP9, QSP1, QSP2, and QSP5 have good selective index and may be selected as a lead compound for the development of novel antitubercular agents. PMID:24302802

Synthesis, spectral, thermal and biological studies of mixed ligand complexes with newly prepared Schiff base and 1,10-phenanthroline ligands

NASA Astrophysics Data System (ADS)

Abd El-Halim, Hanan F.; Mohamed, Gehad G.; Khalil, Eman A. M.

2017-10-01

A series of mixed ligand complexes were prepared from the Schiff base (L1) as a primary ligand, prepared by condensation of oxamide and furan-2-carbaldehyde, and 1,10-phenanthroline (1,10-phen) as a secondary ligand. The Schiff base ligand and its mixed ligand chelates were characterized based on elemental analysis, IR, 1H NMR, thermal analysis, UV-Visible, mass, molar conductance, magnetic moment. X-ray diffraction, solid reflectance and ESR also have been studied. The mixed ligand complexes were found to have the formulae of [M(L1) (1,10-phen)]Clm.nH2O (M = Cr(III) and Fe(III) (m = 3) (n = 0); M = Mn(II), Cu(II) and Cd(II) (m = 2) (n = 0); and M = Co(II) (m = 2) (n = 1), Ni(II) (m = 2) (n = 2) and Zn(II) (m = 2) (n = 3)) and that the geometrical structure of the complexes were octahedral. The parameters of thermodynamic using Coats-Redfern and Horowitz-Metzger equations were calculated. The synthesized Schiff base ligand, 1,10-phenanthroline ligand and Their mixed ligand complexes were also investigated for their antibacterial and antifungal activity against bacterial species (Gram-Ve bacteria: Pseudomonas aeruginosa and Escherichia coli) and (Gram + Ve bacteria: Bacillus subtilis and Streptococcus pneumonia) and fungi (Aspergillus fumigates and Candida albicans). The anticancer activity of the new compounds had been tested against breast (MFC7) and colon (HCT-116) cell lines. The results showed high activity for the synthesized compounds.

DNA incision evaluation, binding investigation and biocidal screening of Cu(II), Ni(II) and Co(II) complexes with isoxazole Schiff bases.

PubMed

Ganji, Nirmala; Chityala, Vijay Kumar; Marri, Pradeep Kumar; Aveli, Rambabu; Narendrula, Vamsikrishna; Daravath, Sreenu; Shivaraj

2017-10-01

Two new series of binary metal complexes [M(L 1 ) 2 ] and [M(L 2 ) 2 ] where, M=Cu(II), Ni(II) & Co(II) and L 1 =4-((3,4-dimethylisoxazol-5-ylimino)methyl)benzene-1,3-diol; L 2 =2-((3,4-dimethylisoxazol-5-ylimino)methyl)-5-methoxyphenol were synthesized and characterized by elemental analysis, 1 H NMR, 13 C NMR, FT-IR, ESI mass, UV-Visible, magnetic moment, ESR, SEM and powder XRD studies. Based on these results, a square planar geometry is assigned for all the metal complexes where the Schiff base acts as uninegatively charged bidentate chelating agent via the hydroxyl oxygen and azomethine nitrogen atoms. DNA binding studies of all the complexes with calf thymus DNA have been comprehensively investigated using electronic absorption spectroscopy, fluorescence quenching and viscosity studies. The oxidative and photo cleavage affinity of metal complexes towards supercoiled pBR322 DNA has been ascertained by agarose gel electrophoresis assay. From the results, it is observed that all the metal complexes bind effectively to CT-DNA via an intercalative mode of binding and also cleave pBR322 DNA in a promising manner. Further the Cu(II) complexes have shown better binding and cleavage properties towards DNA. The antimicrobial activities of the Schiff bases and their metal complexes were studied on bacterial and fungal strains and the results denoted that the complexes are more potent than their Schiff base ligands. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis, spectral and quantum chemical studies and use of (E)-3-[(3,5-bis(trifluoromethyl)phenylimino)methyl]benzene-1,2-diol and its Ni(II) and Cu(II) complexes as an anion sensor, DNA binding, DNA cleavage, anti-microbial, anti-mutagenic and anti-cancer agent

NASA Astrophysics Data System (ADS)

Ünver, Hüseyin; Boyacıoğlu, Bahadır; Zeyrek, Celal Tuğrul; Yıldız, Mustafa; Demir, Neslihan; Yıldırım, Nuray; Karaosmanoğlu, Oğuzhan; Sivas, Hülya; Elmalı, Ayhan

2016-12-01

We report the synthesis of a novel Schiff base (E)-3-[(3,5-bis(trifluoromethyl) phenylimino)methyl] benzene-1,2-diol from the reaction of 2,3-dihydroxybenzaldehyde with 3,5-bis(trifluoromethyl)aniline, and its Ni(II) and Cu(II) complexes. The molecular structure of the Schiff base was experimentally determined using X-ray single-crystal data and was compared to the structure predicted by theoretical calculations using density functional theory (DFT), Hartree-Fock (HF) and Möller-Plesset second-order perturbation (MP2). In addition, nonlinear optical (NLO) effects of the compound was predicted using DFT. The antimicrobial activities of the compounds were investigated for their minimum inhibitory concentration. UV-Vis spectroscopy studies of the interactions between the compounds and calf thymus DNA (CT-DNA) showed that the compounds interacts with CT-DNA via intercalative binding. A DNA cleavage study showed that the Cu(II) complex cleaved DNA without any external agents. The compounds inhibited the base pair mutation in the absence of S9 with high inhibition rate. In addition, in vitro cytotoxicity of the Ni(II) complex towards HepG2 cell line was assayed by the MTT method. Also, the colorimetric response of the Schiff base in DMSO to the addition of equivalent amount of anions (F-, Br-, I-, CN-, SCN-, ClO4-, HSO4-, AcO-, H2PO4-, N3- and OH-) was investigated. In this regard, while the addition of F-, CN-, AcO- and OH- anions into the solution containing Schiff base resulted in a significant color change, the addition of Br-, I-, SCN-, ClO4-, HSO4-, H2PO4- and N3- anions resulted in no color change. The most discernable color change in the Schiff base was caused by CN-, which demonstrated that the ligand can be used to selectively detect CN-.

A chiroptical switch based on supramolecular chirality transfer through alkyl chain entanglement and dynamic covalent bonding.

PubMed

Lv, Kai; Qin, Long; Wang, Xiufeng; Zhang, Li; Liu, Minghua

2013-12-14

Chirality transfer is an interesting phenomenon in Nature, which represents an important step to understand the evolution of chiral bias and the amplification of the chirality. In this paper, we report the chirality transfer via the entanglement of the alkyl chains between chiral gelator molecules and achiral amphiphilic Schiff base. We have found that although an achiral Schiff base amphiphile could not form organogels in any kind of organic solvents, it formed co-organogels when mixed with a chiral gelator molecule. Interestingly, the chirality of the gelator molecules was transferred to the Schiff base chromophore in the mixed co-gels and there was a maximum mixing ratio for the chirality transfer. Furthermore, the supramolecular chirality was also produced based on a dynamic covalent chemistry of an imine formed by the reaction between an aldehyde and an amine. Such a covalent bond of imine was formed reversibly depending on the pH variation. When the covalent bond was formed the chirality transfer occurred, when it was destroyed, the transfer stopped. Thus, a supramolecular chiroptical switch is obtained based on supramolecular chirality transfer and dynamic covalent chemistry.

A Schiff-based colorimetric fluorescent sensor with the potential for detection of fluoride ions.

PubMed

Huang, Cheng-Yin; Wan, Chin-Feng; Chir, Jiun-Ly; Wu, An-Tai

2013-11-01

A simple Schiff-based colorimetric fluorescent receptor 1 was prepared. It exhibits a "turn-on-type" mode with high sensitivity in the presence of F(-). The change in color is very easily observed by the naked eye in the presence of F(-), whereas other anions do not induce such a change. Job plot indicated a 1:2 complexation stoichiometry between receptor 1 and F(-). The association constant for 1-F(-) in CH3CN was determined as 1.32*10(5) M(-2) by a Hill plot.

Macrocyclic metal complexes for metalloenzyme mimicry and sensor development.

PubMed

Joshi, Tanmaya; Graham, Bim; Spiccia, Leone

2015-08-18

Examples of proteins that incorporate one or more metal ions within their structure are found within a broad range of classes, including oxidases, oxidoreductases, reductases, proteases, proton transport proteins, electron transfer/transport proteins, storage proteins, lyases, rusticyanins, metallochaperones, sporulation proteins, hydrolases, endopeptidases, luminescent proteins, iron transport proteins, oxygen storage/transport proteins, calcium binding proteins, and monooxygenases. The metal coordination environment therein is often generated from residues inherent to the protein, small exogenous molecules (e.g., aqua ligands) and/or macrocyclic porphyrin units found, for example, in hemoglobin, myoglobin, cytochrome C, cytochrome C oxidase, and vitamin B12. Thus, there continues to be considerable interest in employing macrocyclic metal complexes to construct low-molecular weight models for metallobiosites that mirror essential features of the coordination environment of a bound metal ion without inclusion of the surrounding protein framework. Herein, we review and appraise our research exploring the application of the metal complexes formed by two macrocyclic ligands, 1,4,7-triazacyclononane (tacn) and 1,4,7,10-tetraazacyclododecane (cyclen), and their derivatives in biological inorganic chemistry. Taking advantage of the kinetic inertness and thermodynamic stability of their metal complexes, these macrocyclic scaffolds have been employed in the development of models that aid the understanding of metal ion-binding natural systems, and complexes with potential applications in biomolecule sensing, diagnosis, and therapy. In particular, the focus has been on "coordinatively unsaturated" metal complexes that incorporate a kinetically inert and stable metal-ligand moiety, but which also contain one or more weakly bound ligands, allowing for the reversible binding of guest molecules via the formation and dissociation of coordinate bonds. With regards to mimicking metallobiosites, examples are presented from our work on tacn-based complexes developed as simplified structural models for multimetallic enzyme sites. In particular, structural comparisons are made between multinuclear copper(II) complexes formed by such ligands and multicopper enzymes featuring type-2 and type-3 copper centers, such as ascorbate oxidase (AO) and laccase (Lc). Likewise, with the aid of relevant examples, we highlight the importance of cooperativity between either multiple metal centers or a metal center and a proximal auxiliary unit appended to the macrocyclic ligand in achieving efficient phosphate ester cleavage. Finally, the critical importance of the Zn(II)-imido and Zn(II)-phosphate interactions in Zn-cyclen-based systems for delivering highly sensitive electrochemical and fluorescent chemosensors is also showcased. The Account additionally highlights some of the factors that limit the performance of these synthetic nucleases and the practical application of the biosensors, and then identifies some avenues for the development of more effective macrocyclic constructs in the future.

Rapid fixation of methylene chloride by a macrocyclic amine.

PubMed

Lee, Jung-Jae; Stanger, Keith J; Noll, Bruce C; Gonzalez, Carlos; Marquez, Manuel; Smith, Bradley D

2005-03-30

A simple macrocyclic amine is alkylated by methylene chloride to give a quaternary ammonium chloride salt. When methylene chloride is the solvent, the reaction exhibits pseudo-first-order kinetics, and the reaction half-life at 25.0 degrees C is 2.0 min. The reaction half-life for a structurally related, acyclic amine is approximately 50 000 times longer. Detailed calculations favor a mechanism where the methylene chloride associates with the macrocycle to form an activated prereaction complex. The macrocyclic nitrogen subsequently attacks the methylene chloride with a classic SN2 trajectory, and although the carbon-chlorine bond breaks, the chloride leaving group does not separate from the newly formed cationic macrocycle, such that the product is a tightly associated ion-pair. X-ray crystal structures of the starting amine and the product salt, as well as kinetic data, support this mechanism.

An eco-compatible strategy for the diversity-oriented synthesis of macrocycles exploiting carbohydrate-derived building blocks.

PubMed

Maurya, Sushil K; Rana, Rohit

2017-01-01

An efficient, eco-compatible diversity-oriented synthesis (DOS) approach for the generation of library of sugar embedded macrocyclic compounds with various ring size containing 1,2,3-triazole has been developed. This concise strategy involves the iterative use of readily available sugar-derived alkyne/azide-alkene building blocks coupled through copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction followed by pairing of the linear cyclo-adduct using greener reaction conditions. The eco-compatibility, mild reaction conditions, greener solvents, easy purification and avoidance of hazards and toxic solvents are advantages of this protocol to access this important structural class. The diversity of the macrocycles synthesized (in total we have synthesized 13 macrocycles) using a set of standard reaction protocols demonstrate the potential of the new eco-compatible approach for the macrocyclic library generation.

Squaraine rotaxanes with boat conformation macrocycles.

PubMed

Fu, Na; Baumes, Jeffrey M; Arunkumar, Easwaran; Noll, Bruce C; Smith, Bradley D

2009-09-04

Mechanical encapsulation of fluorescent, deep-red bis(anilino)squaraine dyes inside Leigh-type tetralactam macrocycles produces interlocked squaraine rotaxanes. The surrounding macrocycles are flexible and undergo rapid exchange of chair and boat conformations in solution. A series of X-ray crystal structures show how the rotaxane co-conformational exchange process involves simultaneous lateral oscillation of the macrocycle about the center of the encapsulated squaraine thread. Rotaxane macrocycles with 1,4-phenylene sidewalls and 2,6-pyridine dicarboxamide bridging units are more likely to adopt boat conformations in the solid state than analogous squaraine rotaxane systems with isophthalamide-containing macrocycles. A truncated squaraine dye, with a secondary amine attached directly to the central C(4)O(2) core, is less electrophilic than the extended bis(anilino)squaraine analogue, but it is still susceptible to chemical and photochemical bleaching. Its stability is greatly enhanced when it is encapsulated as an interlocked squaraine rotaxane. An X-ray crystal structure of this truncated squaraine rotaxane shows the macrocycle in a boat conformation, and NMR studies indicate that the boat is maintained in solution. Encapsulation as a rotaxane increases the dye's brightness by a factor of 6. The encapsulation process appears to constrain the dye and reduce deformation of the chromophore from planarity. This study shows how mechanical encapsulation as a rotaxane can be used as a rational design parameter to fine-tune the chemical and photochemical properties of squaraine dyes.

Squaraine Rotaxanes with Boat Conformation Macrocycles

PubMed Central

Fu, Na; Baumes, Jeffrey M.; Arunkumar, Easwaran; Noll, Bruce C.; Smith, Bradley D.

2010-01-01

Mechanical encapsulation of fluorescent, deep-red bis(anilino)squaraine dyes inside Leigh-type tetralactam macrocycles produces interlocked squaraine rotaxanes. The surrounding macrocycles are flexible and undergo rapid exchange of chair and boat conformations in solution. A series of X-ray crystal structures show how the rotaxane co-conformational exchange process involves simultaneous lateral oscillation of the macrocycle about the center of the encapsulated squaraine thread. Rotaxane macrocycles with 1,4-phenylene-sidewalls and 2,6-pyridine dicarboxamide bridging units are more likely to adopt boat conformations in the solid-state than analogous squaraine rotaxane systems with isophthalamide-containing macrocycles. A truncated squaraine dye, with a secondary amine attached directly to the central C4O2 core, is less electrophilic than the extended bis(anilino)squaraine analogue, but it is still susceptible to chemical and photochemical bleaching. Its stability is greatly enhanced when it is encapsulated as an interlocked squaraine rotaxane. An X-ray crystal structure of this truncated squaraine rotaxane shows the macrocycle in a boat conformation, and NMR studies indicate that the boat is maintained in solution. Encapsulation as a rotaxane increases the dye’s brightness by a factor of six. The encapsulation process appears to constrain the dye and reduce deformation of the chromophore from planarity. This study shows how mechanical encapsulation as a rotaxane can be used as a rational design parameter to fine-tune the chemical and photochemical properties of squaraine dyes. PMID:19639940

Cyanide Scavenging by a Cobalt Schiff-Base Macrocycle: A Cost-Effective Alternative to Corrinoids.

PubMed

Lopez-Manzano, Elisenda; Cronican, Andrea A; Frawley, Kristin L; Peterson, Jim; Pearce, Linda L

2016-06-20

The complex of cobalt(II) with the ligand 2,12-dimethyl-3,7,11,17-tetraazabicyclo-[11.3.1]heptadeca-1(17)2,11,13,15-pentaene (CoN4[11.3.1]) has been shown to bind two molecules of cyanide in a cooperative fashion with an association constant of 2.7 (±0.2) × 10(5). In vivo, irrespective of whether it is initially administered as the Co(II) or Co(III) cation, EPR spectroscopic measurements on blood samples show that at physiological levels of reductant (principally ascorbate) CoN4[11.3.1] becomes quantitatively reduced to the Co(II) form. However, following addition of sodium cyanide, a dicyano Co(III) species is formed, both in blood and in buffered aqueous solution at neutral pH. In keeping with other cobalt-containing cyanide-scavenging macrocycles like cobinamide and cobalt(III) meso-tetra(4-N-methylpyridyl)porphine, we found that CoN4[11.3.1] exhibits rapid oxygen turnover in the presence of the physiological reductant ascorbate. This behavior could potentially render CoN4[11.3.1] cytotoxic and/or interfere with evaluations of the antidotal capability of the complex toward cyanide through respirometric measurements, particularly since cyanide rapidly inhibits this process, adding further complexity. A sublethal mouse model was used to assess the effectiveness of CoN4[11.3.1] as a potential cyanide antidote. The administration of CoN4[11.3.1] prophylactically to sodium cyanide-intoxicated mice resulted in the time required for the surviving animals to recover from "knockdown" (unconsciousness) being significantly decreased (3 ± 2 min) compared to that of the controls (22 ± 5 min). All observations are consistent with the demonstrated antidotal activity of CoN4[11.3.1] operating through a cyanide-scavenging mechanism, which is associated with a Co(II) → Co(III) oxidation of the cation. To test for postintoxication neuromuscular sequelae, the ability of mice to remain in position on a rotating cylinder (RotaRod test) was assessed during and after recovery. While intoxicated animals given CoN4[11.3.1] did recover ∼30 min more quickly than controls given only toxicant, there were no indications of longer-term problems in either group, as determined by continuing the RotaRod testing up to 24 h after the intoxications and routine behavioral observations for a further week.

Novel mixed ligand complexes of bioactive Schiff base (E)-4-(phenyl (phenylimino) methyl) benzene-1,3-diol and 2-aminophenol/2-aminobenzoic acid: Synthesis, spectral characterization, antimicrobial and nuclease studies

NASA Astrophysics Data System (ADS)

Subbaraj, P.; Ramu, A.; Raman, N.; Dharmaraja, J.

2014-01-01

A novel bidentate Schiff base ligand has been synthesized using 2,4-dihydroxybenzophenone and aniline. Its mixed ligand complexes of MAB type [M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); HA = Schiff base and B = 2-aminophenol/2-aminobenzoic acid] have been synthesized and characterized on the basis of spectral data UV-Vis, IR, 1H NMR, FAB-Mass, EPR, SEM and magnetic studies. All the complexes were soluble in DMF and DMSO. Elemental analysis and molar conductance values indicate that the complexes are non-electrolytes. HA binds with M(II) ions through azomethine and deprotonated phenolic group and B binds through the primary amine group and deprotonated phenolic/carboxylic groups. Using FAB-Mass the cleavage pattern of the ligand (HA) has been established. All the complexes adopt octahedral geometry around the metal ions. It has been confirmed with the help of UV-Vis, IR, 1H NMR and FAB-Mass spectral data. DNA binding activities of the complexes 1d and 2d are studied by UV-Vis spectroscopy and cleavage studies of Schiff base ligand and its complexes 1d and 2d have been by agarose gel electrophoresis method. In vitro biological activities of the free ligand (HA) and their metal complexes (1a-1e and 2a-2e) were screened against few bacteria, Escherichia coli, Staphylococcus saphyphiticus, Staphylococcus aureus, Pseudomonas aeruginosa and fungi Aspergillus niger, Enterobacter species, Candida albicans by well diffusion technique.

Efficient Synthesis and Discovery of Schiff Bases as Potent Cholinesterase Inhibitors.

PubMed

Razik, Basma M Abd; Osman, Hasnah; Ezzat, Mohammed O; Basiri, Alireza; Salhin, Abdussalam; Kia, Yalda; Murugaiyah, Vikneswaran

2016-01-01

The search for new cholinesterase inhibitors is still a promising approach for management of Alzheimer`s disease. Schiff bases are considered as important class of organic compounds, which have wide range of applications including as enzyme inhibitors. In the present study, a new green ionic liquid mediated strategy was developed for convenient synthesis of two series of Schiff bases 3(a-j) and 5(a-j) as potential cholinesterase inhibitors using aromatic aldehydes and primary amines in [bmim]Br. The synthesized compounds were evaluated for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory potential by modified Ellman's method. The molecular interactions between the most active compound and the enzyme were analyzed by molecular docking. Among them, 3j displayed higher inhibitory activities than reference drug, galanthamine, with IC50 values of 2.05 and 5.77 µM, for AChE and BChE, respectively. Interestingly, all the compounds except 3b displayed higher BChE inhibitions than galanthamine with IC50 values ranging from 5.77 to 18.52 µM. Molecular docking of compound 3j inside the TcAChE and hBChE completely coincided with the inhibitory activities observed. The compound forms strong hydrogen bonding at the peripheral anionic site of AChE whereas on BChE, it had hydrophobic and mild polar interactions. An efficient and eco-friendly synthetic methodology has been developed to synthesize Schiff bases in a very short reaction time and excellent yields in ionic solvent, whereby the compounds from series 3 showed promising cholinesterase inhibitory activity.

Photo-induced bleaching of sensory rhodopsin II (phoborhodopsin) from Halobacterium salinarum by hydroxylamine: identification of the responsible intermediates.

PubMed

Tamogami, Jun; Kikukawa, Takashi; Ikeda, Yoichi; Demura, Makoto; Nara, Toshifumi; Kamo, Naoki

2012-01-05

Sensory rhodopsin II from Halobacterium salinarum (HsSRII) is a retinal protein in which retinal binds to a specific lysine residue through a Schiff base. Here, we investigated the photobleaching of HsSRII in the presence of hydroxylamine. For identification of intermediate(s) attacked by hydroxylamine, we employed the flash-induced bleaching method. In order to change the concentration of intermediates, such as M- and O-intermediates, experiments were performed under varying flashlight intensities and concentrations of azide that accelerated only the M-decay. We found the proportional relationship between the bleaching rate and area under the concentration-time curve of M, indicating a preferential attack of hydroxylamine on M. Since hydroxylamine is a water-soluble reagent, we hypothesize that for M, hydrophilicity or water-accessibility increases specifically in the moiety of Schiff base. Thus, hydroxylamine bleaching rates may be an indication of conformational changes near the Schiff base. We also considered the possibility that azide may induce a small conformational change around the Schiff base. We compared the hydroxylamine susceptibility between HsSRII and NpSRII (SRII from Natronomonas pharaonis) and found that the M of HsSRII is about three times more susceptible than that of the stable NpSRII. In addition, long illumination to HsSRII easily produced M-like photoproduct, P370. We thus infer that the instability of HsSRII under illumination may be related to this increase of hydrophilicity at M and P370. Copyright © 2011 Elsevier B.V. All rights reserved.

[Synthesis and spectral characteristics of novel di-schiff base derivatives incorporting oxadiazole ring].

PubMed

Chen, Tong-bin; Zhang, Xiong-lu; Fan, Xiao-lin; Li, Xun

2008-12-01

4-nitrobenzoic acid and hydraxine sulfate were cyclized with H3PO4/P2O5 to afford 2,5-bis(4-nitrophenyl)-1, 3,4-oxadiazole(1), then(1)was reduced to 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole using Zn/CaCl2 as reduction reagent, and at last, a series of novel di-schiff base derivatives containing oxadiazole ring were obtained by the reaction of 2,5-bis(4-aminophenyl)-1, 3,4-oxadiazole with aromatic aldehydes (yield: 65%-81%). The structures of these compounds were confirmed by 1H NMR, FTIR and MS. Their UV-Vis spectra as well as fluorescence spectra were studied and the electrochemical properties were tested with cyclic voltammetry. The UV-Vis spectroscopy results show that the characteristic absorption peaks of 1, 3, 4-oxadiazole unit and di-schiff base unit disappeared. The maximum absorption wavelength was detected at 345-357 nm because conjugation effect made the two energy bands partially hybrid and form a new energy band structure. Fluorescence spectroscopy results show that they emit strong blue and purple fluorescence, and the emission maximum wavelengths of di-schiff base are from 390 to 407 nm. Electrochemical properties results show that they have higher affinity energy (2.36-3.04 eV) and ionic potential (5.35-6.06 eV), which indicated that they have better electron-transporting properties than PBD except 3 a and 3 h. The results give a reference to further application to organic electroluminescent devices of the target compound.

Facile Synthesis, Characterization, and Antimicrobial Evaluation of Novel Heterocycles, Schiff Bases, and N-Nucleosides Bearing Phthalazine Moiety.

PubMed

Azab, Mohamed Emad; Rizk, Sameh Ahmed; Mahmoud, Naglaa Fawzy

2016-01-01

The present work describes convenient synthesis of the novel Schiff bases 5a and b by reacting phthalazinones 4a and b with 4-methoxybenzaldehyde Reaction of the Schiff bases with phenylisothiocyanate afforded diazetidine derivatives 7a and b. Also, compounds 4a and b reacted with 2-bromoglucoside tetraacetate giving peracetylated N-glycosides 6a and b, which were deacetylated to afford N-glycosylated phthalazinones 8a and b. On the other hand, when compound 3 was treated with POCl3/PCl5 and/or ethyl chloroacetate, chlorophthalazine and ethyl acetate derivatives 9 and 10 were obtained, respectively. Hydrazinolysis of compounds 9 and 10 produced the hydrazino and hydrazide derivatives 11 and 12, respectively. When compound 11 reacted with 2-furanaldehyde, acetic anhydride, and/or carbon disulphide, it gave compounds 13-15, respectively. Treatment of the hydrazide 12 with aromatic aldehydes, acetic anhydride, ethyl acetoacetate, acetyl acetone, ammonium thiocyanate, and/or phthalic anhydride furnished compounds 17-21. Meanwhile, reacting Schiff base 22 with the chlorophthalazine derivative 9 produced compound 23, which on treatment with furoyl chloride produced compound 24. The structures of the novel compounds were confirmed by IR, (1)H-NMR, (13)C-NMR, MS, and elemental analysis. The newly synthesized compounds were tested against Bacillus subtilis and Staphylococcus aureus as Gram-positive bacteria, Escherichia coli and Pseudomonas aurignosa as Gram-negative bacteria, and Candida albicans and Aspergillus niger as fungi strains. Compounds 5a and b, 23, and 24 showed greater antimicrobial activity than the stranded compounds, suggesting that they could be considered as promising antimicrobial agents.

Synthesis, characterization and biological approach of metal chelates of some first row transition metal ions with halogenated bidentate coumarin Schiff bases containing N and O donor atoms.

PubMed

Prabhakara, Chetan T; Patil, Sangamesh A; Toragalmath, Shivakumar S; Kinnal, Shivashankar M; Badami, Prema S

2016-04-01

The impregnation of halogen atoms in a molecule is an emerging trend in pharmaceutical chemistry. The presence of halogens (Cl, Br, I and F) increases the lipophilic nature of molecule and improves the penetration of lipid membrane. The presence of electronegative halogen atoms increases the bio- activity of core moiety. In the present study, Co(II), Ni(II) and Cu(II) complexes are synthesised using Schiff bases (HL(I) and HL(II)), derived from 8-formyl-7-hydroxy-4-methylcoumarin/3-chloro-8-formyl-7-hydroxy-4-methylcoumarin with 2,4-difluoroaniline/o-toluidine respectively. The synthesized compounds were characterized by spectral (IR, NMR, UV-visible, Mass, ESI-MS, ESR), thermal, fluorescence and molar conductivity studies. All the synthesized metal complexes are completely soluble in DMF and DMSO. The non-electrolytic nature of the metal complexes was confirmed by molar conductance studies. Elemental analysis study suggest [ML2(H2O)2] stoichiometry, here M=Co(II), Ni(II) and Cu(II), L=deprotonated ligand. The obtained IR data supports the binding of metal ion to Schiff base. Thermal study suggests the presence of coordinated water molecules. Electronic spectral results reveal six coordinated geometry for the synthesized metal complexes. The Schiff bases and their metal complexes were evaluated for antibacterial (Pseudomonas aureginosa and Proteus mirabilis), antifungal (Aspergillus niger and Rhizopus oryzae), anthelmintic (Pheretima posthuma) and DNA cleavage (Calf Thymus DNA) activities. Copyright © 2016 Elsevier B.V. All rights reserved.

Secondary Interactions Arrest the Hemiaminal Intermediate To Invert the Modus Operandi of Schiff Base Reaction: A Route to Benzoxazinones.

PubMed

Patel, Ketan; Deshmukh, Satej S; Bodkhe, Dnyaneshwar; Mane, Manoj; Vanka, Kumar; Shinde, Dinesh; Rajamohanan, Pattuparambil R; Nandi, Shyamapada; Vaidhyanathan, Ramanathan; Chikkali, Samir H

2017-04-21

Discovered by Hugo Schiff, condensation between amine and aldehyde represents one of the most ubiquitous reactions in chemistry. This classical reaction is widely used to manufacture pharmaceuticals and fine chemicals. However, the rapid and reversible formation of Schiff base prohibits formation of alternative products, of which benzoxazinones are an important class. Therefore, manipulating the reactivity of two partners to invert the course of this reaction is an elusive target. Presented here is a synthetic strategy that regulates the sequence of Schiff base reaction via weak secondary interactions. Guided by the computational models, reaction between 2,3,4,5,6-pentafluoro-benzaldehyde with 2-amino-6-methylbenzoic acid revealed quantitative (99%) formation of 5-methyl-2-(perfluorophenyl)-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (15). Electron donating and electron withdrawing ortho-substituents on 2-aminobenzoic acid resulted in the production of benzoxazinones 9-36. The mode of action was tracked using low temperature NMR, UV-vis spectroscopy, and isotopic ( 18 O) labeling experiments. These spectroscopic mechanistic investigations revealed that the hemiaminal intermediate is arrested by the hydrogen-bonding motif to yield benzoxazinone. Thus, the mechanistic investigations and DFT calculations categorically rule out the possibility of in situ imine formation followed by ring-closing, but support instead hydrogen-bond assisted ring-closing to prodrugs. This unprecedented reaction represents an interesting and competitive alternative to metal catalyzed and classical methods of preparing benzoxazinone.

Structural basis for precursor protein-directed ribosomal peptide macrocyclization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Kunhua; Condurso, Heather L.; Li, Gengnan

Macrocyclization is a common feature of natural product biosynthetic pathways including the diverse family of ribosomal peptides. Microviridins are architecturally complex cyanobacterial ribosomal peptides that target proteases with potent reversible inhibition. The product structure is constructed via three macrocyclizations catalyzed sequentially by two members of the ATP-grasp family, a unique strategy for ribosomal peptide macrocyclization. Here we describe in detail the structural basis for the enzyme-catalyzed macrocyclizations in the microviridin J pathway of Microcystis aeruginosa. The macrocyclases MdnC and MdnB interact with a conserved α-helix of the precursor peptide using a novel precursor-peptide recognition mechanism. The results provide insight intomore » the unique protein–protein interactions that are key to the chemistry, suggest an origin for the natural combinatorial synthesis of microviridin peptides, and provide a framework for future engineering efforts to generate designed compounds.« less

Acetone-Linked Peptides: A Convergent Approach for Peptide Macrocyclization and Labeling.

PubMed

Assem, Naila; Ferreira, David J; Wolan, Dennis W; Dawson, Philip E

2015-07-20

Macrocyclization is a broadly applied approach for overcoming the intrinsically disordered nature of linear peptides. Herein, it is shown that dichloroacetone (DCA) enhances helical secondary structures when introduced between peptide nucleophiles, such as thiols, to yield an acetone-linked bridge (ACE). Aside from stabilizing helical structures, the ketone moiety embedded in the linker can be modified with diverse molecular tags by oxime ligation. Insights into the structure of the tether were obtained through co-crystallization of a constrained S-peptide in complex with RNAse S. The scope of the acetone-linked peptides was further explored through the generation of N-terminus to side chain macrocycles and a new approach for generating fused macrocycles (bicycles). Together, these studies suggest that acetone linking is generally applicable to peptide macrocycles with a specific utility in the synthesis of stabilized helices that incorporate functional tags. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interference of interchromophoric energy-transfer pathways in π-conjugated macrocycles

DOE PAGES

Alfonso Hernandez, Laura; Nelson, Tammie Renee; Gelin, Maxim F.; ...

2016-11-10

The interchromophoric energy-transfer pathways between weakly coupled units in a π-conjugated phenylene–ethynylene macrocycle and its half-ring analogue have been investigated using the nonadiabatic excited-state molecular dynamics approach. To track the flow of electronic transition density between macrocycle units, we formulate a transition density flux analysis adapted from the statistical minimum flow method previously developed to investigate vibrational energy flow. Following photoexcitation, transition density is primarily delocalized on two chromophore units and the system undergoes ultrafast energy transfer, creating a localized excited state on a single unit. In the macrocycle, distinct chromophore units donate transition density to a single acceptor unitmore » but do not interchange transition density among each other. We find that energy transfer in the macrocycle is slower than in the corresponding half ring because of the presence of multiple interfering energy-transfer pathways. Finally, simulation results are validated by modeling the fluorescence anisotropy decay.« less

Direct comparison of linear and macrocyclic compound libraries as a source of protein ligands.

PubMed

Gao, Yu; Kodadek, Thomas

2015-03-09

There has been much discussion of the potential desirability of macrocyclic molecules for the development of tool compounds and drug leads. But there is little experimental data comparing otherwise equivalent macrocyclic and linear compound libraries as a source of protein ligands. In this Letter, we probe this point in the context of peptoid libraries. Bead-displayed libraries of macrocyclic and linear peptoids containing four variable positions and 0-2 fixed residues, to vary the ring size, were screened against streptavidin and the affinity of every hit for the target was measured. The data show that macrocyclization is advantageous, but only when the ring contains 17 atoms, not 20 or 23 atoms. This technology will be useful for conducting direct comparisons between many different types of chemical libraries to determine their relative utility as a source of protein ligands.

Some metal complexes of three new potentially heptadentate (N4O3) tripodal Schiff base ligands; synthesis, characterizatin and X-ray crystal structure of a novel eight coordinate Gd(III) complex

NASA Astrophysics Data System (ADS)

Golbedaghi, Reza; Moradi, Somaeyh; Salehzadeh, Sadegh; Blackman, Allan G.

2016-03-01

The symmetrical and asymmetrical potentially heptadentate (N4O3) tripodal Schiff base ligands (H3L1-H3L3) were synthesized from the condensation reaction of three tripodal tetraamine ligands tpt (trpn), tris (3-aminopropyl) amine; ppe (abap), (2-aminoethyl)bis(3-aminopropyl)amine, and tren, tris(2-aminoethyl)amine, with 5-methoxysalicylaldehyde. Then, the reaction of Ln(III) (Ln = Gd, La and Sm), Al(III), and Fe(III) metal ions with the above ligands was investigated. The resulting compounds were characterized by IR, mass spectrometry and elemental analysis in all cases and NMR spectroscopy in the case of the Schiff base ligands. The X-ray crystal structure of the Gd complex of H3L3 ligand showed that in addition to all donor atoms of the ligand one molecule of H2O is also coordinated to the metal ion and a neutral eight-coordinate complex is formed.

Synthesis, spectral, thermal and optical properties of Schiff-base complexes derived from 2(E)-2-((z)-4-hydroxypent-3-en-2-ylideneamino)-5-guanidinopentanoic acid and acetylacetone

NASA Astrophysics Data System (ADS)

Hosny, Nasser Mohammed; Hussien, Mostafa A.; Radwan, Fatima M.; Nawar, Nagwa

2017-09-01

New metal complexes derived from the in situ reaction of Cu(II), Co(II), Ni(II) and Zn(II) acetates with the Schiff-base ligand (H2L) resulted from the condensation of 2-amino-5-guanidinopentanoic acid (arginine) and acetylacetone have been synthesized. The resulting complexes have been characterized by, elemental analyses, ES-MS, IR, Raman spectra, UV-Vis., 1HNMR, ESR, thermal analyses (TGA and DTG) and magnetic measurements. The results showed that, The Schiff-base ligand acts as bi-negative tridentate coordinating via azomethine nitrogen, enolic carbonyl oxygen and carboxylate oxygen after displacement of hydrogen. The thermodynamic parameters E∗, ΔH, ΔG and ΔS of the isolated complexes have been calculated. The optical band gap (Eg) values of Cu, Co, Ni and Zn were found to be 3.3, 3.4, 3.7 and 4.3 eV, respectively, arising from direct transitions. Optical band gap measurements indicate the semi-conductivity nature of these complexes.

X-ray crystal structure and theoretical study of a new dinuclear Cu(II) complex with two different geometry centers bridged with an oxo group

NASA Astrophysics Data System (ADS)

Golbedaghi, Reza; Azimi, Saeid; Molaei, Atefeh; Hatami, Masoud; Notash, Behrouz

2017-10-01

A new Schiff base ligand HL, 1,3-bis(2-((Z)-(2-aminoethylimino)methyl)phenoxy)ethylene di amine, has been synthesized from the reaction of a new aldehyde and ethylenediamine. After preparation the Schiff base, a new dinuclear Cu(II) complex with two different geometry for each metal ion was synthesized. Single crystal X-ray structure analysis of the complex Cu(II) showed that the complex is binuclear and all nitrogen and oxygen atoms of ligand (N4O3) are coordinated to two Cu(II) center ions. The crystal structure studying shows, a perchlorate ion has been coordinated to the two Cu(II) metal centers as bridged and another perchlorate coordinated to the one of Cu(II) ion as terminal. However, two interesting structures square pyramidal and distorted octahedral Cu(II) ions are bridged asymmetrically by a perchlorate ion and oxygen of hydroxyl group of Schiff base ligand. In addition, we had a theoretical study to have a comparison of experimental and theoretical results we determined the HOMO and LUMO orbitals.

Label-free offline versus online activity methods for nucleoside diphosphate kinase b using high performance liquid chromatography.

PubMed

Lima, Juliana Maria; Salmazo Vieira, Plínio; Cavalcante de Oliveira, Arthur Henrique; Cardoso, Carmen Lúcia

2016-08-07

Nucleoside diphosphate kinase from Leishmania spp. (LmNDKb) has recently been described as a potential drug target to treat leishmaniasis disease. Therefore, screening of LmNDKb ligands requires methodologies that mimic the conditions under which LmNDKb acts in biological systems. Here, we compare two label-free methodologies that could help screen LmNDKb ligands and measure NDKb activity: an offline LC-UV assay for soluble LmNDKb and an online two-dimensional LC-UV system based on LmNDKb immobilised on a silica capillary. The target enzyme was immobilised on the silica capillary via Schiff base formation (to give LmNDKb-ICER-Schiff) or affinity attachment (to give LmNDKb-ICER-His). Several aspects of the ICERs resulting from these procedures were compared, namely kinetic parameters, stability, and procedure steps. Both the LmNDKb immobilisation routes minimised the conformational changes and preserved the substrate binding sites. However, considering the number of steps involved in the immobilisation procedure, the cost of reagents, and the stability of the immobilised enzyme, immobilisation via Schiff base formation proved to be the optimal procedure.

Syntheses, characterisation and crystal structures of ferrocenyl β-diketones and their Schiff base Nsbnd Nsbnd O ligand derivatives with 2-picolylamine

NASA Astrophysics Data System (ADS)

Artigas, Vania; González, Deborah; Fuentealba, Mauricio

2017-02-01

Ferrocenyl β-diketones compounds β3-4 were synthesised by Claisen condensation reaction between acetylferrocene and ethyl benzoate or 4-bromoethyl benzoate. We also synthesised four new Schiff base ligands L1-4 by condensation reaction between β1-4 and 2-picolylamine. Identities of all these compounds were confirmed by satisfactory elemental analysis, 1H nuclear magnetic resonance (NMR) correlation and infrared (IR) spectroscopy. In addition, all these compounds were authenticated by a single-crystal X-ray diffraction analysis. In solution, 1H NMR spectra of β3 and β4 exhibit a mixture of keto:enol tautomer ratios of 12:88 and 8:92, respectively, calculated by the integration of the free cyclopentadienyl ring. In contrast, the proton NMR spectra of L1-4 showed only the keto-enamine tautomer displacements. In addition, decoupled 13C NMR spectrum clearly confirmed the existence of these tautomers. These results are in accordance with X-ray crystallographic studies, in which the enol and keto-enamine forms were elucidated for β-diketones and Schiff base ligands, respectively.

Spectroscopic and biological activities studies of bivalent transition metal complexes of Schiff bases derived from condensation of 1,4-phenylenediamine and benzopyrone derivatives.

PubMed

Sherif, Omaima E; Abdel-Kader, Nora S

2014-01-03

Many tools of analysis such as elemental analyses, infrared, ultraviolet-visible, electron spin resonance (ESR) and thermal analysis, as well as conductivity and magnetic susceptibility measurements were used to elucidate the structures of the newly prepared Co(II), Ni(II) and Cu(II) complexes with Schiff bases derived from the condensation of 1,4-phenylenediamine with 6-formyl-7-hydroxy-5-methoxy-2-methylbenzo-pyran-4-one (H2L) or 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one (H4L). The data showed that all formed complexes are 1:1 or 2:2 (M:L) and non-electrolyte chelates. The Co(II) and Cu(II) complexes of the two Schiff bases were screened for antibacterial activities by the disk diffusion method. The antibacterial activity was screened using Escherichia coli and Staphylococcus capitis but the antifungal activity was examined by using Aspergillus flavus and Candida albicans. The Results showed that the tested complexes have antibacterial, except CuH4L, but not antifungal activities. Copyright © 2013 Elsevier B.V. All rights reserved.

SOD activity and DNA binding properties of a new symmetric porphyrin Schiff base ligand and its metal complexes.

PubMed

Çay, Sevim; Köse, Muhammet; Tümer, Ferhan; Gölcü, Ayşegül; Tümer, Mehmet

2015-12-05

4-Methoxy-2,6-bis(hydroxymethyl)phenol (1) was prepared from the reaction of 4-methoxyphenol and formaldehyde. The compound (1) was then oxidized to the 4-methoxy-2,6-diformylphenol (2) compound. Molecular structure of compound (2) was determined by X-ray diffraction method. A new symmetric porphyrin Schiff base ligand 4-methoxy-2,6-bis[5-(4-iminophenyl)-10,15,20-triphenylporphyrin]phenol (L) was prepared from the reaction of the 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (TTP-NH2) and the compound (2) in the toluene solution. The metal complexes (Cu(II), Fe(III), Mn(III), Pt(II) and Zn(II)) of the ligand (L) were synthesized and characterized by the spectroscopic and analytical methods. The DNA (fish sperm FSdsDNA) binding studies of the ligand and its complexes were performed using UV-vis spectroscopy. Additionally, superoxide dismutase activities of the porphyrin Schiff base metal complexes were investigated. Additionally, electrochemical, photoluminescence and thermal properties of the compounds were investigated. Copyright © 2015 Elsevier B.V. All rights reserved.

Pharmacological performance of novel poly-(ionic liquid)-grafted chitosan-N-salicylidene Schiff bases and their complexes.

PubMed

Elshaarawy, Reda F M; Refaee, Ayaat A; El-Sawi, Emtithal A

2016-08-01

In our endeavor to develop a new class of pharmacological candidates with antimicrobial and anticancer efficacy, a series of biopolymeric chitosan Schiff bases bearing salicylidene ionic liquid (IL-Sal) brushes (ILCSB1-3, poly-(GlcNHAc-GlcNH2-(GlcN-Sal-IL)) was successfully synthesized by adopting efficient synthetic routes. Unfortunately, metalation trials of these biopolymeric Schiff bases afford the corresponding Ag(I)/M(II) complexes (where M=Co, Pd). These designed architectures were structurally characterized and pharmacologically evaluated for their in vitro antimicrobial, against common bacterial and fungal pathogens, and anticancer activities against human colon carcinoma (HCT-116) cell line. In conclusion functionalization of chitosan with IL-Sal brushes coupled with metalation of formed ILCSBs were synergistically enhanced its antimicrobial and antitumor properties to a great extent. Noteworthy, Ag-ILCSB2 (IC50=9.13μg/mL) was ca. 5-fold more cytotoxic against HCT-116 cell line than ILCSB2 (IC50=43.30μg/mL). Copyright © 2016. Published by Elsevier Ltd.

Hollow latex particles functionalized with chitosan for the removal of formaldehyde from indoor air.

PubMed

Nuasaen, Sukanya; Opaprakasit, Pakorn; Tangboriboonrat, Pramuan

2014-01-30

Chitosan and polyethyleneimine (PEI) functionalized hollow latex (HL) particles were conveniently fabricated by coating poly(methyl methacrylate-co-divinyl benzene-co-acrylic acid) (P(MMA/DVB/AA)) HL particles with 5 wt% chitosan or 14 wt% PEI. The materials were used as formaldehyde adsorbent, where their adsorbent activity was examined by Fourier Transform Infrared (FTIR) spectroscopy. The nucleophilic addition of amines to carbonyls generated a carbinolamine intermediate with a characteristic band at 1,020 cm(-1) and Schiff base product at 1650 cm(-1), whose intensity increased with prolonged formaldehyde exposure times. The major products observed in HL-chitosan were carbinolamine and Schiff base, whereas a small amount of Schiff base was obtained in HL-PEI particles, confirming a chemical bond formation without re-emission of formaldehyde. Compared to HL-PEI, HL-chitosan possesses higher formaldehyde adsorption efficiency. Besides providing opacity and whiteness, the multilayer HL-chitosan particles can effectively remove indoor air pollutants, i.e., formaldehyde gas, and, hence, would be useful in special coating applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

Spectral characterization of novel ternary zinc(II) complexes containing 1,10-phenanthroline and Schiff bases derived from amino acids and salicylaldehyde-5-sulfonates

NASA Astrophysics Data System (ADS)

Boghaei, Davar M.; Gharagozlou, Mehrnaz

2007-07-01

A series of new ternary zinc(II) complexes [Zn(L 1-10)(phen)], where phen is 1,10-phenanthroline and H 2L 1-10 = tridentate Schiff base ligands derived from the condensation of amino acids (glycine, L-phenylalanine, L-valine, L-alanine, and L-leucine) and salicylaldehyde-5-sulfonates (sodium salicylaldehyde-5-sulfonate and sodium 3-methoxy-salicylaldehyde-5-sulfonate), have been synthesized. The complexes were characterized by elemental analysis, IR, UV-vis, 1H NMR, and 13C NMR spectra. The IR spectra of the complexes showed large differences between νas(COO) and νs(COO), Δ ν ( νas(COO) - νs(COO)) of 191-225 cm -1, indicating a monodentate coordination of the carboxylate group. Spectral data showed that in these ternary complexes the zinc atom is coordinated with the Schiff base ligand acts as a tridentate ONO moiety, coordinating to the metal through its phenolic oxygen, imine nitrogen, and carboxyl oxygen, and also with the neutral planar chelating ligand, 1,10-phenanthroline, coordinating through nitrogens.

Biologically active and thermally stable polymeric Schiff base and its metal polychelates: Their synthesis and spectral aspects

NASA Astrophysics Data System (ADS)

Rasool, Raza; Hasnain, Sumaiya

2015-09-01

New metal polychelates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) obtained by the interaction of metal acetates with polymeric Schiff base containing formaldehyde and piperazine, have been investigated. Structural and spectroscopic properties have been evaluated by elemental analysis, FT-IR and 1H-NMR. Geometry of the chelated polymers was confirmed by magnetic susceptibility measurements, UV-Visible spectroscopy and Electron Spin Resonance. The molecular weight of the polymer was determined by gel permeation chromatography (GPC). Thermogravimetric analysis indicated that metal polychelates were more thermally stable than their corresponding ligand. All compounds were screened for their antimicrobial activities against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, (bacteria) and Candida albicans, Microsporum canis, Cryptococcus neoformans (fungi) by agar well diffusion method. Interestingly, the polymeric Schiff base was found to be antimicrobial in nature but less effective as compared to the metal polychelates. On the basis of thermal and antimicrobial behavior, these polymers hold potential applications as thermally resistant antimicrobial and antifouling coating materials as well as antimicrobial packaging materials.

Synthesis and Spectral Characterization of Antifungal Sensitive Schiff Base Transition Metal Complexes

PubMed Central

Sakthivel, A.; Rajasekaran, K.

2007-01-01

New N2O2 donor type Schiff base has been designed and synthesized by condensing acetoacetanilido-4-aminoantipyrine with 2-aminobenzoic acid in ethanol. Solid metal complexes of the Schiff base with Cu(II), Ni(II), Co(II), Mn(II), Zn(II), VO(IV), Hg(II) and Cd(II) metal ions were synthesized and characterized by elemental analyses, magnetic susceptibility, molar conduction, fast atom bombardment (FAB) mass, IR, UV-Vis, and 1H NMR spectral studies. The data show that the complexes have the composition of ML type. The UV-Vis. and magnetic susceptibility data of the complexes suggest a square-planar geometry around the central metal ion except VO(IV) complex which has square-pyramidal geometry. The in vitro antifungal activities of the compounds were tested against fungi such as Aspergillus niger, Aspergillus flavus, Rhizopus stolonifer, Candida albicans, Rhizoctonia bataicola and Trichoderma harizanum. All the metal complexes showed stronger antifungal activities than the free ligand. The minimum inhibitory concentrations (MIC) of the metal complexes were found in the range of 10~31 µg/ml. PMID:24015086

Antimicrobial, spectral, magnetic and thermal studies of Cu(II), Ni(II), Co(II), UO(2)(VI) and Fe(III) complexes of the Schiff base derived from oxalylhydrazide.

PubMed

Melha, Khlood Abou

2008-04-01

The Schiff base ligand, oxalyl [( 2 - hydroxybenzylidene) hydrazone] [corrected].H(2)L, and its Cu(II), Ni(II), Co(II), UO(2)(VI) and Fe(III) complexes were prepared and tested as antibacterial agents. The Schiff base acts as a dibasic tetra- or hexadentate ligand with metal cations in molar ratio 1:1 or 2:1 (M:L) to yield either mono- or binuclear complexes, respectively. The ligand and its metal complexes were characterized by elemental analyses, IR, (1)H NMR, Mass, and UV-Visible spectra and the magnetic moments and electrical conductance of the complexes were also determined. For binuclear complexes, the magnetic moments are quite low compared to the calculated value for two metal ions complexes and this shows antiferromagnetic interactions between the two adjacent metal ions. The ligand and its metal complexes were tested against a Gram + ve bacteria (Staphylococcus aureus), a Gram -ve bacteria (Escherichia coli), and a fungi (Candida albicans). The tested compounds exhibited high antibacterial activities.

Two different forms of metarhodopsin II: Schiff base deprotonation precedes proton uptake and signaling state.

PubMed Central

Arnis, S; Hofmann, K P

1993-01-01

Rhodopsin is a retinal protein and a G-protein-coupled receptor; it shares with both of these families the seven helix structure. To generate the G-interacting helix-loop conformation, generally identified with the 380-nm absorbing metarhodopsin II (MII) photoproduct, the retinal Schiff base bond to the apoprotein must be deprotonated. This occurs as a key event also in the related retinal proteins, sensory rhodopsins, and the proton pump bacteriorhodopsin. In MII, proton uptake from the aqueous phase must be involved as well, since its formation increases the pH of the aqueous medium and is accelerated under acidic conditions. In the native membrane, the pH effect matches MII formation kinetically, suggesting that intramolecular and aqueous protonation changes contribute in concert to the protein transformation. We show here, however, that proton uptake, as indicated by bromocresol purple, and Schiff base deprotonation (380-nm absorption change) show different kinetics when the protein is solubilized in suitable detergents. Our data are consistent with a two-step reaction: Images Fig. 6 PMID:8356093

Solvato-polymorph of [(η6-C6H6)RuCl (L)]PF6 (L = (2,6-dimethyl-phenyl-pyridin-2-yl methylene amine)

NASA Astrophysics Data System (ADS)

Gichumbi, Joel M.; Friedrich, Holger B.; Omondi, Bernard

2016-06-01

A half-sandwich complex salt of ruthenium containing the Schiff base ligand, 2, 6-dimethyl-N-(pyridin-2-ylmethylene)aniline has been synthesized and structurally characterized. The complex salt 1, [(η6-C6H6)RuCl(C5H4NCHdbnd N(2,6-(CH3)2C6H3)]PF6 was obtained from the reaction of the ruthenium arene precursor, [(η6- C6H6)Ru(μ-Cl)Cl]2 with the Schiff base in a 1:2 ratio followed by treatment with NH4PF6. Its acetone solvate 2, [(η6-C6H6)RuCl(C5H4NCHdbnd N (2, 6- (CH3)2C6H3)]PF6. (CH3)2CO was obtained by recrystallization of 1 from a solution of hexane and acetone. 1 and 2 crystallize in the monoclinic P21/c and P21/n space groups as blocks and as prisms respectively. The ruthenium centers in 1 and 2 are coordinated to the bidentate Schiff base, to a chloride atom, and to the arene ring to give a pseudo-octahedral geometry around them. The whole arrangement is referred to as the familiar three-legged piano stool in which the Schiff base and the Cl atom serve as the base while the arene ring serve as the apex of the stool. Polymorph 2 has an acetone molecule in the asymmetric unit. Of interest is the similar behavior of the solvate on heating which shows the crystals shuttering at about 531.6 and 523.4 K for 1 and 2 respectively.

New approach for the quantification of metallic species in healthcare products based on optical switching of a Schiff base possessing ONO donor set.

PubMed

Singh, Jaswant; Parkash, Jyoti; Kaur, Varinder; Singh, Raghubir

2017-10-05

A new method is reported for the quantification of some metallic components of healthcare products utilizing a Schiff base chelator derived from 2-hydroxyacetophenone and ethanolamine. The Schiff base chelator recognizes some metallic species such as iron, copper and zinc (important components of some healthcare products), and cadmium (common contaminant in healthcare products) giving colorimetric/fluorimetric response. It coordinates with Fe 2+ /Fe 3+ and Cu 2+ ions via ONO donor set and switches the colour to bright red, green and orange, respectively. Similarly, it switches 'ON' a fluorometric response when coordinates with Zn 2+ and Cd 2+ ions. In the present approach, detailed studies on the colorimetric and fluorimetric response of ONO Schiff base is investigated in detail. The Job plot for the complexation of ONO switch with various metal ions suggested formation of 1:1 (metal-chelator) complex with Fe 2+ , Fe 3+ , and Cu 2+ while 1:2 (metal-chelator) for Zn 2+ and Cd 2+ ions. The limit of detection, limit of quantification are 6.73, 18.0, 25.0, 0.65, 1.10μM and 27.0, 72.0, 100.0, 2.60 and 4.40μM for Fe 2+ , Fe 3+ , Cu 2+ , Zn 2+ and Cd 2+ ions, respectively. Under the optimized conditions, chelator was used for the quantification of important metals present in healthcare products via direct dissolution and furnace treatment during sample preparation. The results were found precise and accurate for both sample preparation techniques using the developed method. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis, Characterization and Biological Activities of Creatinine Amides and Creatinine Schiff Bases.

PubMed

Mumtaz, Amara; Zahoor, Fareeha; Zaib, Sumera; Nawaz, Muhammad Azhar H; Saeed, Aamer; Waseem, Amir; Khan, Afsar; Hussain, Izhar; Iqbal, Jamshed

2017-01-30

In spite of substantial progress in scientific cognizance and medical technology, still infectious diseases are among the leading cause of morbidity and mortality. Creatinine and Schiff bases are well known for their diverse range of biological activities and thought to be emerging and useful therapeutic target for the treatment of several diseases. The present work was aimed to illustrate the influence of substitution of amides and Schiff bases on creatinine and their antimicrobial, antioxidant and anti-urease effectiveness was determined. Creatinine substituted amides (1-2) and creatinine Schiff bases (3-7) were synthesized and characterized by NMR and IR spectral data in combination with elemental analysis. All the compounds (1-7) were investigated on Jack bean urease for their urease inhibitory potential. Investigation of antimicrobial activity of the compounds was made by the agar dilution method. Moreover, 1,1-diphenyl-2- picrylhydrazyl (DPPH) method was used to determine their antioxidant potential. Molecular docking studies were also carried out to elucidate their relationship with the binding pockets of the enzyme. The compounds were found to be potent inhibitors of urease. The synthesized derivatives exhibited significant inhibition against Gram-positive and Gram-negative bacterial strains, as compared to standard, ciprofloxacin. Creatinine based derivatives exhibited potential antifungal activity when tested on infectious and pathogenic fungal strains. Similarly, most of the compounds exhibited good antioxidant activity. These derivatives may serve as a source of potential antioxidants and also help to retard microbial growth in food industry. Similarly, the studies provide a basis for further research to develop more potent urease inhibitory compounds of medicinal /agricultural interest. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

The syntheses, molecular structure analyses and DFT studies on new benzil monohydrazone based Schiff bases

NASA Astrophysics Data System (ADS)

Elmacı, Gökhan; Duyar, Halil; Aydıner, Burcu; Seferoğlu, Nurgül; Naziri, Mir Abolfazl; Şahin, Ertan; Seferoğlu, Zeynel

2018-06-01

Benzil monohydrazone based Schiff bases were synthesized and characterized by 1H NMR, 13C NMR, HRMS as well as by single crystal X-ray diffraction. The geometries of the compounds was optimized by the DFT method and the results were compared with the X-ray diffraction data. The HOMO and LUMO energy gap and also related parameters (electronic chemical potential (μ) and global hardness (η), global electrophilicity index (ω) and softness (s)) were obtained from ground state calculations. In addition, the thermal properties of the compounds were investigated by DTA-TGA. The results showed that the compounds have good thermal properties for practical applications as optic dye.

Fragment-Based, Structure-Enabled Discovery of Novel Pyridones and Pyridone Macrocycles as Potent Bromodomain and Extra-Terminal Domain (BET) Family Bromodomain Inhibitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Le; Pratt, John K.; Soltwedel, Todd

Members of the BET family of bromodomain containing proteins have been identified as potential targets for blocking proliferation in a variety of cancer cell lines. A two-dimensional NMR fragment screen for binders to the bromodomains of BRD4 identified a phenylpyridazinone fragment with a weak binding affinity (1, Ki = 160 μM). SAR investigation of fragment 1, aided by X-ray structure-based design, enabled the synthesis of potent pyridone and macrocyclic pyridone inhibitors exhibiting single digit nanomolar potency in both biochemical and cell based assays. Advanced analogs in these series exhibited high oral exposures in rodent PK studies and demonstrated significant tumormore » growth inhibition efficacy in mouse flank xenograft models.« less

Fused tetracycles with a benzene or cyclohexadiene core: [2 + 2 + 2] cycloadditions on macrocyclic systems.

PubMed

Brun, Sandra; Garcia, Lídia; González, Iván; Torrent, Anna; Dachs, Anna; Pla-Quintana, Anna; Parella, Teodor; Roglans, Anna

2008-09-28

A series of fused tetracycles with a benzene or cyclohexadiene core (2a-h) is satisfactorily prepared by intramolecular [2 + 2 + 2] cycloadditions of triynic and enediynic macrocycles (1a-h) under RhCl(PPh3)3 catalysis; the enantioselective cycloaddition of macrocycles 1b and 1e and gives chiral tetracycles with moderate enantiomeric excess.

Corona[5]arenes Accessed by a Macrocycle-to-Macrocycle Transformation Route and a One-Pot Three-Component Reaction.

PubMed

Wu, Zhi-Chen; Guo, Qing-Hui; Wang, Mei-Xiang

2017-06-12

Corona[5]arenes, a novel type of macrocyclic compound that is composed of alternating heteroatoms and para-arylenes, were synthesized efficiently by two distinct methods. In a macrocycle-to-macrocycle transformation approach, S 6 -corona[3]arene[3]tetrazine underwent sequential S N Ar reactions with HS-C 6 H 4 -X-C 6 H 4 -SH (X=S, CH 2 , CMe 2 , SO 2 , and O) to produce the corresponding corona[3]arene[2]tetrazines. Different corona[3]arene[2]tetrazine compounds were also constructed in a straightforward manner by a one-pot three-component reaction of HS-C 6 H 4 -X-C 6 H 4 -SH (X=S, CH 2 , CMe 2 , SO 2 , and O) with diethyl 2,5-dimercaptoterephthalate and 2 equiv of 3,6-dichlorotetrazine under very mild conditions. All corona[5]arenes adopted 1,2,4-alternate conformational structures in the crystalline state yielding similar nearly regular pentagonal cavities. Both the cavity size and the electronic property of the acquired macrocycles were fine-tuned by the nature of the bridging element X. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Utility of charge-transfer complexation for the assessment of macrocyclic polyethers: Spectroscopic, thermal and surface morphology characteristics of two highly crown ethers complexed with acido acceptors

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Adam, Abdel Majid A.; Saad, Hosam A.

2015-04-01

The study of the complexing ability of macrocyclic compounds to organic and inorganic substances is of great interest. The aim of this work is to provide basic data that can be used to the assessment of macrocyclic crown ethers quantitatively based on charge-transfer (CT) complexation. This goal was achieved by preparing CT complexes of two interesting mixed nitrogen-oxygen crown ethers with acido acceptors (chloranilic and picric acid), which were fully structurally characterized. The crown ethers are 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (HDHC) and 1,4,10-trioxa-7,13-diaza-cyclopentadecane (TDPD). The obtained complexes were structurally characterized via elemental analysis, IR, Raman, 1H NMR, and UV-visible spectroscopy. Thermal properties of these complexes were also studied, and their kinetic thermodynamic parameters were calculated. Furthermore, the microstructure properties of these complexes have also been investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM).

New tetradentate Schiff bases of 2-amino-3,5-dibromobenzaldehyde with aliphatic diamines and their metal complexes: synthesis, characterization and thermal stability.

PubMed

Mohammadi, Khosro; Azad, Seyyedeh Sedigheh; Amoozegar, Ameneh

2015-07-05

The tetradentate Schiff base ligands (L(1)-L(4)), were synthesized by reaction between 2-amino-3,5-dibromobenzaldehyde and aliphatic diamines. Then, nickel and oxovanadium(IV) complexes of these ligands were synthesized and characterized by (1)H NMR, Mass, IR, UV-Vis spectroscopy and thermogravimetry. The kinetic parameters of oxovanadium(IV) complexes were calculated from thermal studies. According to the results of thermogravimetric data, the thermal stability of oxovanadium(IV) complexes is as follow: [Formula: see text]. Copyright © 2015 Elsevier B.V. All rights reserved.

Fluorescence method for enzyme analysis which couples aromatic amines with aromatic aldehydes

DOEpatents

Smith, R.E.; Dolbeare, F.A.

1980-10-21

Analysis of proteinases is accomplished using conventional amino acid containing aromatic amine substrates. Aromatic amines such as 4-methoxy-2-naphthylamine (4M2NA), 2-naphthylamine, aminoisophthalic acid dimethyl ester, p-nitroaniline, 4-methoxy-1-aminofluorene and coumarin derivatives resulting from enzymatic hydrolysis of the substrate couples with aromatic aldehydes such as 5-nitrosalicylaldehyde (5-NSA), benzaldehyde and p-nitrobenzaldehyde to produce Schiff-base complexes which are water insoluble. Certain Schiff-base complexes produce a shift from blue to orange-red (visible) fluorescence. Such complexes are useful in the assay of enzymes. No Drawings

Fluorescence method for enzyme analysis which couples aromatic amines with aromatic aldehydes

DOEpatents

Smith, Robert E. [557 Escondido Cir., Livermore, CA 94550; Dolbeare, Frank A. [5178 Diane La., Livermore, CA 94550

1980-10-21

Analysis of proteinases is accomplished using conventional amino acid containing aromatic amine substrates. Aromatic amines such as 4-methoxy-2-naphthylamine (4M2NA), 2-naphthylamine, aminoisophthalic acid dimethyl ester, p-nitroaniline, 4-methoxy-1-aminofluorene and coumarin derivatives resulting from enzymatic hydrolysis of the substrate couples with aromatic aldehydes such as 5-nitrosalicylaldehyde (5-NSA), benzaldehyde and p-nitrobenzaldehyde to produce Schiff-base complexes which are water insoluble. Certain Schiff-base complexes produce a shift from blue to orange-red (visible) fluorescence. Such complexes are useful in the assay of enzymes.

Fluorescence method for enzyme analysis which couples aromatic amines with aromatic aldehydes

DOEpatents

Smith, Robert E.; Dolbeare, Frank A.

1979-01-01

Analysis of proteinases is accomplished using conventional amino acid containing aromatic amine substrates. Aromatic amines such as 4-methoxy-2-naphthylamine (4M2NA), 2-naphthylamine, aminoisophthalic acid dimethyl ester, p-nitroaniline, 5-methoxy-1-aminofluorene and coumarin derivatives resulting from enzymatic hydrolysis of the substrate couples with aromatic aldehydes such as 5-nitrosalicylaldehyde (5-NSA), benzaldehyde and p-nitrobenzaldehyde to produce Schiff-base complexes which are water insoluble. Certain Schiff-base complexes produce a shift from blue to orange-red (visible) fluorescence. Such complexes are useful in the assay of enzymes.

Substitution of amino acids Asp-85, Asp-212, and Arg-82 in bacteriorhodopsin affects the proton release phase of the pump and the pK of the Schiff base.

PubMed

Otto, H; Marti, T; Holz, M; Mogi, T; Stern, L J; Engel, F; Khorana, H G; Heyn, M P

1990-02-01

Photocycle and flash-induced proton release and uptake were investigated for bacteriorhodopsin mutants in which Asp-85 was replaced by Ala, Asn, or Glu; Asp-212 was replaced by Asn or Glu; Asp-115 was replaced by Ala, Asn, or Glu; Asp-96 was replaced by Ala, Asn, or Glu; and Arg-82 was replaced by Ala or Gln in dimyristoylphosphatidylcholine/3-[(3-cholamidopropyl)dimethylammonio]-1- propanesulfonate micelles at pH 7.3. In the Asp-85----Ala and Asp-85----Asn mutants, the absence of the charged carboxyl group leads to a blue chromophore at 600 and 595 nm, respectively, and lowers the pK of the Schiff base deprotonation to 8.2 and 7, respectively, suggesting a role for Asp-85 as counterion to the Schiff base. The early part of the photocycles of the Asp-85----Ala and Asp-85----Asn mutants is strongly perturbed; the formation of a weak M-like intermediate is slowed down about 100-fold over wild type. In both mutants, proton release is also slower but clearly precedes the rise of M. The amplitude of the early (less than 0.2 microseconds) reversed photovoltage component in the Asp-85----Asn mutant is very large, and the net charge displacement is close to zero, indicating proton release and uptake on the cytoplasmic side of the membrane. The data suggest an obligatory role for Asp-85 in the efficient deprotonation of the Schiff base and in the proton release phase, probably as proton acceptor. In the Asp-212----Asn mutant, the rise of the absorbance change at 410 nm is slowed down to 220 microsecond, its amplitude is small, and the release of protons is delayed to 1.9 ms. The absorbance changes at 650 nm indicate perturbations in the early time range with a slow K intermediate. Thus Asp-212 also participates in the early events of charge translocation and deprotonation of the Schiff base. In the Arg-82----Gln mutant, no net transient proton release was observed, whereas, in the Arg-82----Ala mutant, uptake and release were reversed. The pK shift of the purple-to-blue transition in the Asp-85----Glu, Arg-82----Ala, and Arg-82----Gln mutants and the similarity in the photocycle and photoelectrical signals of the Asp-85----Ala, Asp-85----Asn, and Asp-212----Asn mutants suggest the interaction between Asp-85, Arg-82, Asp-212, and the Schiff base as essential for proton release.

A soft tissue adhesive based on aldehyde-sodium alginate and amino-carboxymethyl chitosan preparation through the Schiff reaction

NASA Astrophysics Data System (ADS)

Wu, Yu; Yuan, Liu; Sheng, Nai-an; Gu, Zi-qi; Feng, Wen-hao; Yin, Hai-yue; Morsi, Yosry; Mo, Xiu-mei

2017-09-01

Sodium alginate and carboxymethyl chitosan have been extensively applied in tissue engineering and other relative fields due to their low price and excellent biocompatibility. In this paper, we oxidized sodium alginate with sodium periodate to convert 1,2-hydroxyl groups into aldehyde groups to get aldehyde-sodium alginate (ASA). Carboxymethyl chitosan was modified with ethylenediamine (ED) in the presence of water-soluble N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) to introduce additional amino groups to get amino-carboxymethyl chitosan (A-CS). Upon mixing the A-SA and A-CS aqueous solutions together, a gel rapidly formed based on the Schiff's base reaction between aldehyde groups in A-SA and amino groups in A-CS. FTIR analysis confirmed the characteristic peak of Schiff's base group in the hydrogel. It was confirmed that the gelation time be dependent on the aldehyde group content in A-SA and amino group content in A-CS. The fasted hydrogel formation takes place within 10 min. The data of bonding strength and cytotoxicity measurement also showed that the hydrogel had good adhesion and biocompatibility. All these results support that this gel has the potential as soft tissue adhesive.

New phthalimide-appended Schiff bases: Studies of DNA binding, molecular docking and antioxidant activities.

PubMed

Nayab, Pattan Sirajuddin; Akrema; Ansari, Istikhar A; Shahid, Mohammad; Rahisuddin

2017-08-01

Herein, we investigated new phthalimide-based Schiff base molecules as promising DNA-binding and free radical scavenging agents. Physicochemical properties of these molecules were demonstrated on the basis of elemental analysis, ultraviolet-visible (UV-Vis), infra-red (IR), 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy. All spectral data are agreed well with the proposed Schiff base framework. The DNA-binding potential of synthesized compounds were investigated by means of UV-visible, fluorescence, iodide quenching, circular dichroism, viscosity and thermal denaturation studies. The intrinsic binding constants (K b ) were calculated from absorption studies were found to be 1.1 × 10 4 and 1.0 × 10 4  M -1 for compounds 2a and 2b suggesting that compound 2a binding abilities with DNA were stronger than the compound 2b. Our studies showed that the presented compounds interact with DNA through groove binding. Molecular docking studies were carried out to predict the binding between Ct-DNA and test compounds. Interestingly, in silico predictions were corroborated with in vitro DNA-binding conclusions. Furthermore, the title compounds displayed remarkable antioxidant activity compared with reference standard. Copyright © 2016 John Wiley & Sons, Ltd.

Rational design and synthesis of 2-anilinopyridinyl-benzothiazole Schiff bases as antimitotic agents.

PubMed

Shaik, Thokhir B; Hussaini, S M Ali; Nayak, V Lakshma; Sucharitha, M Lakshmi; Malik, M Shaheer; Kamal, Ahmed

2017-06-01

Based on our previous results and literature precedence, a series of 2-anilinopyridinyl-benzothiazole Schiff bases were rationally designed by performing molecular modeling experiments on some selected molecules. The binding energies of the docked molecules were better than the E7010, and the Schiff base with trimethoxy group on benzothiazole moiety, 4y was the best. This was followed by the synthesis of a series of the designed molecules by a convenient synthetic route and evaluation of their anticancer potential. Most of the compounds have shown significant growth inhibition against the tested cell lines and the compound 4y exhibited good antiproliferative activity with a GI 50 value of 3.8µM specifically against the cell line DU145. In agreement with the docking results, 4y exerted cytotoxicity by the disruption of the microtubule dynamics by inhibiting tubulin polymerization via effective binding into colchicine domain, comparable to E7010. Detailed binding modes of 4y with colchicine binding site of tubulin were studied by molecular docking. Furthermore, 4y induced apoptosis as evidenced by biological studies like mitochondrial membrane potential, caspase-3, and Annexin V-FITC assays. Copyright © 2017 Elsevier Ltd. All rights reserved.

Extending the scope of amantadine drug by incorporation of phenolic azo Schiff bases as potent selective inhibitors of carbonic anhydrase II, drug likeness and binding analysis.

PubMed

Channar, Pervaiz Ali; Saeed, Aamer; Shahzad, Danish; Larik, Fayaz Ali; Hassan, Mubashir; Raza, Hussain; Abbas, Qamar; Seo, Sung-Yum

2018-05-16

A series of Amantadine based azo Schiff base dyes 6a-6e have been synthesized and characterized by 1 H NMR and 13 C NMR and evaluated for their in vitro carbonic anhydrase II inhibition activity and antioxidant activity. All of the synthesized showed excellent carbonic inhibition. Compound 6b was found to be the most potent derivative in the series, the IC 50 of 6b was found to be 0.0849 ± 0.00245μM (standard Acetazolamide IC 50 =0.9975±0.049μM). The binding interactions of the most active analogs were confirmed through molecular docking studies. Docking studies showed 6b is interacting by making two hydrogen bonds w at His93 and Ser1 residues respectively. All compounds showed a good drug score and followed Lipinski's rule. In summary, our studies have shown that these amantadine derived phenolic azo Schiff base derivatives are a new class of carbonic anhydrase II inhibitors. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Treatment of MDR1 Mutant Dogs with Macrocyclic Lactones

PubMed Central

Geyer, Joachim; Janko, Christina

2012-01-01

P-glycoprotein, encoded by the multidrug resistance gene MDR1, is an ATP-driven drug efflux pump which is highly expressed at the blood-brain barrier of vertebrates. Drug efflux of macrocyclic lactones by P-glycoprotein is highly relevant for the therapeutic safety of macrocyclic lactones, as thereby GABA-gated chloride channels, which are confined to the central nervous system in vertebrates, are protected from high drug concentrations that otherwise would induce neurological toxicity. A 4-bp deletion mutation exists in the MDR1 gene of many dog breeds such as the Collie and the Australian Shepherd, which results in the expression of a non-functional P-glycoprotein and is associated with multiple drug sensitivity. Accordingly, dogs with homozygous MDR1 mutation are in general prone to neurotoxicity by macrocyclic lactones due to their increased brain penetration. Nevertheless, treatment of these dogs with macrocyclic lactones does not inevitably result in neurological symptoms, since, the safety of treatment highly depends on the treatment indication, dosage, route of application, and the individual compound used as outlined in this review. Whereas all available macrocyclic lactones can safely be administered to MDR1 mutant dogs at doses usually used for heartworm prevention, these dogs will experience neurological toxicity following a high dose regimen which is common for mange treatment in dogs. Here, we review and discuss the neurotoxicological potential of different macrocyclic lactones as well as their treatment options in MDR1 mutant dogs. PMID:22039792

Potent Inhibitors of the Hepatitis C Virus NS3 Protease: Design and Synthesis of Macrocyclic Substrate-Based [beta]-Strand Mimics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goudreau, Nathalie; Brochu, Christian; Cameron, Dale R.

2008-06-30

The virally encoded NS3 protease is essential to the life cycle of the hepatitis C virus (HCV), an important human pathogen causing chronic hepatitis, cirrhosis of the liver, and hepatocellular carcinoma. The design and synthesis of 15-membered ring {beta}-strand mimics which are capable of inhibiting the interactions between the HCV NS3 protease enzyme and its polyprotein substrate will be described. The binding interactions between a macrocyclic ligand and the enzyme were explored by NMR and molecular dynamics, and a model of the ligand/enzyme complex was developed.

Deprotonation of hydrogen bonded Schiff bases by three strong nitrogen bases

NASA Astrophysics Data System (ADS)

Schilf, Wojciech; Cmoch, Piotr; Szady-Chełmieniecka, Anna; Grech, Eugeniusz

2009-03-01

Three Schiff bases obtained from substituted salicylaldehydes and 2-hydroxy-1-naphthaldehyde and aliphatic amines were investigated in terms of possible withdrawal of tautomeric proton from intramolecular hydrogen bridge. Three strong nitrogen bases: 1,8-bis(dimethylamino)naphtalene (DMAN), 1,1,3,3-tetramethylguanidine (TMG) and 1,8-bis(tetramethylguanidino)naphthalene (TMGN) were used as deprotonating agents in acetonitrile solution at room temperature. In the specified conditions it was found that only in the case of 5-nitrosalicylaldehyde and isopropyl amine derivative this process could be performed using TMG and TMGN as a base. The other derivatives, where bridged proton is shifted to oxygen or nitrogen atom, do not undergo such reaction. The deprotonation process was monitored by nitrogen and proton NMR measurements.

Bistable or oscillating state depending on station and temperature in three-station glycorotaxane molecular machines.

PubMed

Busseron, Eric; Romuald, Camille; Coutrot, Frédéric

2010-09-03

High-yield, straightforward synthesis of two- and three-station [2]rotaxane molecular machines based on an anilinium, a triazolium, and a mono- or disubstituted pyridinium amide station is reported. In the case of the pH-sensitive two-station molecular machines, large-amplitude movement of the macrocycle occurred. However, the presence of an intermediate third station led, after deprotonation of the anilinium station, and depending on the substitution of the pyridinium amide, either to exclusive localization of the macrocycle around the triazolium station or to oscillatory shuttling of the macrocycle between the triazolium and monosubstituted pyridinium amide station. Variable-temperature (1)H NMR investigation of the oscillating system was performed in CD(2)Cl(2). The exchange between the two stations proved to be fast on the NMR timescale for all considered temperatures (298-193 K). Interestingly, decreasing the temperature displaced the equilibrium between the two translational isomers until a unique location of the macrocycle around the monosubstituted pyridinium amide station was reached. Thermodynamic constants K were evaluated at each temperature: the thermodynamic parameters DeltaH and DeltaS were extracted from a Van't Hoff plot, and provided the Gibbs energy DeltaG. Arrhenius and Eyring plots afforded kinetic parameters, namely, energies of activation E(a), enthalpies of activation DeltaH( not equal), and entropies of activation DeltaS( not equal). The DeltaG values deduced from kinetic parameters match very well with the DeltaG values determined from thermodynamic parameters. In addition, whereas signal coalescence of pyridinium hydrogen atoms located next to the amide bond was observed at 205 K in the oscillating rotaxane and at 203 K in the two-station rotaxane with a unique location of the macrocycle around the pyridinium amide, no separation of (1)H NMR signals of the considered hydrogen atoms was seen in the corresponding nonencapsulated thread. It is suggested that the macrocycle acts as a molecular brake for the rotation of the pyridinium-amide bond when it interacts by hydrogen bonding with both the amide NH and the pyridinium hydrogen atoms at the same time.

Selective CO2 gas adsorption in the narrow crystalline cavities of flexible peptide metallo-macrocycles.

PubMed

Miyake, Ryosuke; Kuwata, Chika; Masumoto, Yui

2015-02-21

Crystalline peptide Ni(ii)-macrocycles (BF4(-) salt) exhibited moderate CO2 gas adsorption (ca. 6-7 CO2 molecules per macrocycle) into very narrow cavities (narrowest part <2 Å), accompanied by the expansion of the cavities. The BF4(-) salt demonstrated selective uptake of CO2 gas in preference to CH4 and N2 gases.

pH-Dependent Assembly and Conversions of Six Cadmium(II)-Based Coordination Complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Hua-Cai; Zhu, Ji-Qin; Zhou, Li-Jiang

2010-07-07

Six cadmium(II) complexes containing N2O2 donor tetradentate asymmetrical Schiff base ligand 2-{[2-(dimethylamino)ethylimino]methyl}-6-methoxyphenol (HL5), namely, [(Cd3L52Cl4)2]•CH3OH•H2O (1), [Cd(L5)Cl]2•CH3OH (2), [Cd2(HL5)Cl4]n (3), {[Cd3(H2L5)2Cl8]•2H2O}n (4), [(H2L5)2]2+•[CdCl4]2-•H2O (5), and [(H2L5)2]2+•[CdCl4]2- (6), have been synthesized using cadmium(II) chloride and asymmetrical Schiff base ligand HL5 under different pH conditions at room temperature. The diverse structures show the marked sensitivity of the structural chemistry of the tetradentate asymmetrical Schiff base ligand HL5. Complex 1 formed at pH = 10 exhibits a rare zero- dimensional structure of trinuclear cadmium (II). At pH = 8-9, a dinuclear cadmium (II) complex 2 is formed. The reaction at pH = 5-7more » leads to two one-dimensional structures of 3 and 4. A further decrease of the pH to 3-5 results in a zero-dimensional structure 5. Owing to the departure of lattice water molecules in the crystal, complex 5 at room temperature can gradually undergo single-crystal-to-single-crystal transformation to result complex 6. The results further show that conversions of complex 1 to 5 can also be achieved by adjusting the pH value of the reaction solution, 1→2pH=8→5pH=3 and 3→4pH=5. Comparing these experimental results, it is clear that the pH plays a crucial role in the formation of the resulting structures, which simultaneously provide very effective strategies for constructing the CdII compounds with N2O2 donor tetradentate asymmetrical Schiff base ligand. The strong fluorescent emissions of the six compounds (1-6) make them potentially useful photoactive materials. Furthermore, six Schiff base cadmium complexes (1–6), with DPPH (2,2-dipheny1-1-picrylhydrazy1) as a co-oxidant exhibited the stronger scavenging activity.« less

Synthesis, characterization, and biological activity of some novel Schiff bases and their Co(II) and Ni(II) complexes: A new route for Co3O4 and NiO nanoparticles for photocatalytic degradation of methylene blue dye

NASA Astrophysics Data System (ADS)

Nassar, Mostafa Y.; Aly, Hisham M.; Abdelrahman, Ehab A.; Moustafa, Moustafa E.

2017-09-01

Six novel Co(II) and Ni(II)-triazole Schiff base complexes have been successfully synthesized by refluxing the prepared triazole Schiff bases with CoCl2·6H2O or NiCl2·6H2O. The Schiff base ligands were prepared through condensation of 3-R-4-amino-5-hydrazino-1,2,4-triazole with dibenzoylmethane [Rdbnd H, CH3, and CH2CH3; namely, L1, L2, and L3, respectively]. The prepared Co(II) and Ni(II) complexes have been identified using elemental analysis, FT-IR, UV-Vis, magnetic moment, conductivity, and thermal analysis. On the basis of the conductance results, it was concluded that all the prepared complexes are nonelectrolytes. Interestingly, the prepared Co(II) and Ni(II) complexes were employed as precursors for producing of Co3O4 and NiO nanoparticles, respectively. The produced nanostructures have been identified by XRD, HR-TEM, FT-IR and UV-Vis spectra. The produced nanoparticles revealed good photocatalytic activity for the degradation of methylene blue dye under UV illumination in presence of hydrogen peroxide. The percent of degradation was estimated to be 55.71% in 420.0 min and 90.43% in 360.0 min for Co3O4 and NiO, respectively. Moreover, the synthesized complexes, nano-sized Co3O4, and NiO products have been examined, employing modified Bauer- Kirby method, for antifungal (Candida albicans and Aspergillus flavus) and antibacterial (Staphylococcus aureus and Escherichia coli) activities.

Properties of the anion-binding site of pharaonis Halorhodopsin studied by ultrafast pump-probe spectroscopy and low-temperature FTIR spectroscopy.

PubMed

Nakashima, Keisuke; Nakamura, Takumi; Takeuchi, Satoshi; Shibata, Mikihiro; Demura, Makoto; Tahara, Tahei; Kandori, Hideki

2009-06-18

Halorhodopsin (HR) is a light-driven chloride pump. Cl(-) is bound in the Schiff base region of the retinal chromophore, and unidirectional Cl(-) transport is probably enforced by the specific hydrogen-bonding interaction with the protonated Schiff base and internal water molecules. It is known that HR from Natronobacterium pharaonis (pHR) also pumps NO(3)(-) with similar efficiency, suggesting that NO(3)(-) binds to the Cl(-)-binding site. In the present study, we investigated the properties of the anion-binding site by means of ultrafast pump-probe spectroscopy and low-temperature FTIR spectroscopy. The obtained data were surprisingly similar between pHR-NO(3)(-) and pHR-Cl(-), even though the shapes and sizes of the two anions are quite different. Femtosecond pump-probe spectroscopy showed very similar excited-state dynamics between pHR-NO(3)(-) and pHR-Cl(-). Low-temperature FTIR spectroscopy of unlabeled and [zeta-(15)N]Lys-labeled pHR revealed almost identical hydrogen-bonding strengths of the protonated retinal Schiff base between pHR-NO(3)(-) and pHR-Cl(-), which is similarly strengthened after retinal isomerization. There were spectral variations for water stretching vibrations between pHR-NO(3)(-) and pHR-Cl(-), suggesting that the water molecules hydrate each anion. Nevertheless, the overall spectral features were similar for the two species. These observations strongly suggest that the anion-binding site has a flexible structure and that the interaction between retinal and the anions is weak, despite the presence of an electrostatic interaction. Such a flexible hydrogen-bonding network in the Schiff base region in HR appears to be in remarkable contrast to that in light-driven proton-pumping proteins.

Novel mixed ligand complexes of bioactive Schiff base (E)-4-(phenyl (phenylimino) methyl) benzene-1,3-diol and 2-aminophenol/2-aminobenzoic acid: synthesis, spectral characterization, antimicrobial and nuclease studies.

PubMed

Subbaraj, P; Ramu, A; Raman, N; Dharmaraja, J

2014-01-03

A novel bidentate Schiff base ligand has been synthesized using 2,4-dihydroxybenzophenone and aniline. Its mixed ligand complexes of MAB type [M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); HA=Schiff base and B=2-aminophenol/2-aminobenzoic acid] have been synthesized and characterized on the basis of spectral data UV-Vis, IR, (1)H NMR, FAB-Mass, EPR, SEM and magnetic studies. All the complexes were soluble in DMF and DMSO. Elemental analysis and molar conductance values indicate that the complexes are non-electrolytes. HA binds with M(II) ions through azomethine and deprotonated phenolic group and B binds through the primary amine group and deprotonated phenolic/carboxylic groups. Using FAB-Mass the cleavage pattern of the ligand (HA) has been established. All the complexes adopt octahedral geometry around the metal ions. It has been confirmed with the help of UV-Vis, IR, (1)H NMR and FAB-Mass spectral data. DNA binding activities of the complexes 1d and 2d are studied by UV-Vis spectroscopy and cleavage studies of Schiff base ligand and its complexes 1d and 2d have been by agarose gel electrophoresis method. In vitro biological activities of the free ligand (HA) and their metal complexes (1a-1e and 2a-2e) were screened against few bacteria, Escherichia coli, Staphylococcus saphyphiticus, Staphylococcus aureus, Pseudomonas aeruginosa and fungi Aspergillus niger, Enterobacter species, Candida albicans by well diffusion technique. Copyright © 2013 Elsevier B.V. All rights reserved.

Electrogenic steps of light-driven proton transport in ESR, a retinal protein from Exiguobacterium sibiricum.

PubMed

Siletsky, Sergey A; Mamedov, Mahir D; Lukashev, Evgeniy P; Balashov, Sergei P; Dolgikh, Dmitriy A; Rubin, Andrei B; Kirpichnikov, Mikhail P; Petrovskaya, Lada E

2016-11-01

A retinal protein from Exiguobacterium sibiricum (ESR) functions as a light-driven proton pump. Unlike other proton pumps, it contains Lys96 instead of a usual carboxylic residue in the internal proton donor site. Nevertheless, the reprotonation of the Schiff base occurs fast, indicating that Lys96 facilitates proton transfer from the bulk. In this study we examined kinetics of light-induced transmembrane electrical potential difference, ΔΨ, generated in proteoliposomes reconstituted with ESR. We show that total magnitude of ΔΨ is comparable to that produced by bacteriorhodopsin but its kinetic components and their pH dependence are substantially different. The results are in agreement with the earlier finding that proton uptake precedes reprotonation of the Schiff base in ESR, suggesting that Lys96 is unprotonated in the initial state and gains a proton transiently in the photocycle. The electrogenic phases and the photocycle transitions related to proton transfer from the bulk to the Schiff base are pH dependent. At neutral pH, they occur with τ 0.5ms and 4.5ms. At alkaline pH, the fast component ceases and Schiff base reprotonation slows. At pH8.4, a spectrally silent electrogenic component with τ 0.25ms is detected, which can be attributed to proton transfer from the bulk to Lys96. At pH5.1, the amplitude of ΔΨ decreases 10 fold, reflecting a decreased yield and rate of proton transfer, apparently from protonation of the acceptor (Asp85-His57 pair) in the initial state. The features of the photoelectric potential generation correlate with the ESR structure and proposed mechanism of proton transfer. Copyright © 2016 Elsevier B.V. All rights reserved.

Synthesis, structural characterization and photoluminescence properties of a novel La(III) complex

NASA Astrophysics Data System (ADS)

Köse, Muhammet; Ceyhan, Gökhan; Atcı, Emine; McKee, Vickie; Tümer, Mehmet

2015-05-01

In this study, a novel La(III) complex [La(H2L)2(NO3)3(MeOH)] of a Schiff base ligand was synthesized and characterized by spectroscopic and analytical methods. Single crystals of the complex suitable for X-ray diffraction study were obtained by slow diffusion of diethyl ether into a MeOH solution of the complex which was found to crystallise as [La(H2L)2(NO3)3(MeOH)]ṡ2MeOHṡH2O. The structure was solved in monoclinic crystal system, P21/n space group with unit cell parameters a = 10.5641(11), b = 12.6661(16), c = 16.0022(17) Å, α = 67.364(2), β = 83.794(2)°, γ = 70.541(2)°, V = 1862.9(4) Å3 and Z = 2 with R final value of 0.526. In the complex, the La(III) ion is ten-coordinated by O atoms, five of which come from three nitrate ions, four from the two Schiff base ligands and one from MeOH oxygen atom. The Schiff base ligands in the structure are in a zwitter ion form with the phenolic H transferred to the imine N atom. Thermal properties of the La(III) complex were examined by thermogravimetric analysis and the complex was found to be thermally stable up to 310 °C. The Schiff base ligand and its La(II) complex were screened for their in vitro antimicrobial activity against Bacillus megaterium, Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus (Gram positive bacteria), Klebsiella pneumonia, Escherichia coli, Enterobacter aerogenes, Pseudomonas aeruginosa (Gram negative bacteria), Candida albicans,Yarrowia lipolytica (fungus) and Saccharomyces cerevisiae (yeast). The complex shows more antimicrobial activity than the free ligand.

Tetraphenylethylene-Interweaving Conjugated Macrocycle Polymer Materials as Two-Photon Fluorescence Sensors for Metal Ions and Organic Molecules.

PubMed

Li, Xi; Li, Zheng; Yang, Ying-Wei

2018-05-01

A luminescent conjugated macrocycle polymer (CMP) with strong two-photon fluorescence property, namely, P[5]-TPE-CMP, is constructed from ditriflate-functionalized pillar[5]arene and a 1,1,2,2-tetrakis(4-ethynylphenyl)ethylene (TPE) linker through a Sonogashira-Hagihara cross-coupling reaction. Significantly, in sharp contrast with the corresponding conjugated microporous polymer without synthetic macrocycles, P[5]-TPE-CMP shows an outstanding stability against photobleaching and exhibits highly selective cation sensing capability toward Fe 3+ at different excitation wavelengths (both UV and red-near-infrared regions). Meanwhile, its fluorescence could also be sufficiently quenched by 4-amino azobenzene, a frequently used organic dye that is certified to be carcinogenic, as compared with a group of common organic compounds. This work paves a new way for enhancing the properties of porous organic polymers through the introduction of supramolecular macrocycles like macrocyclic arenes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

On-Surface Synthesis and Characterization of Honeycombene Oligophenylene Macrocycles.

PubMed

Chen, Min; Shang, Jian; Wang, Yongfeng; Wu, Kai; Kuttner, Julian; Hilt, Gerhard; Hieringer, Wolfgang; Gottfried, J Michael

2017-01-24

We report the on-surface formation and characterization of [30]-honeycombene, a cyclotriacontaphenylene, which consists of 30 phenyl rings (C 180 H 120 ) and has a diameter of 4.0 nm. This shape-persistent, conjugated, and unsubstituted hexagonal hydrocarbon macrocycle was obtained by solvent-free synthesis on a silver (111) single-crystal surface, making solubility-enhancing alkyl side groups unnecessary. Side products include strained macrocycles with square, pentagonal, and heptagonal shape. The molecules were characterized by scanning tunneling microscopy and density functional theory (DFT) calculations. On the Ag(111) surface, the macrocycles act as molecular quantum corrals and lead to the confinement of surface-state electrons inside the central cavity. The energy of the confined surface state correlates with the size of the macrocycle and is well described by a particle-in-the-box model. Tunneling spectroscopy suggests conjugation within the planar rings and reveals influences of self-assembly on the electronic structure. While the adsorbed molecules appear to be approximately planar, the free molecules have nonplanar conformation, according to DFT.

Synthesis, characterisation and DFT studies of three Schiff bases derived from histamine

NASA Astrophysics Data System (ADS)

Touafri, Lasnouni; Hellal, Abdelkader; Chafaa, Salah; Khelifa, Abdellah; Kadri, Abdelaziz.

2017-12-01

In this paper, we report first, the synthesis and characterisation of three Schiff bases derived from histamine by condensation of histamine with various aldehydes. Then, we present a detailed DFT study based on B3LYP/6-31G(d,p) of geometrical structures and electronic properties of these compounds. The study was extended to the HOMO-LUMO analysis to calculate the energy gap (Δ), Ionisation potential (I), Electron Affinity (A), Global Hardness (η), Chemical Potential (μ), Electrophilicity (ω), Electronegativity (χ) and Polarisability (α). The calculated HOMO and LUMO energy reveals that the charge transfers occurring within the molecule. On the basis of vibration analyses, the thermodynamic properties of the titles compound were also calculated.

Intravenous injection of gadobutrol in an epidemiological study group did not lead to a difference in relative signal intensities of certain brain structures after 5 years.

PubMed

Kromrey, Marie-Luise; Liedtke, Kim Rouven; Ittermann, Till; Langner, Sönke; Kirsch, Michael; Weitschies, Werner; Kühn, Jens-Peter

2017-02-01

To investigate if application of macrocyclic gadolinium-based contrast agents in volunteers is associated with neuronal deposition detected by magnetic resonance imaging in a 5-year longitudinal survey. Three hundred eighty-seven volunteers who participated in a population-based study were enrolled. Subjects underwent plain T1-weighted brain MRI at baseline and 5 years later with identical sequence parameters. At baseline, 271 participants additionally received intravenous injection of the macrocyclic contrast agent gadobutrol (0.15 mmol/kg). A control group including 116 subjects received no contrast agent. Relative signal intensities of thalamus, pallidum, pons and dentate nucleus were compared at baseline and follow-up. No difference in relative signal intensities was observed between contrast group (thalamus, p = 0.865; pallidum, p = 0.263; pons, p = 0.533; dentate nucleus, p = 0.396) and control group (thalamus, p = 0.683; pallidum; p = 0.970; pons, p = 0.773; dentate nucleus, p = 0.232) at both times. Comparison between both groups revealed no significant differences in relative signal intensities (thalamus, p = 0.413; pallidum, p = 0.653; pons, p = 0.460; dentate nucleus, p = 0.751). The study showed no significant change in globus pallidus-to-thalamus or dentate nucleus-to-pons ratios. Five years after administration of a 1.5-fold dose gadobutrol to normal subjects, signal intensity of thalamus, pallidum, pons and dentate nucleus did not differ from participants who had not received gadobutrol. • Gadobutrol does not lead to neuronal signal alterations after 5 years. • Neuronal deposition of macrocyclic contrast agent could not be confirmed. • Macrocyclic contrast agents in a proven dosage are safe.

Regioselective reaction: synthesis, characterization and pharmacological activity of some new Mannich and Schiff bases containing sydnone.

PubMed

Nithinchandra; Kalluraya, B; Aamir, S; Shabaraya, A R

2012-08-01

A novel series of 1-substituted aminomethyl-3-[1-(4-isobutylphenyl)ethyl]-4-(3-aryl-4-sydnonylidene) amino-1,2,4-triazol-5-thiones (9), was prepared from the 3-[1-(4-isobutylphenyl)ethyl]-4-(3-aryl-4-sydnonylidene) amino 5-mercapto-1,2,4-triazoles (8) by aminomethylation with formaldehyde and secondary amine. The structures of Schiff bases (8) and Mannich bases (9) were characterized on the basis of IR, NMR, mass spectra1 data and elemental analysis. The newly synthesized compounds were screened for their anti-inflammatory and analgesic activities. Mannich bases (9) carrying piperidine and morpholine residues showed promising anti-inflammatory and analgesic activity. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

2-[(E)-(1,10-Phenanthrolin-5-yl)imino­meth­yl]phenol methanol monosolvate

PubMed Central

Öztürk Yíldírím, Sema; Demirhan, Nebahat; Elmalí, Fikriye; Butcher, Ray J.

2012-01-01

In the title multi-donor Schiff base compound, C19H13N3O·CH3OH, the dihedral angle between the mean planes of the phenanthroline and phenol rings is 59.3 (1)°. The Schiff base mol­ecule is linked to the solvent mol­ecule by an O—H⋯O hydrogen bond. In the crystal, the components are linked by O—H⋯N hydrogen bonds, weak O—H⋯N inter­actions and π–π stacking inter­actions [centroid–centroid distances = 3.701 (1) and 3.656 (1) Å]. PMID:22606116

A novel coumarin Schiff-base as a Ni(II) ion colorimetric sensor

NASA Astrophysics Data System (ADS)

Wang, Lingyun; Ye, Decheng; Cao, Derong

2012-05-01

A novel coumarin Schiff base compound (L) prepared from 7-diethylaminocoumarin-3-aldehyde and 3-amino-7-hydroxycoumarin was synthesized and evaluated as a chemoselective Ni2+ sensor. Addition of Ni2+ to CH3CN solution of L resulted in a rapid color change from yellow to red together with a large red shift from 465 to 516 nm. Moreover, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. Experimental results indicated that L could be used as a potential Ni2+ colorimetric and naked-eye chemosensor in CH3CN solution.

Rational design of a colorimetric pH sensor from a soluble retinoic acid chaperone.

PubMed

Berbasova, Tetyana; Nosrati, Meisam; Vasileiou, Chrysoula; Wang, Wenjing; Lee, Kin Sing Stephen; Yapici, Ipek; Geiger, James H; Borhan, Babak

2013-10-30

Reengineering of cellular retinoic acid binding protein II (CRABPII) to be capable of binding retinal as a protonated Schiff base is described. Through rational alterations of the binding pocket, electrostatic perturbations of the embedded retinylidene chromophore that favor delocalization of the iminium charge lead to exquisite control in the regulation of chromophoric absorption properties, spanning the visible spectrum (474-640 nm). The pKa of the retinylidene protonated Schiff base was modulated from 2.4 to 8.1, giving rise to a set of proteins of varying colors and pH sensitivities. These proteins were used to demonstrate a concentration-independent, ratiometric pH sensor.

Catalytic asymmetric ring-opening of meso-aziridines with malonates under heterodinuclear rare earth metal Schiff base catalysis.

PubMed

Xu, Yingjie; Lin, Luqing; Kanai, Motomu; Matsunaga, Shigeki; Shibasaki, Masakatsu

2011-04-20

Catalytic asymmetric ring-opening of meso-aziridines with malonates is described. The combined use of two rare earth metal sources with different properties promoted the desired ring-opening reaction. A 1:1:1 mixture of a heterobimetallic La(O-iPr)(3)/Yb(OTf)(3)/Schiff base 1a (0.25-10 mol %) efficiently promoted the reaction of five-, six-, and seven-membered ring cyclic meso-aziridines as well as acyclic meso-aziridines with dimethyl, diethyl, and dibenzyl malonates, giving chiral cyclic and acyclic γ-amino esters in 99-63% yield and >99.5-97% ee.

Schiff bases attached L-glutamine and L-asparagine: first investigation on antimutagenic and antimicrobial analyses.

PubMed

Sakiyan, Iffet; Anar, Mustafa; Oğütcü, Hatice; Agar, Guleray; Sarı, Nurşen

2014-06-01

This study was conducted to evaluate the antimutagenic and antimicrobial activities of Schiff bases attached L-glutamine and L-asparagine. Antibacterial activities of the compounds against S. aureus, Sh. dys. typ 7, L. monocytogenes 4b, E. coli, S. typhi H, S. epidermis, Br. abortus, M. luteus, B. cereus, P. putida, and antifungal activity against Candida albicans were studied. These compounds were investigated for antimutagenic properties against Aflatoxin Bı (AFBı) using micronuclei (MN) assay in human lymphocyte cell culture in vitro. The protective role of these compounds against AFBı-induced MN is probably related to its doses.

Composition, Characterization and Antibacterial activity of Mn(II), Co(II),Ni(II), Cu(II) Zn(II) and Cd(II) mixed ligand complexes Schiff base derived from Trimethoprim with 8-Hydroxy quinoline

NASA Astrophysics Data System (ADS)

Numan, Ahmed T.; Atiyah, Eman M.; Al-Shemary, Rehab K.; Ulrazzaq, Sahira S. Abd

2018-05-01

New Schiff base ligand 2-((4-amino-5-(3, 4, 5-trimethoxybenzyl) pyrimidin-2-ylimino) (phenyl)methyl)benzoic acid] = [HL] was synthesized using microwave irradiation trimethoprim and 2-benzoyl benzoic acid. Mixed ligand complexes of Mn((II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) are reacted in ethanol with Schiff base ligand [HL] and 8-hydroxyquinoline [HQ] then reacted with metal salts in ethanol as a solvent in (1:1:1) ratio. The ligand [HL] is characterized by FTIR, UV-Vis, melting point, elemental microanalysis (C.H.N), 1H-NMR, 13C-NMR, and mass spectra. The mixed ligand complexes are characterized by infrared spectra, electronic spectra, (C.H.N), melting point, atomic absorption, molar conductance and magnetic moment measurements. These measurements indicate that the ligand [HL] coordinates with metal (II) ion in a tridentate manner through the oxygen and nitrogen atoms of the ligand, octahedral structures are suggested for these complexes. Antibacterial activity of the ligands [HL], [HQ] and their complexes are studied against (gram positive) and (gram negative) bacteria.

Synthesis, spectral characterization, molecular modeling, biological activity and potentiometric studies of 4-amino-5-mercapto-3-methyl-S-triazole Schiff's base complexes

NASA Astrophysics Data System (ADS)

Alaghaz, Abdel-Nasser M. A.; Zayed, Mohamed E.; Alharbi, Suliman A.

2015-03-01

The Schiff's base derived from condensation of s-triazole (4-amino-5-mercapto-3-methyl-S-triazole) with pyridine-2-aldehyde and their corresponding Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized. The isolated solid complexes were characterized by elemental analyses, molar conductance, spectral (IR, UV-Vis, 1H NMR, mass), magnetic moment and thermal measurements. The IR spectral data suggest that the ligand coordinate in a tridentate manner (SNN) via the one thiol (SH), one pyridine ring and the azomethine (Cdbnd N) groups. The data show that the complexes have composition of ML2 type. The activation of thermodynamic parameters are calculated using Coats-Redfern, Horowitz-Metzger (HM), and Piloyan-Novikova (PN). The octahedral geometry of the complexes is confirmed using DFT method from DMOL3 calculations and ligand field parameters. Protonation constants of Schiff base and stability constants of their binary metal complexes have been determined potentiometrically in 50% DMSO-water media at 25 °C and ionic strength 0.10 M potassium nitrate. The biological activity of these compounds against various fungi has been investigated.

Co(II) and Cd(II) Complexes Derived from Heterocyclic Schiff-Bases: Synthesis, Structural Characterisation, and Biological Activity

PubMed Central

Ahmed, Riyadh M.; Yousif, Enaam I.; Al-Jeboori, Mohamad J.

2013-01-01

New monomeric cobalt and cadmium complexes with Schiff-bases, namely, N′-[(E)-(3-hydroxy-4-methoxyphenyl)methylidene]furan-2-carbohydrazide (L1) and N′-[(E)-(3-hydroxy-4-methoxyphenyl)methylidene]thiophene-2-carbohydrazide (L2) are reported. Schiff-base ligands L1 and L2 were derived from condensation of 3-hydroxy-4-methoxybenzaldehyde (iso-vanillin) with furan-2-carboxylic acid hydrazide and thiophene-2-carboxylic acid hydrazide, respectively. Complexes of the general formula [M(L)2]Cl2 (where M = Co(II) or Cd(II), L = L1 or L2) have been obtained from the reaction of the corresponding metal chloride with the ligands. The ligands and their metal complexes were characterised by spectroscopic methods (FTIR, UV-Vis, 1H, and 13C NMR spectra), elemental analysis, metal content, magnetic measurement, and conductance. These studies revealed the formation of four-coordinate complexes in which the geometry about metal ion is tetrahedral. Biological activity of the ligands and their metal complexes against gram positive bacterial strain Bacillus (G+) and gram negative bacteria Pseudomonas (G−) revealed that the metal complexes become less resistive to the microbial activities as compared to the free ligands. PMID:24027449

Schiff Base modified on CPE electrode and PCB gold electrode for selective determination of silver ion

NASA Astrophysics Data System (ADS)

Leepheng, Piyawan; Suramitr, Songwut; Phromyothin, Darinee

2017-09-01

The schiff base was synthesized by 2,5-thiophenedicarboxaldehyde and 1,2,4-thiadiazole-3,5-diamine with condensation method. There was modified on carbon paste electrode (CPE) and Printed circuit board (PCB) gold electrode for determination silver ion. The schiff base modified electrodes was characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The electrochemical study was reported by cyclic voltammetry method and impedance spectroscopy using modified electrode as working electrode, platinum wire and Ag/AgCl as counter electrode and reference electrode, respectively. The modified electrodes have suitable detection for Ag+. The determination of silver ions using the modified electrodes depended linearly on Ag+ concentration in the range 1×10-10 M to 1×10-7 M, with cyclic voltammetry sensitivity were 2.51×108 μAM-1 and 1.88×108 μAM-1 for PCB gold electrode and CPE electrode, respectively, limits of detection were 5.33×10-9 M and 1.99×10-8 M for PCB gold electrode and CPE electrode, respectively. The modified electrodes have high accuracy, inexpensive and can applied to detection Ag+ in real samples.

Synthesis, pH dependent photometric and electrochemical investigation, redox mechanism and biological applications of novel Schiff base and its metallic derivatives

NASA Astrophysics Data System (ADS)

Rauf, Abdur; Shah, Afzal; Khan, Abdul Aziz; Shah, Aamir Hassan; Abbasi, Rashda; Qureshi, Irfan Zia; Ali, Saqib

2017-04-01

A novel Schiff base, 1-((2, 4-dimethylphenylimino)methyl)naphthalen-2-ol abbreviated as (HL) and its four metallic complexes were synthesized and confirmed by 1H and 13C NMR, FTIR, TGA and UV-Visible spectroscopy. Schiff base was also characterized by X-ray analysis. The photometric and electrochemical responses of all the synthesized compounds were investigated in a wide pH range. Structures of the compounds were optimized computationally for the evaluation of different physico-chemical parameters. On the basis of electrochemical results the redox mechanistic pathways of the compounds were proposed. The cytotoxicity analysis on Hela cells revealed that HL and its complexes inhibit cell growth as revealed from their IC50 values (HL):106.7 μM, (L2VO): 40.66 μM, (L2Sn): 5.92 μM, (L2Zn): 42.82 and (L2Co): 107.68 μM. The compounds were tested for anti-diabetic, triglyceride, cholesterol, anti-microbial, anti-fungal and enzyme inhibition activities. The results revealed that HL and its complexes are promising new therapeutic options as these compounds exhibit strong activity against cancer cells, diabetics, fungal and microbial inhibition.

Synthesis, biological activity and molecular modeling study of new Schiff bases incorporated with indole moiety.

PubMed

Halawa, Ahmed H; El-Gilil, Shimaa Mohamed Abd; Bedair, Ahmed H; Shaaban, Mohamed; Frese, Marcel; Sewald, Norbert; Eliwa, Essam M; El-Agrody, Ahmed M

2017-10-26

A new series of heterocyclic Schiff bases 2-9 containing indole moiety were synthesized by facile and efficient condensation of indole-3/2/5-carboxaldehyde (1a/1b/1c) with different aromatic and heterocyclic primary amines using conventional and/or microwave irradiation methods. The structures of the obtained compounds were assigned by sophisticated spectroscopic and spectrometric techniques (1D-NMR, 2D-NMR and MS). The synthesized compounds were screened for their cytotoxicity and antibacterial activities. In vitro cytotoxicity screening revealed that compound 5 exhibited moderate activity against KB-3-1 cell line (IC50=57.7 μM) while 5-indolylimino derivative 7 indicated close to the activity (IC50=19.6 μM) in comparison with the positive control (+)-Griseofulvin (IC50=19.2 μM), while the tested compounds 5, 6b, 7 and 9 revealed good or moderate antibacterial activity. In addition, molecular docking study of Schiff bases 2-9 was performed by Molecular Operating Environment (MOE 2014.09) program on the matrix metalloproteinase-8 (MMP-8) (Protein Data Bank (PDB) ID: 1MNC) in an attempt to explore their mode of action as anticancer drugs.

Heterobimetallic transition metal/rare earth metal bifunctional catalysis: a Cu/Sm/Schiff base complex for syn-selective catalytic asymmetric nitro-Mannich reaction.

PubMed

Handa, Shinya; Gnanadesikan, Vijay; Matsunaga, Shigeki; Shibasaki, Masakatsu

2010-04-07

The full details of a catalytic asymmetric syn-selective nitro-Mannich reaction promoted by heterobimetallic Cu/Sm/dinucleating Schiff base complexes are described, demonstrating the effectiveness of the heterobimetallic transition metal/rare earth metal bifunctional catalysis. The first-generation system prepared from Cu(OAc)(2)/Sm(O-iPr)(3)/Schiff base 1a = 1:1:1 with an achiral phenol additive was partially successful for achieving the syn-selective catalytic asymmetric nitro-Mannich reaction. The substrate scope and limitations of the first-generation system remained problematic. After mechanistic studies on the catalyst prepared from Sm(O-iPr)(3), we reoptimized the catalyst preparation method, and a catalyst derived from Sm(5)O(O-iPr)(13) showed broader substrate generality as well as higher reactivity and stereoselectivity compared to Sm(O-iPr)(3). The optimal system with Sm(5)O(O-iPr)(13) was applicable to various aromatic, heteroaromatic, and isomerizable aliphatic N-Boc imines, giving products in 66-99% ee and syn/anti = >20:1-13:1. Catalytic asymmetric synthesis of nemonapride is also demonstrated using the catalyst derived from Sm(5)O(O-iPr)(13).

Synthesis, characterization, single crystal X-ray determination, fluorescence and electrochemical studies of new dinuclear nickel(II) and oxovanadium(IV) complexes containing double Schiff base ligands

NASA Astrophysics Data System (ADS)

Shafaatian, Bita; Ozbakzaei, Zahra; Notash, Behrouz; Rezvani, S. Ahmad

2015-04-01

A series of new bimetallic complexes of nickel(II) and vanadium(IV) have been synthesized by the reaction of the new double bidentate Schiff base ligands with nickel acetate and vanadyl acetylacetonate in 1:1 M ratio. In nickel and also vanadyl complexes the ligands were coordinated to the metals via the imine N and enolic O atoms. The complexes have been found to possess 1:1 metals to ligands stoichiometry and the molar conductance data revealed that the metal complexes were non-electrolytes. The nickel and vanadyl complexes exhibited distorted square planar and square pyramidal coordination geometries, respectively. The emission spectra of the ligands and their complexes were studied in methanol. Electrochemical properties of the ligands and their metal complexes were also investigated in DMSO solvent at 150 mV s-1 scan rate. The ligands and metal complexes showed both quasi-reversible and irreversible processes at this scan rate. The Schiff bases and their complexes have been characterized by FT-IR, 1H NMR, UV/Vis spectroscopies, elemental analysis and conductometry. The crystal structure of the nickel complex has been determined by single crystal X-ray diffraction.

Spectral characterization, thermal and biological activity studies of Schiff base complexes derived from 4,4‧-Methylenedianiline, ethanol amine and benzil

NASA Astrophysics Data System (ADS)

Emam, Sanaa Moustafa

2017-04-01

Some new metal(II) complexes of asymmetric Schiff base ligand were prepared by template technique. The shaped complexes are in binuclear structures and were explained through elemental analysis, molar conductivity, various spectroscopic methods (IR, U.V-Vis, XRD, ESR), thermal (TG) and magnetic moment measurements. The IR spectra were done demonstrating that the Schiff base ligand acts as neutral tetradentate moiety in all metal complexes. The electronic absorption spectra represented octahedral geometry for all complexes, while, the ESR spectra for Cu(II) complex showed axially symmetric g-tensor parameter with g׀׀ > g⊥ > 2.0023 indicating to 2B1g ground state with (dx2-y2)1 configuration. The nature of the solid residue created from TG estimations was affirmed utilizing IR and XRD spectra. The biological activity of the prepared complexes was studied against Land Snails. Additionally, the in vitro antitumor activity of the synthesized complexes with Hepatocellular Carcinoma cell (Hep-G2) was examined. It was observed that Zn(II) complex (5), exhibits a high inhibition of growth of the cell line with IC50 of 7.09 μg/mL.

Macrocyclic BACE inhibitors: Optimization of a micromolar hit to nanomolar leads.

PubMed

Huang, Yifang; Strobel, Eric D; Ho, Chih Y; Reynolds, Charles H; Conway, Kelly A; Piesvaux, Jennifer A; Brenneman, Douglas E; Yohrling, George J; Moore Arnold, H; Rosenthal, Daniel; Alexander, Richard S; Tounge, Brett A; Mercken, Marc; Vandermeeren, Marc; Parker, Michael H; Reitz, Allen B; Baxter, Ellen W

2010-05-15

We have identified macrocyclic inhibitors of the aspartic protease BACE, implicated in the etiology of Alzheimer's disease. An X-ray structure of screening hit 1 in the BACE active site revealed a hairpin conformation suggesting that constrained macrocyclic derivatives may also bind there. Several of the analogs we prepared were >100x more potent than 1, such as 7 (5 nM K(i)). Copyright 2010 Elsevier Ltd. All rights reserved.

Rapid Retinal Release from a Cone Visual Pigment Following Photoactivation*

PubMed Central

Chen, Min-Hsuan; Kuemmel, Colleen; Birge, Robert R.; Knox, Barry E.

2012-01-01

As part of the visual cycle, the retinal chromophore in both rod and cone visual pigments undergoes reversible Schiff base hydrolysis and dissociation following photobleaching. We characterized light-activated retinal release from a short-wavelength sensitive cone pigment (VCOP) in 0.1% dodecyl maltoside using fluorescence spectroscopy. The half-time (t1/2) of retinal release from VCOP was 7.1 s, 250-fold faster than rhodopsin. VCOP exhibited pH-dependent release kinetics, with the t1/2 decreasing from 23 s to 4 s with pH 4.1 to 8, respectively. However, the Arrhenius activation energy (Ea) for VCOP derived from kinetic measurements between 4° and 20°C was 17.4 kcal/mol, similar to 18.5 kcal/mol for rhodopsin. There was a small kinetic isotope (D2O) effect in VCOP, but less than that observed in rhodopsin. Mutation of the primary Schiff base counterion (VCOPD108A) produced a pigment with an unprotonated chromophore (⌊max = 360 nm) and dramatically slowed (t1/2 ~ 6.8 min) light-dependent retinal release. Using homology modeling, a VCOP mutant with two substitutions (S85D/ D108A) was designed to move the counterion one alpha helical turn into the transmembrane region from the native position. This double mutant had a UV-visible absorption spectrum consistent with a protonated Schiff base (⌊max = 420 nm). Moreover, VCOPS85D/D108A mutant had retinal release kinetics (t1/2 = 7 s) and Ea (18 kcal/mol) similar to the native pigment exhibiting no pH-dependence. By contrast, the single mutant VCOPS85D had a ~3-fold decrease in retinal release rate compared to the native pigment. Photoactivated VCOPD108A had kinetics comparable to a rhodopsin counterion mutant, RhoE113Q, both requiring hydroxylamine to fully release retinal. These results demonstrate that the primary counterion of cone visual pigments is necessary for efficient Schiff base hydrolysis. We discuss how the large differences in retinal release rates between rod and cone visual pigments arise, not from inherent differences in the rate of Schiff base hydrolysis, but rather from differences in the non-covalent binding properties of the retinal chromophore to the protein. PMID:22217337

Self-assembled monolayers of shape-persistent macrocycles on graphite: interior design and conformational polymorphism.

PubMed

Vollmeyer, Joscha; Eberhagen, Friederike; Höger, Sigurd; Jester, Stefan-S

2014-01-01

Three shape-persistent naphthylene-phenylene-acetylene macrocycles of identical backbone structures and extraannular substitution patterns but different (empty, apolar, polar) nanopore fillings are self-assembled at the solid/liquid interface of highly oriented pyrolytic graphite and 1,2,4-trichlorobenzene. Submolecularly resolved images of the resulting two-dimensional (2D) crystalline monolayer patterns are obtained by in situ scanning tunneling microscopy. A concentration-dependent conformational polymorphism is found, and open and more dense packing motifs are observed. For all three compounds alike lattice parameters are found, therefore the intermolecular macrocycle distances are mainly determined by their size and symmetry. This is an excellent example that the graphite acts as a template for the macrocycle organization independent from their specific interior.

High-performance liquid chromatographic enantioseparation of 2-aminomono- and dihydroxycyclopentanecarboxylic and 2-aminodihydroxycyclohexanecarboxylic acids on macrocyclic glycopeptide-based phases.

PubMed

Berkecz, Róbert; Ilisz, István; Benedek, Gabriella; Fülöp, Ferenc; Armstrong, Daniel W; Péter, Antal

2009-02-06

The direct separation of the enantiomers of four 2-aminomono- or dihydroxycyclopentanecarboxylic acids and four 2-aminodihydroxycyclohexanecarboxylic acids was performed on chiral stationary phases containing macrocyclic glycopeptide antibiotics such as teicoplanin (Astec Chirobiotic T and T2), teicoplanin aglycone (Chirobiotic TAG) or ristocetin A (Chirobiotic R) as chiral selectors. The effects of the nature of organic modifiers, the pH, the mobile phase composition and the structures of the analytes on the separation were investigated. Chirobiotic TAG, and in some cases Chirobiotic T, proved to be the most useful of these columns. The elution sequence was determined in most cases.

Aggregation of p-Sulfonatocalixarene-Based Amphiphiles and Supra-Amphiphiles

PubMed Central

Basilio, Nuno; Francisco, Vitor; Garcia-Rio, Luis

2013-01-01

p-Sulfonatocalixarenes are a special class of water soluble macrocyclic molecules made of 4-hydroxybenzenesulfonate units linked by methylene bridges. One of the main features of these compounds relies on their ability to form inclusion complexes with cationic and neutral species. This feature, together with their water solubility and apparent biological compatibility, had enabled them to emerge as one the most important host receptors in supramolecular chemistry. Attachment of hydrophobic alkyl chains to these compounds leads to the formation of macrocyclic host molecules with amphiphilic properties. Like other oligomeric surfactants, these compounds present improved performance with respect to their monomeric counterparts. In addition, they hold their recognition abilities and present several structural features that depend on the size of the macrocycle and on the length of the alkyl chain, such as preorganization, flexibility and adopted conformations, which make these molecules very interesting to study structure-aggregation relationships. Moreover, the recognition abilities of p-sulfonatocalixarenes enable them to be applied in the design of amphiphiles constructed from non-covalent, rather than covalent, bonds (supramolecular amphiphiles). In this review, we summarize the developments made on the design and synthesis of p-sulfonatocalixarenes-based surfactants, the characterization of their self-assembly properties and on how their structure affects these properties. PMID:23380960

Coordination of N,O-donor appended Schiff base ligand (H2L1) towards Zinc(II) in presence of pseudohalides: Syntheses, crystal structures, photoluminescence, antimicrobial activities and Hirshfeld surfaces

NASA Astrophysics Data System (ADS)

Majumdar, Dhrubajyoti; Biswas, Jayanta Kumar; Mondal, Monojit; Surendra Babu, M. S.; Metre, Ramesh K.; Das, Sourav; Bankura, Kalipada; Mishra, Dipankar

2018-03-01

A series of dinuclear Zn(II) complexes [Zn2 (L1) (CH3OH)2(SCN) (OAc)](1), [Zn2 (L1) (CH3OH)2(N3)2](2) and [Zn2 (L1) (Cl)2(CH3OH)]·CH3OH (3) have been synthesized by the reaction of compartmental Schiff base ligand (H2L1) [N,N‧-Bis(3-ethoxysalicylidenimino)-1,3-diaminopropane] with Zn(OAc)2·2H2O in presence of coligand like KSCN, NaN3 and NaCl respectively. X-ray diffraction analysis revealed that all the complexes are neutral and possess a 4-membered Zn2 (μ2-O)2 ring fastened by the unified coordination action of a doubly deprotonated ligand. In addition, solid state structure of the complexes display extensive intermolecular interaction which has been supported theoretically by Hirshfeld surface analysis with 2D Fingerprint plots. The synthesized Zn(II) metal complexes observed enhancement of luminescence emission compared to the parent Schiff base due to emanating ligand based intraligand (π→π∗) fluorescence. Additionally, Zn(II) metal complexes exhibited considerable antimicrobial potency against some important Gram +ve and Gram -ve bacteria.

Affinity to bovine serum albumin and anticancer activity of some new water-soluble metal Schiff base complexes

NASA Astrophysics Data System (ADS)

Asadi, Mozaffar; Asadi, Zahra; Zarei, Leila; Sadi, Somaye Barzegar; Amirghofran, Zahra

2014-12-01

Metal Schiff-base complexes show biological activity but they are usually insoluble in water so four new water-soluble metal Schiff base complexes of Na2[M(5-SO3-1,2-salben]; (5-SO3-1,2-salben denoted N,N";-bis(5-sulphosalicyliden)-1,2-diaminobenzylamine and M = Mg, Mn, Cu, Zn) were synthesized and characterized. The formation constants of the metal complexes were determined by UV-Vis absorption spectroscopy. The interaction of these complexes with bovine serum albumin (BSA) was studied by fluorescence spectroscopy. Type of quenching, binding constants, number of binding sites and binding stoichiometries were determined by fluorescence quenching method. The results showed that the mentioned complexes strongly bound to BSA. Thermodynamic parameters indicated that hydrophobic association was the major binding force and that the interaction was entropy driven and enthalpically disfavoured. The displacement experiment showed that these complexes could bind to the subdomain IIA (site I) of albumin. Furthermore the synchronous fluorescence spectra showed that the microenvironment of the tryptophan residues was not apparently changed. Based on the Förster theory of non-radiation energy transfer, the distance between the donor (Trp residues) and the acceptor metal complexes was obtained. The growth inhibitory effect of complexes toward the K562 cancer cell line was measured.

Synthesis, antimicrobial evaluation and docking studies of some novel quinazolinone Schiff base derivatives

PubMed Central

Nasab, Rezvan Rezaee; Mansourian, Mahboubeh; Hassanzadeh, Farshid

2018-01-01

The quinazolin-4(3H)-one structural motif possesses a wide spectrum of biological activities. DNA gyrase play an important role in induction of bacterial death. It has been shown that many quinazolin-4(3H)-one derivatives have antibacterial effects through inhibition of DNA gyrase. Based on this information we decided to synthesize novel quinazolinone Schiff base derivatives in order to evaluate their antibacterial effects. A series of novel quinazolinone Schiff base derivatives were designed and synthesized from benzoic acid. The potential DNA gyrase inhibitory activity of these compounds was investigated using in silico molecular docking simulation. All new synthesized derivatives were screened for their antimicrobial activities against three species of Gram-negative bacteria including Escherichia coli, Pseudomonas aeruginosa, Salmonella entritidis and three species of Gram-positive bacteria comprising of Staphylococcus aurous, Bacillus subtilis, Listeria monocitogenes as well as for antifungal activities against Candida albicans using the conventional micro dilution method. Most of the compounds have shown good antibacterial activities, especially against E. coli at 128 µg/mL concentration while no remarkable antifungal activities were observed for these compounds. All the synthesized compounds exhibit dock score values between -5.96 and -8.58 kcal/mol. The highest dock score among them was -8.58 kcal/mol for compound 4c. PMID:29853931

Deep Eutectic Solvents as Convenient Media for Synthesis of Novel Coumarinyl Schiff Bases and Their QSAR Studies.

PubMed

Molnar, Maja; Komar, Mario; Brahmbhatt, Harshad; Babić, Jurislav; Jokić, Stela; Rastija, Vesna

2017-09-05

Deep eutectic solvents, as green and environmentally friendly media, were utilized in the synthesis of novel coumarinyl Schiff bases. Novel derivatives were synthesized from 2-((4-methyl-2-oxo-2 H -chromen-7-yl)oxy)acetohydrazide and corresponding aldehyde in choline chloride:malonic acid (1:1) based deep eutectic solvent. In these reactions, deep eutectic solvent acted as a solvent and catalyst as well. Novel Schiff bases were synthesized in high yields (65-75%) with no need for further purification, and their structures were confirmed by mass spectra, ¹H and 13 C NMR. Furthermore, their antioxidant activity was determined and compared to antioxidant activity of previously synthesized derivatives, thus investigating their structure-activity relationship utilizing quantitative structure-activity relationship QSAR studies. Calculation of molecular descriptors has been performed by DRAGON software. The best QSAR model ( R tr = 0.636; R ext = 0.709) obtained with three descriptors ( MATS3m , Mor22u , Hy ) implies that the pairs of atoms higher mass at the path length 3, three-dimensional arrangement of atoms at scattering parameter s = 21 Å - ¹, and higher number of hydrophilic groups (-OH, -NH) enhanced antioxidant activity. Electrostatic potential surface of the most active compounds showed possible regions for donation of electrons to 1,1-diphenyl-2-picryhydrazyl (DPPH) radicals.

New group 6 metal carbonyl complexes with 4,5-dimethyl-N,N-bis(pyridine-2-yl-methylene)benzene-1,2-diimine Schiff base: synthesis, spectral, cyclic voltammetry and biological activity studies.

PubMed

Mohamed, Rania G; Elantabli, Fatma M; Helal, Nadia H; El-Medani, Samir M

2015-04-15

Thermal reaction of M(CO)6 (M=Cr, Mo or W) with a Schiff base (DMPA) derived from the condensation of 4,5-dimethyl-1,2-phenylenediamine and pyridine-2-carboxaldehyde in THF in absence and presence of a secondary ligand; 2-aminobenzimidazole (Abz), thiourea (Tu) or 2-(2'-pyridyl)benzimidazole (pybz) were studied. The reaction of Cr(CO)6 gave the four complexes Cr2(CO)2(DMPA)2; 1, Cr(DMPA)2(Abz)2; 2, Cr2(CO)4(DMPA)2(Tu)2; 3 and Cr(DMPA)2(Pybz); 4, while the thermal reaction of Mo(CO)6 resulted in the formation of the two complexes Mo2(O)6(DMPA)2; 5, and Mo2(O)2(CO)2(DMPA)2(Tu)2; 6. Thermal reaction of W(CO)6 and the Schiff base DMPA gave the complex W(O)2(DMPA)2; 7. The ligand DMPA and its metal complexes have been reported and characterized based on elemental analyses, IR, (1)H NMR, magnetic measurements, and thermal analysis. Cyclic voltammetry and biological activity were also investigated. Copyright © 2015 Elsevier B.V. All rights reserved.

Catalytic "active-metal" template synthesis of [2]rotaxanes, [3]rotaxanes, and molecular shuttles, and some observations on the mechanism of the cu(i)-catalyzed azide-alkyne 1,3-cycloaddition.

PubMed

Aucagne, Vincent; Berna, José; Crowley, James D; Goldup, Stephen M; Hänni, Kevin D; Leigh, David A; Lusby, Paul J; Ronaldson, Vicki E; Slawin, Alexandra M Z; Viterisi, Aurélien; Walker, D Barney

2007-10-03

A synthetic approach to rotaxane architectures is described in which metal atoms catalyze covalent bond formation while simultaneously acting as the template for the assembly of the mechanically interlocked structure. This "active-metal" template strategy is exemplified using the Huisgen-Meldal-Fokin Cu(I)-catalyzed 1,3-cycloaddition of azides with terminal alkynes (the CuAAC "click" reaction). Coordination of Cu(I) to an endotopic pyridine-containing macrocycle allows the alkyne and azide to bind to metal atoms in such a way that the metal-mediated bond-forming reaction takes place through the cavity of the macrocycle--or macrocycles--forming a rotaxane. A variety of mono- and bidentate macrocyclic ligands are demonstrated to form [2]rotaxanes in this way, and by adding pyridine, the metal can turn over during the reaction, giving a catalytic active-metal template assembly process. Both the stoichiometric and catalytic versions of the reaction were also used to synthesize more complex two-station molecular shuttles. The dynamics of the translocation of the macrocycle by ligand exchange in these two-station shuttles could be controlled by coordination to different metal ions (rapid shuttling is observed with Cu(I), slow shuttling with Pd(II)). Under active-metal template reaction conditions that feature a high macrocycle:copper ratio, [3]rotaxanes (two macrocycles on a thread containing a single triazole ring) are also produced during the reaction. The latter observation shows that under these conditions the mechanism of the Cu(I)-catalyzed terminal alkyne-azide cycloaddition involves a reactive intermediate that features at least two metal ions.

Structural basis of nonribosomal peptide macrocyclization in fungi.

PubMed

Zhang, Jinru; Liu, Nicholas; Cacho, Ralph A; Gong, Zhou; Liu, Zhu; Qin, Wenming; Tang, Chun; Tang, Yi; Zhou, Jiahai

2016-12-01

Nonribosomal peptide synthetases (NRPSs) in fungi biosynthesize important pharmaceutical compounds, including penicillin, cyclosporine and echinocandin. To understand the fungal strategy of forging the macrocyclic peptide linkage, we determined the crystal structures of the terminal condensation-like (C T ) domain and the holo thiolation (T)-C T complex of Penicillium aethiopicum TqaA. The first, to our knowledge, structural depiction of the terminal module in a fungal NRPS provides a molecular blueprint for generating new macrocyclic peptide natural products.

An autonomous chemically fuelled small-molecule motor

NASA Astrophysics Data System (ADS)

Wilson, Miriam R.; Solà, Jordi; Carlone, Armando; Goldup, Stephen M.; Lebrasseur, Nathalie; Leigh, David A.

2016-06-01

Molecular machines are among the most complex of all functional molecules and lie at the heart of nearly every biological process. A number of synthetic small-molecule machines have been developed, including molecular muscles, synthesizers, pumps, walkers, transporters and light-driven and electrically driven rotary motors. However, although biological molecular motors are powered by chemical gradients or the hydrolysis of adenosine triphosphate (ATP), so far there are no synthetic small-molecule motors that can operate autonomously using chemical energy (that is, the components move with net directionality as long as a chemical fuel is present). Here we describe a system in which a small molecular ring (macrocycle) is continuously transported directionally around a cyclic molecular track when powered by irreversible reactions of a chemical fuel, 9-fluorenylmethoxycarbonyl chloride. Key to the design is that the rate of reaction of this fuel with reactive sites on the cyclic track is faster when the macrocycle is far from the reactive site than when it is near to it. We find that a bulky pyridine-based catalyst promotes carbonate-forming reactions that ratchet the displacement of the macrocycle away from the reactive sites on the track. Under reaction conditions where both attachment and cleavage of the 9-fluorenylmethoxycarbonyl groups occur through different processes, and the cleavage reaction occurs at a rate independent of macrocycle location, net directional rotation of the molecular motor continues for as long as unreacted fuel remains. We anticipate that autonomous chemically fuelled molecular motors will find application as engines in molecular nanotechnology.

Minimum structural requirements for cell membrane leakage-mediated anti-MRSA activity of macrocyclic bis(bibenzyl)s.

PubMed

Fujii, Kana; Morita, Daichi; Onoda, Kenji; Kuroda, Teruo; Miyachi, Hiroyuki

2016-05-01

Macrocyclic bis(bibenzyl)-type phenolic natural products, found exclusively in bryophytes, exhibit potent antibacterial activity towards methicillin-resistant Staphylococcus aureus (anti-MRSA activity). Here, in order to identify the minimum essential structure for cell membrane leakage-mediated anti-MRSA activity of these compounds, we synthesized acyclic fragment structures and evaluated their anti-MRSA activity. The activities of all of the acyclic fragments tested exhibited similar characteristics to those of the macrocycles, i.e., anti-MRSA bactericidal activity, an enhancing effect on influx and efflux of ethidium bromide (EtBr: fluorescent DNA-binder) in Staphylococcus aureus cells, and bactericidal activity towards a Staphylococcus aureus strain resistant to 2-phenoxyphenol (4). The latter result suggests that they have a different mechanism of action from 4, which is a FabI inhibitor previously proposed to be the minimum active fragment of riccardin-type macrocycles. Thus, cyclic structure is not a necessary condition for cell membrane leakage-mediated anti-MRSA activity of macrocyclic bis(bibenzyl)s. Copyright © 2016 Elsevier Ltd. All rights reserved.

A 26-Membered Macrocycle Obtained by a Double Diels-Alder Cycloaddition Between Two 2H-Pyran-2-one Rings and Two 1,1'-(Hexane-1,6-diyl)bis (1H-pyrrole-2,5-dione)s.

PubMed

Turek, Bor Lucijan; Kočevar, Marijan; Kranjc, Krištof; Perdih, Franc

2017-12-01

With the application of a double dienophile 1,1'-(hexane-1,6-diyl)bis(1H-pyrrole-2,5-dione) for a [4+2] cycloaddition with a substituted 2H-pyran-2-one a novel 26-membered tetraaza heteromacrocyclic system 3 was prepared via a direct method under solvent-free conditions with microwave irradiation. The macrocycle prepared is composed of two units of the dienophile and two of the diene. The structure of the macrocycle was characterized on the basis of IR, 1H and 13C NMR and mass spectroscopy, as well as by the elemental analysis and melting point determination. With X-ray diffraction of a single crystal of the macrocycle we have determined that the two acetyl groups (attached to the bridging double bond of the bicyclo[2.2.2]octene fragments) are oriented towards each other (and also towards the inside of the cavity of the macrocycle), therefore, mostly filling it completely.

Anion-free bambus[6]uril and its supramolecular properties.

PubMed

Svec, Jan; Dusek, Michal; Fejfarova, Karla; Stacko, Peter; Klán, Petr; Kaifer, Angel E; Li, Wei; Hudeckova, Edita; Sindelar, Vladimir

2011-05-09

Methods for the preparation of anion-free bambus[6]uril (BU6) are presented. They are based on the oxidation of iodide anion, which is bound inside the macrocycle, utilizing dark oxidation by hydrogen peroxide or photooxidation in the presence of titanium dioxide. Anion-free BU6 was found to be insoluble in any of the investigated solvents; however, it dissolves in methanol/chloroform (1:1) or acetonitrile/water (1:1) mixtures in the presence of the tetrabutylammonium salt of a suitable anion. The association constants with halide ions, BF(4)(-), NO(3)(-), and CN(-), were measured by (1)H NMR spectroscopy. The highest association constant (8.9×10(5) M(-1)) was found for the 1:1 complex of BU6 with I(-) in acetonitrile/water mixture. A number of crystal structures of BU6 complexes with various anions were obtained. The influence of the anion size on the macrocycle diameter is discussed together with an unusual arrangement of the macrocycles into separate layers. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of Schiff and Mannich bases of isatin derivatives with 4-amino-4,5-dihydro-1H-1,2,4-triazole-5-ones.

PubMed

Bekircan, Olcay; Bektas, Hakan

2008-09-10

Ethyl imidate hydrochlorides 1 were prepared by passing HCl gas through solutions of substituted benzyl cyanides and absolute ethanol. Ethoxycarbonylhydrazones 2 were synthesized from the reaction of compounds 1 with ethyl carbazate. Treatment of 2 with hydrazine hydrate leads to the formation of substituted 4-amino-4,5-dihydro-1H-1,2,4-triazole-5-ones 3. Isatin and 5-chloroisatin were added to 3 to form Schiff bases 4 and N-Mannich bases 5 of these compounds were synthesized by reacting with formaldehyde and piperidine. Their chemical structures were confirmed by means of IR, (1)H- and (13)C-NMR data and by elemental analysis.

Binaphthyl-containing Schiff base complexes with carboxyl groups for dye sensitized solar cell: An experimental and theoretical study

NASA Astrophysics Data System (ADS)

Tsaturyan, Arshak; Machida, Yosuke; Akitsu, Takashiro; Gozhikova, Inna; Shcherbakov, Igor

2018-06-01

We report on synthesis and characterization of binaphthyl containing Schiff base Ni(II), Cu(II), and Zn(II) complexes as promising photosensitizers for dye-sensitized solar cells (DSSC). Based on theoretical and experimental data, the possibility of their application in DSSC was confirmed. To our knowledge, we find dye performance of complex is steric and rigid structure widely spread to efficiency. The spatial and electronic structures of the complexes were studied by means of the quantum chemical modeling using DFT and TD-DFT approaches. The adsorption energies of the complexes on TiO2 cluster were calculated and appeared to be very close in value. The Zn(II) complex has the biggest value of molar extinction.

Synthesis, characterization and antimicrobial evaluation of some new schiff, mannich and acetylenic Mannich bases incorporating a 1,2,4-triazole nucleus.

PubMed

Aouad, Mohamed R

2014-11-18

A series of Schiff and Mannich bases derived from 4-amino-5-(3-fluoro-phenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione were synthesized. The alkylation of 4-phenyl-5-(3-fluorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione with propargyl bromide afforded the corresponding thiopropargylated derivative which upon treatment with the appropriate secondary amines in the presence of CuCl2 furnished the desired acetylenic Mannich bases. The synthesized compounds were characterized on the basis of their spectral (IR, 1H- and 13C-NMR) data and evaluated for their biological activities. Some of the compounds were found to exhibit significant antimicrobial activity.

Schiff Base as Additive for Preventing Gas Evolution in Li4Ti5O12-Based Lithium-Ion Battery.

PubMed

Daigle, Jean-Christophe; Asakawa, Yuichiro; Hovington, Pierre; Zaghib, Karim

2017-11-29

Lithium titanium oxide (Li 4 Ti 5 O 12 )-based electrodes are very promising for long-life cycle batteries. However, the surface reactivity of Li 4 Ti 5 O 12 in organic electrolytes leading to gas evolution is still a problem that may cause expansion of pouch cells. In this study, we report the use of Schiff base (1,8-diazabicyclo[5.4.0]undec-7-ene) as an additive that prevents gas evolution during cell aging by a new mechanism involving the solid electrolyte interface on the anode surface. The in situ ring opening polymerization of cyclic carbonates occurs during the first cycles to decrease gas evolution by 9.7 vol % without increasing the internal resistance of the battery.

Kinetic Analysis for Macrocyclizations Involving Anionic Template at the Transition State

PubMed Central

Martí-Centelles, Vicente; Burguete, M. Isabel; Luis, Santiago V.

2012-01-01

Several kinetic models for the macrocyclization of a C2 pseudopeptide with a dihalide through a SN2 reaction have been developed. These models not only focus on the kinetic analysis of the main macrocyclization reaction, but also consider the competitive oligomerization/polymerization processes yielding undesired oligomeric/polymeric byproducts. The effect of anions has also been included in the kinetic models, as they can act as catalytic templates in the transition state reducing and stabilizing the transition state. The corresponding differential equation systems for each kinetic model can be solved numerically. Through a comprehensive analysis of these results, it is possible to obtain a better understanding of the different parameters that are involved in the macrocyclization reaction mechanism and to develop strategies for the optimization of the desired processes. PMID:22666148

Aureoverticillactam, a novel 22-atom macrocyclic lactam from the marine actinomycete Streptomyces aureoverticillatus.

PubMed

Mitchell, Scott S; Nicholson, Benjamin; Teisan, Sy; Lam, Kin S; Potts, Barbara C M

2004-08-01

During the course of our screening program designed to discover novel anticancer and anti-infective agents from marine microorganisms, a strain of Streptomyces aureoverticillatus (NPS001583) isolated from a marine sediment was found to produce a novel macrocyclic lactam with cytotoxicity against various tumor cell lines. Using extensive MS, UV, and NMR spectral analyses, the structure has been established as compound 1, aureoverticillactam, a 22-atom macrocyclic lactam incorporating both triene and tetraene conjugated olefins.

Macrocycles

DOEpatents

Raymond, Kenneth N.; Xu, Jide; Pham, Tiffany A.

2016-09-13

The invention provides macrocycles useful in chelating metal ions, particularly radionuclides, to provide metal ion complexes. The invention also provides methods of using the compounds and complexes of the invention, such as in therapeutic and diagnostic applications.

New insights into the coordination chemistry of Schiff bases derived from amino acids: Planar [Ni4] complexes with tyrosine side-chains

NASA Astrophysics Data System (ADS)

Muche, Simon; Hołyńska, Małgorzata

2017-08-01

Structure and properties of a rare metal complex of the chiral Schiff base ligand derived from ortho-vanillin and L-tyrosine are presented. This study is a continuation of research on ligands containing biologically compatible moieties. The ligand is also fully characterized in form of a sodium salt, in particular in solution, for the first time. The metal complex contains a unique bowl-shaped [Ni4] core. Its structure is investigated both in solution (ESI-MS, NMR) and in solid state (X-ray diffraction studies). Under certain conditions the complex can be isolated as crystalline DMF solvate which is studied in solid state.

Synthesis and characterization of copper complexes of Schiff base derived from isatin and salicylic hydrazide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lekshmy, R. K., E-mail: lekshmyulloor@gmail.com, E-mail: tharapradeepkumar@yahoo.com; Thara, G. S., E-mail: lekshmyulloor@gmail.com, E-mail: tharapradeepkumar@yahoo.com

A series of novel metal complexes of Schiff base have been prepared by the interaction of Cu(II) with isatin salicylic hydrazide. All the new compounds were characterized by elemental analysis, conductance measurement, magnetic moment determination, IR, UV, NMR, Mass and EPR spectral studies, thermal studies and microbial activities. The results indicate that the ligand acts as a tridentate chelating ligand coordinating through nitrogen and oxygen atoms. The ligand and complexes show inactive against Escherichia coli and active against Staphylococcus aureus and B.substilis. By analyzing the results of spectral, thermal and elemental analysis square planar geometry is proposed for all themore » complexes.« less

Synthesis, crystal structures, molecular docking and urease inhibition studies of Ni(II) and Cu(II) Schiff base complexes

NASA Astrophysics Data System (ADS)

Sangeeta, S.; Ahmad, K.; Noorussabah, N.; Bharti, S.; Mishra, M. K.; Sharma, S. R.; Choudhary, M.

2018-03-01

[Ni(L)2] 1 and [Cu(L)2] 2 [HL = 2-((E)-(2-methoxyphenylimino)methyl)-4,6-dichlorophenol] Schiff base complexes have been successfully synthesized and were characterized by FT-IR, UV-Vis, fluorescence spectroscopy and thermogravimetric analysis. The crystal structures of the two complexes were determined through X-ray crystallography. Its inhibitory activity against Helicobacter pylori urease was evaluated in vitro and showed strong inhibitory activity against H. pylori urease compared with acetohydroxamic acid (IC50 = 42.12 μmolL-1), which is a positive reference. A docking analysis using the AutoDock 4.0 program could explain the inhibitory activity of the complex against urease.

Antibacterial activity of Pd(II) complexes with salicylaldehyde-amino acids Schiff bases ligands.

PubMed

Rîmbu, Cristina; Danac, Ramona; Pui, Aurel

2014-01-01

Palladium(II) complexes with Schiff bases ligands derived from salicylaldehyde and amino acids (Ala, Gly, Met, Ser, Val) have been synthesized and characterized by Fourier transform (FT)-IR, UV-Vis and (1)H-NMR spectroscopy. The electrospray mass spectrometry (ES-MS) spectrometry confirms the formation of palladium(II) complexes in 1/2 (M/L) molar ratio. All the Pd(II) complexes 1, [Pd(SalAla)2]Cl2; 2, [Pd(SalGly)2]Cl2; 3, [Pd(SalMet)2]Cl2; 4, [Pd(SalSer)2]Cl2; 5, [Pd(SalVal)2]Cl2; have shown antibacterial activity against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli.

Kinetics of acid hydrolysis and reactivity of some antibacterial hydrophilic iron(II) imino-complexes

NASA Astrophysics Data System (ADS)

Shaker, Ali Mohamed; Nassr, Lobna Abdel-Mohsen Ebaid; Adam, Mohamed Shaker Saied; Mohamed, Ibrahim Mohamed Abdelhalim

2015-05-01

Kinetic study of acid hydrolysis of some hydrophilic Fe(II) Schiff base amino acid complexes with antibacterial properties was performed using spectrophotometry. The Schiff base ligands were derived from sodium 2-hydroxybenzaldehyde-5-sulfonate and glycine, L-alanine, L-leucine, L-isoleucine, DL-methionine, DL-serine, or L-phenylalanine. The reaction was studied in aqueous media under conditions of pseudo-first order kinetics. Moreover, the acid hydrolysis was studied at different temperatures and the activation parameters were calculated. The general rate equation was suggested as follows: rate = k obs [Complex], where k obs = k 2 [H+]. The evaluated rate constants and activation parameters are consistent with the hydrophilicity of the investigated complexes.

Catalytic activity of enzymes immobilized on AlGaN /GaN solution gate field-effect transistors

NASA Astrophysics Data System (ADS)

Baur, B.; Howgate, J.; von Ribbeck, H.-G.; Gawlina, Y.; Bandalo, V.; Steinhoff, G.; Stutzmann, M.; Eickhoff, M.

2006-10-01

Enzyme-modified field-effect transistors (EnFETs) were prepared by immobilization of penicillinase on AlGaN /GaN solution gate field-effect transistors. The influence of the immobilization process on enzyme functionality was analyzed by comparing covalent immobilization and physisorption. Covalent immobilization by Schiff base formation on GaN surfaces modified with an aminopropyltriethoxysilane monolayer exhibits high reproducibility with respect to the enzyme/substrate affinity. Reductive amination of the Schiff base bonds to secondary amines significantly increases the stability of the enzyme layer. Electronic characterization of the EnFET response to penicillin G indicates that covalent immobilization leads to the formation of an enzyme (sub)monolayer.

Cycloaddition Reactions of Cobalt-Complexed Macrocyclic Alkynes: The Transannular Pauson-Khand Reaction.

PubMed

Karabiyikoglu, Sedef; Boon, Byron A; Merlic, Craig A

2017-08-04

The Pauson-Khand reaction is a powerful tool for the synthesis of cyclopentenones through the efficient [2 + 2 + 1] cycloaddition of dicobalt alkyne complexes with alkenes. While intermolecular and intramolecular variants are widely known, transannular versions of this reaction are unknown and the basis of this study. Macrocyclic enyne and dienyne complexes were readily synthesized by palladium(II)-catalyzed oxidative macrocyclizations of bis(vinyl boronate esters) or ring-closing metathesis reactions followed by complexation with dicobalt octacarbonyl. Several reaction modalities of these macrocyclic complexes were uncovered. In addition to the first successful transannular Pauson-Khand reactions, other intermolecular and transannular cycloaddition reactions included intermolecular Pauson-Khand reactions, transannular [4 + 2] cycloaddition reactions, intermolecular [2 + 2 + 2] cycloaddition reactions, and intermolecular [2 + 2 + 1 + 1] cycloaddition reactions. The structural and reaction requirements for each process are presented.

Structural characterization of synthetic and protein-bound porphyrins in terms of the lowest-frequency normal coordinates of the macrocycle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jentzen, W.; Song, X.Z.; Shelnutt, J.A.

1997-02-27

The X-ray crystal structures of synthetic and protein-bound metalloporphyrins are analyzed using a new normal structural decomposition method for classifying and quantifying their out-of-plane and in-plane distortions. These distortions are characterized in terms of equivalent displacements along the normal coordinates of the D{sub 4h}-symmetric porphyrin macrocycle (normal deformations). It is shown that the macrocyclic structure is, even in highly distorted porphyrins, accurately represented by displacements along only the lowest-frequency normal coordinates. Accordingly, the macrocyclic structure obtained from just the out-of-plane normal deformations of the saddling (sad, B{sub 2u})-, ruffling (ruf, B{sub 1u})-, doming (dom, A{sub 2u})-, waving [wav(x), wav(y); E{submore » g}]-, and propellering (pro, A{sub 1u})-type essentially simulates the out-of-plane distortion of the X-ray crystal structure. Similarly, the observed in-plane distortions are decomposed into in-plane normal deformations corresponding to the lowest-frequency vibrational modes including macrocycle stretching in the direction of the meso-carbon atoms (meso-str, B{sub 2g}), stretching in the direction of the nitrogen atoms (N-str, B{sub 1g}), x and y pyrrole translations [trn(x), trn(y); E{sub u}], macrocycle breathing (bre, A{sub 1g}), and pyrrole rotation (rot, A{sub 2g}). 71 refs., 9 figs., 4 tabs.« less

Supramolecular Assembly of Uridine Monophosphate (UMP) and Thymidine Monophosphate (TMP) with a Dinuclear Copper(II) Receptor.

PubMed

Rhaman, Md Mhahabubur; Powell, Douglas R; Hossain, Md Alamgir

2017-11-30

Understanding the intermolecular interactions between nucleotides and artificial receptors is crucial to understanding the role of nucleic acids in living systems. However, direct structural evidence showing precise interactions and bonding features of a nucleoside monophosphate (NMP) with a macrocycle-based synthetic molecule has not been provided so far. Herein, we present two novel crystal structures of uridine monophosphate (UMP) and thymidine monophosphate (TMP) complexes with a macrocycle-based dinuclear receptor. Structural characterization of these complexes reveals that the receptor recognizes UMP through coordinate-covalent interactions with phosphates and π-π stackings with nucleobases and TMP through coordinate-covalent interactions with phosphate groups. Furthermore, the receptor has been shown to effectively bind nucleoside monophosphates in the order of GMP > AMP > UMP > TMP > CMP in water at physiological pH, as investigated by an indicator displacement assay.

Synthesis and Mossbauer spectroscopy of macrocyclic complexes of iron(III)

NASA Astrophysics Data System (ADS)

Mishra, A.; Sura, Kamaljeet S.; Sharma, P.

2016-10-01

The article deals with a fresh series of the complexes of the type: [Fe(III)(TML)Cl]Cl2; where TML is a tetra-dentate macrocyclic ligand; has been synthesized by condensation of o-phenylenediamine, diethyl malonate and diazonium ion in the ethanolic medium, through refluxing with FeCl3.The synthesized metal complexes were characterized by Mossbauer spectroscopy. Mossbauer measurements were carried out using standard PC-based spectrometer equipped with Weissel velocity drive operating in the constant acceleration mode. Mossbauer study interprets paramagnetic nature of complexes. Mossbauer measurement of complex 1 and 2 has been taken to find out the value of isomer shift and quadrapole splitting and oxidation state after complaxsation.

Synthesis and spectroscopic studies of binuclear metal complexes of a tetradentate N2O2 Schiff base ligand derived from 4,6-diacetylresorcinol and benzylamine.

PubMed

Shebl, Magdy

2008-09-01

A tetradentate N2O2 donor Schiff base ligand, H2L, was synthesized by the condensation of 4,6-diacetylresorcinol with benzylamine. The structure of the ligand was elucidated by elemental analyses, IR, 1H NMR, electronic and mass spectra. Reaction of the Schiff base ligand with nickel(II), cobalt(II), iron(III), cerium(III), vanadyl(IV) and uranyl(VI) ions in 1:2 molar ratio afforded binuclear metal complexes. Also, reaction of the ligand with several copper(II) salts, including Cl-, NO3-, AcO-, ClO4- and SO42- afforded different metal complexes that reflect the non-coordinating or weakly coordinating power of the ClO(4)(-) anion as compared to the strongly coordinating power of SO42- and Cl- anions. Characterization and structure elucidation of the prepared complexes were achieved by elemental and thermal analyses, IR, 1H NMR, electronic, mass and ESR spectra as well as magnetic susceptibility measurements. The metal complexes exhibited different geometrical arrangements such as square planar, octahedral, square pyramidal and pentagonal bipyramidal arrangements. The variety in the geometrical arrangements depends on the nature of both the anion and the metal ion.

Synthesis, characterization, antimicrobial screening and computational studies of 4-[3-(4-methoxy-phenyl)-allylideneamino]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one

NASA Astrophysics Data System (ADS)

Obasi, L. N.; Kaior, G. U.; Rhyman, L.; Alswaidan, Ibrahim A.; Fun, Hoong-Kun; Ramasami, P.

2016-09-01

The Schiff base, 4-[3-(4-methoxy-phenyl)-allylideneamino]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (TPMC/AAP) was synthesized by the condensation of 4-aminoantipyrine (4-amino-1,5-dimethyl-2-phenylpyrazole-3-one) and trans-para-methoxycinnamaldehyde (trans-3,4-methoxyphenyl-2-propenal) in dry methanol at 75 °C. The compound was characterized using elemental microanalysis, IR, NMR, UV spectroscopies and single-crystal X-ray crystallography. The X-ray structure determination shows that the Schiff base, (TPMC/AAP) is orthorhombic with the Pbca space group. The anti-microbial screening of the compound was carried out with Escherichia coli, Bacillus subtillis, Staphylococcus aureus, Pseudemonas aeruginosa, Candida albicans and Aspergillus niger using agar well diffusion method. The Schiff base possesses significant antimicrobial activity. The minimum inhibitory concentration (MIC) of the compound was also determined and the activity was compared with that of conventional drugs ciprofloxacin and ketoconazole. The compound (TPMC/AAP) showed varying activity against the cultured bacteria and fungi used. To complement the experimental data, density functional theory (DFT) was used to have deeper understanding into the molecular parameters and infrared spectra of the compound.

The reaction of hydroxylamine with bacteriorhodopsin studied with mutants that have altered photocycles: selective reactivity of different photointermediates.

PubMed Central

Subramaniam, S; Marti, T; Rösselet, S J; Rothschild, K J; Khorana, H G

1991-01-01

The reaction of the retinylidene Schiff base in bacteriorhodopsin (bR) to the water-soluble reagent hydroxylamine is enhanced by greater than 2 orders of magnitude under illumination. We have used this reaction as a probe for changes in Schiff base reactivity during the photocycle of wild-type bR and mutants defective in proton transport. We report here that under illumination at pH 6, the D85N mutant has a 20-fold lower rate and the D212N mutant has a greater than 4-fold higher rate for the light-dependent reaction with hydroxylamine compared with wild-type bR. In contrast, the reactivities of wild-type bR and the D96N and T46V mutants are similar. It has been previously shown that the D96N and T46V replacements have no significant effect on the kinetics of "M" formation but have dramatic effects on rate of the decay of M. We therefore conclude that the hydroxylamine reaction occurs before formation of the M intermediate. Most likely it occurs at the "L" stage of the cycle and reflects increased water accessibility to the Schiff base due to a light-driven change in protein conformation. PMID:2006195

1,2,4-triazole derivative with Schiff base; thiol-thione tautomerism, DFT study and antileishmanial activity

NASA Astrophysics Data System (ADS)

Süleymanoğlu, Nevin; Ustabaş, Reşat; Direkel, Şahin; Alpaslan, Yelda Bingöl; Ünver, Yasemin

2017-12-01

Thiol-thione tautomerism of 1,2,4-triazole derivative with Schiff base was investigated by spectroscopic methods and quantum mechanical calculations. Theoretical study of thiol-thione tautomeric forms of 1,2,4-triazole derivative with Schiff base; 1,2,4-triazole-thiol form, 1-((5-mercapto-4-(thiophene-2-ylmethyleneamino)-4H-1,2,4-triazole-3-yl)methyl)-3-(thiophene-2-ylmethyl)-4-(thiophene-2-ylmethyleneamino)-1H-1,2,4-triazole-5(4H)-one (I) and 1,2,4-triazole-thione form, 3-(thiophene-2-ylmethyl)-4-(thiophene-2-ylmethyleneamino)-1-((4-(thiophene-2-ylmethyleneamino)-5-thioxo-4,5-dihydro-1H-1,2,4-triazole-3-yl)methyl)-1H-1,2,4-triazole-5(4H)-one (II) was performed by the density functional theory (DFT) method with 6-311++G(d,p) basis set. Structural parameters were obtained and spectral parameters of NMR, FTIR and UV-vis were compared with experimental ones to determine structural details. In vitro antileishmanial activity was studied against Leishmania infantum promastigots by microdilution broth assay with Alamar Blue Dye. The results indicate that 1,2,4-triazole derivative exists in both thiol and thione form and, can be evaluated as antiparasitic in term of antileishmanial activity.

Synthesis, characterization, and spectroscopic investigation of benzoxazole conjugated Schiff bases.

PubMed

Santos, Fabiano S; Costa, Tania M H; Stefani, Valter; Gonçalves, Paulo F B; Descalzo, Rodrigo R; Benvenutti, Edilson V; Rodembusch, Fabiano S

2011-11-24

Two Schiff bases were synthesized by reaction of 2-(4'-aminophenyl)benzoxazole derivatives with 4-N,N-diethylaminobenzaldehyde. UV-visible (UV-vis) and steady-state fluorescence in solution were applied in order to characterize its photophysical behavior. The Schiff bases present absorption in the UV region with fluorescence emission in the blue-green region, with a large Stokes' shift. The UV-vis data indicates that each dye behaves as two different chromophores in solution in the ground state. The fluorescence emission spectra of the dye 5a show that an intramolecular proton transfer (ESIPT) mechanism takes place in the excited state, whereas a twisted internal charge transfer (TICT) state is observed for the dye 5b. Theoretical calculations were performed in order to study the conformation and polarity of the molecules at their ground and excited electronic states. Using density functional theory (DFT) methods at theoretical levels BLYP/Aug-SV(P) for geometry optimizations and B3LYP/6-311++G(2d,p) for single-point energy evaluations, the calculations indicate that the lowest energy conformations are in all cases nonplanar and that the dipole moments of the excited state relaxed structures are much larger than those of the ground state structures, which corroborates the experimental UV-vis absorption results.

New asymmetric and symmetric 2-((pyridin-4-yl)methylenamino)-3 aminomaleo nitrile and 2,3-bis((pyridin-4-yl)methylenamino)maleonitrile Schiff bases: Synthesis, experimental characterization along with theoretical studies

NASA Astrophysics Data System (ADS)

Zare, Nahid; Zabardasti, Abedien; Dusek, Michal; Eigner, Vaclav

2018-07-01

Two novel Schiff bases 2-((pyridin-4-yl)methelenamino)-3-aminomaleonitrile (L1) and 2,3-bis((pyridin-yl)methylenamino)maleonitrile (L2) were synthesized by the condensation of 2,3-diaminomaleonitrile and 4-pyridine carboxaldehyde using the reflux in absolute methanol. The light yellow crystalline precipitates of L1 were used for single-crystal X-ray crystallography. Two ligans L1 and L2 were characterized by UV-Vis, FT-IR and 1H/13C NMR spectroscopy. Also the FT-IR, 1H NMR and 13C NMR spectra of the compounds were calculated at the B3LYP/6-31 + G(d) level of theory. The Schiff base L1 with unit cell parameters: a = 19.8380(9), b = 4.7221(2), c = 12.9703(6) Å, V = 1215.02(9) Å3, Z = 4 crystallizes in the orthorhombic crystal system with space group Pna21. The crystal structure was solved by charge flipping using single crystal X-ray diffraction data collected at 120 K. For both ligands, the experimentally obtained NMR and IR spectra were a good agreement with their calculated counterparts.

New fluorescent azo-Schiff base Cu(II) and Zn(II) metal chelates; spectral, structural, electrochemical, photoluminescence and computational studies

NASA Astrophysics Data System (ADS)

Purtas, Fatih; Sayin, Koray; Ceyhan, Gokhan; Kose, Muhammet; Kurtoglu, Mukerrem

2017-06-01

A new Schiff base containing azo chromophore group obtained by condensation of 2-hydroxy-4-[(E)-phenyldiazenyl]benzaldehyde with 3,4-dimethylaniline (HL) are used for the syntheses of new copper(II) and zinc(II) chelates, [Cu(L)2], and [Zn(L)2], and characterized by physico-chemical and spectroscopic methods such as 1H and 13C NMR, IR, UV.-Vis. and elemental analyses. The solid state structure of the ligand was characterized by single crystal X-ray diffraction study. X-ray diffraction data was then used to calculate the harmonic oscillator model of aromaticity (HOMA) indexes for the rings so as to investigate of enol-imine and keto-amine tautomeric forms in the solid state. The phenol ring C10-C15 shows a considerable deviation from the aromaticity with HOMA value of 0.837 suggesting the shift towards the keto-amine tautomeric form in the solid state. The analytical data show that the metal to ligand ratio in the chelates was found to be 1:2. Theoretical calculations of the possible isomers of the ligand and two metal complexes are performed by using B3LYP method. Electrochemical and photoluminescence properties of the synthesized azo-Schiff bases were also investigated.

Rational Design and Synthesis of New, High Efficiency, Multipotent Schiff Base-1,2,4-triazole Antioxidants Bearing Butylated Hydroxytoluene Moieties.

PubMed

Yehye, Wageeh A; Abdul Rahman, Noorsaadah; Saad, Omar; Ariffin, Azhar; Abd Hamid, Sharifah Bee; Alhadi, Abeer A; Kadir, Farkaad A; Yaeghoobi, Marzieh; Matlob, Abdulsalam A

2016-06-28

A new series of multipotent antioxidants (MPAOs), namely Schiff base-1,2,4-triazoles attached to the oxygen-derived free radical scavenging moiety butylated hydroxytoluene (BHT) were designed and subsequently synthesized. The structure-activity relationship (SAR) of the designed antioxidants was established alongside the prediction of activity spectra for substances (PASS). The antioxidant activities of the synthesized compounds 4-10 were tested by the DPPH bioassay. The synthesized compounds 4-10 inhibited stable DPPH free radicals at a level that is 10(-4) M more than the well-known standard antioxidant BHT. Compounds 8-10 with para-substituents were less active than compounds 4 and 5 with trimethoxy substituents compared to those with a second BHT moiety (compounds 6 and 7). With an IC50 of 46.13 ± 0.31 µM, compound 6 exhibited the most promising in vitro inhibition at 89%. Therefore, novel MPAOs containing active triazole rings, thioethers, Schiff bases, and BHT moieties are suggested as potential antioxidants for inhibiting oxidative stress processes and scavenging free radicals, hence, this combination of functions is anticipated to play a vital role in repairing cellular damage, preventing various human diseases and in medical therapeutic applications.

Synthesis and characterization of a series of transition metal complexes with a new symmetrical polyoxaaza macroacyclic Schiff base ligand: X-ray crystal structure of cobalt(II) and nickel(II) complexes and their antibacterial properties

NASA Astrophysics Data System (ADS)

Keypour, Hassan; Shayesteh, Maryam; Rezaeivala, Majid; Chalabian, Firoozeh; Valencia, Laura

2013-01-01

A new symmetrical [N4O2] hexadentate Schiff base ligand, (E)-N-(pyridin-2-ylmethylene)-2-(3-(2-((E)-pyridin-2-lmethyleneamino)phenoxy)naphthalen-2-yloxy)benzenamine, abbreviated to L, and its complexes of Ni(II), Cu(II), Zn(II), Co(II), Cd(II) and Mn(II) have been synthesized in the presence of metal ions. The complexes were structurally characterized by elemental analyses, IR, UV-Vis, NMR and molar conductivity. The crystal structures of two complexes, [NiL(ONO2)2]·2H2O and [CoLCl2]CH3OH·0.5H2O, have been determined by a single crystal X-ray diffraction study. In these complexes, the ligand is coordinated in a neutral form via pyridine and azomethine nitrogen atoms. The metal ions complete their six coordination with two coordinated nitrate or chloride ions, forming a distorted octahedral geometry. The synthesized compounds have antibacterial activity against the three Gram-positive bacteria: Enterococcus faecalis, Bacillus cereus and Staphylococcus epid and also against the three Gram-negative bacteria: Citrobacter freundii, Enterobacter aerogenes and Salmonella typhi. The activity data show that the complexes are more potent antibacterials than the parent Schiff base.

Synthesis, spectroscopy and biological investigations of manganese(III) Schiff base complexes derived from heterocyclic β-diketone with various primary amine and 2,2'-bipyridyl

NASA Astrophysics Data System (ADS)

Surati, Kiran R.

2011-06-01

The mixed ligand mononuclear complex [Mn(bipy)(HPMFP)(OAc)]ClO 4 was synthesized by reaction of Mn(OAc) 3·2H 2O with HPMFP and 2,2'-bipyridyl. The corresponding Schiff base complexes were prepared by condensation of [Mn(bipy)(HPMFP)(OAc)]ClO 4 with ethylenediamine, ethanolamine and glycine (where HPMFP = 1-phenyl-3methyl-4-formyl-2-pyrazolin-5one, bipy = 2,2'-bipyridyl). All the compounds have been characterized by elemental analysis, magnetic susceptibility, conductometry measurements and 1H and 13C NMR, FT-IR, mass spectrometry. Electronic spectral and magnetic susceptibility measurements indicate square pyramidal geometry around manganese(III) ion. The thermal stabilities, activation energy E*, entropy change Δ S*, enthalpy change Δ H* and heat capacity of thermal degradation for these complexes were determined by TGA and DSC. The in vitro antibacterial and antifungal activity of four coordination compounds and ligand HPMFP were investigated. In vitro activates of Bacillus subtillis (MTCC-619), Staphylococcus aureus (MTCC-96), Escherichia coli (MTCC-722) and Klebsiella pneumonia (MTCC-109) bacteria and the fungus Candida albicans (ATCC-90028) were determined. All the compounds showed good antimicrobial activity. The antimicrobial activities increased as formation of Schiff base.

Structural, spectral and biological studies of binuclear tetradentate metal complexes of N 3O Schiff base ligand synthesized from 4,6-diacetylresorcinol and diethylenetriamine

NASA Astrophysics Data System (ADS)

Emara, Adel A. A.

2010-09-01

The binuclear Schiff base, H 2L, ligand was synthesized by reaction of 4,6-diacetylresorcinol with diethylenetriamine in the molar ratio 1:2. The coordination behavior of the H 2L towards Cu(II), Ni(II), Co(II), Zn(II), Fe(III), Cr(III), VO(IV) and UO 2(VI) ions has been investigated. The elemental analyses, magnetic moments, thermal studies and IR, electronic, 1H NMR, ESR and mass spectra were used to characterize the isolated ligand and its metal complexes. The ligand acts as dibasic with two N 3O-tetradentate sites and can coordinate with two metal ions to form binuclear complexes. The bonding sites are the nitrogen atoms of the azomethine and amine groups and the oxygen atoms of the phenolic groups. The metal complexes exhibit either square planar, tetrahedral, square pyramid or octahedral structures. The Schiff base ligand and its metal complexes were tested against four pathogenic bacteria ( Staphylococcus aureus and Streptococcus pyogenes) as Gram-positive bacteria, and ( Pseudomonas fluorescens and Pseudomonas phaseolicola) as Gram-negative bacteria and two pathogenic fungi ( Fusarium oxysporum and Aspergillus fumigatus) to assess their antimicrobial properties. Most of the complexes exhibit mild antibacterial and antifungal activities against these organisms.

Synthesis, characterization and molecular weight monitoring of a novel Schiff base polymer containing phenol group: Thermal stability, conductivity and antimicrobial properties

NASA Astrophysics Data System (ADS)

Yılmaz Baran, Nuray; Saçak, Mehmet

2017-10-01

A novel Schiff base polymer containing phenol group, Poly(3-[[4-(dimethylamino)benzylidene]amino]phenol) P(3-DBAP), was prepared by oxidative polycondensation reaction of 3-[[4-(dimethylamino)benzylidene]amino]phenol (3-DBAP) using NaOCl, H2O2, O2 oxidants in aqueous alkaline medium. Yield and molecular weight distribution of P(3-DBAP) were monitored depending on oxidant types and concentration, monomer concentration and as well as polymerization temperature and time. UV-Vis, FTIR and 1HNMR techniques were used to identify the structures of Schiff base monomer and polymer. Thermal behavior of P(3-DBAP), which was determined to be thermally stable up to 1200 °C via TG-DTG techniques, was illuminated by Thermo-IR spectra recorded in the temperature range of 25-800 °C. It was determined that the electrical conductivity value of the P(3-DBAP) increased 108 fold after doped with iodine for 24 h at 60 °C according to undoped form and it was measured 4.6 × 10-4 S/cm. Also, antibacterial and antifungal activities of the monomer and polymer were assayed against Sarcina lutea, Enterobacter aerogenes, Escherichia coli, Enterococcus Feacalis, Klebsiella pneumoniae, Bacillus subtilis bacteria, and Candida albicans, Saccharomyces cerevisiae fungi.

Reactions of copper macrocycles with antioxidants and HOCl: potential for biological redox sensing.

PubMed

Sowden, Rebecca J; Trotter, Katherine D; Dunbar, Lynsey; Craig, Gemma; Erdemli, Omer; Spickett, Corinne M; Reglinski, John

2013-02-01

A series of simple copper N(2)S(2) macrocycles were examined for their potential as biological redox sensors, following previous characterization of their redox potentials and crystal structures. The divalent species were reduced by glutathione or ascorbate at a biologically relevant pH in aqueous buffer. A less efficient reduction was also achieved by vitamin E in DMSO. Oxidation of the corresponding univalent copper species by sodium hypochlorite resulted in only partial (~65 %) recovery of the divalent form. This was concluded to be due to competition between metal oxidation and ligand oxidation, which is believed to contribute to macrocycle demetallation. Electrospray mass spectrometry confirmed that ligand oxidation had occurred. Moreover, the macrocyclic complexes could be demetallated by incubation with EDTA and bovine serum albumin, demonstrating that they would be inappropriate for use in biological systems. The susceptibility to oxidation and demetallation was hypothesized to be due to oxidation of the secondary amines. Consequently these were modified to incorporate additional oxygen donor atoms. This modification led to greater resistance to demetallation and ligand oxidation, providing a better platform for further development of copper macrocycles as redox sensors for use in biological systems.

Design, synthesis, and anaplastic lymphoma kinase (ALK) inhibitory activity for a novel series of 2,4,8,22-tetraazatetracyclo[14.3.1.1³,⁷.1⁹,¹³]docosa-1(20),3(22),4,6,9(21),10,12,16,18-nonaene macrocycles.

PubMed

Breslin, Henry J; Lane, Brandon M; Ott, Gregory R; Ghose, Arup K; Angeles, Thelma S; Albom, Mark S; Cheng, Mangeng; Wan, Weihua; Haltiwanger, R Curtis; Wells-Knecht, Kevin J; Dorsey, Bruce D

2012-01-12

A novel set of 2,4,8,22-tetraazatetracyclo[14.3.1.1(3,7).1(9,13)]docosa-1(20),3(22),4,6,9(21),10,12,16,18-nonaene macrocycles were prepared as potential anaplastic lymphoma kinase (ALK) inhibitors, designed to rigidly lock an energy-minimized bioactive conformation of the diaminopyrimidine (DAP) scaffold, a well-documented kinase platform. From 13 analogues prepared, macrocycle 2m showed the most promising in vitro ALK enzymatic (IC(50) = 0.5 nM) and cellular (IC(50) = 10 nM) activities. In addition, macrocycle 2m exhibited a favorable kinase selectivity preference for inhibition of ALK relative to the highly homologous insulin receptor (IR) kinase (IR/ALK ratio of 173). The inclusive in vitro biological results for this set of macrocycles validate this scaffold as a viable kinase template and further corroborate recent DAP/ALK solid state studies indicating that the inverted "U" shaped conformation of the acyclic DAPs is a preferred bioactive conformation.

REDOX-SWITCHABLE CALIX[6]ARENE-BASED ISOMERIC ROTAXANES.

PubMed

Zanichelli, Valeria; Bazzoni, Margherita; Arduini, Arturo; Franchi, Paola; Lucarini, Marco; Ragazzon, Giulio; Secchi, Andrea; Silvi, Serena

2018-04-16

Operating molecular machines are based on switchable systems, whose components can be set in motion in a controllable fashion. The presence of non-symmetric elements is a mandatory requirement to obtain and demonstrate the unidirectionality of motion. Calixarene-based macrocycles have proven very efficient hosts in the design of oriented rotaxanes and of pseudorotaxanes with a strict control on the direction of complexation. We have synthesized and characterized a series of two-station rotaxanes based on bypiridinium-ammonium axles. We have exploited a recently reported supramolecular-assisted strategy for the synthesis of different orientational isomers and we identified the ammonium unit as a proper secondary station for the calixarene. We were able to trigger the displacement of the macrocycle upon electrochemical reduction of the bipyridinium primary station and we demonstrated that the shuttling is influenced both by the length of the chain of the axle component and by the position of the secondary station with respect to the calixarene rims. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Construction of a carbon ionic liquid paste electrode based on multi-walled carbon nanotubes-synthesized Schiff base composite for trace electrochemical detection of cadmium.

PubMed

Afkhami, Abbas; Khoshsafar, Hosein; Bagheri, Hasan; Madrakian, Tayyebeh

2014-02-01

A simple, highly sensitive and selective carbon nanocomposite electrode has been developed for the electrochemical trace determination of cadmium. This sensor was designed by incorporation of multi-walled carbon nanotubes (MWCNTs) and a new synthesized Schiff base into the carbon paste ionic liquid electrode (CPE(IL)) which provides remarkably improved sensitivity and selectivity for the electrochemical stripping assay of Cd(II). The detection limit of the method was found to be 0.08 μg L(-1) (S/N=3) that is lower than the maximum contaminant level of Cd(II) allowed by the Environmental Protection Agency (EPA) in standard drinking waters. The proposed electrode exhibits good applicability for monitoring Cd(II) in various real samples. © 2013.

Apoptotic effect of novel Schiff based CdCl₂(C₁₄H₂₁N₃O₂) complex is mediated via activation of the mitochondrial pathway in colon cancer cells.

PubMed

Hajrezaie, Maryam; Paydar, Mohammadjavad; Looi, Chung Yeng; Moghadamtousi, Soheil Zorofchian; Hassandarvish, Pouya; Salga, Muhammad Saleh; Karimian, Hamed; Shams, Keivan; Zahedifard, Maryam; Majid, Nazia Abdul; Ali, Hapipah Mohd; Abdulla, Mahmood Ameen

2015-03-13

The development of metal-based agents has had a tremendous role in the present progress in cancer chemotherapy. One well-known example of metal-based agents is Schiff based metal complexes, which hold great promise for cancer therapy. Based on the potential of Schiff based complexes for the induction of apoptosis, this study aimed to examine the cytotoxic and apoptotic activity of a CdCl2(C14H21N3O2) complex on HT-29 cells. The complex exerted a potent suppressive effect on HT-29 cells with an IC50 value of 2.57 ± 0.39 after 72 h of treatment. The collapse of the mitochondrial membrane potential and the elevated release of cytochrome c from the mitochondria to the cytosol indicate the involvement of the intrinsic pathway in the induction of apoptosis. The role of the mitochondria-dependent apoptotic pathway was further proved by the significant activation of the initiator caspase-9 and the executioner caspases-3 and -7. In addition, the activation of caspase-8, which is associated with the suppression of NF-κB translocation to the nucleus, also revealed the involvement of the extrinsic pathway in the induced apoptosis. The results suggest that the CdCl2(C14H21N3O2) complex is able to induce the apoptosis of colon cancer cells and is a potential candidate for future cancer studies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Otto, H.; Marti, T.; Holz, M.

Photocycle and flash-induced proton release and uptake were investigated for bacteriorhodopsin mutants in which Asp-85 was replaced by Ala, Asn, or Glu; Asp-212 was replaced by Asn or Glu; Asp-115 was replaced by Ala, Asn, or Glu; Asp-96 was replaced by Ala, Asn, or Glu; and Arg-82 was replaced by Ala or Gln in dimyristoylphosphatidylcholine/3-((3-cholamidopropyl)dimethylammonio)-1- propanesulfonate micelles at pH 7.3. In the Asp-85----Ala and Asp-85----Asn mutants, the absence of the charged carboxyl group leads to a blue chromophore at 600 and 595 nm, respectively, and lowers the pK of the Schiff base deprotonation to 8.2 and 7, respectively, suggesting amore » role for Asp-85 as counterion to the Schiff base. The early part of the photocycles of the Asp-85----Ala and Asp-85----Asn mutants is strongly perturbed; the formation of a weak M-like intermediate is slowed down about 100-fold over wild type. In both mutants, proton release is also slower but clearly precedes the rise of M. The amplitude of the early reversed photovoltage component in the Asp-85----Asn mutant is very large, and the net charge displacement is close to zero, indicating proton release and uptake on the cytoplasmic side of the membrane. The data suggest an obligatory role for Asp-85 in the efficient deprotonation of the Schiff base and in the proton release phase, probably as proton acceptor. In the Asp-212----Asn mutant, the rise of the absorbance change at 410 nm is slowed down to 220 microsecond, its amplitude is small, and the release of protons is delayed to 1.9 ms. The absorbance changes at 650 nm indicate perturbations in the early time range with a slow K intermediate. Thus Asp-212 also participates in the early events of charge translocation and deprotonation of the Schiff base.« less

Design, characterization, teratogenicity testing, antibacterial, antifungal and DNA interaction of few high spin Fe(II) Schiff base amino acid complexes

NASA Astrophysics Data System (ADS)

Abdel-Rahman, Laila H.; El-Khatib, Rafat M.; Nassr, Lobna A. E.; Abu-Dief, Ahmed M.; Lashin, Fakhr El-Din

2013-07-01

In this study, new Fe(II) Schiff base amino acid chelates derived from the condensation of o-hydroxynaphthaldehyde with L-alanine, L-phenylalanine, L-aspartic acid, L-histidine and L-arginine were synthesized and characterized via elemental, thermogravimetric analysis, molar conductance, IR, electronic, mass spectra and magnetic moment measurements. The stoichiometry and the stability constants of the complexes were determined spectrophotometrically. Correlation of all spectroscopic data suggested that Schiff bases ligands exhibited tridentate with ONO sites coordinating to the metal ions via protonated phenolic-OH, azomethine-N and carboxylate-O with the general formulae [Fe(HL)2]·nH2O. But in case of L-histidine, the ligand acts as tetradentate via deprotonated phenolic-OH, azomethine-N, carboxylate-O and N-imidazole ring ([FeL(H2O)2]·2H2O), where HL = mono anion and L = dianion of the ligand. The structure of the prepared complexes is suggested to be octahedral. The prepared complexes were tested for their teratogenicity on chick embryos and found to be safe until a concentration of 100 μg/egg with full embryos formation. Moreover, the interaction between CT-DNA and the investigated complexes were followed by spectrophotometric and viscosity measurements. It was found that, the prepared complexes bind to DNA via classical intercalative mode and showed a different DNA activity with the sequence: nhi > nari > nali > nasi > nphali. Furthermore, the free ligands and their complexes are screened for their in vitro antibacterial and antifungal activity against three types of bacteria, Escherichia coli, Pseudomonas aeruginosa and Bacillus cereus and three types of anti fungal cultures, Penicillium purpurogenium, Aspergillus flavus and Trichotheium rosium in order to assess their antimicrobial potential. The results show that the metal complexes are more reactive with respect to their corresponding Schiff base amino acid ligands.

Synthesis and luminescence properties of polymer-rare earth complexes containing salicylaldehyde-type bidentate Schiff base ligand.

PubMed

Zhang, Dandan; Gao, Baojiao; Li, Yanbin

2017-08-01

Using molecular design and polymer reactions, two types of bidentate Schiff base ligands, salicylaldehyde-aniline (SAN) and salicylaldehyde-cyclohexylamine (SCA), were synchronously synthesized and bonded onto the side chain of polysulfone (PSF), giving two bidentate Schiff base ligand-functionalized PSFs, PSF-SAN and PSF-SCA, referred to as macromolecular ligands. Following coordination reactions between the macromolecular ligands and Eu(III) and Tb(III) ions (the reaction occurred between the bonded ligands SAN or SCA and the lanthanide ion), two series of luminescent polymer-rare earth complexes, PSF-SAN-Eu(III) and PSF-SCA-Tb(III), were obtained. The two macromolecular ligands were fully characterized by Fourier transform infrared (FTIR), 1 H NMR and UV absorption spectroscopy, and the prepared complexes were also characterized by FTIR, UV absorption spectroscopy and thermo-gravity analysis. On this basis, the photoluminescence properties of these complexes and the relationships between their structure and luminescence were investigated in depth. The results show that the bonded bidentate Schiff base ligands, SAN and SCA, can effectively sensitize the fluorescence emission of Eu(III) and Tb(III) ions, respectively. PSF-SAN-Eu(III) series complexes, namely the binary complex PSF-(SAN) 3 -Eu(III) and the ternary complex PSF-(SAN) 3 -Eu(III)-(Phen) 1 (Phen is the small-molecule ligand 1,10-phenanthroline), produce strong red luminescence, suggesting that the triplet state energy level of SAN is lower and well matched with the resonant energy level of the Eu(III) ion. By contrast, PSF-SAN-Eu(III) series complexes, namely the binary complex PSF-(SCA) 3 -Tb(III) and the ternary complex PSF-(SCA) 3 -Tb(III)-(Phen) 1 , display strong green luminescence, suggesting that the triplet state energy level of SCA is higher and is well matched with the resonant energy level of Tb(III). Copyright © 2017 John Wiley & Sons, Ltd.

Proof of Principle: Immobilisation of Robust CuII3 TbIII -Macrocycles on Small, Suitably Pre-functionalised Gold Nanoparticles.

PubMed

Feltham, Humphrey L C; Dumas, Christophe; Mannini, Matteo; Otero, Edwige; Sainctavit, Philippe; Sessoli, Roberta; Meledandri, Carla J; Brooker, Sally

2017-02-21

In a proof-of-principle study, a soluble macrocyclic single-molecule magnet (SMM) containing a Cu II 3 Tb III magnetic core was covalently grafted onto small gold nanoparticles pre-functionalised with carboxylate-terminated tethers. A modified microemulsion method allowed production of the small and monodisperse nanoparticles (approximately 3.5 nm in diameter) for the chemisorption of a large amount of intact macrocyclic complexes in the hybrid system. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Luminescent macrocyclic lanthanide complexes

DOEpatents

Raymond, Kenneth N; Corneillie, Todd M; Xu, Jide

2014-05-20

The present invention provides a novel class of macrocyclic compounds as well as complexes formed between a metal (e.g., lanthanide) ion and the compounds of the invention. Preferred complexes exhibit high stability as well as high quantum yields of lanthanide ion luminescence in aqueous media without the need for secondary activating agents. Preferred compounds incorporate hydroxy-isophthalamide moieties within their macrocyclic structure and are characterized by surprisingly low, non-specific binding to a variety of polypeptides such as antibodies and proteins as well as high kinetic stability. These characteristics distinguish them from known, open-structured ligands.

Conformational change during photocycle of bacteriorhodopsin and its proton-pumping mechanism.

PubMed

Chou, K C

1993-06-01

Based on the recent finding on the structural difference of seven helix bundles in the all-trans and 13-cis bacteriorhodopsins, the distances among the key groups performing the function of proton translocation as well as their microenvironments have been investigated. Consequently, a pore-gated model was proposed for the light-driven proton-pumping mechanism of bacteriorhodopsin. According to this model, the five double-bounded polyene chain in retinal chromophore can be phenomenologically likened to a molecular "lever," whose one end links to a "piston" (the beta-ionone ring) and the other end to a pump "relay station" (the Schiff base). During the photocycle of bacteriorhodopsin, the molecular "lever" is moving up and down as marked by the position change of the "piston," so as to trigger the gate of pore to open and close alternately. When the "piston" is up, the pore-controlled gate is open so that the water channel from Asp-96 to the Schiff base and that from the Schiff base to Asp-85 is established; when the "piston" is down, the pore-controlled gate is closed and the water channels for proton transportation in both the cytoplasmic half and extracellular half are blocked. The current model allows a consistent interpretation of a great deal of experimental data and also provides a useful basis for further investigating the mechanism of proton pumping by bacteriorhodopsin.

Palladium(II) and zinc(II) complexes of neutral [N2O2] donor Schiff bases derived from furfuraldehyde: synthesis, characterization, fluorescence and corrosion inhibitors of ligands.

PubMed

Ali, Omyma A M

2014-11-11

Metal complexes of Schiff bases derived from furfuraldehyde and 4,5-dimethyl-1,2-phenylendiamine (L1) or 4,5-dichloro-1,2-phenylendiamine (L2) have been reported and characterized based on elemental analyses, IR, 1H NMR, UV-Vis, magnetic moment, molar conductance and thermal analysis. The complexes are found to have the formulae [PdL1-2]Cl2 and [ZnL1-2](AcO)2·H2O. The molar conductance data reveal that Pd(II) and Zn(II) chelates are ionic in nature and are of the type 2:1 electrolytes. The spectral data are consistent with a square planar and tetrahedral geometry around Pd(II) and Zn(II), respectively, in which the ligands act as tetradentate ligands. The thermal behavior of some chelates is studied and the activation thermodynamic parameters are calculated using Coats-Redfern method. The corrosion inhibition of stainless steel types 410 and 304 in 1 M HCl using the synthesized Schiff bases as inhibitors have been studied by weight loss method. The obtained data considered these ligands as efficient corrosion inhibitors. The ligands and their metal complexes exhibited considerable antibacterial activity against Staphylococcusaureus, and Escherichiacoli and antifungal activity against Candida albicans. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis, Structural, DNA Binding and Cleavage Studies of Cu(II) Complexes Containing Benzothiazole Cored Schiff Bases.

PubMed

Tejaswi, Somapangu; Kumar, Marri Pradeep; Rambabu, Aveli; Vamsikrishna, Narendrula; Shivaraj

2016-11-01

Novel benzothiazole Schiff bases L 1 [1-((4,6-difluorobenzo[d]thiazol-2-ylimino)methyl) naphthalen-2-ol], L 2 [3-((4,6-difluorobenzo[d]thiazol-2-ylimino) methyl)benzene-1,2-diol], L 3 [2-((4,6-difluorobenzo[d]thiazol-2-ylimino)methyl)-5-methoxyphenol], L 4 [2-((4,6-difluorobenzo[d]thiazol-2-ylimino)methyl)-4-chlorophenol] and their binary Cu(II) complexes were synthesized. The structures of all the compounds have been discussed on the basis of elemental analysis, FT-IR, NMR, UV-Visible, ESI-Mass, TGA, ESR, SEM, powder XRD and magnetic moments. Based on the analytical and spectral data a square planar geometry has been assigned to all complexes in which the Schiff bases act as monobasic bidentate ligands, coordinating through the azomethine nitrogen and phenolic oxygen atom. DNA binding ability of these complexes was studied on CT-DNA by using UV-Vis absorption, fluorescence and viscometry. DNA cleavage ability of the complexes was examined on pBR322 DNA by using gel electrophoresis method. All the DNA binding studies reveal that they are good intercalators. The bioefficacy of the ligands and their complexes was examined against the growth of bacteria and fungi in vitro to evaluate their antimicrobial potential. The screening data revealed that the complexes showed more antimicrobial activity than the corresponding free ligands.

Determination of retinal chromophore structure in bacteriorhodopsin with resonance Raman spectroscopy.

PubMed

Smith, S O; Lugtenburg, J; Mathies, R A

1985-01-01

The analysis of the vibrational spectrum of the retinal chromophore in bacteriorhodopsin with isotopic derivatives provides a powerful "structural dictionary" for the translation of vibrational frequencies and intensities into structural information. Of importance for the proton-pumping mechanism is the unambiguous determination of the configuration about the C13=C14 and C=N bonds, and the protonation state of the Schiff base nitrogen. Vibrational studies have shown that in light-adapted BR568 the Schiff base nitrogen is protonated and both the C13=C14 and C=N bonds are in a trans geometry. The formation of K625 involves the photochemical isomerization about only the C13=C14 bond which displaces the Schiff base proton into a different protein environment. Subsequent Schiff base deprotonation produces the M412 intermediate. Thermal reisomerization of the C13=C14 bond and reprotonation of the Schiff base occur in the M412------O640 transition, resetting the proton-pumping mechanism. The vibrational spectra can also be used to examine the conformation about the C--C single bonds. The frequency of the C14--C15 stretching vibration in BR568, K625, L550 and O640 argues that the C14--C15 conformation in these intermediates is s-trans. Conformational distortions of the chromophore have been identified in K625 and O640 through the observation of intense hydrogen out-of-plane wagging vibrations in the Raman spectra (see Fig. 2). These two intermediates are the direct products of chromophore isomerization. Thus it appears that following isomerization in a tight protein binding pocket, the chromophore cannot easily relax to a planar geometry. The analogous observation of intense hydrogen out-of-plane modes in the primary photoproduct in vision (Eyring et al., 1982) suggests that this may be a general phenomenon in protein-bound isomerizations. Future resonance Raman studies should provide even more details on how bacterio-opsin and retinal act in concert to produce an efficient light-energy convertor. Important unresolved questions involve the mechanism by which the protein catalyzes deprotonation of the L550 intermediate and the mechanism of the thermal conversion of M412 back to BR568. Also, it has been shown that under conditions of high ionic strength and/or low light intensity two protons are pumped per photocycle (Kuschmitz & Hess, 1981). How might this be accomplished?(ABSTRACT TRUNCATED AT 400 WORDS)

Syntheses, solid state and solution structures of the palladium(II) complexes of malonamide-derived open-chain and macrocyclic ligands.

PubMed

Gavrish, Sergey P; Lampeka, Yaroslaw D; Pritzkow, Hans; Lightfoot, Philip

2010-09-07

The crystal structures of the palladium(II) complexes of the open-chain and macrocyclic ligands PdL(1).3H(2)O, PdL(2).6H(2)O and PdL(3).5H(2)O have been determined (H(2)L(1) = 1,4,8,11-tetraazaundecane-5,7-dione, H(2)L(2) = 1,4,8,11-tetraazacyclotetradecane-5,7-dione, H(2)L(3) = 1,4,8,11-tetraazacyclotridecane-5,7-dione). The coordination polyhedra of the palladium(II) ions in all complexes are formed by two deprotonated amide and two amine donors with Pd-N distances being similar in PdL(1) and PdL(2) and substantially shorter in PdL(3). A detailed analysis of the (1)H NMR spectra of the macrocyclic complexes supports the formation in aqueous solution of only N-meso isomers of both compounds in agreement with the X-ray data. The spectra of the palladium(II) macrocyclic complexes are shifted downfield as a whole as compared to those of the nickel(II) analogues with the shifts being essentially non-uniform. The latter feature can be related to the differences in magnetic anisotropy of the M-N bonds. The maxima of d-d absorption bands of the palladium(II) complexes demonstrate weaker dependence on the macrocycle size as compared to those of the nickel(II) analogues. Both macrocyclic compounds PdL(2).6H(2)O and PdL(3).5H(2)O are characterized by lamellar crystal structures consisting of interleaved layers formed by macrocyclic units and by water molecules with similar metal complex layers and different 2D water sheets. A columnar crystal structure is inherent for PdL(1).3H(2)O with the water molecules present as discrete (H(2)O)(3) clusters.

Preparation and Characterization of Organic-Inorganic Hybrid Macrocyclic Compounds: Cyclic Ladder-like Polyphenylsilsesquioxanes.

PubMed

Zhang, Wenchao; Wang, Xiaoxia; Wu, Yiwei; Qi, Zhi; Yang, Rongjie

2018-04-02

Organic-inorganic hybrid macrocyclic compounds, cyclic polyphenylsilsesquioxanes (cyc-PSQs), have been synthesized through hydrolysis and condensation reactions of phenyltrichlorosilane. Structural characterization has revealed that cyc-PSQs consist of a closed-ring double-chain siloxane inorganic backbone bearing organic phenyl groups. The cyc-PSQ molecules have been simulated and structurally optimized using the Forcite tool as implemented in Materials Studio. Structurally optimized cyc-PSQs are highly symmetrical and regular with high stereoregularity, consistent with the dimensions of their experimentally derived structures. Thermogravimetric analysis showed that these macrocyclic compounds have excellent thermal stability. In addition to these perfectly structured compounds, macrocyclic compounds with the same ring ladder structure but bearing an additional Si-OH group, cyc-PSQs-OH, have also been synthesized. A possible mechanism for the formation of the closed-ring molecular structures of cyc-PSQs and cyc-PSQs-OH is proposed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alfonso Hernandez, Laura; Nelson, Tammie Renee; Gelin, Maxim F.

The interchromophoric energy-transfer pathways between weakly coupled units in a π-conjugated phenylene–ethynylene macrocycle and its half-ring analogue have been investigated using the nonadiabatic excited-state molecular dynamics approach. To track the flow of electronic transition density between macrocycle units, we formulate a transition density flux analysis adapted from the statistical minimum flow method previously developed to investigate vibrational energy flow. Following photoexcitation, transition density is primarily delocalized on two chromophore units and the system undergoes ultrafast energy transfer, creating a localized excited state on a single unit. In the macrocycle, distinct chromophore units donate transition density to a single acceptor unitmore » but do not interchange transition density among each other. We find that energy transfer in the macrocycle is slower than in the corresponding half ring because of the presence of multiple interfering energy-transfer pathways. Finally, simulation results are validated by modeling the fluorescence anisotropy decay.« less

Response of a benzoxainone derivative linked to monoaza-15-crown-5 with divalent heavy metals.

PubMed

Addleman, R S; Bennett, J; Tweedy, S H; Elshani, S; Wai, C M

1998-08-01

The response of a monoaza-15-crown-5 with an optically active aminobenzoxazinone moiety to divalent cations was investigated. The crown ether was found to undergo a strong emission shift to the blue when complexed with specific divalent metals that have ionic diameters between 1.9-2.4 A. Consequently the photoactive macrocycle is responsive to Mg(2+), Ca(2+), Ba(2+), Sr(2+), Cd(2+), and particularly responsive to Hg(2+)and Pb(2+). Macrocycle emission spectra are shown to be a function of cation concentration. Alkaline metal cations and smaller transition metals ions such as Ni(2+), Co(2+)and Zn(2+)do not cause significant changes in the macrocycle emission spectra. Emission, absorption, and complex stability constants are determined. Mechanisms of cation selectivity and spectral emission shifts are discussed. Challenges involving immobilization of the macrocycle while preserving its spectral response to cations are explored.

Lorentz-violating contributions to the nuclear Schiff moment and nuclear EDM

NASA Astrophysics Data System (ADS)

Araujo, Jonas B.; Casana, Rodolfo; Ferreira, Manoel M.

2018-03-01

In the context of an atom endowed with nuclear electric dipole moments (EDM), we consider the effects on the Schiff moment of C P T -even Lorentz-violating (LV) terms that modify the Coulomb potential. First, we study the modifications on the Schiff moment when the nucleus interacts with the electronic cloud by means of a Coulomb potential altered only by the P -even LV components. Next, by supposing the existence of an additional intrinsic LV EDM generated by other LV sources, we assess the corrections to the Schiff moment when the interaction nucleus-electrons runs mediated by a Coulomb potential modified by both the P -odd and P -even LV components. We then use known estimates and EDM measurements to discuss upper bounds on the new Schiff moment components and the possibility of a nuclear EDM component ascribed to LV effects.

Mössbauer study of novel iron(II) complexes synthesized with Schiff bases

NASA Astrophysics Data System (ADS)

Várhelyi, Cs.; Lengyel, A.; Homonnay, Z.; Szalay, R.; Pokol, Gy.; Szilágyi, I.-M.; Huszthy, P.; Papp, J.; Goga, F.; Golban, L.-M.; Várhelyi, M.; Tomoaia-Cotisel, M.; Szőke, Á.; Kuzmann, E.

2017-11-01

Novel [Fe(4-benzyl-2-hydroxyphenyl-propylidene)2ethylene-diamine], and [Fe (2,4,6-trihydroxy-benzyl-4-metoxiphenyl-methylidene)2ethylene-diamine] complexes were synthesized by reacting FeII salt with the indicated Schiff-base ligands. The compounds were characterized by57Fe Mössbauer spectroscopy, FTIR, UV-VIS, TG-DTA-DTG, MS, AFM, XRD, cyclic voltammetry and biological activity measurements. 295 K and 78 K Mössbauer spectra revealed that iron is dominantly in high spin FeII state in both complexes while simultaneously a minor low spin FeII was also present in both complexes, furthermore a minor high spin FeIII was observed in [Fe(2,4,6-trihydroxy-benzyl-4-metoxiphenyl- methylidene) 2ethylene-diamine], too.

A novel Schiff base derivative: Synthesis, two-photon absorption properties and application for bioimaging

NASA Astrophysics Data System (ADS)

Wang, Hui; Fang, Bin; Kong, Lin; Li, Xiangzi; Feng, Zhijun; Wu, Yunjun; Uvdal, Kajsa; Hu, Zhangjun

2018-06-01

A novel donor-π-acceptor-π-donor type (D-π-A-π-D‧) Schiff base derivative (L) has been designed and synthesized. The structure of L is confirmed by single-crystal X-ray diffraction analysis as well. The photophysical properties of compound L were comprehensively investigated by using both experimental and theoretical methods. The results indicate that L exhibits large Stokes shift and moderate two-photon action (2PA) cross-section in the near infrared (NIR) region. Furthermore, the confocal microscopy imaging study demonstrates that compound L could penetrate into cells and target the cellular mitochondria compartment. Due to its low cytotoxicity, compound L provides a promising tool for directly lighting up the mitochondria compartment in living HepG2 cells.

Bio-important antipyrine derived Schiff bases and their transition metal complexes: Synthesis, spectroscopic characterization, antimicrobial, anthelmintic and DNA cleavage investigation

NASA Astrophysics Data System (ADS)

Manjunath, M.; Kulkarni, Ajaykumar D.; Bagihalli, Gangadhar B.; Malladi, Shridhar; Patil, Sangamesh A.

2017-01-01

Spectroscopic (IR, NMR, UV-vis, ESR, ESI-mass), magnetic and TGA studies suggests octahedral geometry for all the CoII, NiII and CuII complexes of the Schiff bases, derived from 4-aminoantipyrine and 8-formyl-7-Hydroxy-4-methylcoumarin/5-formyl-6-hydroxycoumarin, coordinated through ONO donor sites. Antibacterial (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella typhi), antifungal (Aspergillus niger, Aspergillus flavus and Cladosporium) and DNA cleavage properties of the metal complexes are investigated. The results suggested that some of the synthesized compounds are potential antimicrobials. The synthesized compounds tested for their anthelmintic activities and it was found that CoII and NiII complexes exhibited good anthelmintic properties.

Synthesis, antioxidant and analgesic activities of Schiff bases of 4-amino-1,2,4-triazole derivatives containing a pyrazole moiety.

PubMed

Karrouchi, K; Chemlal, L; Taoufik, J; Cherrah, Y; Radi, S; El Abbes Faouzi, M; Ansar, M

2016-11-01

A series of Schiff bases of 4-amino-1,2,4-triazole derivatives containing pyrazole (5a-h) were synthesized from condensation of 4-amino-5-(5-methyl-1H-pyrazol-3-yl)-4H-1,2,4-triazole-3-thiol (3) derivative with various aromatic aldehydes (4a-h). The structures of the synthesized compounds were elucidated by IR, 1 H NMR, 13 C NMR, and mass spectrometry. All the synthesized compounds (5a-h) were screened for their in vivo analgesic and in vitro antioxidant activities revealing significant analgesic and antioxidant properties. Copyright © 2016 Académie Nationale de Pharmacie. Published by Elsevier Masson SAS. All rights reserved.

Strategies for the control of Rhipicephalus microplus ticks in a world of conventional acaricide and macrocyclic lactone resistance.

PubMed

Rodriguez-Vivas, Roger I; Jonsson, Nicholas N; Bhushan, Chandra

2018-01-01

Infestations with the cattle tick, Rhipicephalus microplus, constitute the most important ectoparasite problem for cattle production in tropical and subtropical regions worldwide, resulting in major economic losses. The control of R. microplus is mostly based on the use of conventional acaricides and macrocyclic lactones. However, the intensive use of such compounds has resulted in tick populations that exhibit resistance to all major acaricide chemical classes. Consequently, there is a need for the development of alternative approaches, possibly including the use of animal husbandry practices, synergized pesticides, rotation of acaricides, pesticide mixture formulations, manual removal of ticks, selection for host resistance, nutritional management, release of sterile male hybrids, environmental management, plant species that are unfavourable to ticks, pasture management, plant extracts, essential oils and vaccination. Integrated tick management consists of the systematic combination of at least two control technologies aiming to reduce selection pressure in favour of acaricide-resistant individuals, while maintaining adequate levels of animal production. The purpose of this paper is to present a current review on conventional acaricide and macrocyclic lactone resistance for better understanding and control of resistant ticks with particular emphasis on R. microplus on cattle.

Two Macrocycles in One Shot: Synthesis, Spectroscopy, Photophysics, and Tautomerism of 23-Oxahemiporphycene and 21-Oxacorrole-5-carbaldehyde.

PubMed

Ostapko, Jakub; Kelm, Anna; Kijak, Michał; Leśniewska, Barbara; Waluk, Jacek

2018-04-19

The synthesis of 23-oxahemiporphycene, the first monooxa analogue of hemiporphycene, a structural isomer of porphyrin, is reported. Its generation under McMurry reaction conditions is surprisingly accompanied by the appearance of a formyl derivative of oxacorrole, 21-oxacorrole-5-carbaldehyde. A mechanism for the formation of the latter is proposed, relying on pinacol rearrangement of titanium pinacolate. The structures of the most stable tautomeric forms are established for both compounds based on IR and NMR spectra combined with DFT calculations. Spectral and photophysical characteristics are compared with those of structurally similar macrocycles. Replacement of one nitrogen by oxygen in hemiporphycene has only a minor impact. In contrast, for corrole it leads to the enhancement of stability and to strongly reduced rates of nonradiative deactivation of the lowest excited singlet state. This is explained by the planarity of oxacorroles, achieved by removing one of the inner hydrogen atoms from the inner cavity. Unusual crystal packing is observed for the protonated form of 23-oxahemiporphycene, which exhibits a π-π stacked columnar alignment of positively charged macrocycle units. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Schiff base-derived copper (II) complex is a potent inducer of apoptosis in colon cancer cells by activating the intrinsic pathway.

PubMed

Hajrezaie, Maryam; Paydar, Mohammadjavad; Moghadamtousi, Soheil Zorofchian; Hassandarvish, Pouya; Gwaram, Nura Suleiman; Zahedifard, Maryam; Rouhollahi, Elham; Karimian, Hamed; Looi, Chung Yeng; Ali, Hapipah Mohd; Abdul Majid, Nazia; Abdulla, Mahmood Ameen

2014-01-01

Metal-based drugs with extensive clinical applications hold great promise for the development of cancer chemotherapeutic agents. In the last few decades, Schiff bases and their complexes have become well known for their extensive biological potential. In the present study, we examined the antiproliferative effect of a copper (II) complex on HT-29 colon cancer cells. The Cu(BrHAP)2 Schiff base compound demonstrated a potent antiproliferative effect in HT-29 cells, with an IC50 value of 2.87  μg/ml after 72 h of treatment. HT-29 cells treated with Cu (II) complexes underwent apoptosis death, as exhibited by a progressive elevation in the proportion of the G1 cell population. At a concentration of 6.25  μg/ml, the Cu(BrHAP)2 compound caused significant elevation in ROS production following perturbation of mitochondrial membrane potential and cytochrome c release, as assessed by the measurement of fluorescence intensity in stained cells. Furthermore, the activation of caspases 3/7 and 9 was part of the Cu (II) complex-induced apoptosis, which confirmed the involvement of mitochondrial-mediated apoptosis. Meanwhile, there was no significant activation of caspase-8. Taken together, these results imply that the Cu(BrHAP)2 compound is a potential candidate for further in vivo and clinical colon cancer studies to develop novel chemotherapeutic agents derived from metal-based agents.

A Schiff Base-Derived Copper (II) Complex Is a Potent Inducer of Apoptosis in Colon Cancer Cells by Activating the Intrinsic Pathway

PubMed Central

Hajrezaie, Maryam; Paydar, Mohammadjavad; Zorofchian Moghadamtousi, Soheil; Hassandarvish, Pouya; Gwaram, Nura Suleiman; Zahedifard, Maryam; Rouhollahi, Elham; Karimian, Hamed; Looi, Chung Yeng; Ali, Hapipah Mohd; Abdul Majid, Nazia; Abdulla, Mahmood Ameen

2014-01-01

Metal-based drugs with extensive clinical applications hold great promise for the development of cancer chemotherapeutic agents. In the last few decades, Schiff bases and their complexes have become well known for their extensive biological potential. In the present study, we examined the antiproliferative effect of a copper (II) complex on HT-29 colon cancer cells. The Cu(BrHAP)2 Schiff base compound demonstrated a potent antiproliferative effect in HT-29 cells, with an IC50 value of 2.87 μg/ml after 72 h of treatment. HT-29 cells treated with Cu (II) complexes underwent apoptosis death, as exhibited by a progressive elevation in the proportion of the G1 cell population. At a concentration of 6.25 μg/ml, the Cu(BrHAP)2 compound caused significant elevation in ROS production following perturbation of mitochondrial membrane potential and cytochrome c release, as assessed by the measurement of fluorescence intensity in stained cells. Furthermore, the activation of caspases 3/7 and 9 was part of the Cu (II) complex-induced apoptosis, which confirmed the involvement of mitochondrial-mediated apoptosis. Meanwhile, there was no significant activation of caspase-8. Taken together, these results imply that the Cu(BrHAP)2 compound is a potential candidate for further in vivo and clinical colon cancer studies to develop novel chemotherapeutic agents derived from metal-based agents. PMID:24737979

Supramolecular Assembly of Uridine Monophosphate (UMP) and Thymidine Monophosphate (TMP) with a Dinuclear Copper(II) Receptor

PubMed Central

2017-01-01

Understanding the intermolecular interactions between nucleotides and artificial receptors is crucial to understanding the role of nucleic acids in living systems. However, direct structural evidence showing precise interactions and bonding features of a nucleoside monophosphate (NMP) with a macrocycle-based synthetic molecule has not been provided so far. Herein, we present two novel crystal structures of uridine monophosphate (UMP) and thymidine monophosphate (TMP) complexes with a macrocycle-based dinuclear receptor. Structural characterization of these complexes reveals that the receptor recognizes UMP through coordinate–covalent interactions with phosphates and π–π stackings with nucleobases and TMP through coordinate–covalent interactions with phosphate groups. Furthermore, the receptor has been shown to effectively bind nucleoside monophosphates in the order of GMP > AMP > UMP > TMP > CMP in water at physiological pH, as investigated by an indicator displacement assay. PMID:29214233

Contorted Organic Semiconductors for Molecular Electronics

NASA Astrophysics Data System (ADS)

Zhong, Yu

This thesis focuses on the synthesis, properties and applications of two types of contorted organic molecules: contorted molecular ribbons and conjugated corrals. We utilized the power of reaction chemistry to writing information into conjugated molecules with contorted structures and studied "structure-property" relationships. The unique properties of the molecules were expressed in electronic and optoelectronic devices such as field-effect transistors, solar cells, photodetectors, etc. In Chapter 2, I describe the design and synthesis of a new graphene ribbon architecture that consists of perylenediimide (PDI) subunits fused together by ethylene bridges. We created a prototype series of oligomers consisting of the dimer, trimer, and tetramer. The steric congestion at the fusion point between the PDI units creates helical junctions, and longer oligomers form helical ribbons. Thin films of these oligomers form the active layer in n-type field effect transistors. UV-vis spectroscopy reveals the emergence of an intense long-wavelength transition in the tetramer. From DFT calculations, we find that the HOMO-2 to LUMO transition is isoenergetic with the HOMO to LUMO transition in the tetramer. We probe these transitions directly using femtosecond transient absorption spectroscopy. The HOMO-2 to LUMO transition electronically connects the PDI subunits with the ethylene bridges, and its energy depends on the length of the oligomer. In Chapter 3, I describe an efficiency of 6.1% for a solution processed non-fullerene solar cell using a helical PDI dimer as the electron acceptor. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces, indicating that charge carriers are created from photogenerated excitons in both the electron donor and acceptor phases. Light-intensity-dependent current?voltage measurements suggested different recombination rates under short-circuit and open-circuit conditions. In Chapter 4, I discuss helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometers in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells. In Chapter 5, I compare analogous cyclic and acyclic pi-conjugated molecules as n-type electronic materials and find that the cyclic molecules have numerous benefits in organic photovoltaics. We designed two conjugated cycles for this study. Each comprises four subunits; one combines four electron-accepting, redox-active, diphenyl-perylenediimide subunits, and the other alternates two electron-donating bithiophene units with two diphenyl-perylenediimide units. We compare the macrocycles to acyclic versions of these molecules and find that, relative to the acyclic analogs, the conjugated macrocycles have bathochromically shifted UV-vis absorbances and are more easily reduced. In blended films, macrocycle-based devices show higher electron mobility and good morphology. All of these factors contribute to the more than doubling of the power conversion efficiency observed in organic photovoltaic devices with these macrocycles as the n-type, electron transporting material. This study highlights the importance of geometric design in creating new molecular semiconductors. In Chapter 6, I describe a new molecular design that enables high performance organic photodetectors. We use a rigid, conjugated macrocycle as the electron acceptor in devices to obtain high photocurrent and low dark current. We directly compare the macrocyclic acceptor devices to an acyclic control device; we find that the superior performance of the macrocycle originates from its rigid, conjugated, and cyclic structure. The macrocycle's rigid structure reduces the number of charged defects originating from deformed sp 2 carbons and covalent defects from photo/thermo-activation. With this molecular design we are able to suppress dark current density while retaining high responsivity in an ultra-sensitive non-fullerene organic photodetector. Importantly, we achieve a detectivity of 1014 Jones at near zero bias voltage. This is without the need for extra carrier blocking layers commonly employed in fullerene-based devices. Our devices are comparable to the best fullerene-based photodetectors, and the sensitivity at low working voltages (< 0.1 V) is a record for non-fullerene OPDs.

How to synthesize macrocycles efficiently by using virtual combinatorial libraries.

PubMed

Storm, Ole; Lüning, Ulrich

2002-02-15

The selection of different diimines 4 a-c by alkaline earth ions from a virtual combinatorial library (VCL) is described. The products were stabilized by reduction to the diamines 6 a-c; this allowed easy analysis. The library can be directed toward different target molecules 6 a-c upon addition of alkaline earth ions with different radii. Competition experiments show the possibility of synthesizing the macrocycles 6 a, 6 b, and 6 c simultaneously when using Mg(2+), Ca(2+), and Ba(2+) as template ions. The scope of this thermodynamically controlled, reversible approach for macrocycle syntheses is illustrated.

Self-assembled photosynthesis-inspired light harvesting material and solar cells containing the same

DOEpatents

Lindsey, Jonathan S [Raleigh, NC; Chinnasamy, Muthiah [Raleigh, NC; Fan, Dazhong [Raleigh, NC

2009-12-15

A solar cell is described that comprises: (a) a semiconductor charge separation material; (b) at least one electrode connected to the charge separation material; and (c) a light-harvesting film on the charge separation material, the light-harvesting film comprising non-covalently coupled, self-assembled units of porphyrinic macrocycles. The porphyrinic macrocycles preferably comprise: (i) an intramolecularly coordinated metal; (ii) a first coordinating substituent; and (iii) a second coordinating substituent opposite the first coordinating substituent. The porphyrinic macrocycles can be assembled by repeating intermolecular coordination complexes of the metal, the first coordinating substituent and the second coordinating substituent.

Interlocked Photo-degradable Macrocycles Allow One-Off Photo-triggerable Gelation of Organo- and Hydrogelators.

PubMed

Tung, Shun-Te; Cheng, Hung-Te; Inthasot, Alex; Hsueh, Fang-Che; Gu, Ting-Jia; Yan, Pei-Cong; Lai, Chien-Chen; Chiu, Sheng-Hsien

2018-02-01

[2]Rotaxanes displaying one-off photo-triggerable gelation properties have been synthesized through the "clipping" of photo-degradable macrocycles around the amide or urea functionalities of organo- and hydrogelators. Irradiation with UV-light cleaved the photo-labile macrocyclic components from the [2]rotaxanes, resulting in the free gelators being released into solution and, thereafter, forming gels. When the rate of gelation was sufficiently rapid, selective gelation of specific regions of the solution-and, indeed, photo-patterning of the solution-was possible. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gas Sorption and Storage Properties of Calixarenes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patil, Rahul S.; Banerjee, Debasis; Atwood, Jerry L.

2016-12-01

Calixarenes, a class of organic macrocyclic molecules have shown interesting gas sorption properties towards industrially important gases such as carbon di-oxide, hydrogen, methane and acetylene. These macrocycles are involved in weak van der Waals interaction to form multidimensional supramolecular frameworks. The gas-diffusion and subsequent sorption occurs due to a cooperative behavior between neighboring macrocycles. Furthermore, the flexibility at the upper rim functional group also plays a key role in the overall gas uptake of calixarene. In this book chapter, we give a brief account of interaction and diffusion of gases in calixarene and selected derivatives.

Total synthesis of complestatin: development of a Pd(0)-mediated indole annulation for macrocyclization.

PubMed

Shimamura, Hiroyuki; Breazzano, Steven P; Garfunkle, Joie; Kimball, F Scott; Trzupek, John D; Boger, Dale L

2010-06-09

Full details of the initial development and continued examination of a powerful intramolecular palladium(0)-mediated indole annulation for macrocyclization closure of the strained 16-membered biaryl ring system found in complestatin (1, chloropeptin II) and the definition of factors impacting its intrinsic atropodiastereoselectivity are described. Its examination and use in an alternative, second-generation total synthesis of complestatin are detailed in which the order of the macrocyclization reactions was reversed from our first-generation total synthesis. In this approach and with the ABCD biaryl ether ring system in place, the key Larock cyclization was conducted with substrate 36 (containing four phenols, five secondary amides, one carbamate, and four labile aryl chlorides) and provided the product 37 (56%) exclusively as a single atropisomer (>20:1, detection limits) possessing the natural (R)-configuration. In this instance, the complexity of the substrate and the reverse macrocyclization order did not diminish the atropodiastereoselectivity; rather, it provided an improvement over the 4:1 selectivity that was observed with the analogous substrate used to provide the isolated DEF ring system in our first-generation approach. Just as significant, the atroposelectivity represents a complete reversal of the diasteroselectivity observed with analogous macrocyclizations conducted using a Suzuki biaryl coupling.

Complexes of DOTA-bisphosphonate conjugates: probes for determination of adsorption capacity and affinity constants of hydroxyapatite.

PubMed

Vitha, Tomas; Kubícek, Vojtech; Hermann, Petr; Kolar, Zvonimir I; Wolterbeek, Hubert Th; Peters, Joop A; Lukes, Ivan

2008-03-04

The adsorption on hydroxyapatite of three conjugates of a bisphosphonate and a macrocycle having C1, C2, and C3 spacers and their terbium complexes was studied by the radiotracer method using 160Tb as the label. The radiotracer-containing complex of the conjugate with the C3 spacer was used as a probe for the determination of the adsorption parameters of other bisphosphonates that lack a DOTA unit. A physicochemical model describing the competitive adsorption was successfully applied in the fitting of the obtained data. The maximum adsorption capacity of bisphosphonates containing bulky substituents is determined mainly by their size. For bisphosphonates having no DOTA moiety, the maximum adsorption capacity is determined by the electrostatic repulsion between negatively charged bisphosphonate groups. Compounds with a hydroxy or amino group attached to the alpha-carbon atom show higher affinities. Macrocyclic compounds containing a short spacer between the different bisphosphonic acid groups and the macrocyclic unit exhibit high affinities, indicating a synergic effect of the bisphosphonic and the macrocyclic groups during adsorption. The competition method described uses a well-characterized complex and allows a simple evaluation of the adsorption behavior of bisphosphonates. The application of the macrocycle-bisphosphonate conjugates allows easy radiolabeling via complexation of a suitable metal isotope.

Fabrication of reduced graphene oxide/macrocyclic cobalt complex nanocomposites as counter electrodes for Pt-free dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Tsai, Chih-Hung; Shih, Chun-Jyun; Wang, Wun-Shiuan; Chi, Wen-Feng; Huang, Wei-Chih; Hu, Yu-Chung; Yu, Yuan-Hsiang

2018-03-01

In this study, macrocyclic Co complexes were successfully grafted onto graphene oxide (GO) to produce GO/Co nanocomposites with a large surface area, high electrical conductivity, and excellent catalytic properties. The novel GO/Co nanocomposites were applied as counter electrodes for Pt-free dye-sensitized solar cells (DSSCs). Various ratios of macrocyclic Co complexes were used as the reductant to react with the GO, with which the surface functional groups of the GO were reduced and the macrocyclic ligand of the Co complexes underwent oxidative dehydrogenation, after which the conjugated macrocyclic Co systems were grafted onto the surface of the reduced GO to form GO/Co nanocomposites. The surface morphology, material structure, and composition of the GO/Co composites and their influences on the power-conversion efficiency of DSSC devices were comprehensively investigated. The results showed that the GO/Co (1:10) counter electrode (CE) exhibited an optimal power conversion efficiency of 7.48%, which was higher than that of the Pt CE. The GO/Co (1:10) CE exhibited superior electric conductivity, catalytic capacity, and redox capacity. Because GO/Co (1:10) CEs are more efficient and cheaper than Pt CEs, they could potentially be used as a replacement for Pt electrodes.

Dynamical correlation effects on photoisomerization: Ab initio multiple spawning dynamics with MS-CASPT2 for a model trans-protonated Schiff base

DOE PAGES

Liu, Lihong; Liu, Jian; Martinez, Todd J.

2015-12-17

Here, we investigate the photoisomerization of a model retinal protonated Schiff base (trans-PSB3) using ab initio multiple spawning (AIMS) based on multi-state second order perturbation theory (MSPT2). Discrepancies between the photodynamical mechanism computed with three-root state-averaged complete active space self-consistent field (SA-3-CASSCF, which does not include dynamic electron correlation effects) and MSPT2 show that dynamic correlation is critical in this photoisomerization reaction. Furthermore, we show that the photodynamics of trans-PSB3 is not well described by predictions based on minimum energy conical intersections (MECIs) or minimum energy conical intersection (CI) seam paths. Instead, most of the CIs involved in the photoisomerizationmore » are far from MECIs and minimum energy CI seam paths. Thus, both dynamical nuclear effects and dynamic electron correlation are critical to understanding the photochemical mechanism.« less

The preparation of a new type of ferrocene-based compounds with large conjugated system containing symmetrical aromatic vinyl with Schiff base moieties and the study of their third-order nonlinear optical properties

NASA Astrophysics Data System (ADS)

Yu, Weiguo; Jia, Jianhong; Gao, Jianrong; Han, Liang; Li, Yujin

2016-09-01

Herein we reported the preparation of a new type of ferrocene-based compounds with large conjugated system containing symmetrical aromatic vinyl and Schiff base moieties and the study of their third-order nonlinear optical (NLO) properties. Their third-order NLO properties were measured using femtosecond laser and degenerate four-wave mixing (DFWM) technique. The obtained χ(3), n2 and γ values of these molecules were found in the range of 0.998-1.429 × 10-12 esu,1.847-2.646 × 10-11 esu and 1.026-1.449 × 10-30 esu, respectively. The response time ranged from 43.65 fs to 61.71 fs. The results indicate that these compounds have potential nonlinear optical applications.

High-performance liquid chromatographic enantioseparation of monoterpene-based 2-amino carboxylic acids on macrocyclic glycopeptide-based phases.

PubMed

Sipos, László; Ilisz, István; Pataj, Zoltán; Szakonyi, Zsolt; Fülöp, Ferenc; Armstrong, Daniel W; Péter, Antal

2010-10-29

The enantiomers of five monoterpene-based 2-amino carboxylic acids were directly separated on chiral stationary phases containing macrocyclic glycopeptide antibiotics such as teicoplanin (Astec Chirobiotic T and T2) and teicoplanin aglycone (Chirobiotic TAG) as chiral selectors. The effects of pH, the mobile phase composition, the structure of the analyte and temperature on the separations were investigated. Experiments were performed at constant mobile phase compositions in the temperature range 10-40°C to study the effects of temperature and thermodynamic parameters on separations. Apparent thermodynamic parameters and T(iso) values were calculated from plots of ln k or ln α versus 1/T. Some mechanistic aspects of the chiral recognition process are discussed with respect to the structures of the analytes. It was found that the enantioseparations were in most cases enthalpy driven. The sequence of elution of the enantiomers was determined in all cases. Copyright © 2010 Elsevier B.V. All rights reserved.

Methods and intermediates for the synthesis of dipyrrin-substituted porphyrinic macrocycles

DOEpatents

Yu, Lianhe; Muthukumaran, Kannan; Sreedharan, Prathapan; Lindsey, Jonathan S.

2010-05-25

The present invention provides dipyrrin substituted porphyrinic macrocycles, intermediates useful for making the same, and methods of making the same. Such compounds may be used for purposes including the making of molecular memory devices, solar cells and light harvesting arrays.

Apoptotic effect of novel Schiff Based CdCl2(C14H21N3O2) complex is mediated via activation of the mitochondrial pathway in colon cancer cells

PubMed Central

Hajrezaie, Maryam; Paydar, Mohammadjavad; Looi, Chung Yeng; Moghadamtousi, Soheil Zorofchian; Hassandarvish, Pouya; Salga, Muhammad Saleh; Karimian, Hamed; Shams, Keivan; Zahedifard, Maryam; Majid, Nazia Abdul; Ali, Hapipah Mohd; Abdulla, Mahmood Ameen

2015-01-01

The development of metal-based agents has had a tremendous role in the present progress in cancer chemotherapy. One well-known example of metal-based agents is Schiff based metal complexes, which hold great promise for cancer therapy. Based on the potential of Schiff based complexes for the induction of apoptosis, this study aimed to examine the cytotoxic and apoptotic activity of a CdCl2(C14H21N3O2) complex on HT-29 cells. The complex exerted a potent suppressive effect on HT-29 cells with an IC50 value of 2.57 ± 0.39 after 72 h of treatment. The collapse of the mitochondrial membrane potential and the elevated release of cytochrome c from the mitochondria to the cytosol indicate the involvement of the intrinsic pathway in the induction of apoptosis. The role of the mitochondria-dependent apoptotic pathway was further proved by the significant activation of the initiator caspase-9 and the executioner caspases-3 and -7. In addition, the activation of caspase-8, which is associated with the suppression of NF-κB translocation to the nucleus, also revealed the involvement of the extrinsic pathway in the induced apoptosis. The results suggest that the CdCl2(C14H21N3O2) complex is able to induce the apoptosis of colon cancer cells and is a potential candidate for future cancer studies. PMID:25764970

Synthesis, Characterization and Biological Evaluation of Transition Metal Complexes Derived from N, S Bidentate Ligands

PubMed Central

Md Yusof, Enis Nadia; Ravoof, Thahira Begum S. A.; Tiekink, Edward R. T.; Veerakumarasivam, Abhimanyu; Crouse, Karen Anne; Mohamed Tahir, Mohamed Ibrahim; Ahmad, Haslina

2015-01-01

Two bidentate NS ligands were synthesized by the condensation reaction of S-2-methylbenzyldithiocarbazate (S2MBDTC) with 2-methoxybenzaldehyde (2MB) and 3-methoxybenzaldehyde (3MB). The ligands were reacted separately with acetates of Cu(II), Ni(II) and Zn(II) yielding 1:2 (metal:ligand) complexes. The metal complexes formed were expected to have a general formula of [M(NS)2] where M = Cu2+, Ni2+, and Zn2+. These compounds were characterized by elemental analysis, molar conductivity, magnetic susceptibility and various spectroscopic techniques. The magnetic susceptibility measurements and spectral results supported the predicted coordination geometry in which the Schiff bases behaved as bidentate NS donor ligands coordinating via the azomethine nitrogen and thiolate sulfur. The molecular structures of the isomeric S2M2MBH (1) and S2M3MBH (2) were established by X-ray crystallography to have very similar l-shaped structures. The Schiff bases and their metal complexes were evaluated for their biological activities against estrogen receptor-positive (MCF-7) and estrogen receptor-negative (MDA-MB-231) breast cancer cell lines. Only the Cu(II) complexes showed marked cytotoxicity against the cancer cell lines. Both Schiff bases and other metal complexes were found to be inactive. In concordance with the cytotoxicity studies, the DNA binding studies indicated that Cu(II) complexes have a strong DNA binding affinity. PMID:25988384

Synthesis, structure, DNA/BSA binding and antibacterial studies of NNO tridentate Schiff base metal complexes

NASA Astrophysics Data System (ADS)

Sakthi, Marimuthu; Ramu, Andy

2017-12-01

A new salicylaldehyde derived 2,4-diiodo-6-((2-phenylaminoethylimino)methyl)phenol Schiff base(L) and its transition metal complexes of the type MLCl where, M = Cu(II), Ni(II), Co(II), Mn(II) and Zn(II) have been synthesized. The coordination mode of Schiff base holding NNO donor atoms with metal ions was well investigated by elemental analysis, ESI-mass as well as IR, UV-vis, CV and NMR spectral studies. The binding efficiency and mode of these complexes with biological macromolecules viz., herring sperm DNA (HS- DNA) and bovine serum albumin (BSA) have been explored through various spectroscopic techniques. The characteristic changes in absorption, emission and, circular dichroism spectra of the complexes with DNA indicate the noticeable interaction between them. From the all spectral information complexes could interact with DNA via non-intercalation mode of binding. The hyperchromisim in absorption band and hypochromisim in emission intensity of BSA with different complex concentrations shown significant information, and the binding affinity value has been predicted from Stern-Volmer plots. Further, all the complexes could cleave the circular plasmid pUC19 DNA efficiently by using an activator H2O2. The ligand and all metal(II) complexes showed good antibacterial activities. The molecular docking studies of the complexes with DNA were performed in order to make a comparison and conclusion with spectral technic results.

Synthesis of metal complexes involving Schiff base ligand with methylenedioxy moiety: spectral, thermal, XRD and antimicrobial studies.

PubMed

Sundararajan, M L; Jeyakumar, T; Anandakumaran, J; Karpanai Selvan, B

2014-10-15

Metal complexes of Zn(II), Cd(II), Ni(II), Cu(II), Fe(III), Co(II), Mn(II) Hg(II), and Ag(I) have been synthesized from Schiff base ligand, prepared by the condensation of 3,4-(methylenedioxy)aniline and 5-bromo salicylaldehyde. All the compounds have been characterized by using elemental analysis, molar conductance, FT-IR, UV-Vis, (1)H NMR, (13)C NMR, mass spectra, powder XRD and thermal analysis (TG/DTA) technique. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). The FT-IR, (1)H NMR, (13)C NMR and UV-Vis spectral data suggest that the ligand coordinate to the metal atom by imino nitrogen and phenolic oxygen as bidentate manner. Mass spectral data further support the molecular mass of the compounds and their structure. Powder XRD indicates the crystalline state and morphology of the ligand and its metal complexes. The thermal behaviors of the complexes prove the presence of lattice as well as coordinated water molecules in the complexes. Melting point supports the thermal stability of all the compounds. The in vitro antimicrobial effects of the synthesized compounds were tested against five bacterial and three fungal species by well diffusion method. Antioxidant activities have also been performed for all the compounds. Metal complexes show more biological activity than the Schiff base. Copyright © 2014 Elsevier B.V. All rights reserved.

Spectroscopic studies of the intramolecular hydrogen bonding in o-hydroxy Schiff bases, derived from diaminomaleonitrile, and their deprotonation reaction products

NASA Astrophysics Data System (ADS)

Szady-Chełmieniecka, Anna; Kołodziej, Beata; Morawiak, Maja; Kamieński, Bohdan; Schilf, Wojciech

2018-01-01

The structural study of five Schiff bases derived from diaminomaleonitrile (DAMN) and 2-hydroxy carbonyl compounds was performed using 1H, 13C and 15N NMR methods in solution and in the solid state as well. ATR-FTIR and X-Ray spectroscopies were used for confirmation of the results obtained by NMR method. The imine obtained from DAMN and benzaldehyde was synthesized as a model compound which lacks intramolecular hydrogen bond. Deprotonation of all synthesized compounds was done by treating with tetramethylguanidine (TMG). NMR data revealed that salicylidene Schiff bases in DMSO solution exist as OH forms without intramolecular hydrogen bonds and independent on the substituents in aromatic ring. In the case of 2-hydroxy naphthyl derivative, the OH proton is engaged into weak intramolecular hydrogen bond. Two of imines (salDAMN and 5-BrsalDAMN) exist in DMSO solution as equilibrium mixtures of two isomers (A and B). The structures of equilibrium mixture in the solid state have been studied by NMR, ATR-FTIR and X-Ray methods. The deprotonation of three studied compounds (salDAMN, 5-BrsalDAMN, and 5-CH3salDAMN) proceeded in two different ways: deprotonation of oxygen atom (X form) or of nitrogen atom of free primary amine group of DAMN moiety (Y form). For 5-NO2salDAMN and naphDAMN only one form (X) was observed.

Synthesis, spectral characterization, structural investigation and antimicrobial studies of mononuclear Cu(II), Ni(II), Co(II), Zn(II) and Cd(II) complexes of a new potentially hexadentate N2O4 Schiff base ligand derived from salicylaldehyde

NASA Astrophysics Data System (ADS)

Keypour, Hassan; Shayesteh, Maryam; Rezaeivala, Majid; Chalabian, Firoozeh; Elerman, Yalcin; Buyukgungor, Orhan

2013-01-01

A new potentially hexadentate N2O4 Schiff base ligand, H2L derived from condensation reaction of an aromatic diamine and salicylaldehyde, and its metal complexes were characterized by elemental analyses, IR, UV-Vis, EI-MS, 1H and 13C NMR spectra, as well as conductance measurements. It has been originated that the Schiff base ligand with Cu(II), Ni(II), Co(II), Cd(II) and Zn(II) ions form mononuclear complexes on 1:1 (metal:ligand) stoichiometry. The conductivity data confirm the non-electrolytic nature of the complexes. Also the crystal structures of the complexes [ZnL] and [CoL] have also been determined by using X-ray crystallographic technique. The Zn(II) and Co(II) complexes show a tetrahedral configuration. Electronic absorption spectra of the Cu(II) and Ni(II) complexes suggest a square-planar geometry around the central metal ion. The synthesized compounds have antibacterial activity against the three Gram-positive bacteria: Bacillus cereus, Enterococcus faecalis and Listeria monocytogenes and also against the three Gram-negative bacteria: Salmonella paraB, Citrobacter freundii and Enterobacter aerogenes. The results showed that in some cases the antibacterial activity of complexes were more than nalidixic acid and amoxicillin as standards.

Green synthesis of nano sized transition metal complexes containing heterocyclic Schiff base: Structural and morphology characterization and bioactivity study

NASA Astrophysics Data System (ADS)

Jawoor, Shailaja S.; Patil, Sangamesh A.; Kumbar, Mahantesh; Ramawadgi, Prashant B.

2018-07-01

In the current involvement of our research work in coordination chemistry, novel transition metal complexes were synthesized from regular reflux method and hydrothermal method using Schiff base prepared via condensation of ethyl 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate with 8-carbaldehyde-7-hydroxy-4-methylcoumarin. All the synthesized compounds were interpreted using different analytical, physicochemical and spectral methods such as magnetic moment measurement, FT-IR, 1H and 13C NMR, GCMS/ESI-MS, UV/Vis spectroscopy and TGA. The size and morphology of the nano metal complexes were determined using atomic force microscope (AFM), field emission scanning electron spectroscopy (FE-SEM) and X-ray powder diffraction (PXRD). The non-electrolytic nature of the metal complexes was confirmed by molar conductance studies. The obtained FT-IR data supports the binding of metal ion to Schiff base. Elemental analysis study suggests [ML2(H2O)2] stoichiometry, here M = Co(II), Ni(II) and Cu(II), L = deprotonated ligand. Electronic spectral results reveal six-coordinated geometry for the synthesized metal complexes. All the tested compounds show good DNA cleavage (Calf Thymus DNA) and in vitro anticancer activity (PA-I cell line), the activity results for the tested compounds are prominent and compound 9 exhibited a little enhanced activity than the other tested compounds.

Synthesis, crystal structure and interaction of L-valine Schiff base divanadium(V) complex containing a V2O3 core with DNA and BSA.

PubMed

Guo, Qiong; Li, Lianzhi; Dong, Jianfang; Liu, Hongyan; Xu, Tao; Li, Jinghong

2013-04-01

A divanadium(V) complex, [V2O3(o-van-val)2] (o-van-val=Schiff base derived from o-vanillin and L-valine), has been synthesized and structurally characterized. The crystal structure shows that both of the vanadium centers in the complex have a distorted octahedral coordination environment composed of tridentate Schiff base ligand. A V2O3 core in molecular structure adopts intermediate between cis and trans configuration with the O1V1⋯V1AO1A torsion angle 115.22 (28)° and the V1⋯V1A distance 3.455Å. The binding properties of the complex with calf thymus DNA (CT-DNA) have been investigated by UV-vis absorption, fluorescence, CD spectra and viscosity measurement. The results indicate that the complex binds to CT-DNA in non-classical intercalative mode. Meanwhile, the interaction of the complex with bovine serum albumin (BSA) has been studied by UV-vis absorption, fluorescence and CD spectra. Results indicated that the complex can markedly quench the intrinsic fluorescence of BSA via a static quenching process, and cause its conformational change. The calculated apparent binding constant Kb was 1.05×10(6)M(-1) and the binding site number n was 1.18. Copyright © 2013 Elsevier B.V. All rights reserved.

Mesoporous silica nanoparticles supported copper(II) and nickel(II) Schiff base complexes: Synthesis, characterization, antibacterial activity and enzyme immobilization

NASA Astrophysics Data System (ADS)

Tahmasbi, Leila; Sedaghat, Tahereh; Motamedi, Hossein; Kooti, Mohammad

2018-02-01

Mesoporous silica nanoparticles (MSNs) were prepared by sol-gel method and functionalized with 3-aminopropyltriethoxysilane. Schiff base grafted mesoporous silica nanoparticle was synthesized by the condensation of 2-hydroxy-3-methoxybenzaldehyde and amine-functionalized MSNs. The latter material was then treated with Cu(II) and Ni(II) salts separately to obtain copper and nickel complexes anchored mesoporous composites. The newly prepared hybrid organic-inorganic nanocomposites have been characterized by several techniques such as FT-IR, LA-XRD, FE-SEM, TEM, EDS, BET and TGA. The results showed all samples have MCM-41 type ordered mesoporous structure and functionalization occurs mainly inside the mesopore channel. The presence of all elements in synthesized nanocomposites and the coordination of Schiff base via imine nitrogen and phenolate oxygen were confirmed. MSNs and all functionalized MSNs have uniform spherical nanoparticles with a mean diameter less than 100 nm. The as-synthesized mesoporous nanocomposites were investigated for antibacterial activity against Gram-positive (B. subtilis and S. aureus) and Gram-negative (E. coli and P. aeruginosa) bacteria, as carrier for gentamicin and also for immobilization of DNase, coagulase and amylase enzymes. MSN-SB-Ni indicated bacteriocidal effect against S.aureus and all compounds were found to be good carrier for gentamicin. Results of enzyme immobilization for DNase and coagulase and α-amylase revealed that supported metal complexes efficiently immobilized enzymes.

Antibody-catalyzed benzoin oxidation as a mechanistic probe for nucleophilic catalysis by an active site lysine.

PubMed

Sklute, Genia; Oizerowich, Rachel; Shulman, Hagit; Keinan, Ehud

2004-05-03

Aldolase antibody 24H6, which was obtained by reactive immunization against a 1,3-diketone hapten, is shown to catalyze additional reactions, including H/D exchange and oxidation reactions. Comparison of the H/D exchange reaction at the alpha-position of a wide range of aldehydes and ketones by 24H6 and by other aldolase antibodies, such as 38C2, pointed at the significantly larger size of the 24H6 active site. This property allowed for the catalysis of the oxidation of substituted benzoins to benzils by potassium ferricyanide. This reaction was used as a mechanistic probe to learn about the initial steps of the 24H6-catalyzed aldol condensation reaction. The Hammett correlation (rho=4.7) of log(k(cat)) versus the substituent constant, sigma, revealed that the reaction involves rapid formation of a Schiff base intermediate from the ketone and an active site lysine residue. The rate-limiting step in this oxidation reaction is the conversion of the Schiff base to an enamine intermediate. In addition, linear correlation (rho=3.13) was found between log(K(M)) and sigma, indicating that electronic rather than steric factors are dominant in the antibody-substrate binding phenomenon and confirming that the reversible formation of a Schiff base intermediate comprises part of the substrate-binding mechanism.

m-Diethynylbenzene macrocycles: syntheses and self-association behavior in solution.

PubMed

Tobe, Yoshito; Utsumi, Naoto; Kawabata, Kazuya; Nagano, Atsushi; Adachi, Kiyomi; Araki, Shunji; Sonoda, Motohiro; Hirose, Keiji; Naemura, Koichiro

2002-05-15

m-Diethynylbenzene macrocycles (DBMs), buta-1,3-diyne-bridged [4(n)]metacyclophanes, have been synthesized and their self-association behaviors in solution were investigated. Cyclic tetramers, hexamers, and octamers of DBMs having exo-annular octyl, hexadecyl, and 3,6,9-trioxadecyl ester groups were prepared by intermolecular oxidative coupling of dimer units or intramolecular cyclization of the corresponding open-chain oligomers. The aggregation properties were investigated by two methods, the (1)H NMR spectra and the vapor pressure osmometry (VPO). Although some discrepancies were observed between the association constants obtained from the two methods, the qualitative view was consistent with each other. The analysis of self-aggregation by VPO revealed unique aggregation behavior of DBMs in acetone and toluene, which was not elucidated by the NMR method. Namely, the association constants for infinite association are several times larger than the dimerization constant, suggesting that the aggregation is enhanced by the formation of dimers (a nucleation mechanism). In polar solvents, DBMs aggregate more strongly than in chloroform due to the solvophobic interactions between the macrocyclic framework and the solvents. Moreover, DBMs self-associate in aromatic solvents such as toluene and o-xylene more readily than in chloroform. In particular, the hexameric DBM having a large macrocyclic cavity exhibits extremely large association constants in aromatic solvents. By comparing the aggregation properties of DBMs with the corresponding acyclic oligomers, the effect of the macrocyclic structure on the aggregation propensity was clarified. Finally, it turned out that DBMs tend to aggregate more readily than the corresponding phenylacetylene macrocycles, acetylene-bridged [2(n)]metacyclophanes, owing to the withdrawal of the electron density from the aromatic rings by the butadiyne linkages which facilitates pi-pi stacking interactions.

Electroanalytical and naked eye determination of Cu(2+) ion in various environmental samples using 5-amino-1,3,4-thiadiazole-2-thiol based Schiff bases.

PubMed

Bandi, Koteswara Rao; Singh, Ashok Kumar; Upadhyay, Anjali

2014-01-01

Novel polydentate Schiff bases 4-(5-mercapto-1,3,4-thiadiazol-2-ylimino)pentan-2-one (S1) and (2-(indol-3-yl)vinyl)-1,3,4-thiadiazole-2-thiol (S2) were synthesized and explored as Cu(2+) selective polymeric membrane electrodes (PME) using different plasticizers and anionic excluders. The potentiometric data revealed that the PME having the membrane composition (S2: NaTPB: TBP: PVC as 4: 2: 58: 36 (w/w; mg)) is shown to have good results. Thus the coated graphite electrode (CGE) with the same composition as the best PME was also fabricated and investigated as Cu(2+) selective electrode. It was found that CGE showed better response characteristics than PME with respect to low detection limit (1.2×10(-8)molL(-1)), near Nernstian slope (29.8±0.4mV decade(-1) of activity), wide working concentration range (6.4×10(-8)-1.0×10(-1)molL(-1)), long shelf life (90days) and fast response time (9s). The CGE was used successfully as an indicator electrode for the potentiometric determination of Cu(2+) ion against EDTA and also used to quantify Cu(2+) ion in soil, water, medicinal plants, vegetables and edible oil samples. The Schiff base S2 is used as chemosensor for the selective determination of Cu(2+) ion. © 2013.

Synthesis, characterization and biological activity of Cu(II), Ni(II) and Zn(II) complexes of biopolymeric Schiff bases of salicylaldehydes and chitosan.

PubMed

de Araújo, Eliene Leandro; Barbosa, Hellen Franciane Gonçalves; Dockal, Edward Ralph; Cavalheiro, Éder Tadeu Gomes

2017-02-01

Schiff bases have been prepared from biopolymer chitosan and salicylaldehyde, 5-methoxysalicylaldehyde, and 5-nitrosalicylaldehyde. Ligands were synthesized in a 1:1.5mol ratio, and their Cu(II), Ni(II) and Zn(II) complexes in a 1:1mol ratio (ligand:metal). Ligands were characterized by 1 H NMR and FTIR, resulting in degrees of substitution from 43.7 to 78.7%. Complexes were characterized using FTIR, electronic spectra, XPRD. The compounds were confirmed by the presence of an imine bond stretching in the 1630-1640cm -1 and νMetal-N and νMetal-O at <600cm -1 . Electronic spectra revealed that both Cu(II) and Ni(II) complexes present a square plane geometry. The crystallinity values were investigated by X-ray powder diffraction. Thermal behavior of all compounds was evaluated by TGA/DTG and DTA curves with mass losses related to dehydration and decomposition, with characteristic events for ligand and complexes. Schiff base complexes presented lower thermal stability and crystallinity than the starting chitosan. Residues were the metallic oxides as confirmed by XPRD, whose amounts were used in the calculation of the percentage of complexed metal ions. Surface morphologies were analyzed with SEM-EDAX. Preliminary cytotoxicity tests were performed using MTT assay with HeLa cells. Despite the differences in solubility, the free bases presented relatively low toxicity. Copyright © 2016 Elsevier B.V. All rights reserved.

Interpreting medium ring canonical conformers by a triangular plane tessellation of the macrocycle

NASA Astrophysics Data System (ADS)

Khalili, Pegah; Barnett, Christopher B.; Naidoo, Kevin J.

2013-05-01

Cyclic conformational coordinates are essential for the distinction of molecular ring conformers as the use of Cremer-Pople coordinates have illustrated for five- and six-membered rings. Here, by tessellating medium rings into triangular planes and using the relative angles made between triangular planes we are able to assign macrocyclic pucker conformations into canonical pucker conformers such as chairs, boats, etc. We show that the definition is straightforward compared with other methods popularly used for small rings and that it is computationally simple to implement for complex macrocyclic rings. These cyclic conformational coordinates directly couple to the motion of individual nodes of a ring. Therefore, they are useful for correlating the physical properties of macrocycles with their ring pucker and measuring the dynamic ring conformational behavior. We illustrate the triangular tessellation, assignment, and pucker analysis on 7- and 8-membered rings. Sets of canonical states are given for cycloheptane and cyclooctane that have been previously experimentally analysed.

Lysine-Tryptophan-Crosslinked Peptides Produced by Radical SAM Enzymes in Pathogenic Streptococci.

PubMed

Schramma, Kelsey R; Seyedsayamdost, Mohammad R

2017-04-21

Macrocycles represent a common structural framework in many naturally occurring peptides. Several strategies exist for macrocyclization, and the enzymes that incorporate them are of great interest, as they enhance our repertoire for creating complex molecules. We recently discovered a new peptide cyclization reaction involving a crosslink between the side chains of lysine and tryptophan that is installed by a radical SAM enzyme. Herein, we characterize relatives of this metalloenzyme from the pathogens Streptococcus agalactiae and Streptococcus suis. Our results show that the corresponding enzymes, which we call AgaB and SuiB, contain multiple [4Fe-4S] clusters and catalyze Lys-Trp crosslink formation in their respective substrates. Subsequent high-resolution-MS and 2D-NMR analyses located the site of macrocyclization. Moreover, we report that AgaB can accept modified substrates containing natural or unnatural amino acids. Aside from providing insights into the mechanism of this unusual modification, the substrate promiscuity of AgaB may be exploited to create diverse macrocyclic peptides.

A superconducting gyroscope to test Einstein's general theory of relativity

NASA Technical Reports Server (NTRS)

Everitt, C. W. F.

1978-01-01

Schiff (1960) proposed a new test of general relativity based on measuring the precessions of the spin axes of gyroscopes in earth orbit. Since 1963 a Stanford research team has been developing an experiment to measure the two effects calculated by Schiff. The gyroscope consists of a uniform sphere of fused quartz 38 mm in diameter, coated with superconductor, electrically suspended and spinning at about 170 Hz in vacuum. The paper describes the proposed flight apparatus and the current state of development of the gyroscope, including techniques for manufacturing and measuring the gyro rotor and housing, generating ultralow magnetic fields, and mechanizing the readout.

Phenoxyacetohydrazide Schiff bases: β-glucuronidase inhibitors.

PubMed

Jamil, Waqas; Perveen, Shagufta; Shah, Syed Adnan Ali; Taha, Muhammad; Ismail, Nor Hadiani; Perveen, Shahnaz; Ambreen, Nida; Khan, Khalid M; Choudhary, Muhammad I

2014-06-25

Phenoxyacetohydrazide Schiff base analogs 1-28 have been synthesized and their in vitro β-glucouoronidase inhibition potential studied. Compounds 1 (IC50=9.20±0.32 µM), 5 (IC50=9.47±0.16 µM), 7 (IC50=14.7±0.19 µM), 8 (IC50=15.4±1.56 µM), 11 (IC50=19.6±0.62 µM), 12 (IC50=30.7±1.49 µM), 15 (IC50=12.0±0.16 µM), 21 (IC50=13.7±0.40 µM) and 22 (IC50=22.0±0.14 µM) showed promising β-glucuronidase inhibition activity, better than the standard (D-saccharic acid-1,4-lactone, IC50=48.4±1.25 µM).

Pyrrole-Based Macrocyclic Small-Molecule Inhibitors That Target Oocyte Maturation.

PubMed

Gunasekaran, Pethaiah; Lee, So-Rim; Jeong, Seung-Min; Kwon, Jeong-Woo; Takei, Toshiki; Asahina, Yuya; Bang, Geul; Kim, Seongnyeon; Ahn, Mija; Ryu, Eun Kyung; Kim, Hak Nam; Nam, Ki-Yub; Shin, Song Yub; Hojo, Hironobu; Namgoong, Suk; Kim, Nam-Hyung; Bang, Jeong Kyu

2017-04-20

Polo-like kinase 1 (PLK1) plays crucial roles in various stages of oocyte maturation. Recently, we reported that the peptidomimetic compound AB103-8, which targets the polo box domain (PBD) of PLK1, affects oocyte meiotic maturation and the resumption of meiosis. However, to overcome the drawbacks of peptidic compounds, we designed and synthesized a series of pyrrole-based small-molecule inhibitors and tested them for their effects on the rates of porcine oocyte maturation. Among them, the macrocyclic compound (E/Z)-3-(2,16-dioxo-19-(4-phenylbutyl)-3,19-diazabicyclo[15.2.1]icosa-1(20),6,17-trien-3-yl)propyl dihydrogen phosphate (4) showed the highest inhibitory activity with enhanced inhibition against embryonic blastocyst formation. Furthermore, the addition of this compound to culture media efficiently blocked the maturation of porcine and mouse oocytes, indicating its ability to penetrate the zona pellucida and cell membrane. We investigated mouse oocytes treated with compound 4, and the resulting impairment of spindle formation confirmed PLK1 inhibition. Finally, molecular modeling studies with PLK1 PBD also confirmed the presence of significant interactions between compound 4 and PLK1 PBD binding pocket residues, including those in the phosphate, tyrosine-rich, and pyrrolidine binding pockets. Collectively, these results suggest that the macrocyclic compound 4 may serve as a promising template for the development of novel contraceptive agents. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chiral Recognition with Macrocyclic Glycopeptides: Mechanisms and Applications

NASA Astrophysics Data System (ADS)

Berthod, Alain; Qiu, Hai Xiao; Staroverov, Sergey M.; Kuznestov, Mikhail A.; Armstrong, Daniel W.

The macrocyclic glycopeptide chiral selectors are natural molecules produced by bacterial fermentation. Purified and bonded to silica particles, they make very useful chiral stationary phases (CSP) with a broad spectrum of applicability in enantiomeric separation. The macrocyclic glycopeptide CSPs are multimodal, the same column being able to work in normal phase mode with apolar mobile phase, in reversed-phase mode, or in polar ionic mode with 100% alcoholic mobile phase of adjusted pH. The role of the carbohydrate units is described as well as the critical charge-charge docking interaction responsible for the amino acid enantiomer recognition. The complimentary phenomenon is also exposed.

New macrocyclic lactones with acaricidal and nematocidal activities from a genetically engineered strain Streptomyces bingchenggensis BCJ60.

PubMed

Li, Jian-Song; Zhang, Hui; Zhang, Shao-Yong; Wang, Hai-Yan; Zhang, Ji; Chen, An-Liang; Wang, Ji-Dong; Xiang, Wen-Sheng

2017-04-01

Two new macrocyclic lactones, 4,25-diethyl-4,25-demethyl-milbemycin β 3 (1) and 27-formaldehyde-milbemycin β 14 (2), were isolated from a genetically engineered strain Streptomyces bingchenggensis BCJ60. Their structures were determined on the basis of spectroscopic analysis, including 1D and 2D NMR techniques as well as ESI-MS and comparison with data from the literature. The acaricidal and nematocidal capacities of compounds 1 and 2 were evaluated against Tetranychus cinnabarinus and Bursaphelenchus xylophilus, respectively. The results showed that the two new macrocyclic lactones 1 and 2 possessed potent acaricidal and nematocidal activities.

A Macrocyclic β-Iodoallenolate Intermediate is Key: Synthesis of the ABD Core of Phomactin A

PubMed Central

Ciesielski, Jennifer; Cariou, Kevin

2012-01-01

An enantioselective strategy for the synthesis of phomactin natural products is described. The Lewis acid-triggered cyclization of a β-iodoallenolate embedded in a 12-membered macrocycle was used to obtain a highly functionalized bicyclo[9.3.1]pentadecane in good yield and high diastereoselectivity. This iodoenone contains the substituents of the AD ring system of the phomactin family of natural products, appropriate for further functionalization. Synthesis of the oxadecalin core of phomactin A from the AD iodoenone intermediate was achieved. In this unusual strategy, rings A and B are both fashioned within a macrocyclic precursor. PMID:22853449

2 H-1,2,3-Triazole-Based Dipeptidyl Nitriles: Potent, Selective, and Trypanocidal Rhodesain Inhibitors by Structure-Based Design.

PubMed

Giroud, Maude; Kuhn, Bernd; Saint-Auret, Sarah; Kuratli, Christoph; Martin, Rainer E; Schuler, Franz; Diederich, François; Kaiser, Marcel; Brun, Reto; Schirmeister, Tanja; Haap, Wolfgang

2018-04-26

Macrocyclic inhibitors of rhodesain (RD), a parasitic cysteine protease and drug target for the treatment of human African trypanosomiasis, have shown low metabolic stability at the macrocyclic ether bridge. A series of acyclic dipeptidyl nitriles was developed using structure-based design (PDB ID: 6EX8 ). The selectivity against the closely related cysteine protease human cathepsin L (hCatL) was substantially improved, up to 507-fold. In the S2 pocket, 3,4-dichlorophenylalanine residues provided high trypanocidal activities. In the S3 pocket, aromatic residues provided enhanced selectivity against hCatL. RD inhibition ( K i values) and in vitro cell-growth of Trypanosoma brucei rhodesiense (IC 50 values) were measured in the nanomolar range. Triazole-based ligands, obtained by a safe, gram-scale flow production of ethyl 1 H-1,2,3-triazole-4-carboxylate, showed excellent metabolic stability in human liver microsomes and in vivo half-lives of up to 1.53 h in mice. When orally administered to infected mice, parasitaemia was reduced but without complete removal of the parasites.

A macrocyclic ellagitannin trimer, oenotherin T(1), from Oenothera species.

PubMed

Taniguchi, Shoko; Imayoshi, Yoko; Yabu-uchi, Ryoko; Ito, Hideyuki; Hatano, Tsutomu; Yoshida, Takashi

2002-01-01

Oenotherin T(1) was isolated from leaves of Oenothera tetraptera as a major ellagitannin. Its structure, that of a macrocyclic trimer with a new acyl group, an isodehydrovaloneoyl group, was established. This compound was also produced by callus tissues induced from O. laciniata leaves.

Photoswitchable Dihydroazulene Macrocycles for Solar Energy Storage: The Effects of Ring Strain.

PubMed

Vlasceanu, Alexandru; Frandsen, Benjamin N; Skov, Anders B; Hansen, Anne Schou; Rasmussen, Mads Georg; Kjaergaard, Henrik G; Mikkelsen, Kurt V; Nielsen, Mogens Brøndsted

2017-10-06

Efficient energy storage and release are two major challenges of solar energy harvesting technologies. The development of molecular solar thermal systems presents one approach to address these issues by tuning the isomerization reactions of photo/thermoswitches. Here we show that the incorporation of photoswitches into macrocyclic structures is a particularly attractive solution for increasing the storage time. We present the synthesis and properties of a series of macrocycles incorporating two dihydroazulene (DHA) photoswitching subunits, bridged by linkers of varying chain length. Independent of ring size, all macrocycles exhibit stepwise, light-induced, ring-opening reactions (DHA-DHA to DHA-VHF to VHF-VHF; VHF = vinylheptafulvene) with the first DHA undergoing isomerization with a similar efficiency as the uncyclized parent system while the second (DHA-VHF to VHF-VHF) is significantly slower. The energy-releasing, VHF-to-DHA, ring closures also occur in a stepwise manner and are systematically found to proceed slower in the more strained (smaller) cycles, but in all cases with a remarkably slow conversion of the second VHF to DHA. We managed to increase the half-life of the second VHF-to-DHA conversion from 65 to 202 h at room temperature by simply decreasing the ring size. A computational study reveals the smallest macrocycle to have the most energetic VHF-VHF state and hence highest energy density.

The hydrophobic substituent in aminophospholipids affects the formation kinetics of their Schiff bases.

PubMed

Caldés, Catalina; Vilanova, Bartolomé; Adrover, Miquel; Donoso, Josefa; Muñoz, Francisco

2013-04-01

Schiff bases (SBs) are the initial products of non-enzymatic glycation reactions, which are associated to some diabetes-related diseases. In this work, we used physiological pH and temperature conditions to study the formation kinetics of the SBs of 1,2-dihexanoyl-sn-glycero-3-phosphoethanolamine (DPHE) and 1,2-dihexanoyl-sn-glycero-3-phospho-l-serine (DHPS) with various glycating compounds and with pyridoxal 5'-phosphate (an effective glycation inhibitor). Based on the obtained results, the hydrophobic environment simultaneously decreases the nucleophilic character of the amino group (k1) and increases its pKa, thereby increasing the formation rate of SB (kobs). Therefore, the presence of hydrophobic chains in aminophospholipids facilitates the formation and stabilization of SBs, and also, in a biological environment, their glycation. Additionally, the results confirm the inhibitory action of B6 vitamers on aminophospholipid glycation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Optoelectronic and Photovoltaic Performances of Pyridine Based Monomer and Polymer Capped ZnO Dye-Sensitized Solar Cells.

PubMed

Singh, Satbir; Raj, Tilak; Singh, Amarpal; Kaur, Navneet

2016-06-01

The present research work describes the comparative analysis and performance characteristics of 4-pyridine based monomer and polymer capped ZnO dye-sensitized solar cells. The N, N-dimethyl-N4-((pyridine-4yl)methylene) propaneamine (4,monomer) and polyamine-4-pyridyl Schiff base (5, polymer) dyes were synthesized through one step condensation reaction between 4-pyridinecarboxaldehyde 1 and N, N-dimethylpropylamine 2/polyamine 3. Products obtained N, N-dimethyl-N4-((pyridine-4yl)methylene)propaneamine (4) and polyamine-4-pyridyl Schiff base (5) were purified and characterized using 1H, 13C NMR, mass, IR and CHN spectroscopy. Both the dyes 4 and 5 were further coated over ZnO nanoparticles and characterized using SEM, DLS and XRD analysis. Absorption profile and emission profile was monitored using fluorescence and UV-Vis absorption spectroscopy. A thick layer of these inbuilt dye linked ZnO nanoparticles of dyes (4) and (5) was pasted on one of the conductive side of ITO glass followed with a liquid electrolyte and counter electrode of the same conductive glass. Polyamine-4-pyridyl Schiff base polymer (5) decorated dye sensitized solar cell has shown better exciting photovoltaic properties in the form of short circuit current density (J(sc) = 6.3 mA/cm2), open circuit photo voltage (V(oc) = 0.7 V), fill factor (FF = 0.736) than monomer decorated dye sensitized solar cell. Polymer dye (5) based ZnO solar cell has shown a maximum solar power to electrical conversion efficiency of 3.25%, which is enhanced by 2.16% in case of monomer dye based ZnO solar cell under AM 1.5 sun illuminations.

Effect of intramolecular charge transfer on fluorescence and singlet oxygen production of phthalocyanine analogues.

PubMed

Vachova, Lenka; Novakova, Veronika; Kopecky, Kamil; Miletin, Miroslav; Zimcik, Petr

2012-10-14

Intramolecular charge transfer (ICT) was studied on a series of magnesium, metal-free and zinc complexes of unsymmetrical tetrapyrazinoporphyrazines and tribenzopyrazinoporphyrazines bearing two dialkylamino substituents (donors) and six alkylsulfanyl or aryloxy substituents (non-donors). The dialkylamino substituents were responsible for ICT that deactivated excited states and led to considerable decrease of fluorescence and singlet oxygen quantum yields. Photophysical and photochemical properties were compared to corresponding macrocycles that do not bear any donor centers. The data showed high feasibility of ICT in the tetrapyrazinoporphyrazine macrocycle and significantly lower efficiency of this deactivation process in the tribenzopyrazinoporphyrazine type molecules. Considerable effect of non-donor peripheral substituents on ICT was also described. The results imply that tetrapyrazinoporphyrazines may be more suitable for development of new molecules investigated in applications based on ICT.

Photochemical Dual-Catalytic Synthesis of Alkynyl Sulfides.

PubMed

Santandrea, Jeffrey; Minozzi, Clémentine; Cruché, Corentin; Collins, Shawn K

2017-09-25

A photochemical dual-catalytic cross-coupling to form alkynyl sulfides via C(sp)-S bond formation is described. The cross-coupling of thiols and bromoalkynes is promoted by a soluble organic carbazole-based photocatalyst using continuous flow techniques. Synthesis of alkynyl sulfides bearing a wide range of electronically and sterically diverse aromatic alkynes and thiols can be achieved in good to excellent yields (50-96 %). The simple continuous flow setup also allows for short reaction times (30 min) and high reproducibility on gram scale. In addition, we report the first application of photoredox/nickel dual catalysis towards macrocyclization, as well as the first example of the incorporation of an alkynyl sulfide functional group into a macrocyclic scaffold. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photophysics of a coumarin based Schiff base in solvents of varying polarities

NASA Astrophysics Data System (ADS)

Ghosh, Saptarshi; Roy, Nayan; Singh, T. Sanjoy; Chattopadhyay, Nitin

2018-01-01

The present work reports detailed photophysics of a coumarin based Schiff base, namely, (E)-7-(((8-hydroxyquinolin-2-yl)methylene)amino)-4-methyl-2H-chromen-2-one (HMC) in different solvents of varying polarity exploiting steady state absorption, fluorescence and time resolved fluorescence spectroscopy. The dominant photophysical features of HMC are discussed in terms of emission from an intramolecular charge transfer (ICT) excited state. Molecular orbital (MO) diagrams as obtained from DFT based computational analysis confirms the occurrence of charge transfer from 8‧-hydroxy quinoline moiety of the molecule to the coumarin part. The notable difference in the photophysical response of HMC from its analogous coumarin (C480) lies in a lower magnitude of fluorescence quantum yield of the former, particularly in the solvents of low polarity, which is rationalized by considering the higher rate of non-radiative decay of HMC in apolar solvents. Phosphorescence emission as well as phosphorescence lifetime of HMC has also been reported in 77 K frozen matrix.

LANTHANIDE ENHANCE LUMINESCENCE (LEL) WITH ONE AND TWO PHOTON EXCITATION OF QUANTUM DYES LANTHANIDE (III) - MACROCYCLES

EPA Science Inventory

Title: Lanthanide Enhance Luminescence (LEL) with one and two photon excitation of Quantum Dyes? Lanthanide(III)-Macrocycles
Principal Author:
Robert C. Leif, Newport Instruments
Secondary Authors:
Margie C. Becker, Phoenix Flow Systems
Al Bromm, Virginia Commonw...

Metacridamides A and B, bioactive macrocycles from conidia of the entomopathogenic fungus Metarhizium acridum

USDA-ARS?s Scientific Manuscript database

Metarhizium acridum, an entomopathogenic fungus, has been commercialized and used successfully for biocontrol of grasshopper pests in Africa and Australia. Its conidia produce two novel 17-membered macrocycles, metacridamides A (1) and B (2), which consist of a Phe unit condensed with a nonaketide....

Synthesis, X-ray crystal structure, photo luminescent property, antimicrobial activities and DFT computational study of Zn(II) coordination polymer derived from multisite N,O donor Schiff base ligand (H2L1)

NASA Astrophysics Data System (ADS)

Majumdar, Dhrubajyoti; Surendra Babu, M. S.; Das, Sourav; Biswas, Jayanta Kumar; Mondal, Monojit; Hazra, Suman

2017-06-01

A unique thiocyanato linked 1D chain of Zn(II) coordination polymer [Zn2L1(μ1,3-SCN)(η1SCN)]n (1) has been synthesized using potential multisite compartmental N,O donor Schiff base blocker ligand (L1H2) in presence of Zn(OAc)2 and KSCN. The Schiff base ligand [N, N‧-bis(3-methoxysalicylidenimino)-1,3-daminopropane] (L1H2) is 2:1 M ratio condensation product of O-vaniline and 1,3-diaminopropane in methanol medium. The characterization of Complex 1 was accomplished by means of different micro analytical techniques like elemental analyses, IR, UV-Vis, 1H NMR, emission spectroscopy and Single X-ray crystallographic study. Complex 1 crystallizes in Orthorhombic system, space group Pbca, with values a = 11.579(2), b = 18.538(3), and c = 22.160(4) Å; α = β = γ = 90.00°; V = 4756.6(14) and Z = 8. The single crystal X-ray revealed that the one dimensional chain system with the repeating unit [Zn2(μ1,3-SCN)(η1SCN)(L1)]n bridge by an end to end μ1,3 thiocyanate anion. Within each repeating unit two different types of Zn(II) ions are present. One of these is five-coordinate in a square pyramidal geometry while the other is six-coordinate in an octahedral geometry. A brief but lucid comparative approach has been demonstrated in between Schiff base (L1H2) and complex 1 with respect to their photoluminescence activities. Active luminescence behavior of complex 1 in presence of ligand (L1H2) is due to quenching of PET process which is mediated by 'chelating effect'. Complex 1 exhibits strong antimicrobial efficacy against some important Gram + ve and Gram -ve bacteria. Apart from antimicrobial potential, a combined experimental and theoretical investigation has been performed via DFT on molecular structure of complex 1 with respect to Hirshfeld surface analysis.

Structural changes due to the deprotonation of the proton release group in the M-photointermediate of bacteriorhodopsin as revealed by time-resolved FTIR spectroscopy.

PubMed

Morgan, Joel E; Vakkasoglu, Ahmet S; Lugtenburg, Johan; Gennis, Robert B; Maeda, Akio

2008-11-04

One of the steps in the proton pumping cycle of bacteriorhodopsin (BR) is the release of a proton from the proton-release group (PRG) on the extracellular side of the Schiff base. This proton release takes place shortly after deprotonation of the Schiff base (L-to-M transition) and results in an increase in the pKa of Asp85, which is a crucial mechanistic step for one-way proton transfer for the entire photocycle. Deprotonation of the PRG can also be brought about without photoactivation, by raising the pH of the enzyme (pKa of PRG; approximately 9). Thus, comparison of the FTIR difference spectrum for formation of the M intermediate (M minus initial unphotolyzed BR state) at pH 7 to the corresponding spectrum generated at pH 10 may reveal structural changes specifically associated with deprotonation of the PRG. Vibrational bands of BR that change upon M formation are distributed across a broad region between 2120 and 1685 cm(-1). This broad band is made up of two parts. The band above 1780 cm(-1), which is insensitive to C15-deuteration of the retinal, may be due to a proton delocalized in the PRG. The band between 1725 and 1685 cm(-1), on the lower frequency side of the broad band, is sensitive to C15-deuteration. This band may arise from transition dipole coupling of the vibrations of backbone carbonyl groups in helix G with the side chain of Tyr57 and with the C15H of the Schiff base. In M, these broad bands are abolished, and the 3657 cm(-1) band, which is due to the disruption of the hydrogen bonding of a water molecule, probably with Arg82, appears. Loss of the interaction of the backbone carbonyl groups in helix G with Tyr57 and the Schiff base, and separation of Tyr57 from Arg82, may be causes of these spectral changes, leading to the stabilization of the protonated Asp85 in M.

Synthesis and Characterization of Macrocyclic Polyether N,N'-Diallyl-7,16-diaza-1,4,10,13-tetraoxa-dibenzo-18-crown-6.

PubMed

Toeri, Julius; Laborie, Marie-Pierre

2016-01-29

In this study an efficient and direct production procedure for a macrocyclic polyether N,N'-diallyl-7,16-diaza-1,4,10,13-tetraoxa-dibenzo-18-crown-6 from the reaction of catechol and N,N-bis(2-chloroethyl)prop-2-en-1-amine in n-butanol in the presence of a strong base is reported. The synthesis involves a two-step addition of sodium hydroxide to enhance the cyclization process, and at the end of the reaction, the reaction mixture is neutralized and the solvent replaced with water in-situ through distillation to afford a relatively pure precipitate that is easily recrystallized from acetone. The yield of the macrocycle was 36%-45% and could be scaled-up to one-mole quantities. The structure and purity of this compound was verified on the basis of elemental analysis, IR, UV-Vis, ¹H-, (13)C-NMR, 2D-NMR, mass spectroscopy, and thermal analysis. The white crystalline compound has a sharp melting point of 124 °C and a crystallization temperature of 81.4 °C determined by differential scanning calorimetry. Our motivation behind the synthesis of the bibracchial lariat azacrown polyether ligand was to examine its possible applications in ion-selective polymer-supported materials.

Occurrence of Stachybotrys chartarum chemotype S in dried culinary herbs.

PubMed

Biermaier, Barbara; Gottschalk, Christoph; Schwaiger, Karin; Gareis, Manfred

2015-02-01

Stachybotrys (S.) chartarum is an omnipresent cellulolytic mould which produces secondary metabolites, such as the highly toxic macrocyclic trichothecenes. While it is known to occur in animal feed like hay and straw as well as in water-damaged indoor environments, there is little knowledge about the occurrence of S. chartarum and its secondary metabolites in food. The objective of the present study was to examine selected dried culinary herbs for the presence of S. chartarum chemotype S, to assess the potential risk of a contamination of foods with macrocyclic trichothecenes. In total, 50 Stachybotrys isolates from different types of culinary herbs (n=100) such as marjoram (Origanum majorana Linné (L.)), oregano (Origanum vulgare L.), thyme (Thymus vulgaris L.), and savory (Satureja hortensis L.) were examined by MTT-cell culture test (effect-based bioassay), ELISA, and by liquid chromatography tandem mass spectrometry (LC-MS/MS). Selected toxic and non-toxic isolates (n=15) were genetically characterized by PCR and sequencing. Five isolates (10%) were highly toxic in the MTT-cell culture test, and the production of macrocyclic trichothecenes was proven by ELISA and LC-MS/MS. These five isolates were genetically confirmed as S. chartarum chemotype S. To the best of our knowledge, this is the first report about a contamination of dried culinary herbs with toxigenic S. chartarum.

Reactivity-based drug discovery using vitamin B(6)-derived pharmacophores.

PubMed

Wondrak, Georg T

2008-05-01

Endogenous reactive intermediates including photoexcited states of tissue chromophores, reactive oxygen species (ROS), reactive carbonyl species (RCS), transition metal ions, and Schiff bases have been implicated in the initiation and progression of diverse human pathologies including tumorigenesis, atherosclerosis, diabetes, and neurodegenerative disease. In contrast to structure-based approaches that target macromolecules by selective ligands, reactivity-based drug discovery uses chemical reagents as therapeutics that target reactive chemical species involved in human pathology. Reactivity-based design of prototype agents that effectively antagonize, modulate, and potentially even reverse the chemistry underlying tissue damage from oxidative and carbonyl stress therefore holds great promise in delivering significant therapeutic benefit. Apart from its established role as an essential cofactor for numerous enzymes, a large body of evidence suggests that B(6)-vitamers contain reactive pharmacophores that mediate therapeutically useful non-vitamin drug actions as potent antioxidants, metal chelators, carbonyl scavengers, Schiff base forming agents, and photosensitizers. Based on the fascinating chemical versatility of B(6)-derived pharmacophores, B(6)-vitamers are therefore promising lead compounds for reactivity-based drug design.

Synthesis, Characterization and Biological Studies of New Linear Thermally Stable Schiff Base Polymers with Flexible Spacers.

PubMed

Qureshi, Farah; Khuhawar, Muhammad Yar; Jahangir, Taj Muhammad; Channar, Abdul Hamid

2016-01-01

Five new linear Schiff base polymers having azomethine structures, ether linkages and extended aliphatic chain lengths with flexible spacers were synthesized by polycondensation of dialdehyde (monomer) with aliphatic and aromatic diamines. The formation yields of monomer and polymers were obtained within 75-92%. The polymers with flexible spacers of n-hexane were somewhat soluble in acetone, chloroform, THF, DMF and DMSO on heating. The monomer and polymers were characterized by melting point, elemental microanalysis, FT-IR, (1)HNMR, UV-Vis spectroscopy, thermogravimetry (TG), differential thermal analysis (DTA), fluorescence emission, scanning electron microscopy (SEM) and viscosities and thermodynamic parameters measurements of their dilute solutions. The studies supported formation of the monomer and polymers and on the basis of these studies their structures have been assigned. The synthesized polymers were tested for their antibacterial and antifungal activities.

Fluorescence properties of Schiff base - N,N‧-bis(salicylidene) - 1,2-Phenylenediamine in presence of bile acid host

NASA Astrophysics Data System (ADS)

Roy, Nayan; Paul, Pradip C.; Singh, T. Sanjoy

2015-05-01

Fluorescence properties of Schiff base - N,N‧-bis(salicylidene) - 1,2-phenylenediamine (LH2) is used to study the micelles formed by aggregation of different important bile acids like cholic acid, deoxycholic acid, chenodeoxycholic acid and glycocholic acid by steady state and picosecond time-resolved fluorescence spectroscopy. The fluorescence band intensity was found out to increase with concomitant red shift with gradual addition of different bile acids. Binding constant of the probe with different bile acids as well as critical micelle concentration was obtained from the variation of fluorescence intensity on increasing concentration of bile acids in the medium. The increase in fluorescence quantum yields, fluorescence decay times and substantial decrease in nonradiative decay rate constants in bile acids micellar environment points to the restricted motion of the fluorophore inside the micellar subdomains.

Synthesis and characterization of Heck-cross coupling 4-(4-nitrostyryl) aniline as potential precursor in Schiff-base synthesis

NASA Astrophysics Data System (ADS)

Hassan, Norhafiefa; Izwani, Fatin; Yusoff, H. M.

2017-09-01

This is a preliminary study of alkoxy substituted Heck-schiff base compound as recognition layer in electrochemical DNA sensor for liver cancer. 4-(4-nitrostyryl)aniline was synthesized by bis (triphenylphosphine) palladium (II) dichloride as catalyst and has been characterized by using Fourier transform-infrared spectrometer (FTIR), UV-Vis spectrophotometer and Nuclear Magnetic Resonance (NMR) spectra. The result obtained from FTIR show that there are formation of N=O (NO2) asymmetric stretching vibrations 1340 cm-1. In UV-vis, absorbance of NO2 can be observed at peak 410 nm. While in the 1H NMR and 13C NMR the peak of C-C coupling was found in the range of δH 6.84-7.09 ppm and δC 125.23 ppm.

Carbonic anhydrase inhibition of Schiff base derivative of imino-methyl-naphthalen-2-ol: Synthesis, structure elucidation, molecular docking, dynamic simulation and density functional theory calculations

NASA Astrophysics Data System (ADS)

Abbas, Saghir; Nasir, Hafiza Huma; Zaib, Sumera; Ali, Saqib; Mahmood, Tariq; Ayub, Khurshid; Tahir, Muhammad Nawaz; Iqbal, Jamshed

2018-03-01

In the present study, we have designed and synthesized a Schiff base derivative 3 and characterized by FT-IR, 1H and 13C NMR spectroscopy. Single crystal X-ray diffraction and NMR studies were also performed. The synthetic compound was screened for its inhibitory potential against carbonic anhydrase II. The experimental results were validated by molecular docking and dynamic simulations of compound 3 in the active pocket of enzyme. Important binding interactions with the key residues in the active site of the carbonic anhydrase enzyme were revealed. Moreover, supramolecular assembly of the title compound was analyzed by density functional theory (DFT) calculations. These studies rendered a more clear understanding for the demonstration of novel molecular mechanism involved in CA II inhibition by the synthesized compound.

NMR structural study of the prototropic equilibrium in solution of Schiff bases as model compounds.

PubMed

Ortegón-Reyna, David; Garcías-Morales, Cesar; Padilla-Martínez, Itzia; García-Báez, Efren; Aríza-Castolo, Armando; Peraza-Campos, Ana; Martínez-Martínez, Francisco

2013-12-31

An NMR titration method has been used to simultaneously measure the acid dissociation constant (pKa) and the intramolecular NHO prototropic constant ΔKNHO on a set of Schiff bases. The model compounds were synthesized from benzylamine and substituted ortho-hydroxyaldehydes, appropriately substituted with electron-donating and electron-withdrawing groups to modulate the acidity of the intramolecular NHO hydrogen bond. The structure in solution was established by 1H-, 13C- and 15N-NMR spectroscopy. The physicochemical parameters of the intramolecular NHO hydrogen bond (pKa, ΔKNHO and ΔΔG°) were obtained from 1H-NMR titration data and pH measurements. The Henderson-Hasselbalch data analysis indicated that the systems are weakly acidic, and the predominant NHO equilibrium was established using Polster-Lachmann δ-diagram analysis and Perrin model data linearization.

Mass Spectrometric Evidence of Malonaldehyde and 4-Hydroxynonenal Adductions to Radical-Scavenging Soy Peptides

PubMed Central

Zhao, Jing; Chen, Jing; Zhu, Haining; Xiong, Youling L.

2012-01-01

Antioxidative peptides in food systems are potential targets of lipid oxidation-generated reactive aldehydes, such as malonaldehyde (MDA) and 4-hydroxynonenal (HNE). In this study, covalent modifications on radical-scavenging peptides prepared from soy protein hydrolysate by MDA and HNE were characterized by liquid chromatography–electrospray ionization-mass spectrometry (LC-ESI-MS/MS). MS/MS analyses detected the formation of Schiff base type adducts of MDA on the side chain groups of lysine, histidine, arginine, glutamine, and asparagine residues as well as the N-termini of peptides. MDA also formed a fluorescent product with lysine residues. HNE adducted on lysine residues through Schiff base formation and on histidine, arginine, glutamine, and asparagine residues mainly through Michael addition. In spite of the extensive MDA modification, peptide cross-linking by this potential mechanism was undetectable. PMID:22946674

A novel Schiff base derivative: Synthesis, two-photon absorption properties and application for bioimaging.

PubMed

Wang, Hui; Fang, Bin; Kong, Lin; Li, Xiangzi; Feng, Zhijun; Wu, Yunjun; Uvdal, Kajsa; Hu, Zhangjun

2018-06-05

A novel donor-π-acceptor-π-donor type (D-π-A-π-D') Schiff base derivative (L) has been designed and synthesized. The structure of L is confirmed by single-crystal X-ray diffraction analysis as well. The photophysical properties of compound L were comprehensively investigated by using both experimental and theoretical methods. The results indicate that L exhibits large Stokes shift and moderate two-photon action (2PA) cross-section in the near infrared (NIR) region. Furthermore, the confocal microscopy imaging study demonstrates that compound L could penetrate into cells and target the cellular mitochondria compartment. Due to its low cytotoxicity, compound L provides a promising tool for directly lighting up the mitochondria compartment in living HepG2 cells. Copyright © 2018 Elsevier B.V. All rights reserved.

Synthesis, structural characterization and DFT calculation on a square-planar Ni(II) complex of a compartmental Schiff base ligand

NASA Astrophysics Data System (ADS)

Biswas, Surajit; Dolai, Malay; Dutta, Arpan; Ali, Mahammad

2016-12-01

Reaction of a symmetric compartmental Schiff-base ligand, (H2L) with nickel(II) perchlorate hexahydrate in 1:1 M ratio in methanol gives rise to a mononuclear nickel(II) compound, NiL (1). The compound has been characterized by C, H, N microanalyses and UV-Vis spectra. The single crystal X-ray diffraction studies reveal a square planar geometry around the Ni(II) center. The compound crystallizes in monoclinic system with space group C2/c with a = 21.6425(6), b = 9.9481(3), c = 13.1958(4) Å, β = 107.728(2)°, V = 2706.16(14) Å3 and Z = 4. Ground state DFT optimization and TDDFT calculations on the ligand and complex were performed to get their UV-Vis spectral pattern.

Spectral Characterization and 3D Molecular Modeling Studies of Metal Complexes Involving the O, N-Donor Environment of Quinazoline-4(3H)-one Schiff Base and Their Biological Studies

PubMed Central

Siddappa, Kuruba; Mane, Sunilkumar B.

2014-01-01

A simple condensation of 3-amino-2-methylquinazoline-4-one with 2-hydroxy-1-naphthaldehyde produced new tridentate ONO donor Schiff base ligand with efficient yield. The structural characterization of ligand and its Cu(II), Ni(II), Co(II), Mn(II), Zn(II), and Cd(II) complexes were achieved by the aid of elemental analysis, spectral characterization such as (UV-visible, IR, NMR, mass, and ESR), and magnetic data. The analytical and spectroscopic studies suggest the octahedral geometries of Cu(II), Co(II), Ni(II) and Mn(II) complexes and tetrahedral geometry of Zn(II) and Cd(II) complexes with the tridentate ONO Schiff base ligand. Furthermore, the conclusions drawn from these studies afford further support to the mode of bonding discussed on the basis of their 3D molecular modeling studies by considering different bond lengths, bond angles, and bond distance. The ligand and its metal complexes evaluated for their antimicrobial activity against Staphylococcus aureus (MTCC number 7443), Bacillus subtilis (MTCC number 9878), Escherichia coli (MTCC number 1698), Aspergillus niger (MTCC number 281), and Aspergillus flavus (MTCC number 277). The MIC of these compounds was found to be most active at 10 μg/mL concentration in inhibiting the growth of the tested organisms. The DNA cleavage activity of all the complexes was studied by gel electrophoresis method. PMID:24678278

Synthesis, physicochemical studies, embryos toxicity and DNA interaction of some new Iron(II) Schiff base amino acid complexes

NASA Astrophysics Data System (ADS)

Abdel-Rahman, Laila H.; El-Khatib, Rafat M.; Nassr, Lobna A. E.; Abu-Dief, Ahmed M.

2013-05-01

New Fe(II) Schiff base amino acid complexes derived from the condensation of o-hydroxynaphthaldehyde with L-alanine, L-phenylalanine, L-aspartic acid, L-histidine and L-arginine were synthesized and characterized by elemental analysis, IR, electronic spectra, and conductance measurements. The stoichiometry and the stability constants of the complexes were determined spectrophotometrically. The investigated Schiff bases exhibited tridentate coordination mode with the general formulae [Fe(HL)2]·nH2O for all amino acids except L-histidine. But in case of L-histidine, the ligand acts as tetradentate ([FeL(H2O)2]·2H2O), where HL = mono anion and L = dianion of the ligand. The structure of the prepared complexes is suggested to be octahedral. The prepared complexes were tested for their toxicity on chick embryos and found to be safe until a concentration of 100 μg/egg with full embryos formation. The interaction between CT-DNA and the investigated complexes were followed by spectrophotometry and viscosity measurements. It was found that, the prepared complexes bind to DNA via classical intercalative mode and showed a different DNA cleavage activity with the sequence: nhi > nari > nali > nasi > nphali. The thermodynamic Profile of the binding of nphali complex and CT-DNA was constructed by analyzing the experimental data of absorption titration and UV melting studies with the McGhee equation, van't Hoff's equation, and the Gibbs-Helmholtz equation.

Alkylated hydroxylamine derivatives eliminate peripheral retinylidene Schiff bases but cannot enter the retinal binding pocket of light-activated rhodopsin.

PubMed

Piechnick, Ronny; Heck, Martin; Sommer, Martha E

2011-08-23

Besides Lys-296 in the binding pocket of opsin, all-trans-retinal forms adducts with peripheral lysine residues and phospholipids, thereby mimicking the spectral and chemical properties of metarhodopsin species. These pseudophotoproducts composed of nonspecific retinylidene Schiff bases have long plagued the investigation of rhodopsin deactivation and identification of decay products. We discovered that, while hydroxylamine can enter the retinal binding pocket of light-activated rhodopsin, the modified hydroxylamine compounds o-methylhydroxylamine (mHA), o-ethylhydroxylamine (eHA), o-tert-butylhydroxylamine (t-bHA), and o-(carboxymethyl)hydroxylamine (cmHA) are excluded. However, the alkylated hydroxylamines react quickly and efficiently with exposed retinylidene Schiff bases to form their respective retinal oximes. We further investigated how t-bHA affects light-activated rhodopsin and its interaction with binding partners. We found that both metarhodopsin II (Meta II) and Meta III are resistant to t-bHA, and neither arrestin nor transducin binding is affected by t-bHA. This discovery suggests that the hypothetical solvent channel that opens in light-activated rhodopsin is extremely stringent with regard to size and/or polarity. We believe that alkylated hydroxylamines will prove to be extremely useful reagents for the investigation of rhodopsin activation and decay mechanisms. Furthermore, the use of alkylated hydroxylamines should not be limited to in vitro studies and could help elucidate visual signal transduction mechanisms in the living cells of the retina. © 2011 American Chemical Society

Spectroscopic studies of the intramolecular hydrogen bonding in o-hydroxy Schiff bases, derived from diaminomaleonitrile, and their deprotonation reaction products.

PubMed

Szady-Chełmieniecka, Anna; Kołodziej, Beata; Morawiak, Maja; Kamieński, Bohdan; Schilf, Wojciech

2018-01-15

The structural study of five Schiff bases derived from diaminomaleonitrile (DAMN) and 2-hydroxy carbonyl compounds was performed using 1 H, 13 C and 15 N NMR methods in solution and in the solid state as well. ATR-FTIR and X-Ray spectroscopies were used for confirmation of the results obtained by NMR method. The imine obtained from DAMN and benzaldehyde was synthesized as a model compound which lacks intramolecular hydrogen bond. Deprotonation of all synthesized compounds was done by treating with tetramethylguanidine (TMG). NMR data revealed that salicylidene Schiff bases in DMSO solution exist as OH forms without intramolecular hydrogen bonds and independent on the substituents in aromatic ring. In the case of 2-hydroxy naphthyl derivative, the OH proton is engaged into weak intramolecular hydrogen bond. Two of imines (salDAMN and 5-BrsalDAMN) exist in DMSO solution as equilibrium mixtures of two isomers (A and B). The structures of equilibrium mixture in the solid state have been studied by NMR, ATR-FTIR and X-Ray methods. The deprotonation of three studied compounds (salDAMN, 5-BrsalDAMN, and 5-CH 3 salDAMN) proceeded in two different ways: deprotonation of oxygen atom (X form) or of nitrogen atom of free primary amine group of DAMN moiety (Y form). For 5-NO 2 salDAMN and naphDAMN only one form (X) was observed. Copyright © 2017 Elsevier B.V. All rights reserved.

Impact of proton transfer phenomena on the electronic structure of model Schiff bases: an AIM/NBO/ELF study.

PubMed

Panek, Jarosław J; Filarowski, Aleksander; Jezierska-Mazzarello, Aneta

2013-10-21

Understanding of the electronic structure evolution due to a proton dynamics is a key issue in biochemistry and material science. This paper reports on density functional theory calculations of Schiff bases containing short, strong intramolecular hydrogen bonds where the bridged proton is located: (i) at the donor site, (ii) strongly delocalized, and (iii) at the acceptor site. The mobility of the bridged proton and its influence on the molecular structure and properties of the chosen Schiff base derivatives have been investigated on the basis of Atoms in Molecules, Natural Bond Orbitals, and Electron Localization Function theories. It has been observed that the extent of the bridged proton delocalization is strongly modified by the steric and inductive effects present in the studied compounds introduced by various substituents. It has been shown that: (i) potential energy profiles for the proton motion are extremely dependent on the substitution of the aromatic ring, (ii) the topology of the free electron pairs present at the donor∕acceptor site, as well as their electron populations, are affected qualitatively by the bridged proton position, (iii) the distortion of the molecular structure due to the bridged proton dynamics includes the atomic charge fluctuations, which are in some cases non-monotonic, and (iv) topology of the ELF recognizes events of proton detachment from the donor and attachment to the acceptor. The quantitative and qualitative results shed light onto molecular consequences of the proton transfer phenomena.

Design, spectral characterization and biological studies of transition metal(II) complexes with triazole Schiff bases

NASA Astrophysics Data System (ADS)

Hanif, Muhammad; Chohan, Zahid H.

2013-03-01

A new series of three biologically active triazole derived Schiff base ligands L1-L3 have been synthesized in equimolar reaction of 3-amino-1H-1,2,4-triazole with pyrrol-2-carboxaldehyde, 4-bromo-thiophene-2-carboxaldehyde, and 5-iodo-2-hydroxy benzaldehyde. The prepared Schiff bases were used for further complex formation reaction with different metal elements like Co(II), Ni(II), Cu(II) and Zn(II) as chlorides by using a molar ratio of ligand:metal as 2:1. The structure and bonding nature of all the compounds were identified by their physical, spectral and analytical data. All the metal(II) complexes possessed an octahedral geometry except the Cu(II) complexes which showed a distorted octahedral geometry. All the synthesized compounds, were studied for their in vitro antibacterial, and antifungal activities, against four Gram-negative (Escherichia coli, Shigella sonnei, Pseudomonas aeruginosa and Salmonella typhi) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and against six fungal strains (Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glabrata) by using agar-well diffusion method. It has been shown that all the synthesized compounds showed moderate to significant antibacterial activity against one or more bacterial strains. In vitro Brine Shrimp bioassay was also carried out to investigate the cytotoxic properties of these compounds. The data also revealed that the metal complexes showed better activity than the ligands due to chelation/coordination.

Reaction Mechanism of Covalent Modification of Phosphatidylethanolamine Lipids by Reactive Aldehydes 4-Hydroxy-2-nonenal and 4-Oxo-2-nonenal.

PubMed

Vazdar, Katarina; Vojta, Danijela; Margetić, Davor; Vazdar, Mario

2017-03-20

4-Hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE) are biologically important reactive aldehydes formed during oxidative stress in phospholipid bilayers. They are highly reactive species due to presence of several reaction centers and can react with amino acids in peptides and proteins, as well as phosphoethanolamine (PE) lipids, thus modifying their biological activity. The aim of this work is to study in a molecular detail the reactivity of HNE and ONE toward PE lipids in a simplified system containing only lipids and reactive aldehydes in dichloromethane as an inert solvent. We use a combination of quantum chemical calculations, 1 H NMR measurements, FT-IR spectroscopy, and mass spectrometry experiments and show that for both reactive aldehydes two types of chemical reactions are possible: formation of Michael adducts and Schiff bases. In the case of HNE, an initially formed Michael adduct can also undergo an additional cyclization step to a hemiacetal derivative, whereas no cyclization occurs in the case of ONE and a Michael adduct is identified. A Schiff base product initially formed when HNE is added to PE lipid can also further cyclize to a pyrrole derivative in contrast to ONE, where only a Schiff base product is isolated. The suggested reaction mechanism by quantum-chemical calculations is in a qualitative agreement with experimental yields of isolated products and is also additionally investigated by 1 H NMR measurements, FT-IR spectroscopy, and mass spectrometry experiments.