These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Design, synthesis, and biological activities of aromatic gossypol Schiff base derivatives.  

PubMed

A series of aromatic gossypol Schiff bases have been successfully synthesized via a feasible chemical modification. The antiviral activity against tobacco mosaic virus (TMV) of these gossypol Schiff bases has been tested for the first time. The bioassay studies indicated most of these derivatives exhibited excellent anti-TMV activity, in which o-trifluoromethylaniline Schiff base (19) displayed the best antiviral activities. Furthermore, compound 19 exhibited an eminent anti-TMV effect in the field and low toxicity to mice. These results suggest it is a promising candidate for the inhibitor of plant virus. PMID:25386768

Li, Ling; Li, Zheng; Wang, Kailiang; Zhao, Sheng; Feng, Jiming; Li, Jiarui; Yang, Peiwen; Liu, Yuxiu; Wang, Lizhong; Li, Yongqiang; Shang, Hui; Wang, Qingmin

2014-11-19

2

Molecular compounds of dichloro- p-benzoquinone derivatives with hydroxy aromatic Schiff's bases  

NASA Astrophysics Data System (ADS)

The molecular complexes of some hydroxy aromatic Schiff's bases with 2,3-dichloro-5,6-dicyano- p-benzoquinone and chloranilic acid are prepared and investigated using electronic absorption, i.r. and 1H-NMR spectroscopy. Molecular compounds with the former reagent are formed through charge transfer while those with chloranilic acid are formed through proton and electron transfer.

Issa, Y. M.

3

Ionic liquid mediated synthesis and molecular docking study of novel aromatic embedded Schiff bases as potent cholinesterase inhibitors.  

PubMed

Novel aromatic embedded Schiff bases have been synthesized in ionic liquid [bmim]Br and evaluated in vitro for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes inhibitory activities. Among the newly synthesized compounds, 5f, 5h and 7j displayed higher AChE enzyme inhibitory activities than standard drug, galanthamine, with IC50 values of 1.88, 2.05 and 2.03?M, respectively. Interestingly, all the compounds except for compound 5c displayed higher BChE inhibitories than standard with IC50 values ranging from 3.49 to 19.86?M. Molecular docking analysis for 5f and 7j possessing the most potent AChE and BChE inhibitory activities, disclosed their binding interaction templates to the active site of AChE and BChE enzymes, respectively. PMID:25462993

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

2014-12-01

4

Complete ?* intramolecular aromatic hydroxylation mechanism through O2 activation by a Schiff base macrocyclic dicopper(I) complex  

PubMed Central

Summary In this work we analyze the whole molecular mechanism for intramolecular aromatic hydroxylation through O2 activation by a Schiff hexaazamacrocyclic dicopper(I) complex, [CuI 2(bsH2m)]2+. Assisted by DFT calculations, we unravel the reaction pathway for the overall intramolecular aromatic hydroxylation, i.e., from the initial O2 reaction with the dicopper(I) species to first form a CuICuII-superoxo species, the subsequent reaction with the second CuI center to form a ?-?2:?2-peroxo-CuII 2 intermediate, the concerted peroxide OO bond cleavage and CO bond formation, followed finally by a proton transfer to an alpha aromatic carbon that immediately yields the product [CuII 2(bsH2m-O)(?-OH)]2+. PMID:23616799

Sol, Miquel

2013-01-01

5

Anomeric and tautomeric equilibria in D-2-glucosamine Schiff bases  

NASA Astrophysics Data System (ADS)

The structure of some glucosamine Schiff bases has been studied by means of ab initio RHF and DFT calculation and CP/MAS 13C and 15N NMR measurements. The anomeric and tautomeric equilibria in a DMSO solution have been studied by 1H, 13C and 15N NMR spectroscopy. The anomeric composition of D-2-glucosamine Schiff bases in the solid state and in DMSO solution has been shown to depends on the tautomeric form of Schiff bases and electronic properties of substituents on the aromatic ring.

Ko?odziej, B.; Grech, E.; Schilf, W.; Kamie?ski, B.; Makowski, M.; Rozwadowski, Z.; Dziembowska, T.

2007-11-01

6

Synthesis and biological evaluation of Schiffs bases and 2-azetidinones of isonocotinyl hydrazone as potential antidepressant and nootropic agents  

Microsoft Academic Search

The synthesis and pharmacological activity of N?-[(1Z)-(substituted aromatic) methylidene] pyridine-4-carbohydrazides (3ak) and N-[3-chloro-2-(substituted aromatic)-4-oxoazetidin-1-yl]pyridine-4-carboxamides (5ak) are described. Synthesis of 2-azetidinones was performed by novel methods of stirring and sonication involving the cyclocondensation of the appropriate Schiffs bases (3ak) with chloroacetyl chloride, followed by the addition of triethyl amine in the presence of molecular sieves. The compounds were investigated for their

Asha B. Thomas; Rabindra K. Nanda; Lata P. Kothapalli; Sunil C. Hamane

7

Electronic spectra of carotenoids. Schiff's bases of carotenal and carotenones  

Microsoft Academic Search

Visible absorption bands of beta-apo-8'-carotenal, citranaxanthin, and reticulataxanthin Schiff's bases are measured and analyzed in relation to the visual chromophore, retinal Schiff's base. The former shows a strong red shift of the absorption maxima upon protonation in ethanol, and the magnitude of the band shift is comparable to that of retinal Schiff's base. Molecular orbital analysis of the ground and

Thomas A. Moore; Pill-Soon Song

1974-01-01

8

Synthesis and characterization of Schiff's bases of sulfamethoxazole  

PubMed Central

Background Schiff's bases are excellent ligands which are synthesized from the condensation of primary amines with carbonyl groups. Findings The classical reaction for the synthesis of Schiff's bases in an ethanolic solution and glacial acetic acid as a catalyst was followed in the synthesis of substituted sulfamethoxazole compounds. Conclusions Some Schiff's bases containing sulfamethoxazole nucleus have been synthesized and characterized. The present compounds are hoped to be applied in the photostability of PVC. PMID:24576663

2014-01-01

9

Ruthenium(II) hydrazone Schiff base complexes: Synthesis, spectral study and catalytic applications  

NASA Astrophysics Data System (ADS)

Ruthenium(II) hydrazone Schiff base complexes of the type [RuCl(CO)(B)(L)] (were B = PPh 3, AsPh 3 or Py; L = hydrazone Schiff base ligands) were synthesized from the reactions of hydrazone Schiff base ligand (obtained from isonicotinoylhydrazide and different hydroxy aldehydes) with [RuHCl(CO)(EPh 3) 2(B)] (where E = P or As; B = PPh 3, AsPh 3 or Py) in 1:1 molar ratio. All the new complexes have been characterized by analytical and spectral (FT-IR, electronic, 1H, 13C and 31P NMR) data. They have been tentatively assigned an octahedral structure. The synthesized complexes have exhibited catalytic activity for oxidation of benzyl alcohol to benzaldehyde and cyclohexanol to cyclohexanone in the presence of N-methyl morpholine N-oxide (NMO) as co-oxidant. They were also found to catalyze the transfer hydrogenation of aliphatic and aromatic ketones to alcohols in KOH/Isopropanol.

Manikandan, R.; Viswanathamurthi, P.; Muthukumar, M.

2011-12-01

10

Corrosion inhibition of mild steel by schiff base compounds in various aqueous solutions: part 1  

Microsoft Academic Search

The corrosion inhibition by Schiff base compounds derived from diamines and o-hydroxy, o-methoxy aromatic aldehydes was investigated by weight loss, electrochemical measurements and surface analysis of SS 400 in various aqueous solutions such as tap water (LC), concentrated tap water (HC) and HCl solutions. The maximum inhibition efficiency (?) of N,N?-bis (salicylaldehyde)-1,12-diaminododecane (Saldn) for SS 400 in HCl solution approached

H Shokry; M Yuasa; I Sekine; R. M Issa; H. Y El-baradie; G. K Gomma

1998-01-01

11

Recent pharmacological advancements in schiff bases: a review.  

PubMed

Schiff bases are the biologically privileged scaffolds in organic chemistry, commonly synthesized from the condensation reaction of carbonyl functional group with amines. Naturally occurring and synthetically prepared Schiff bases are active molecules with many pharmacological activities like antibacterial, anti-cancer, anti-fungal, anti-malarial, antioxidant and many more. This review article summarizes pharmacological developments in the recent few years and gives a brief overview of their therapeutic potential. PMID:25272879

Murtaza, Ghulam; Mumtaz, Amara; Khan, Farhan Ahmed; Ahmad, Saeed; Azhar, Saira; Khan, Shujaat Ali; Najam-Ul-Haq, Muhammad; Atif, Muhammad; Khan, Shujaat Ali; Maalik, Aneela; Azhar, Saira; Murtaza, Ghulam

2014-01-01

12

Monodentate Schiff base ligands: Their structural characterization, photoluminescence, anticancer, electrochemical and sensor properties  

NASA Astrophysics Data System (ADS)

Two Schiff base compounds, N,N?-bis(2-methoxy phenylidene)-1,5-diamino naphthalene (L1) and N,N?-bis(3,4,5-trimethoxy phenylidene)-1,5-diamino naphthalene (L2) were synthesized and characterized by the analytical and spectroscopic methods. The electrochemical and photoluminescence properties of the Schiff bases were investigated in the different conditions. The compounds L1 and L2 show the reversible redox processes at some potentials. The sensor properties of the Schiff bases were examined and color changes were observed upon addition of the metal cations, such as Hg(II), Cu(II), Co(II) and Al(III). The Schiff base compounds show the bathochromic shift from 545 to 585 nm. The single crystals of the compounds (L1) and (L2) were obtained from the methanol solution and characterized structurally by the X-ray crystallography technique. The molecule L2 is centrosymmetric whereas the L1 has no crystallographically imposed molecular symmetry. However, the molecular structures for these compounds are quite similar, differing principally in the conformation about methoxy groups and the dihedral angle between the two aromatic rings and diamine naphthalene.

Kse, Muhammet; Ceyhan, Gkhan; Tmer, Mehmet; Demirta?, ?brahim; Gnl, ?lyas; McKee, Vickie

2015-02-01

13

Tautomeric design of ortho-hydroxyheterocyclic Schiff bases  

NASA Astrophysics Data System (ADS)

The article reports on the synthesis and crystallographic and theoretical studies on various heterocyclic derivatives of ortho-hydroxy Schiff bases. The prevailing of one of the two (enolimine - OH and ketoamine - NH) tautomeric forms has been stated in studied compounds depending on the substitutes in heterocyclic formation, the nitrogen and carbon atoms of the imine group. A specific situation has been shown in (1E)-1-(5-chloro-2-hydroxy-3-nitrophenyl)ethanone oxime compound. The potentials on the proton transfer of the hydrogen bridges in these compounds have been found out. Grounded on the obtained potential curves the influence of the protonation on nitrogen in the pyridoxal derivative of the studied ortho-hydroxy Schiff bases has been analysed. The most efficient method of the impact (by means of various substitutes) on the intramolecular tautomeric equilibrium in ortho-hydroxy Schiff bases has been presented.

Kwocz, Agnieszka; Kochel, Andrzej; Chudoba, Dorota; Filarowski, Aleksander

2015-01-01

14

Ruthenium(II) hydrazone Schiff base complexes: synthesis, spectral study and catalytic applications.  

PubMed

Ruthenium(II) hydrazone Schiff base complexes of the type [RuCl(CO)(B)(L)] (were B=PPh(3), AsPh(3) or Py; L=hydrazone Schiff base ligands) were synthesized from the reactions of hydrazone Schiff base ligand (obtained from isonicotinoylhydrazide and different hydroxy aldehydes) with [RuHCl(CO)(EPh(3))(2)(B)] (where E=P or As; B=PPh(3), AsPh(3) or Py) in 1:1 molar ratio. All the new complexes have been characterized by analytical and spectral (FT-IR, electronic, (1)H, (13)C and (31)P NMR) data. They have been tentatively assigned an octahedral structure. The synthesized complexes have exhibited catalytic activity for oxidation of benzyl alcohol to benzaldehyde and cyclohexanol to cyclohexanone in the presence of N-methyl morpholine N-oxide (NMO) as co-oxidant. They were also found to catalyze the transfer hydrogenation of aliphatic and aromatic ketones to alcohols in KOH/Isopropanol. PMID:21924947

Manikandan, R; Viswanathamurthi, P; Muthukumar, M

2011-12-01

15

Cu(II) Schiff base as catalyst in the synthesis of 1,8-dioxodecahydroacridine.  

PubMed

The catalytic property of Cu(II) Schiff-base complex in an efficient synthesis of 1,8-dioxodecahydroacridines was investigated. The one-pot three component reaction of dimedone, aromatic aldehydes and aromatic amines or ammonium acetate in water afforded the corresponding 1,8-dioxodecahydroacridines with excellent yields. This reaction was carried out in the presence of 1 mol% of catalysts at room temperature. The reusability of the catalysts was demonstrated by a five-run test without loss of its activity. Also, this catalyst possesses several advantages including mild reaction conditions, lower catalytic loading, shorter reaction times, high yield of the products, inexpensive and cleaner (Green chemistry) reactions. PMID:22998593

Vahdat, Seyed Mohammad; Mardani, Hamid Reza; Golchoubian, Hamid; Khavarpour, Maryam; Baghery, Saeed; Roshankouhi, Ziba

2013-01-01

16

Application of a Schiff Base Derived from Sulfanilamide as an AcidBase Indicator  

Microsoft Academic Search

The present paper firstly announces the possibility of using a Schiff base as an acid-base indicator. This surprising phenomenon can be considered as an interest due to the fact that Schiff bases are usually unstable in solutions and definitely undergo hydrolysis. It was found that such a specific observation depends merely upon the chemical structure and type of the substitute

R. A. Khalil; A. H. Jalil; A. Y. Abd-Alrazzak

17

The role of the retinylidene Schiff base counterion in rhodopsin in determining wavelength absorbance and Schiff base pKa.  

PubMed Central

Glu-113 serves as the retinylidene Schiff base counterion in bovine rhodopsin. Purified mutant rhodopsin pigments were prepared in which Glu-113 was replaced individually by Gln (E113Q), Asp (E113D), Asn (E113N), or Ala (E113A). E113Q, E113N, and E113A existed as pH-dependent equilibrium mixtures of unprotonated and protonated Schiff base (PSB) forms. The Schiff base pKa values determined by spectrophotometric titration were 6.00 (E113Q), 6.71 (E113N), and 5.70 (E113A). Thus, mutation of Glu-113 markedly reduced the Schiff base pKa. The addition of NaCl promoted the formation of a PSB in E113Q and E113A. An exogenously supplied solute anion replaced Glu-113 to compensate for the positive charge of the PSB in these mutants. The lambda max values of the PSB forms of the mutants in NaCl were 496 nm (E113Q), 506 nm (E113A), 510 nm (E113D), and 520 nm (E113N). To evaluate the effect of different types of solute anions on lambda max values, mutants were prepared in sodium salts of halides, perchlorate, and a series of carboxylic acids of various sizes and acidity. The lambda max values of E113Q and E113A depended on the solute anion present and ranged from 488 nm to 522 nm for E113Q and from 486 nm to 528 nm for E113A. The solute anion affected the lambda max values of E113N and E113D to lesser degrees. The reactivities of the mutants to hydroxylamine were also studied. Whereas rhodopsin was stable to hydroxylamine in the dark, E113N reacted slowly and E113Q reacted rapidly under these conditions, indicating structural differences in the Schiff base environments. The lambda max values and solute anion dependencies of the Glu-113 mutants indicate that interactions between Schiff base and its counterion play a significant role in determining the lambda max of rhodopsin. PMID:2014228

Sakmar, T P; Franke, R R; Khorana, H G

1991-01-01

18

Synthesis and degradation of schiff bases containing heterocyclic pharmacophore.  

PubMed

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

Lede?i, Ionu?; Alexa, Anda; Bercean, Vasile; Vlase, Gabriela; Vlase, Titus; ?uta, Lenu?a-Maria; Fulia?, Adriana

2014-01-01

19

Synthesis and Degradation of Schiff Bases Containing Heterocyclic Pharmacophore  

PubMed Central

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

Lede?i, Ionu?; Alexa, Anda; Bercean, Vasile; Vlase, Gabriela; Vlase, Titus; ?uta, Lenu?a-Maria; Fulia?, Adriana

2015-01-01

20

Oxidative peptide /and amide/ formation from Schiff base complexes  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

21

Mononuclear and tetranuclear Fe(III) complexes with two different types of N, O donor Schiff base ligands  

NASA Astrophysics Data System (ADS)

A mononuclear Fe(III) complex of a tetradentate N2O2 donor Schiff base ligand derived from 3-ethoxysalicaldehyde and ethylenediamine has been reported. In addition two tetranuclear Fe(III) complexes with discrete Fe4III(?4-O) cores have been synthesized and characterized using two Schiff base ligands (H2L1-2) derived from two different aromatic acid hydrazides and diacetyl monoxime. The mononuclear Fe(III) and one of the tetranuclear Fe(III) complexes have been structurally characterized by single-crystal X-ray crystallography. The mononuclear complex has a highly distorted octahedral geometry. The tetranuclear Fe(III) complexes are found to be rare examples with discrete neutral alkoxido-oxido clusters with Fe4III(?4-O) cores.

Sutradhar, Manas; Roy Barman, Tannistha; Drew, Michael G. B.; Rentschler, Eva

2013-06-01

22

Chelating ability and biological activity of hesperetin Schiff base.  

PubMed

Hydrazone hesperetin Schiff base (HHSB) - N-[()-[5,7-dihydroxy-2-(3-hydroxy-4-methoxy-phenyl)chroman-4-ylidene]amino]benzamide has been synthesized and its crystal structure was determined. This compound was used for the formation of Cu(II) complexes in solid state and in solution which were characterized using different spectroscopic methods. The analyses of potentiometric titration curves revealed that monomeric and dimeric complexes of Cu(II) are formed above pH7. The ESI-MS (electrospray ionization-mass spectrometry) spectra confirmed their formation. The EPR and UV-visible spectra evidenced the involvement of oxygen and nitrogen atoms in Cu(II) coordination. Hydrazone hesperetin Schiff base can show keto-enol tautomerism and coordinate Cu(II) in the keto (O(-), N, Oket) and in the enolate form (O(-), N, O(-)enol). The semi-empirical molecular orbital method PM6 and DFT (density functional theory) calculations have revealed that the more stable form of the dimeric complex is that one in which the ligand is present in the enol form. The CuHHSB complex has shown high efficiency in the cleavage of plasmid DNA in aqueous solution, indicating its potential as chemical nuclease. Studies on DNA interactions, antimicrobial and cytotoxic activities have been undertaken to gain more information on the biological significance of HHSB and copper(II)-HHSB chelate species. PMID:25486205

Lodyga-Chruscinska, Elzbieta; Symonowicz, Marzena; Sykula, Anna; Bujacz, Anna; Garribba, Eugenio; Rowinska-Zyrek, Magdalena; Oldziej, Stanislaw; Klewicka, Elzbieta; Janicka, Magdalena; Krolewska, Karolina; Cieslak, Marcin; Brodowska, Katarzyna; Chruscinski, Longin

2014-11-28

23

Novel dipodal Schiff base compounds: Synthesis, characterization and spectroscopic studies  

NASA Astrophysics Data System (ADS)

Two novel dipodal Schiff base compounds 1,2-benzyloxy-bis-[2-(benzylideneamino)phenol, L1 and 1,2-benzyloxy-bis[3-(benzylideneamino)pyridine], L2 were synthesized. Their sensing actions were confirmed by UV-Vis absorbance and emission spectroscopic studies in presence of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Sn(II), Cd(II) and Pb(II) in methanol medium (1 10-4 M). It was found that the dipodal compounds can selectively bind to Cu(II) and Pb(II) metal ions with a significant change in its emission and absorption spectra, while the addition of other metal ions (Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Sn(II), Cd(II) and Pb(II)) produces insignificant or minor changes. The host-guest complexes formed were determined by Job's plot method. As a chemosensor, L1 and L2 dipodal Schiff base compounds shows a specific selectivity towards Cu(II) and Pb(II) ions in according to all spectroscopic data.

Obali, Aslihan Yilmaz; Ucan, Halil Ismet

2015-02-01

24

Photoisomerization acceleration in retinal protonated Schiff-base models.  

PubMed

The results of new and recently reported CASSCF/6-31G* photoisomerization path computations of a series of models of the 11-cis retinal chromophore of the visual pigment rhodopsin are discussed. The results indicate that, with respect to the chromophore in vacuo, certain structural, intramolecular and environmental factors are capable of speeding up the excited-state decay associated with the cis --> trans isomerization motion. Using suitable protonated Schiff-base models, it is shown that three structural factors can potentially speed up the isomerization: (i) reducing the length of the conjugated chain, (ii) twisting of the hydrocarbon end of the conjugated chain with respect to the protonated Schiff-base end and (iii) ring locking of the conjugated chain with an eight-membered ring. All these factors operate through increasing the slope of the excited-state energy surface and enhancing the coupling between stretching and torsional modes. We argue that the protein catalysis seen in rhodopsin may, at least partly, exploit the same principles. PMID:14717218

Sinicropi, Adalgisa; Migani, Annapaola; De Vico, Luca; Olivucci, Massimo

2003-12-01

25

Interaction of Schiff base ligand with tin dioxide nanoparticles: optical studies.  

PubMed

Interaction between 1,4 Bis ((2-Methyl) thio) Phenylamino methyl benzene (BMTPMB) Schiff base with tin dioxide nanoparticles (SnO2 NPs) of various concentrations in methanol have been studied using UV-Visible and Fluorescence spectroscopic techniques. The low value of Stern-Volmer quenching constant and non-linear plot of Benesi-Hildebrand equation suggests the less affinity of SnO2 NPs towards the adsorption of BMTPMB Schiff base. The Scott equation has been employed to determine molar absorptivity of the Schiff base-NPs system. PMID:23770505

Rani, J Suvetha; Ramakrishnan, V

2013-10-01

26

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

PubMed

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. PMID:25328181

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

2014-10-01

27

Deng & Schiff, Amorphous Silicon Based Solar Cells rev. 7/30/2002, Page 1 Amorphous Silicon Based Solar Cells  

E-print Network

Deng & Schiff, Amorphous Silicon Based Solar Cells rev. 7/30/2002, Page 1 Amorphous Silicon Based Solar Cells Xunming Deng and Eric A. Schiff Table of Contents 1 Overview 3 1.1 Amorphous Silicon: The First Bipolar Amorphous Semiconductor 3 1.2 Designs for Amorphous Silicon Solar Cells: A Guided Tour 6

Deng, Xunming

28

Chromotropism Behavior and Biological Activity of some Schiff Base-Mixed Ligand Transition Metal Complexes  

Microsoft Academic Search

We report about a series of mono-nuclear and bi-nuclear complexes with acyclic as well as macro-cyclic ligands, which have been synthesized with Schiff base ligands in tri- tetra and pentadentate forms. The bonding sites on complex formation are mainly the azomethine groups and\\/or imide nitrogen, ketonic oxygen or sulphur atoms. Complexes of two series of Schiff base ligands, H2La and

Azza A. A. Abou-Hussen; Wolfgang Linert

2009-01-01

29

Ag/ThioClickFerrophos-catalyzed enantioselective Mannich reaction and amination of glycine Schiff base.  

PubMed

The AgOAc/ThioClickFerrophos complex catalyzed the asymmetric Mannich reaction of glycine Schiff base with N-tosylimines effectively to give a mixture of syn and anti adducts (syn/anti = 60/40-70/30) at high yields with high enantioselectivities (up to 98% ee). The complex also catalyzed the asymmetric amination of glycine Schiff base with di-tert-butyl azodicarboxylate with high enantioselectivity. PMID:21410238

Imae, Kazumi; Shimizu, Kenta; Ogata, Kenichi; Fukuzawa, Shin-ichi

2011-05-01

30

Synthesis, characterization, and thermodynamics of some new unsymmetrical Schiff bases of salicylaldehyde with 3,4-diaminopyridine and their cobalt(III) complexes.  

PubMed

Some new Schiff bases derived from 3,4-diaminopyridine (3,4-DAP) and their new unsymmetrical Co(III) five coordinate complexes described as [Co(Chel)(L)]ClO4?H2O where (Chel) is the deprotonated form of a series of unsymmetric ligands containing 3,4-diaminopyridine (3,4-DAP) and substituted salicylaldehyde moieties and a new Co(III) six coordinate Co(III) complex, were synthesized and characterized by (1)H NMR, IR, UV-Vis, and elemental analysis. For the new synthesized five coordinate complexes, the formation constants of the interaction of the Co(III) Schiff bases with various donors were measured spectrophotometrically. The trend of the formation constants of the five coordinate Co(III) Schiff base complexes toward a given phosphine is as follow: 5-H>5-Br and the formation constants trend of these donors are as follow: PBu3>PPh2Me. Furthermore the adduct formation of the five coordinate [Co(3,4-Salpyr)(PBu3)] ClO4?H2O, with aromatic amines shows the following binding trend: Im>2-MeIm>2-EtIm>BzIm. The trend of the formation constants of Co(III) Schiff base complexes toward a given donor according to the phosphine axial ligand is as follow: PBu3>PPh2Me. PMID:24342295

Asadi, Mozaffar; Torabi, Susan; Mohammadi, Khosro

2014-03-25

31

Chemical reactivity and skin sensitization potential for benzaldehydes: can Schiff base formation explain everything?  

PubMed

Skin sensitizers chemically modify skin proteins rendering them immunogenic. Sensitizing chemicals have been divided into applicability domains according to their suspected reaction mechanism. The widely accepted Schiff base applicability domain covers aldehydes and ketones, and detailed structure-activity-modeling for this chemical group was presented. While Schiff base formation is the obvious reaction pathway for these chemicals, the in silico work was followed up by limited experimental work. It remains unclear whether hydrolytically labile Schiff bases can form sufficiently stable epitopes to trigger an immune response in the living organism with an excess of water being present. Here, we performed experimental studies on benzaldehydes of highly differing skin sensitization potential. Schiff base formation toward butylamine was evaluated in acetonitrile, and a detailed SAR study is presented. o-Hydroxybenzaldehydes such as salicylaldehyde and the oakmoss allergens atranol and chloratranol have a high propensity to form Schiff bases. The reactivity is highly reduced in p-hydroxy benzaldehydes such as the nonsensitizing vanillin with an intermediate reactivity for p-alkyl and p-methoxy-benzaldehydes. The work was followed up under more physiological conditions in the peptide reactivity assay with a lysine-containing heptapeptide. Under these conditions, Schiff base formation was only observable for the strong sensitizers atranol and chloratranol and for salicylaldehyde. Trapping experiments with NaBH?CN showed that Schiff base formation occurred under these conditions also for some less sensitizing aldehydes, but the reaction is not favored in the absence of in situ reduction. Surprisingly, the Schiff bases of some weaker sensitizers apparently may react further to form stable peptide adducts. These were identified as the amides between the lysine residues and the corresponding acids. Adduct formation was paralleled by oxidative deamination of the parent peptide at the lysine residue to form the peptide aldehyde. Our results explain the high sensitization potential of the oakmoss allergens by stable Schiff base formation and at the same time indicate a novel pathway for stable peptide-adduct formation and peptide modifications by aldehydes. The results thus may lead to a better understanding of the Schiff base applicability domain. PMID:22950880

Natsch, Andreas; Gfeller, Hans; Haupt, Tina; Brunner, Gerhard

2012-10-15

32

A new copper(II) Schiff base complex containing asymmetrical tetradentate N2O2 Schiff base ligand: Synthesis, characterization, crystal structure and DFT study  

NASA Astrophysics Data System (ADS)

A new copper (II) Schiff base complex, CuL1, was prepared from the reaction of asymmetrical Schiff base ligand of L1 and Cu(OAC)2 (L1 = salicylidene imino-ethylimino-pentan-2-one). The Schiff base ligand, L1, and its copper (II) complex, CuL1, have been characterized by elemental analysis (CHN) and FT-IR and UV-vis spectroscopy. In addition, 1H NMR was employed for characterization of the ligand. Thermogrametric analysis of the CuL1 reveals its thermal stability and its decomposition pattern shows that it is finally decomposed to the copper oxide (CuO). The crystal structure of CuL1 was determined by the single crystal X-ray analysis. The CuL1 complex crystallizes in the monoclinic system, with space group P21/n and distorted square planar coordination around the metal ion. The Schiff base ligand of L1 acts as a chelating ligand and coordinates via two nitrogen and two oxygen atoms to the copper (II) ion with C1 symmetry. The structure of the CuL1 complex was also studied theoretically at different levels of DFT and basis sets. According to calculated results the Csbnd O bond length of the salicylate fragment is slightly higher than that in the acetylacetonate fragment of ligand, which could be interpreted by resonance increasing between phenyl and chelated rings in ligand in relative to the acetylacetonate fragment.

Grivani, Gholamhossein; Baghan, Sara Husseinzadeh; Vakili, Mohammad; Khalaji, Aliakbar Dehno; Tahmasebi, Vida; Eigner, Vclav; Duek, Michal

2015-02-01

33

Mononuclear Ru(III) Schiff base complexes: Synthesis, spectral, redox, catalytic and biological activity studies  

NASA Astrophysics Data System (ADS)

An octahedral ruthenium(III) Schiff base complexes of the type [RuX(EPh 3)(L)] (where, X = Cl/Br; E = As/P; L = dianion of the Schiff bases derived from acetoacetanilide with o-phenylenediamine and salicylaldehyde/ o-hydroxyacetophenone/ o-vanillin/2-hydroxy-1-naphthaldehyde) have been synthesized from the reactions of equimolar reactions of [RuX 3(EPh 3) 3] and Schiff bases in benzene. The new Ru(III) Schiff base complexes have been characterized by elemental analyses, FT-IR, electronic, 1H NMR and 13C NMR spectra, EPR spectral studies, powder X-ray diffraction (XRD) and electrochemical studies. The new complexes were found to be effective catalysts for aryl-aryl coupling and the oxidation of alcohols into their corresponding carbonyl compounds, respectively, using molecular oxygen atmosphere at ambient temperature. Further, the new Ru(III) Schiff base complexes were screened for their antibacterial activity against Pseudomonas aeruginosa, Vibrio cholera, Salomonella typhi and Staphylococcus aureaus.

Priya, N. Padma; Arunachalam, S.; Manimaran, A.; Muthupriya, D.; Jayabalakrishnan, C.

2009-04-01

34

La(III) complex involving the O,N-donor environment of quinazoline-4(3H)-one Schiffs base and their antimicrobial attributes against methicillin-resistant Staphylococcus aureus (MRSA)  

NASA Astrophysics Data System (ADS)

The incidence of methicillin-resistant Staphylococcus aureus increased during the past few decades, so there is an urgent need of new antimicrobial agents if public health is concerned. Though the Schiffs bases and La(III) complex have enormous biological activity, but less attention was given in their synthesis. In the present investigation, we synthesized a new (E)-3-((2-hydroxynaphthalen-1-yl) methyleneamino)-2-methylquinazoline-4(3H)-one HNMAMQ Schiffs base by the condensation of 3-(2-aminophenyl) quinazolin-2-methyl-4(3H)-one and 2-hydroxy-1-naphthaldehyde. The Schiffs base HNMAMQ and its La(III) complex were characterized by elemental analyses, IR, NMR, mass spectra, and thermal studies. The newly synthesized Schiffs base HNMAMQ and its La(III) complex were evaluated for their antimicrobial activity against methicillin-resistant Staphylococcus aureus isolated from the Gulbarga region in India. The Schiffs base HNMAMQ and its La(III) complex showed good antimicrobial activity and thus represents a potential new drug of choice.

Siddappa, K.; Mane, Sunilkumar B.; Manikprabhu, Deene

2014-09-01

35

Synthesis and characterization of higher amino acid Schiff bases, as monosodium salts and neutral forms. Investigation of the intramolecular hydrogen bonding in all Schiff bases, antibacterial and antifungal activities of neutral forms  

NASA Astrophysics Data System (ADS)

Schiff bases derived from 5-nitro-salicylaldehyde and 4-aminobutyric acid, 5-aminopentanoic acid and 6-aminohexanoic acid were synthesized both as monosodium salts (1a-3a) and neutral forms (1b-3b). The monosodium-Schiff bases were characterized by elemental analysis, 1H/13C NMR, IR, powder XRD, UV-vis spectra and conductivity measurements. The neutral-Schiff bases were characterized by elemental analysis, 1H/13C NMR, 2D NMR (HMQC), mass, IR, powder XRD, UV-vis spectra and conductivity measurements. The intramolecular hydrogen bonding and related tautomeric equilibria in all the Schiff bases were studied by UV-vis and 1H NMR spectra in solution. Additionally, the neutral-Schiff bases were screened against Staphylococcus aureus-EB18, S. aureus-ATCC 25923, Escherichia coli-ATCC 11230, Candida albicans-M3 and C. albicans-ATCC 16231.

Gngr, zlem; Grkan, Perihan

2014-09-01

36

Schiff Base Protonation Changes in Siberian Hamster Ultraviolet Cone Pigment Photointermediates  

PubMed Central

Molecular structure and function studies of vertebrate ultraviolet (UV) cone visual pigments are needed to understand the molecular evolution of these photoreceptors, which uniquely contain unprotonated Schiff base linkages between the 11-cis retinal chromophore and the opsin proteins. In this study, the Siberian hamster ultraviolet cone pigment (SHUV) was expressed and purified in an n-dodecyl-?-D-maltoside suspension for optical characterization. Time-resolved absorbance measurements, over a spectral range from 300 to 700 nm, were made on the purified pigment at time delays from 30 ns to 4.64 seconds after photoexcitation using 7 ns pulses of 355 nm light. The resulting data were fit globally to a sum of exponential functions after noise reduction using singular value decomposition. Four exponentials best fit the data with lifetimes of 1.4 s, 210 s, 47 ms and 1 s. The first photointermediate species characterized here is an equilibrated mixture similar to the one formed after rhodopsin's Batho intermediate decays into equilibrium with its successor, BSI. The extremely large red shift of the SHUV Batho component relative to the pigment suggests that SHUV Batho has a protonated Schiff base and that the SHUV cone pigment itself has an unprotonated Schiff base. In contrast to SHUV Batho, the portion of the equilibrated mixture's spectrum corresponding to SHUV BSI is well fit by a model spectrum with an unprotonated Schiff base. The spectra of the next two photointermediate species revealed that they both have unprotonated Schiff bases and suggest they are analogous to rhodopsin's Lumi I and Lumi II species. After decay of SHUV Lumi II, correspondence with rhodopsin photointermediates breaks down and the next photointermediate, presumably including the G protein-activating species, is a mixture of protonated and unprotonated Schiff base photointermediate species. PMID:22394396

Mooney, Victoria L.; Szundi, Istvan; Lewis, James W.; Yan, Elsa C. Y.; Kliger, David S.

2012-01-01

37

Fluorescence method for enzyme analysis which couples aromatic amines with aromatic aldehydes  

DOEpatents

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.

Smith, Robert E. [557 Escondido Cir., Livermore, CA 94550; Dolbeare, Frank A. [5178 Diane La., Livermore, CA 94550

1980-10-21

38

Fluorescence method for enzyme analysis which couples aromatic amines with aromatic aldehydes  

DOEpatents

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

Smith, R.E.; Dolbeare, F.A.

1980-10-21

39

Recent advances in cooperative bimetallic asymmetric catalysis: dinuclear Schiff base complexes.  

PubMed

Cooperative catalysis has proven to be a powerful strategy for realizing high reactivity and selectivity in asymmetric transformations. A variety of cooperative asymmetric catalysts have been developed over the last two decades. In this feature article, recent advances from our research on cooperative asymmetric catalysis, focusing on dinuclear Schiff base catalysis, are described. Design of dinuclear Schiff base catalysts and their applications in several asymmetric C-C and C-N bond-forming reactions under simple proton transfer conditions with perfect atom-economy are discussed in detail. PMID:24281133

Matsunaga, Shigeki; Shibasaki, Masakatsu

2014-02-01

40

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

PubMed

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. PMID:23321220

Asadi, Zahra; Shorkaei, Mohammad Ranjkesh

2013-03-15

41

Optical chemosensors based on transmetalation of salen-based Schiff base complexes.  

PubMed

We report our systematic studies of novel, simple, selective, and sensitive optical (both colorimetric and fluorescent) chemosensors for detecting Al(3+) based on transmetalation reactions (metal displacement or exchange reactions) of a series of K(I), Ca(II), Zn(II), Cu(II), and Pt(II) complexes containing different ligands of salen-based Schiff bases. Both the chemical structure of the salen ligand and the identity of the central metal ion have a tremendous impact on the sensing performance, which is mainly determined by the stability constant of the complex. Moreover, the selectivities of the salen-complex-based chemosensors are much better than those of the corresponding free salen ligands because of the shielding function of the filled-in metal ion in the complex. Therefore, the present work potentially provides a new and simple way to design optical probes via complex-based transmetalation reactions. PMID:24559169

Cheng, Jinghui; Ma, Xiaofeng; Zhang, Yuhui; Liu, Jiaoyan; Zhou, Xiangge; Xiang, Haifeng

2014-03-17

42

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

PubMed Central

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

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

2013-01-01

43

Syntheses, crystal structure and biological evaluation of Schiff bases and copper complexes derived from 4-formylpyrazolone  

NASA Astrophysics Data System (ADS)

Two new pyrazolone based Schiff base ligands 4-((2,4-dimethylphenylimino)methyl)-4,5-dihydro-3-methyl-1-p-tolyl-1H-pyrazol-5-ol [PTPMP-ME] and 4-((3,4-difluorophenylimino)methyl)-4,5-dihydro-3-methyl-1-p-tolyl-1H-pyrazol-5-ol [PTPMP-F] were synthesized. Using these Schiff base ligands two new Copper(II) complexes, [Cu(PTPMP-ME)2] (1) and [Cu(PTPMP-F)2] (2) were synthesized. The ligands and their copper complexes were characterized by IR, 1H NMR, mass, UV-Visible spectroscopy, molar conductivity and magnetic measurement. The molecular geometry of Schiff base ligand PTPMP-ME and copper complexes were determined by single-crystal X-ray analysis. On the basis of single crystal X-ray analysis and spectroscopic techniques, square planar geometry of the complexes was proposed. The Schiff base ligands and their metal complexes were tested for antimicrobial activity against Gram-positive bacteria; Staphylococcus aureus and Bacillus subtilis and Gram-negative bacteria; Escherichia coli and Pseudomonas aeruginosa.

Joseph, V. A.; Pandya, J. H.; Jadeja, R. N.

2015-02-01

44

[Synthesis and theoretical study on fluorescence property of 4- (2-hydroxybenzylideneamino) phenyl ethanone schiff base].  

PubMed

Using salicylaldehyde and 4-aminophenyl ethanone as raw material, a Schiff base derivative 4-(2-hydroxybenzylidene-amino) phenyl ethanone was synthesized by the solid phase reaction method at room temperature. The structure of the product was characterized by elemental analysis and 1 HNMR The UV spectra, fluorescence emission spectra and fluorescence quantum yield of the title Schiff base derivative were investigated. The results showed that this Schiff base displayed superior fluorescence property. The ground state configuration of the title Schiff base was optimized by density functional theory (DFT) method at the B3LYP/6-311G level. After vibrational analysis, there is no imaginary frequency, which indicates that the structure is stable. Then the ground state configuration was optimized to the excited state configuration by the method of single excited interactions CIS. Based on the optimized structure for the ground state and excited state time-dependent density functional theory (TD-DFT) calculations were carried out at the B3LYP/6-31G level to predict the absorption spectra and the fluorescence spectra. The results show that the computed spectra were comparable with the spectra from the experiments. The relationship between the molecular structure and the fluorescence property of 4-(2-hydroxybenzylideneamino) phenyl ethanone was also discussed. The results obtained may provide some theoretical guidance for the design of new fluorescence compounds. PMID:24611382

Liang, Xiao-Rui; Wang, Gang; Jiang, Yan-Lan; Qu, Cheng-Li; Wang, Xiu-Juan; Zhao, Bo

2013-12-01

45

Rapid Photodynamics of Vitamin B6 Coenzyme Pyridoxal 5-Phosphate and Its Schiff Bases in Solution  

E-print Network

Rapid Photodynamics of Vitamin B6 Coenzyme Pyridoxal 5-Phosphate and Its Schiff Bases in Solution, 2007; In Final Form: February 4, 2008 The active form of vitamin B6, pyridoxal 5-phosphate (PLP (absorbing at 410 nm) tautomers in solution. 1. Introduction Pyridoxal 5-phosphate (PLP), one form of vitamin

Toney, Michael

46

Synthesis, spectroscopic and cytotoxic studies of biologically active new schiff bases derived from p-nitrobenzaldehyde.  

PubMed

Thirteen new Schiff bases derived from p-nitrobenzaldehyde were synthesized by condensation with the appropriate amines. An unusual reduction of the p-nitrobenzaldehyde to the corresponding alcohol was also observed in one of the reactions. The structures of the compounds were identified using spectroscopic techniques. Cytotoxicity for the titled compounds was studied against Brine Shrimp, used as the test animal. PMID:17603204

Iqbal, Amjid; Siddiqui, Hamid Latif; Ashraf, Chaudhary Muhammad; Bukhari, Mujahid Hussain; Akram, Chaudhary Muhammad

2007-07-01

47

Towards dipyrrins: oxidation and metalation of acyclic and macrocyclic Schiff-base dipyrromethanes.  

PubMed

Oxidation of acyclic Schiff-base dipyrromethanes cleanly results in dipyrrins, whereas the macrocyclic 'Pacman' analogues either decompose or form new dinuclear copper(ii) complexes that are inert to ligand oxidation; the unhindered hydrogen substituent at the meso-carbon allows new structural motifs to form. PMID:25563854

Pankhurst, James R; Cadenbach, Thomas; Betz, Daniel; Finn, Colin; Love, Jason B

2015-01-20

48

Evaluation of a chiral cubane-based Schiff base ligand in asymmetric catalysis reactions  

PubMed Central

Summary Recently, a novel chiral cubane-based Schiff base ligand was reported to yield modest enantioselectivity in the Henry reaction. To further explore the utility of this ligand in other asymmetric organic transformations, we evaluated its stereoselectivity in cyclopropanation and Michael addition reactions. Although there was no increase in stereocontrol, upon computational evaluation using both M06L and B3LYP calculations, it was revealed that a pseudo six-membered ring exists, through H-bonding of a cubyl hydrogen to the copper core. This decreases the steric bulk above the copper center and limits the asymmetric control with this ligand. PMID:23209516

Biegasiewicz, Kyle F; Ingalsbe, Michelle L; St. Denis, Jeffrey D; Gleason, James L; Ho, Junming; Coote, Michelle L; Savage, G Paul

2012-01-01

49

Octopus photoreceptor membranes. Surface charge density and pK of the Schiff base of the pigments.  

PubMed Central

The chromophore of octopus rhodopsin is 11-cis retinal, linked via a protonated Schiff base to the protein backbone. Its stable photoproduct, metarhodopsin, has all-trans retinal as its chromphore. The Schiff base of acid metarhodopsin (lambda max = 510 nm) is protonated, whereas that of alkaline metarhodopsin (lambda max = 376 nm) is unprotonated. Metarhodopsin in photoreceptor membranes was titrated and the apparent pK of the Schiff base was measured at different ionic strengths. From these salt-dependent pKs the surface charge density of the octopus photoreceptor membranes and the intrinsic Schiff base pK of metarhodopsin were obtained. The surface charge density is sigma = -1.6 +/- 0.1 electronic charges per 1,000 A2. Comparison of the measured surface charge density with values from octopus rhodopsin model structures suggests that the measured value is for the extracellular surface and so the Schiff base in metarhodopsin is freely accessible to protons from the extracellular side of the membrane. The intrinsic Schiff base pK of metarhodopsin is 8.44 +/- 0.12, whereas that of rhodopsin is found to be 10.65 +/- 0.10 in 4.0 M KCl. These pK values are significantly higher than the pK value around 7.0 for a retinal Schiff base in a polar solvent; we suggest that a plausible mechanism to increase the pK of the retinal pigments is the preorganization of their chromophore-binding sites. The preorganized site stabilizes the protonated Schiff base with respect to the unprotonated one. The difference in the pK for the octopus rhodopsin compared with metarhodopsin is attributed to the relative freedom of the latter's chromophore-binding site to rearrange itself after deprotonation of the Schiff base. PMID:2207250

Koutalos, Y; Ebrey, T G; Gilson, H R; Honig, B

1990-01-01

50

A water-soluble polylysine-retinaldehyde Schiff base. Stability in aqueous and nonaqueous environments.  

PubMed

In order to improve the existing models of retinal-protein Schiff bases, a water-soluble polylysine-retinaldehyde imine has been synthesized and its stability assessed under a variety of conditions through changes in the visible absorption spectrum. The compound absorbs at 342 nm and consists of a 90-kDa poly-L-lysine containing a retinal Schiff base in about 2% of the lysyl epsilon-amino ends. Retinal is mostly in the all-trans form; under no conditions is more than 15% of the 13-cis isomer detected. The absorption maximum exhibits a pH-dependent reversible shift to 402 nm, with an apparent pKa approximately 3.4. In the presence of the anionic surfactant sodium dodecyl sulfate, this pKa is shifted to approximately 8.9, probably because of electric neutralization of lysyl epsilon-amino groups. Other detergents (cetyltrimethylammonium bromide, Triton X-100) do not modify the Schiff base pKa, but rather promote its hydrolysis; in this case detergents act in the same way as certain solvent mixtures, by providing an amphiphillic environment to the imine that in turn stabilizes the products of hydrolysis. Our results suggest that once the surfactant reaches the Schiff base, preferential partition of retinal into detergent micelles is the main factor facilitating imine bond breakdown. The response of our synthetic Schiff base to changes in pH or solvent polarity point together to an important role of the supporting polypeptide in providing a suitable environment to the chromophore. PMID:2303414

Viguera, A R; Villa, M J; Goi, F M

1990-02-15

51

Preparation of chiral amino esters by asymmetric phase-transfer catalyzed alkylations of Schiff bases in a ball mill.  

PubMed

The asymmetric alkylation of Schiff bases under basic conditions in a ball mill was performed. The starting Schiff bases of glycine were prepared beforehand by milling protected glycine hydrochloride and benzophenone imine, in the absence of solvent. The Schiff base was then reacted with a halogenated derivative in a ball mill in the presence of KOH. By adding a chiral ammonium salt derived from cinchonidine, the reaction proceeded asymmetrically under phase-transfer catalysis conditions, giving excellent yields and enantiomeric excesses up to 75?%. Because an equimolar amount of starting material was used, purification was greatly simplified. PMID:22322525

Nun, Pierrick; Prez, Violaine; Calms, Monique; Martinez, Jean; Lamaty, Frdric

2012-03-19

52

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

53

Investigation of triazole derived Schiff bases as corrosion inhibitors for mild steel in hydrochloric acid medium  

Microsoft Academic Search

3,5-Diamino-1,2,4-triazole Schiff base derivatives and their inhibition efficiency, based on the effect of changing functional\\u000a groups, were reported to establish a relationship between inhibitor efficiency and molecular structure using weight loss method,\\u000a electrochemical and Fourier transform infrared spectral techniques. It was found that the molecules containing more electron\\u000a donating groups have higher inhibition efficiency than the corresponding compounds with low

D. Gopi; K. M. Govindaraju; L. Kavitha

2010-01-01

54

The aromatic fluctuation index (FLU): A new aromaticity index based on electron delocalization  

NASA Astrophysics Data System (ADS)

In this work, the aromatic fluctuation index (FLU) that describes the fluctuation of electronic charge between adjacent atoms in a given ring is introduced as a new aromaticity measure. This new electronic criterion of aromaticity is based on the fact that aromaticity is related to the cyclic delocalized circulation of ? electrons. It is defined not only considering the amount of electron sharing between contiguous atoms, which should be substantial in aromatic molecules, but also taking into account the similarity of electron sharing between adjacent atoms. For a series of rings in 15 planar polycyclic aromatic hydrocarbons, we have found that, in general, FLU is strongly correlated with other widely used indicators of local aromaticity, such as the harmonic-oscillator model of aromaticity, the nucleus independent chemical shift, and the para-delocalization index (PDI). In contrast to PDI, the FLU index can be applied to study the aromaticity of rings with any number of members and it can be used to analyze both the local and global aromatic character of rings and molecules.

Matito, Eduard; Duran, Miquel; Sol, Miquel

2005-01-01

55

Synthesis, Dioxygen Affinities and Biomimetic Catalytic Oxidation Performance of Crown Ether-tethered Schiff Base Transition-Metal Complexes  

Microsoft Academic Search

Mono-Schiff bases containing crown ether ring (HL1, HL2, HL3 and HL4) and their transition-metal complexes were synthesized and characterized by 1H NMR, IR, MS spectra and elemental analysis. The crystal structures of HL1, HL3 and CoL21 were determined from X-ray diffraction data. The oxygenation constants (Ko2) of Schiff-base Co (II) complexes were measured over a range of ?5C to 25C,

Wei Zeng; Zhihua Mao; Xingyao Wei; Jianzhang Li; Zhou Hong; Shengying Qin

2002-01-01

56

The Synthesis and Characterization of New Schiff Bases and Investigating them in Solvent Extraction of Chromium and Copper  

Microsoft Academic Search

New Schiff bases containing nitrogen, sulfur and oxygen donor atoms, were designed and synthesized in a multistep reaction sequence. The Schiff base(I) was used in solvent extraction of metal chlorides such as Cu(II) from aqueous phase to the organic phase. The influences of the parameter functions, such as pH, solvent, ionic strength of aqueous phase, aqueous to organic phase, and

Farouk Kandil; Wail Al Zoubi; Mohamad Khaled Chebani

2012-01-01

57

Schiff base ligands and their transition metal complexes in the mixtures of ionic liquid + organic solvent: a thermodynamic study.  

PubMed

Schiff bases and their metal complexes in the mixtures of ionic liquid (IL) + organic solvent have shown great potential in attractive oxidation catalytic processes. The efficiency of such a process is strongly dependent on the various molecular interactions occurring between components. Thermodynamic properties of these systems can provide valuable information about structural interactions. Therefore, in this work, the interactions of the IL 1-hexyl-3-methylimidazolium chloride ([HMIm]Cl) with Schiff bases in organic solvents were studied through the measurements of density, viscosity, and electrical conductivity. The effect of solvent on the interactions was examined by the solutions of IL + BPIC Schiff base + solvent (C2H6O-C3H8O-C4H10O). Moreover, the influence of Schiff base ligand and Schiff base complex structures was probed by the solutions of IL + DMA + ligand (salcn/salpr/salen) and IL + DMA + complex (VO(3-OMe-salen)/VO(salophen)/VO(salen)), respectively. Using the experimental data, some important thermodynamic properties, such as standard partial molar volume (V), experimental slope (Sv), viscosity B-coefficient, solvation number (B/V), and limiting molar conductivity (?0) were calculated and discussed in terms of solute-solvent (IL-DMF/alcohol) and solute-cosolute (IL-Schiff base) interactions. PMID:25482659

Shekaari, Hemayat; Kazempour, Amir; Khoshalhan, Maryam

2015-01-21

58

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

PubMed Central

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.

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

2008-01-01

59

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

NASA Astrophysics Data System (ADS)

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.

Gndz, Z. Yurtman; Gndz, C.; zp?nar, C.; Urucu, O. Ayd?n

2015-02-01

60

[Photochromic properties of complexes of curcumin aniline schiff base with rare earth].  

PubMed

Using Ce, La, Nd (III) nitrate and a curcumin aniline schiff base and a curcumin bis (4-methyl aniline) schiff base as raw materials, six complexes were synthesized. Through the molar conductance, IR, TG-DTA and element analysis motheds, the structures of complexes were characterized. Moreover, the properties of UV-Visible spectra and photochromic properties of the complex, and the solvatechromic performance in organic solvents were explored. The experiments showed that the complexes have good photochromic and solvate-chromic properties. The fluorescence intensity and UV-Visible spectra intensity were reduced under exposure,and the color of the complex solution became light. The complexes have different UV-Visible spectra in difference organic solvents. The relationship between photochromic properties and time was also studied. PMID:24611370

Song, Yu-Min; Yang, Mei-Ling; Ma, Jun-Huai; Zhang, Yu-Mei

2013-12-01

61

Docking of ethanamine Schiff base imines & metal (II) complexes, cytotoxicity & DNA interaction studies  

NASA Astrophysics Data System (ADS)

The present study deals with a series of biologically and stereo chemically important novel transition metal (II) Schiff base chelates. The Cu (II), Co (II), Mn (II) and Ni (II) ions containing complexes were synthesized by using diphenylethanamine and 2-hydroxy/2, 4-dihydroxy/2-hydroxy-4-methoxybenzaldehydes. The synthesized complexes were characterized using micro analytical, IR, NMR, ESI-Mass, UV-Visible, cyclic voltammetry and the EPR spectroscopic techniques. The spectral data evidenced the action of ligands as a neutral bidentate Schiff bases, coordinating through azomethine nitrogen and oxygen atom of hydroxyl group. The interaction studies revealed the groove binding nature of complexes with CT-DNA. The ligand and synthesized metal complexes showed cytotoxicity against cancerous cells. The strong binding affinity of the imine and metal complexes was also confirmed by molecular docking studies.

Sujarani, S.; Ramu, A.

2015-01-01

62

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

NASA Astrophysics Data System (ADS)

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).

Selvi, Canan; Nartop, Dilek

2012-09-01

63

A dinuclear cadmium(II) Schiff base thiocyanato complex: crystal structure and fluorescence.  

PubMed

A new dinuclear cadmium(II) complex, [Cd(L)(NCS)]2 (1) has been synthesized using a potentially tetradentate Schiff base ligand HL, 2-((E)-(2-(diethylamino)ethylimino)methyl)-6-methoxyphenol, obtained by the condensation of 2-diethylaminoethylamine and o-vanillin, and characterized by different physicochemical techniques. Crystal structure of the title complex was unambiguously established by single crystal X-ray diffraction which reveals that metal centers are connected by bridging phenolato and chelating methoxy oxygen atoms of the coordinating Schiff bases and embedded in severely distorted octahedral geometries. Fluorescence properties of the ligand and its complex, studied at room temperature indicate that later may serve as strong fluorescent emitter. PMID:24664327

Shit, Shyamapada; Sankolli, Ravish; Guru Row, Tayur N

2014-01-01

64

Studies on synthesis, characterization, DNA interaction and cytotoxicity of ruthenium(II) Schiff base complexes.  

PubMed

The synthesis and characterization of three hexa-coordinated ruthenium(II) Schiff base complexes of the type [RuCl(CO)(B)L] (B=PPh(3)/AsPh(3)/py and L=monobasic tridentate Schiff base ligand derived by the condensation of salicylaldehyde with 4-aminoantipyrine) are reported. IR, electronic, NMR and mass spectral data of the complexes are discussed. An octahedral geometry has been tentatively proposed for all the complexes. DNA binding properties of the ligand and its ruthenium(II) complexes have been investigated by electronic absorption spectroscopy. Two of the complexes were tested for DNA cleavage property. Finally, in vitro study of the cytotoxicity of the ligand and the complex [RuCl(CO)(PPh(3))L] on HeLa were tested. The IC(50) value for the ligand and the complex were 52.3 and 31.6?m respectively. PMID:22522297

Raja, Gunasekaran; Butcher, Ray J; Jayabalakrishnan, Chinnasamy

2012-08-01

65

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

PubMed

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. PMID:25437845

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

2015-03-01

66

Coordination chemistry, thermodynamics and DFT calculations of copper(II) NNOS Schiff base complexes.  

PubMed

Synthesis, magnetic and spectroscopy techniques are described for five copper(II) containing tetradentate Schiff bases are synthesized from methyl-2-(N-2'-aminoethane), (1-methyl-2'-aminoethane), (3-aminopropylamino)cyclopentenedithiocarboxylate. Molar conductance and infrared spectral evidences indicate that the complexes are four-coordinate in which the Schiff bases are coordinated as NNOS ligands. Room temperature ?eff values for the complexes are 1.71-1.80B.M. corresponding to one unpaired electron respectively. The formation constants and free energies were measured spectrophotometrically, at constant ionic strength 0.1M (NaClO4), at 25?C in DMF solvent. Also, the DFT calculations were carried out to determine the structural and the geometrical properties of the complexes. The DFT results are further supported by the experimental formation constants of these complexes. PMID:24992917

Esmaielzadeh, Sheida; Azimian, Leila; Shekoohi, Khadijeh; Mohammadi, Khosro

2014-12-10

67

Synthesis and characterization of modified Schiff base silatranes (MSBS) via 'Click Silylation'  

NASA Astrophysics Data System (ADS)

Schiff bases (1a-1d) were modified into terminal alkynes (2a-2d) which on Click Silylation with 3-azidopropyltriethoxysilane (AzPTES) yielded 1,2,3-triazole capped triethoxysilanes (3a-3d). These triethoxysilanes on transesterification with triethanolamine afforded corresponding modified Schiff base silatranes (MSBS) (4a-4d) in high yield and purity. All the synthesized compounds were well characterized by IR, NMR (1H, 13C), mass spectroscopy, elemental analysis and complete structure elucidation by X-ray diffraction studies for 2b and 4b. Starting alkynes and final silatranes are further compared by their absorption spectra and TGA analysis. Synthesized MSBS are the first compounds of their kind which being hydrolytically stable can be put to further use in the field of medical and material research.

Singh, Gurjaspreet; Arora, Aanchal; Mangat, Satinderpal Singh; Singh, Jandeep; Chaudhary, Sunita; Kaur, Navneet; Choquesillo-Lazarte, Duane

2015-01-01

68

Coordination chemistry, thermodynamics and DFT calculations of copper(II) NNOS Schiff base complexes  

NASA Astrophysics Data System (ADS)

Synthesis, magnetic and spectroscopy techniques are described for five copper(II) containing tetradentate Schiff bases are synthesized from methyl-2-(N-2";-aminoethane), (1-methyl-2";-aminoethane), (3-aminopropylamino)cyclopentenedithiocarboxylate. Molar conductance and infrared spectral evidences indicate that the complexes are four-coordinate in which the Schiff bases are coordinated as NNOS ligands. Room temperature ?eff values for the complexes are 1.71-1.80 B.M. corresponding to one unpaired electron respectively. The formation constants and free energies were measured spectrophotometrically, at constant ionic strength 0.1 M (NaClO4), at 25?C in DMF solvent. Also, the DFT calculations were carried out to determine the structural and the geometrical properties of the complexes. The DFT results are further supported by the experimental formation constants of these complexes.

Esmaielzadeh, Sheida; Azimian, Leila; Shekoohi, Khadijeh; Mohammadi, Khosro

2014-12-01

69

Transition Metal(II) Complexes with Cefotaxime-Derived Schiff Base: Synthesis, Characterization, and Antimicrobial Studies  

PubMed Central

New [ML2(H2O)2] complexes, where M?=?Co(II), Ni(II), Cu(II), and Zn(II) while L corresponds to the Schiff base ligand, were synthesized by condensation of cefotaxime with salicylaldehyde in situ in the presence of divalent metal salts in ethanolic medium. The complexes were characterized by elemental analyses, conductance, and magnetic measurements, as well as by IR and UV-Vis spectroscopy. The low values of the molar conductance indicate nonelectrolyte type of complexes. Based on spectral data and magnetic moments, an octahedral geometry may be proposed for Co(II), Ni(II), and Zn(II) complexes while a tetragonal geometry for Cu(II) complex. Molecular structure of the Schiff base ligand and its complexes were studied using programs dedicated to chemical modeling and quantomolecular calculation of chemical properties. All the synthesized complexes were tested for in vitro antibacterial activity against some pathogenic bacterial strains, namely Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus. The MIC values shown by the complexes against these bacterial strains revealed that the metal complexes possess superior antibacterial activity than the Schiff base. PMID:24688454

Amzoiu, Emilia; Spnu, Cezar Ionu?

2014-01-01

70

Corrosion inhibition of mild steel with Schiff base compounds in 1 M HCl  

Microsoft Academic Search

The corrosion inhibition of mild steel with Schiff base compounds derived from salicylaldehyde and the corresponding amine was studied in relation to the concentration using electrochemical techniques. The maximum inhibition efficiency (?) was obtained for the N-(2-methyl phenyl)salicyaldimine compound with the three-electrochemical techniques applied. The N-(2-methyl phenyl)salicyaldimine and N-(2-methoxyphenyl)salicyaldimine compounds were seen to obey the Temkin adsorption isotherm whereas N-(2-hydroxyphenyl)salicyaldimine

Kaan C Emregl; O Atakol

2003-01-01

71

A novel Schiff base: Synthesis, structural characterisation and comparative sensor studies for metal ion detections  

NASA Astrophysics Data System (ADS)

A novel Schiff base ligand was synthesized by the condensation reaction of 2,6-diformylpyridine and 4-aminoantipyrine in MeOH and characterised by its melting point, elemental analysis, FT-IR, 1H, 13C NMR and mass spectroscopic studies. Molecular structure of the ligand was determined by single crystal X-ray diffraction technique. The electrochemical properties of the Schiff base ligand were studied in different solvents at various scan rates. Sensor ability of the Schiff base ligand was investigated by colorimetric and fluorometric methods. Visual colour change of the ligand was investigated in MeOH solvent in presence of various metal ions Na+, Mg2+, Al3+, K+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+. Upon addition of Al3+ ion into a MeOH solution of the ligand, an orange colour developed which is detectable by naked eye. Fluorescence emission studies showed that the ligand showed single emission band at 630-665 nm upon excitation at 560 nm. Addition of metal ions Na+, Mg2+, K+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ (1:1 M ratio) cause fluorescence quenching, however addition of Al+3 resulted in an increase in fluorescence intensity. No significant variation was observed in the fluorescence intensity caused by Al3+ in presence of other metal ions. Therefore, the Schiff base ligand can be used for selective detection of Al3+ ions in the presence of the other metal ions studied.

Kse, Muhammet; Purtas, Savas; Gngr, Seyit Ali; Ceyhan, Gkhan; Akgn, Eyup; McKee, Vickie

2015-02-01

72

A novel Schiff base: Synthesis, structural characterisation and comparative sensor studies for metal ion detections.  

PubMed

A novel Schiff base ligand was synthesized by the condensation reaction of 2,6-diformylpyridine and 4-aminoantipyrine in MeOH and characterised by its melting point, elemental analysis, FT-IR, (1)H, (13)C NMR and mass spectroscopic studies. Molecular structure of the ligand was determined by single crystal X-ray diffraction technique. The electrochemical properties of the Schiff base ligand were studied in different solvents at various scan rates. Sensor ability of the Schiff base ligand was investigated by colorimetric and fluorometric methods. Visual colour change of the ligand was investigated in MeOH solvent in presence of various metal ions Na(+), Mg(2+), Al(3+), K(+), Cr(3+), Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+). Upon addition of Al(3+) ion into a MeOH solution of the ligand, an orange colour developed which is detectable by naked eye. Fluorescence emission studies showed that the ligand showed single emission band at 630-665nm upon excitation at 560nm. Addition of metal ions Na(+), Mg(2+), K(+), Cr(3+), Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+) (1:1M ratio) cause fluorescence quenching, however addition of Al(+3) resulted in an increase in fluorescence intensity. No significant variation was observed in the fluorescence intensity caused by Al(3+) in presence of other metal ions. Therefore, the Schiff base ligand can be used for selective detection of Al(3+) ions in the presence of the other metal ions studied. PMID:25459697

Kse, Muhammet; Purtas, Savas; Gngr, Seyit Ali; Ceyhan, Gkhan; Akgn, Eyup; McKee, Vickie

2014-10-18

73

Catalytic enantioselective desymmetrization of meso-glutaric anhydrides using a stable Ni2-Schiff base catalyst.  

PubMed

We describe the desymmetrization of meso-glutaric anhydrides to chiral hemiesters using a bench-stable homodinuclear Ni(2)-(Schiff base) complex as the catalyst in good to excellent yield (up to 99%) and enantioselectivity (up to 94%). Using the opposite enantiomer of the catalyst, we obtained the same yield and enantioselectivity with the opposite configuration, thereby gaining access to both hemiester enantiomers. PMID:22339049

Gopinath, Purushothaman; Watanabe, Takumi; Shibasaki, Masakatsu

2012-03-01

74

Synthesis and spectral characterization of ternary mixed-vanadyl ?-diketonate complexes with Schiff bases.  

PubMed

A new method to synthesize some mononuclear ternary oxovanadium(IV) complexes of the general formula [VO(?-dike)(SB)] (where H?-dike=acetylacetone; benzoylacetone or dibenzoylmethane, HSB=Schiff bases) has been explored by stepwise substitutions of acetylacetonate ion of VO(acac)(2) with Schiff bases. The substituted acetylacetone could be fractionated out with p-xylene as an azeotrope. The complexes were characterized by elemental analyses, molecular weight determinations, spectral (electronic, infrared, (1)H NMR, EPR and powder XRD) studies, magnetic susceptibility measurements and cyclic voltammetry. Molar conductance measurements indicated the complexes to be non-electrolytes in nitrobenzene. Bidentate chelating nature of ?-diketones and Schiff base anions in the complexes was established by infrared and NMR spectra. Molecular weight determinations confirmed mononuclear nature of the complexes. The EPR spectra illustrated coupling of the unpaired electron with (51)V nucleus (I=7/2). Cyclic voltammograms of all the complexes displayed two-step oxidation processes. The oxidation peak potential corresponded to the quasireversible one-electron oxidation process of the metal center, yielding V(V) species. Transmission electron microscopy (TEM) indicated spherical particles of ?200 nm diameter. The synthesized complexes are mixed-ligand complexes showing a considerable hydrolytic stability in which vanadium is having coordination number 5. A square pyramidal geometry around vanadium has been assigned in all the complexes. PMID:22387685

Baranwal, Balram Prasad; Tripathi, Kiran; Singh, Alok Kumar; Tripathi, Saurabh

2012-06-01

75

Antioxidant properties of phenolic Schiff bases: structure-activity relationship and mechanism of action.  

PubMed

Phenolic Schiff bases are known for their diverse biological activities and ability to scavenge free radicals. To elucidate (1) the structure-antioxidant activity relationship of a series of thirty synthetic derivatives of 2-methoxybezohydrazide phenolic Schiff bases and (2) to determine the major mechanism involved in free radical scavenging, we used density functional theory calculations (B3P86/6-31+(d,p)) within polarizable continuum model. The results showed the importance of the bond dissociation enthalpies (BDEs) related to the first and second (BDEd) hydrogen atom transfer (intrinsic parameters) for rationalizing the antioxidant activity. In addition to the number of OH groups, the presence of a bromine substituent plays an interesting role in modulating the antioxidant activity. Theoretical thermodynamic and kinetic studies demonstrated that the free radical scavenging by these Schiff bases mainly proceeds through proton-coupled electron transfer rather than sequential proton loss electron transfer, the latter mechanism being only feasible at relatively high pH. PMID:24243063

Anouar, El Hassane; Raweh, Salwa; Bayach, Imene; Taha, Muhammad; Baharudin, Mohd Syukri; Di Meo, Florent; Hasan, Mizaton Hazizul; Adam, Aishah; Ismail, Nor Hadiani; Weber, Jean-Frdric F; Trouillas, Patrick

2013-11-01

76

Synthesis, spectrochemical characterisation and catalytic activity of transition metal complexes derived from Schiff base modified chitosan  

NASA Astrophysics Data System (ADS)

Three novel quadridentate Schiff base complexes, [Cu(OIAC)Cl2], [Co(OIAC)Cl2] and [Ni(OIAC)Cl2] [OIAC, a Schiff base ligand: (([2-oxo-1H-indol-3-ylidene]amino)chitosan)] have been synthesized. The molecular structure of the complexes has been characterised by elemental analyses, magnetic measurements, molar conductance studies, vibrational (FT-IR), electronic (UV-Vis) and 1H NMR spectroscopic techniques. Thermal properties of the complexes have been investigated with TG-DTG analyses. The surface morphological difference of ligand and the complexes has been explored with scanning electron microscopy. The crystallinity of the compounds was analysed by powder X-ray diffraction technique and it was found to be less for the Schiff base (OIAC) and the complexes as compared to the chitosan. The catalytic activities of the complexes have been studied in the oxidation of cyclohexane, using environmental friendly oxidant, hydrogen peroxide. Complex with rough surface has shown higher catalytic activity compared to the other complexes.

Antony, R.; Theodore David, S.; Saravanan, K.; Karuppasamy, K.; Balakumar, S.

2013-02-01

77

Colorimetric chemosensor for multi-signaling detection of metal ions using pyrrole based Schiff bases  

NASA Astrophysics Data System (ADS)

Pyrrole based Schiff bases act as a highly sensitive probe for metal ions in aqueous medium. Both receptors R1 and R2 are sensitive towards Fe3+, Cu2+, Hg2+ and Cr3+ among the other metal ions. The sensing ability of the receptors are investigated via colorimetric, optical and emission spectroscopic studies. The binding stoichiometries of R1 and R2 with metal ions have been determined as 2:1 by using Job's plot. The colorimetric receptors exhibited high sensitivity with a low detection limit of ?M levels. In the presence of metal ions both receptors shows fluorescence quenching. This might be due to the photo induced electron transfer mechanism. The quenching constant was further determined using Stern-Volmer plot.

Udhayakumari, Duraisamy; Velmathi, Sivan

2014-03-01

78

Fluorescence sensors for Zn(2+) based on conjugated indole Schiff base.  

PubMed

Two novel fluorescence probes based on conjugated Schiff base for the detection of Zn(2+) were developed. Corresponding molecular geometries, orbital energies, electron contributions and absorption properties of the fluorescence probes were calculated at B3LYP/6-31G(?) by density functional theory. The fluorescence properties of the probes were investigated by UV-vis and fluorescence spectrometer. Results indicate that the probes exhibit excellent sensitivity and selectivity for Zn(2+) compared with metal ions examined. For example, the enhancement efficiency of the compound 2 for Zn(2+) is up to 846%. The detection limit of the sensor toward Zn(2+) could low to 1.010(-7)M. Moreover, mechanisms for the high selectivity and sensitivity of the probes to Zn(2+) were studied. PMID:25541397

Xu, Ting; Duan, Hongdong; Wang, Xingjian; Meng, Xia; Bu, Juan

2015-03-01

79

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

PubMed Central

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

2013-01-01

80

Synthesis and antioxidant activity of thymol and carvacrol based Schiff bases.  

PubMed

Thymol and carvacrol are well known antioxidants found in the extract of the plants of thyme species. The Schiff bases of 2-iso-propyl-5-methyl-phenol (thymol/1a), 2-tert-butyl-5-methyl-phenol (1b) and 5-iso-propyl-2-methyl-phenol (carvacrol/1c) exhibited much better antioxidant activity than thymol and carvacrol in DPPH assay. Ten compounds (4k, 4l, 4r, 5k, 5l, 5q, 5r, 6k, 6l and 6r) showed better or similar activity as compared to the reference compound ascorbic acid. Twenty-four most active compounds were also screened by ABTS method and showed 60-90% inhibition at 5 ?g/mL concentration. PMID:23273412

Beena; Kumar, Deepak; Rawat, Diwan S

2013-02-01

81

Heterobimetallic transition metal/rare earth metal bifunctional catalysis: a Cu/Sm/Schiff base complex for syn-selective catalytic asymmetric nitro-Mannich reaction.  

PubMed

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). PMID:20218689

Handa, Shinya; Gnanadesikan, Vijay; Matsunaga, Shigeki; Shibasaki, Masakatsu

2010-04-01

82

The NMR and X-ray study of L-arginine derived Schiff bases and its cadmium complexes  

NASA Astrophysics Data System (ADS)

The structure study of five Schiff bases derived from L-arginine (L-Arg) and 2-hydroxy carbonyl compounds were performed in both solution and solid state using NMR and X-ray methods. Both analytical methods applied to the solid state sample of two Schiff bases showed a significant difference in molecular structures of unsubstituted and 7-CH3 substituted compounds. This effect was explained as a steric interaction of methyl group. Additionally the structure of two Cd2+ complexes with some Schiff bases were determined by NMR methods in DMSO solution and in the solid state. On the base of heteronuclear NMR measurement (13C, 15N and 113Cd) it was possible to define the complexation site on nitrogen atom. The large set of spectral parameters: chemical shifts, homo- and heteronuclear coupling constants, were used in structure study.

Ko?odziej, B.; Grech, E.; Schilf, W.; Kamie?ski, B.; Pazio, A.; Wo?niak, K.

2014-04-01

83

Synthesis and characterization of chromium(III) Schiff base complexes: Antimicrobial activity and its electrocatalytic sensing ability of catechol.  

PubMed

A series of acyclic Schiff base chromium(III) complexes were synthesized with the aid of microwave irradiation method. The complexes were characterized on the basis of elemental analysis, spectral analysis such as UV-Visible, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) spectroscopies and electrospray ionization (ESI) mass spectrometry. Electrochemical analysis of the complexes indicates the presence of chromium ion in +3 oxidation state. Cr (III) ion is stabilized by the tetradentate Schiff base ligand through its nitrogen and phenolic oxygen. From the spectral studies it is understood that the synthesized chromium(III) complexes exhibits octahedral geometry. Antimicrobial activity of chromium complexes was investigated towards the Gram positive and Gram negative bacteria. In the present work, an attempt was made to fabricate a new kind of modified electrode based on chromium Schiff base complexes for the detection of catechol at nanomolar level. PMID:25576940

Praveen Kumar, S; Suresh, R; Giribabu, K; Manigandan, R; Munusamy, S; Muthamizh, S; Narayanan, V

2015-03-15

84

Schiff bases of indoline-2,3-dione (isatin) with potential antiproliferative activity  

PubMed Central

Background Cancer is one of the most dreaded diseases and it is a leading cause of mankind death worldwide. Recent reports documented a remarkable antiproliferative activity of isatin nucleus against various cancer cell lines. The current work describes the antiproliferative activity of Schiff bases of combinatorial mixtures of the isatin derivatives M1-M22 as well as the individual compounds 1-11(A-K) of these combinatorial mixtures. Results The designed combinatorial library composed from eleven hydrazides A-K and eleven isatin derivatives 1-11 has been synthesized to formally generate 22 mixtures, M1-M22 of 121 Schiff bases, and their antiproliferative activity against K562 chronic myelogenous leukemia cells was evaluated. The indexed method of analysis of the prepared library was applied to elucidate the active components in the tested mixtures M1-M22. The predictions from the crossing procedure was validated through evaluation of the antiproliferative activity of individual compounds 1-11(A-K) of the library. Individual compounds 1-11(A-K) were also evaluated against the non-tumorigenic MCF-12A cell line to investigate their selectivity. A pharmacophore model was developed to further optimize the antiproliferative activity among this series of compounds. Conclusions Variable antiproliferative activity was revealed with the investigated mixtures M1-M22 and the individual compounds 1-11(A-K). Most of the tested mixtures and several individual Schiff bases displayed high potency with IC50 values in the low micromolar range. A considerable selectivity of some individual compounds to the tumorigenic K562 cell line compared with the non-tumorigenic MCF-12A cell line was observed as indicated by their selectivity index (SI). PMID:22647272

2012-01-01

85

A Novel Potentiometric Membrane Sensor for Quick Determination of Trace Amount of Based on a ZincSchiff's Base  

Microsoft Academic Search

Poly(vinylchloride) (PVC) based membrane of ZincSchiff's base (ZSB) with hexadecyltrimethyl ammonium bromide (HTAB), hexadecylpyridinum bromide (HDPB) as cation excluders and dibutyl phthalate (DBP) and benzyl acetate (BA) as plasticizing solvent mediators were prepared and investigated as -selective electrode. The best performance was observed with the membrane having the composition ZSBPVCHTABBA in the ratio 5%: 32%:3%:60%, which works well over a

Mohammad Reza Ganjali; Morteza Rezapour; Mohammad Reza Pourjavid; Masoud Salavati-Niasari; Tahereh Poursaberi

2003-01-01

86

Synthesis and characterization of copper complexes of Schiff base derived from isatin and salicylic hydrazide  

NASA Astrophysics Data System (ADS)

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 the complexes.

Lekshmy, R. K.; Thara, G. S.

2014-10-01

87

Synthesis and electrochromic, acidochromic properties of Schiff bases containing triphenylamine and thiophene units.  

PubMed

A series of Schiff bases (SBs) were designed and prepared from 2-thiophenecarboxaldehyde and different triphenylamine (TPA) derivatives. The structures of the compounds were characterized by Fourier transform infrared (FT-IR), hydrogen nuclear magnetic resonance ((1)H NMR). The optical and electrochemical properties were tested by ultraviolet-visible (UV-vis) spectroscopy and cyclic voltammetry (CV) techniques. The SBs exhibited stable and reversible electrochromic properties. Furthermore, multiple reversible colors states were also observed with the change of pH. Consequently, the SBs can be used as electrochromic and acidochromic materials. PMID:25617980

Wu, Xiaotong; Wang, Wen; Li, Bin; Hou, Yanjun; Niu, Haijun; Zhang, Yanhong; Wang, Shuhong; Bai, Xuduo

2015-04-01

88

A novel coumarin Schiff-base as a Ni(II) ion colorimetric sensor  

NASA Astrophysics Data System (ADS)

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.

Wang, Lingyun; Ye, Decheng; Cao, Derong

2012-05-01

89

Synthesis, characterization and antibacterial activity of a tridentate Schiff base derived from cephalothin and sulfadiazine, and its transition metal complexes.  

PubMed

Metal(II) coordination compounds of a cephalothin Schiff base (H2L) derived from the condensation of cephalothin antibiotic with sulfadiazine were synthesized. The Schiff base ligand, mononuclear [ML(H2O)3] (M(II)=Mn,Co,Ni,Zn) complexes and magnetically diluted dinuclear copper(II) complex [CuL(H2O)3]2 were characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and (1)H NMR spectral studies. The cephalothin Schiff base ligand H2L behaves as a dianionic tridentate NOO chelating agent. The biological applications of complexes have been studied on two bacteria strains (Escherichia coli and Staphylococcus aureus) by agar diffusion disc method. PMID:25194315

Anacona, J R; Noriega, Natiana; Camus, Juan

2015-02-25

90

Synthesis, characterization and antibacterial activity of a Schiff base derived from cephalexin and sulphathiazole and its transition metal complexes.  

PubMed

Metal(II) coordination compounds of a cephalexin Schiff base (HL) derived from the condensation of cephalexin antibiotic with sulphathiazole were synthesized. The Schiff base ligand, mononuclear [ML(OAc)(H2O)2] (M(II)=Mn, Co, Ni, Zn) complexes and magnetically diluted trinuclear copper(II) complex [Cu3L(OH)5] were characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and (1)H NMR spectral studies. The analytical and molar conductance values indicated that the acetate ions coordinate to the metal ions. The Schiff base ligand HL behaves as a monoanionic tridentate NNO and tetradentate NNOO chelating agent in the mono and trinuclear complexes respectively. PMID:24727167

Anacona, J R; Rodriguez, Juan Luis; Camus, Juan

2014-08-14

91

Synthesis, characterization and antibacterial activity of a tridentate Schiff base derived from cephalothin and sulfadiazine, and its transition metal complexes  

NASA Astrophysics Data System (ADS)

Metal(II) coordination compounds of a cephalothin Schiff base (H2L) derived from the condensation of cephalothin antibiotic with sulfadiazine were synthesized. The Schiff base ligand, mononuclear [ML(H2O)3] (M(II) = Mn, Co, Ni, Zn) complexes and magnetically diluted dinuclear copper(II) complex [CuL(H2O)3]2 were characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and 1H NMR spectral studies. The cephalothin Schiff base ligand H2L behaves as a dianionic tridentate NOO chelating agent. The biological applications of complexes have been studied on two bacteria strains (Escherichia coli and Staphylococcus aureus) by agar diffusion disc method.

Anacona, J. R.; Noriega, Natiana; Camus, Juan

2015-02-01

92

Synthesis, characterization and antibacterial activity of a Schiff base derived from cephalexin and sulphathiazole and its transition metal complexes  

NASA Astrophysics Data System (ADS)

Metal(II) coordination compounds of a cephalexin Schiff base (HL) derived from the condensation of cephalexin antibiotic with sulphathiazole were synthesized. The Schiff base ligand, mononuclear [ML(OAc)(H2O)2] (M(II) = Mn, Co, Ni, Zn) complexes and magnetically diluted trinuclear copper(II) complex [Cu3L(OH)5] were characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and 1H NMR spectral studies. The analytical and molar conductance values indicated that the acetate ions coordinate to the metal ions. The Schiff base ligand HL behaves as a monoanionic tridentate NNO and tetradentate NNOO chelating agent in the mono and trinuclear complexes respectively.

Anacona, J. R.; Rodriguez, Juan Luis; Camus, Juan

2014-08-01

93

Synthetic, Structural, and Biochemical Studies of Organotin(IV) With Schiff Bases Having Nitrogen and Sulphur Donor Ligands  

PubMed Central

Three bidentate Schiff bases having nitrogen and sulphur donor sequences were prepared by condensing S-benzyldithiocarbazate (NH2NHCS2CH2C6H5) with heterocyclic aldehydes. The reaction of diphenyltin dichloride with Schiff bases leads to the formation of a new series of organotin(IV) complexes. An attempt has been made to prove their structures on the basis of elemental analyses, conductance measurements, molecular weights determinations, UV, infrared, and multinuclear magnetic resonance (1H, 13C, and 119Sn) spectral studies. Organotin(IV) complexes were five- and six-coordinate. Schiff bases and their corresponding organotin complexes have also been screened for their antibacterial and antifungal activities and found to be quite active in this respect. PMID:17497003

Singh, Har Lal; Varshney, A. K.

2006-01-01

94

Crystal structure of Schiff base derivative of 2,2?-dihydroxybiphenyl-3-carbaldehyde with n-butylamine  

Microsoft Academic Search

Crystals of the Schiff base derivative of 2,2?-dihydroxybiphenyl-3-carbaldehyde with n-butylamine were examined using X-ray diffraction, FT-IR and CPMAS spectroscopy. Their space group is P-1 with a=8.377(2),b=12.214(2),c=14.774(3)A?,?=76.62(3),?=81.34(3),?=86.62(3) and Z=4. The unit cell contains two symmetry-independent zwitterions. The hydrogen atom of the protonated N atom of the Schiff base is linked to the oxygen atom of the carbonyl group at position 2,

Grzegorz Wojciechowski; Ma?gorzata Ratajczak-Sitarz; Andrzej Katrusiak; Wojciech Schilf; Piotr Przybylski; Bogumi? Brzezinski

2003-01-01

95

Effects of copper ions on DNA binding and cytotoxic activity of a chiral salicylidene Schiff base.  

PubMed

A chiral Schiff base HL N-(5-bromo-salicylaldehyde)dehydroabietylamine (1) and its chiral dinuclear copper complex [Cu2L4]4DMF (2) have been synthesized and fully characterized. The interactions of 1 and 2 with salmon sperm DNA have been investigated by viscosity measurements, UV, fluorescence and circular dichroism (CD) spectroscopic techniques. Absorption spectral (Kb=3.30 10(5)M(-)(1) (1), 6.63 10(5)M(-)(1)(2)), emission spectral (Ksv=7.58 10(3)M(-)(1) (1), 1.52 10(4)M(-)(1) (2)), and viscosity measurements reveal that 1 and 2 interact with DNA through intercalation and 2 exhibits a higher DNA binding ability. In addition, CD study indicates 2 cause a more evident perturbation on the base stacking and helicity of B-DNA upon binding to it. In fluorimetric studies, the enthalpy (?H>0) and entropy (?S>0) changes of the reactions between the compounds with DNA demonstrate hydrophobic interactions. 1 and 2 were also screened for their cytotoxic ability and 2 demonstrates higher growth inhibition of the selected cancer cells at concentration of 50 ?M, this result is identical with their DNA binding ability order. All the experimental results show that the involvement of Cu (II) centers has some interesting effect on DNA binding ability and cytotoxicity of the chiral Schiff base. PMID:24583369

Fei, Bao-Li; Xu, Wu-Shuang; Tao, Hui-Wen; Li, Wen; Zhang, Yu; Long, Jian-Ying; Liu, Qing-Bo; Xia, Bing; Sun, Wei-Yin

2014-03-01

96

New 3,4-diaminobenzoic acid Schiff base compounds and their complexes: synthesis, characterization and thermodynamics.  

PubMed

Some new tetradentate Schiff base ligands (H3L) were prepared via condensation of 3,4-diaminobenzoic acid with 2-hydroxybenzaldehyde derivatives, such as 3,4-bis((E)-2,4-dihydroxybenzylideneamino)benzoic acid (H3L(1)), 3,4-bis((E)-2-hydroxy-3-methoxybenzylideneamino)benzoic acid (H3L(2)) and 3,4-bis((E)-5-bromo-2-hydroxybenzylideneamino)benzoic acid (H3L(4)). Additionally, a tetradentate Schiff base ligand 3,4-bis((E)-2-hydroxybenzylideneamino)benzoic acid (H3L(3)) and its complexes were synthesized. Their metal complexes of Co(II), Ni(II), Cu(II) and Zn(II) were prepared in good yields from the reaction of the ligands with the corresponding metal acetate. They were characterized based on IR, (1)H NMR, Mass spectroscopy and UV-Vis spectroscopy. Also, the formation constants of the complexes were measured by UV-Vis spectroscopic titration at constant ionic strength 0.1M (NaClO4), at 25 C in dimethylformamide (DMF) as a solvent. PMID:24309180

Mohammadi, Khosro; Niad, Mahmood; Jafari, Tahereh

2014-03-25

97

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

PubMed

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 10(2) to 10(5) 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. PMID:24566120

Raman, N; Sakthivel, A; Pravin, N

2014-05-01

98

A new Schiff's base ligand immobilized agarose membrane optical sensor for selective monitoring of mercury ion.  

PubMed

A highly selective optical sensor was developed for the Hg(2+) determination by chemical immobilization of 2-[(2-sulfanylphenyl)ethanimidoyl]phenol (L), on an agarose membrane. Spectrophotometric studies of complex formation between the Schiff's base ligand L and Hg(2+), Sr(2+), Mn(2+), Cu(2+), Al(3+), Cd(2+), Zn(2+), Co(2+) and Ag(+) metal ions in methanol solution indicated a substantially larger stability constant for the mercury ion complex. Consequently, the Schiff's base L was used as an appropriate ionophore for the preparation of a selective Hg(2+) optical sensor, by its immobilization on a transparent agarose film. A distinct color change, from yellow to green-blue, was observed by contacting the sensing membrane with Hg(2+) ions at pH 4.5. The effects of pH, ionophore concentration, ionic strength and reaction time on the immobilization of L were studied. A linear relationship was observed between the membrane absorbance at 650 nm and Hg(2+) concentrations in a range from 110(-2) to 110(-5) mol L(-1) with a detection limit (3?) of 110(-6) mol L(-1). No significant interference from 100 times concentrations of a number of potentially interfering ions was detected for the mercury ion determination. The optical sensor was successfully applied to the determination of mercury in amalgam alloy and spiked water samples. PMID:21232854

Alizadeh, Kamal; Parooi, Razieh; Hashemi, Payman; Rezaei, Behrooz; Ganjali, Mohammad Reza

2011-02-28

99

Magnetic properties and structure of a Cu IIDy III heterodinuclear Schiff base complex  

NASA Astrophysics Data System (ADS)

The crystal structure of a new heterodinuclear lanthanide complex, L 2Cu(Me 2CO)Dy(NO 3) 3 (L 2= N, N'-bis(2-hydroxy-3-methoxy-benzylidene)-ethylenediamine) has determined and the magnetic properties of the complex investigated. (C 18H 18N 2O 4)Cu(C 3H 6O)Dy(NO 3) 3, monoclinic, space group P2 1/ c, with a=9.875(2), b=18.870(7), c=15.675(8) , ?=95.45(3), V=2908(2) 3, Z=4. The structure consists of ordered dinuclear units with Cu II and Dy III ions bridged by two phenolato oxygen atoms of the Schiff base ligand. The Cu II ion has a square-pyramidal geometry involving the basal N 2O 2 donor atoms of the Schiff base ligands and one oxygen atom of the acetone molecule at the apex position. The Dy III ion is decacoordinated by the four oxygen atoms of L 2 and six oxygen atoms from the three bidentate nitrate ions. The Cu⋯Dy separation is 3.461(2) . The ?T versus T plots, ? being the molar magnetic susceptibility per Cu IIDy III unit and T the temperature, has been measured in the 4.5-300 K temperature range. The magnetic properties of the compound are dominated by the crystal field effect on the Dy III site, masking the magnetic interaction between the paramagnetic centers.

Elmali, A.; Elerman, Y.

2005-02-01

100

Design, spectral characterization and biological studies of transition metal(II) complexes with triazole Schiff bases.  

PubMed

A new series of three biologically active triazole derived Schiff base ligands L(1)-L(3) 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. PMID:23277183

Hanif, Muhammad; Chohan, Zahid H

2013-03-01

101

Spectrophotometric investigation of interaction between iodine and pentadentate Schiff base ligands.  

PubMed

The interaction between iodine as an electron acceptor (A), and three pentadentate Schiff bases, 1,3-bis(salicylideneamino)-2-propanol (SB1), 1,3-bis(2-hydroxy-1-naphthylideneamino)-2-propanol (SB2), and 1,3-bis[1-(pyridine-2-yl)methylideneamino]-2-propanol (SB3), as electron donor systems (D), was studied spectrophotometrically in methanol at 28 C. Equilibrium constants K(AD) and molar extinction coefficients ?(AD) of the donor-acceptor complexes (AD) were determined using the modified Benesi-Hildebrand equation in conjunction with the non linear fit analysis. The method shows the formation of 1:1 type complexes as major species in solution. The free energy changes ?G and the energy of the charge transfer band E(CT) were also calculated for all complexes. The iodine complex derived from SB2 seems to be more stable than those derived from SB3 and SB1. On the other hand, the ionization potential I(D) of each Schiff base was estimated from the corresponding complex band energy, using an empirical equation. An inverse relationship between I(D) and K(AD) values was found. Blue and red shift observed for the 445 nm band of iodine were also discussed on the basis of theoretical considerations. PMID:24530710

Khouba, Z; Benabdallah, T; Maschke, U

2014-05-01

102

Ultrafast Excited State Dynamics of the Protonated Schiff Base of All-trans Retinal in Solvents  

PubMed Central

We present a comparative study of the ultrafast photophysics of all-trans retinal in the protonated Schiff base form in solvents with different polarities and viscosities. Steady-state spectra of retinal in the protonated Schiff base form show large absorption-emission Stokes shifts (65008100 cm?1) for both polar and nonpolar solvents. Using a broadband fluorescence up-conversion experiment, the relaxation kinetics of fluorescence is investigated with 120 fs time resolution. The time-zero spectra already exhibit a Stokes-shift of ?6000 cm?1, indicating depopulation of the Franck-Condon region in ?100 fs. We attribute it to relaxation along skeletal stretching. A dramatic spectral narrowing is observed on a 150 fs timescale, which we assign to relaxation from the S2 to the S1 state. Along with the direct excitation of S1, this relaxation populates different quasistationary states in S1, as suggested from the existence of three distinct fluorescence decay times with different decay associated spectra. A 0.50.65 ps decay component is observed, which may reflect the direct repopulation of the ground state, in line with the small isomerization yield in solvents. Two longer decay components are observed and are attributed to torsional motion leading to photo-isomerization. The various decay channels show little or no dependence with respect to the viscosity or dielectric constant of the solvents. This suggests that in the protein, the bond selectivity of isomerization is mainly governed by steric effects. PMID:15792984

Zgrabli?, Goran; Votchovsky, Kislon; Kindermann, Maik; Haacke, Stefan; Chergui, Majed

2005-01-01

103

Glutamic acid-113 serves as the retinylidene Schiff base counterion in bovine rhodopsin.  

PubMed Central

The characteristic wavelength at which a visual pigment absorbs light is regulated by interactions between protein (opsin) and retinylidene Schiff base chromophore. By using site-directed mutagenesis, charged amino acids in bovine rhodopsin transmembrane helix C were systematically replaced. Substitution of glutamic acid-134 or arginine-135 did not affect spectral properties. However, substitution of glutamic acid-122 by glutamine or by aspartic acid formed pigments that were blue-shifted in light absorption (lambda max = 480 nm and 475 nm, respectively). While the substitution of glutamic acid-113 by aspartic acid gave a slightly red-shifted pigment (lambda max = 505 nm), replacement by glutamine formed a pigment that was strikingly blue-shifted in light absorption (lambda max = 380 nm). The 380-nm species existed in a pH-dependent equilibrium with a 490-nm species such that at acidic pH all of the pigment was converted to lambda max = 490 nm. We conclude that glutamic acid-113 serves as the retinylidene Schiff base counterion in rhodopsin. We believe that this opsin-chromophore interaction is an example of a general mechanism of color regulation in the visual pigments. PMID:2573063

Sakmar, T P; Franke, R R; Khorana, H G

1989-01-01

104

Peroxygenase based sensor for aromatic compounds.  

PubMed

We report on the redox behaviour of the peroxygenase from Agrocybe aegerita (AaeAPO) which has been electrostatically immobilized in a matrix of chitosan-embedded gold nanoparticles on the surface of a glassy carbon electrode. AaeAPO contains a covalently bound heme-thiolate as the redox active group that exchanges directly electrons with the electrode via the gold nanoparticles. The formal potential E' of AaeAPO in the gold nanoparticles-chitosan film was estimated to be -(2869) mV at pH 7.0. The heterogeneous electron transfer rate constant (k(s)) increases from 3.7 in the scan rate range from 0.2 to 3.0 V s(-1) and level off at 63.7 s(-1). Furthermore, the peroxide-dependent hydroxylation of aromatic compounds was applied to develop a sensor for naphthalene and nitrophenol. The amperometric measurements of naphthalene are based on the indication of H(2)O(2) consumption. For the chitosan-embedded gold nanoparticle system, the linear range extends from 4 to 40 ?M naphthalene with a detection limit of 4.0 ?M (S/N=3) and repeatability of 5.7% for 40 ?M naphthalene. PMID:20719491

Peng, Lei; Wollenberger, Ulla; Kinne, Matthias; Hofrichter, Martin; Ullrich, Ren; Scheibner, Katrin; Fischer, Anna; Scheller, Frieder W

2010-12-15

105

Synthesis, characterization and the interaction of some new water-soluble metal Schiff base complexes with human serum albumin.  

PubMed

Some new water-soluble Schiff base complexes of Na2[M(L)(H2O)n]; (M=Zn, Cu, Ni, Mn) with a new water-soluble Schiff base ligand where L denotes an asymmetric N2O2 Schiff base ligands; N,N'-bis(5-sulfosalicyliden)-3,4-diaminobenzophenone (5-SO3-3,4-salbenz) were synthesized and characterized. The formation constants of the water soluble Schiff base complexes were calculated by Ketelaar's equation. The theoretical molecular structure for the complexes was computed by using the HF method and the 6-311G basis set. The mechanism of binding of Na2[M(L)(H2O)n] with human serum albumin (HSA) was studied by fluorescence spectroscopic technique. The results of fluorescence titration showed that the intrinsic fluorescence of HSA was quenched by the complexes; which was rationalized in terms of the dynamic quenching mechanism. The values of Stern-Volmer constants, quenching rate constants, binding constants, binding sites and average aggregation number of HSA have been determined. The thermodynamic parameters, were calculated by van't Hoff equation, indicate that the binding is entropy driven and enthalpically disfavored. Based on the Frster theory of non-radiation energy transfer, the efficiency of energy transfer and the distance between the donor (Trp residues) and the acceptor (complex) were obtained. Finally, the growth inhibitory effects of the complexes toward the K562 cancer cell line were measured. PMID:24299984

Asadi, Mozaffar; Asadi, Zahra; Sadi, Somaye Barzegar; Zarei, Leila; Baigi, Fatemeh Moosavi; Amirghofran, Zahra

2014-03-25

106

Metal complexes of ONO donor Schiff base ligand as a new class of bioactive compounds: synthesis, characterization and biological evolution.  

PubMed

Present work reviews that, the synthesis of (E)-N'-((7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzohydrazide [L] ligand and their metal complexes. The colored complexes were prepared of type [M(2+)L]X2, where M(2+)=Mn, Co, Ni, Cu, Sr and Cd, L=(7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzohydrazide, X=Cl(-). Ligand derived from the condensation of 8-formyl-7-hydroxy-4-methylcoumarin and benzohydrazide in the molar ratio 1:1 and in the molar ratio 1:2 for metal complexes have been prepared. The chelation of the ligand to metal ions occurs through the both oxygen groups, as well as the nitrogen atoms of the azomethine group of the ligand. Reactions of the Schiff base ligand with Manganese(II), Cobalt(II), Nickel(II), Copper(II), Strontium(II), and Cadmium(II) afforded the corresponding metal complexes. The structures of the obtained ligand and their respective metal complexes were elucidated by infra-red, elemental analysis, Double beam UV-visible spectra, conductometric measurements, magnetic susceptibility measurements and also thermochemical studies. The metal complex exhibits octahedral coordination geometrical arrangement. Schiff base ligand and their metal complexes were tested against antioxidants, antidiabetic and antimicrobial activities have been studied. The Schiff base metal complexes emerges effective ?-glucosidase inhibitory activity than free Schiff base ligand. PMID:24858195

Kumar Naik, K H; Selvaraj, S; Naik, Nagaraja

2014-10-15

107

Self-assembly of a 15-nickel metallamacrocyclic complex derived from the L-glutamic acid Schiff base ligand.  

PubMed

An intriguing 15-nickel metallamacrocyclic complex, [Ni15(EVan)10(H2O)20], (EVan = Schiff base formed between l-glutamic acid and o-vanillin), has been synthesized and characterized by single-crystal X-ray diffraction and spectroscopic analyses. adopts a Ni-O-Ni-O-Ni-O configuration and can be divided into five discrete trinuclear units. PMID:24615170

Thio, Yude; Toh, Shi Wei; Xue, Feng; Vittal, Jagadese J

2014-04-28

108

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

PubMed Central

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, ultravioletvisible 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. PMID:24070648

Abou-Hussein, Azza A.; Linert, Wolfgang

2014-01-01

109

Study of the effect induced by the substituents on the ring-chain tautomerism of Schiff bases derived from norephedrine.  

PubMed

The solution behavior and the spectroscopic properties of the novel Schiff bases (1S,2R)-R(1)CH=NCH(Me)CH(OH)Ph [with R(1) = ferrocenyl-[Fc (2b)], 5- or 3-methylthienyl [hereafter referred to as 5-MeTf and 3-MeTf (2c and 2d), respectively

Talancn, Daniel; Bosque, Ramon; Lpez, Concepcin

2010-05-21

110

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

PubMed

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. PMID:24005576

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

2013-11-21

111

Coordination properties of hydralazine Schiff base. Synthesis and equilibrium studies of some metal ion complexes  

NASA Astrophysics Data System (ADS)

In the present study, a new ligand is prepared by condensation of hydralazine (1-Hydralazinophthalazine) with 2-butanon-3-oxime. The acid-base equilibria of the schiff-base and the complex formation equilibria with the metal ions as Cu(II), Ni(II), Co(II), Cd(II), Mn(II) and Zn(II) are investigated potentiometrically. The stability constants of the complexes are determined and the concentration distribution diagrams of the complexes are evaluated. The effect of metal ion properties as atomic number, ionic radius, electronegativity and ionization potential are investigated. The isolated solid complexes are characterized by conventional chemical and physical methods. The potential coordination sites are assigned using the i.r. and 1H NMR spectra. The structures of the isolated solid complexes are proposed on the basis of the spectral and magnetic studies.

Shoukry, Azza A.; Shoukry, Mohamed M.

2008-08-01

112

Synthesis and characterization of some aliphaticaromatic poly(Schiff base)s  

Microsoft Academic Search

Polymers with azomethine structure containing 1,5-naphthyl or 1,4-phenyl moieties were synthesised through polycondensation of some dialdehydes with diamines. Both monomers and polymers were characterised by IR and 1H-NMR techniques. Thermogravimetric analyses were made for all the synthesised polymers in order to study their thermal behaviour.

Otilia Catanescu; Mircea Grigoras; Georgiana Colotin; Alina Dobreanu; Nicolae Hurduc; Cristofor I Simionescu

2001-01-01

113

``Test kit'' for detection of biologically important anions: A salicylidene-hydrazine based Schiff base  

NASA Astrophysics Data System (ADS)

Test paper coated with Schiff base [(N,N/-bis(5-nitro-salicylidene)hydrazine] receptor 1 (host) can selectively detect fluoride and acetate ions (guest) by developing yellow color which can be detected by naked-eye both in aqueous-acetonitrile solution and in solid supported test kit. UV-vis spectral analysis shows that the absorption peaks at 288 and 345 nm of receptor 1 gradually decrease its initial intensity and new red shifted absorption bands at 397 nm and 455 nm gradually appear upon addition of increasing amount of F- and AcO- ions over several tested anions such as HPO4-, Cl, Br, I, NO3-, NO2-, HSO4-, HSO3-, and ClO4- in aqueous-acetonitrile solvent. The colorimetric test results and UV-vis spectral analysis are in well agreement with 1H NMR titration results in d6-DMSO solvent. The receptor 1 forms 1:2 stable complexes with F- and AcO- ions. However, similar kind of observation obtained from UV-vis titrations in presence of AcOH corresponds to 1:1 complexation ratio indicating the formation of H-bonding interaction between the receptor and anions (F- and AcO- ions). So, the observed 1:2 complexation ratio can only be explained on the basis of deprotonation (1 eqv.) and H-bonding (1 eqv.) interactions [1]. The ratiometric analysis of host-guest complexes corroborates well with the proposed theoretical model optimization at Density Functional Theory (DFT) level.

Dalapati, Sasanka; Alam, Md Akhtarul; Jana, Sankar; Karmakar, Saswati; Guchhait, Nikhil

2013-02-01

114

Synthesis, antibacterial activities and molecular docking studies of peptide and Schiff bases as targeted antibiotics.  

PubMed

A series of peptide and Schiff bases (PSB) were synthesized by reacting salicylic acid, primary diamines with salicylaldehyde or its derivatives, and 40 of which were newly reported. The inhibitory activities against Escherichia coli beta-ketoacyl-acyl carrier protein synthase III (ecKAS III) were investigated in vitro and molecular docking simulation also surveyed. Top 10 PSB compounds which possess both good inhibitory activity and well binding affinities were picked out, and their antibacterial activities against Gram-negative and Gram-positive bacterial strains were tested, expecting to exploit potent antibacterial agent with broad-spectrum antibiotics activity. The results demonstrate compound N-(3-(5-bromo-2-hydroxybenzylideneamino)propyl)-2-hydroxybenzamide (2d) can be as a potential antibiotics agent, displaying minimal inhibitory concentration values in the range of 0.39-3.13 microg/mL against various bacteria. PMID:19884012

Cheng, Kui; Zheng, Qing-Zhong; Qian, Yong; Shi, Lei; Zhao, Jing; Zhu, Hai-Liang

2009-12-01

115

Crystal structure and fluorescence sensing properties of tetramethoxyresorcinarene functionalized Schiff bases  

NASA Astrophysics Data System (ADS)

A series of tertamethoxyresorcinarene functionalized Schiff bases were conveniently prepared by the reaction of resorcinarene ester derivatives with excess of ethylenediamine and then condensation with salicylaldehyde. The single crystal analysis of five products shows that tetramethoxyresorcinarenes existed in chair conformation. The complexing properties of these polydentated ligands to transition metal ions were studied by UV-Vis and fluorescence spectroscopy. The results demonstrate that these polydentated ligands are more efficient for recognition of Zn2+ in preference to other metal ions, accompanying a remarkable fluorescence intensity enhancement. Taking 4a as an example, it exhibits a 13-fold fluorescence enhancement upon the addition of 3 equiv. of Zn2+ in CH3OH/CH3CN (1:9 v/v) solution.

Li, Liang; Sun, Jing; Zhang, Li-Li; Yao, Rong; Yan, Chao-Guo

2015-02-01

116

Vibronic coupling in polyenes: High resolution optical spectroscopy of a simple Schiff base  

NASA Astrophysics Data System (ADS)

High resolution fluroescence and fluroescence excitation spectra of a model polyene Schiff base have been obtained. 4.2 K spectra of N-(2, 4, 6, 8, 10-dodecapentaenylidine)butyl amine in n-tetradecane exhibit well-resolved electronic spectra (??*) from a single mixed crystal site. The major vibronic features, in common with those of polyene hydrocarbons, are due to combinations of symmetric carbon-carbon stretching vibrations. These are dominated by a double bond mode which decreases from 1589 to 1544 cm-1 upon electronic excitation. This decrease contrasts the 150-200 cm-1 increases seen in analogous polyene hydrocarbons. This difference is discussed in terms of vibronic coupling in a model previously applied to the hydrocarbons.

Girard, Mark; Arvidson, Eric; Christensen, Ronald

1984-03-01

117

Crystal structures of transition metal complexes with an asymmetrical tridentate Schiff-base ligand  

NASA Astrophysics Data System (ADS)

The asymmetrical tridentate Schiff base ( H 2L = (E)-N'-(2-hydroxybenzylidene)-4-hydroxybenzohydrazide) has been designed and synthesized. The four transition metal complexes with this ligand [Cu(HL)(NO 3)](H 2O) ( 1), [Zn 2(HL) 2(bipy)(H 2O) 2](NO 3) 2 ( 2), [Cu(HL)(H 2O)] 2(NO 3) 2 ( 3) and [Cu(HL)(Me 2NCO)] 2 ( 4) have been studied. The unsaturated coordination site of metal ion in complexes 1 and 2 is occupied by secondary ligand of nitrate and 4,4'-bipyridine. The crystal structure of complex 1 exhibits supramolecular framework with homochirality. Complexes 3 and 4 are dinuclear complexes bridged by the phenol oxygen atoms and the fifth coordination is occupied by H 2O molecular and DMF anion respectively. Hydrogen bonding and ?-? stacking exist in all four complexes to construct supramolecular architecture.

Tang, Bei-bei; Sun, Xiao-ping; Liu, Gui-lei; Li, Hui

2010-12-01

118

Spectroscopic and electrochemical characterization of some Schiff base metal complexes containing benzoin moiety  

NASA Astrophysics Data System (ADS)

The ligation behavior of bis-benzoin ethylenediamine (B2ED) and benzoin thiosemicarbazone (BTS) Schiff bases towards Ru3+, Rh3+, Pd2+, Ni2+ and Cu2+ were determined. The bond length of M-N and spectrochemical parameters (10Dq, ?, B and LFSE) of the complexes were evaluated. The redox characteristics of selected complexes were explored by cyclic voltammetry (CV) at Pt working electrode in non aqueous solvents. Au mesh (100 w/in.) optically transparent thin layer electrode (OTTLE) was also used for recording thin layer CV for selected Ru complex. Oxidation of some complexes occurs in a consecutive chemical reaction of an EC type mechanism. The characteristics of electron transfer process of the couples M2+/M3+ and M3+/M4+ (M = Ru3+, Rh3+) and the stability of the complexes towards oxidation and/or reduction were assigned. The nature of the electroactive species and reduction mechanism of selected electrode couples were assigned.

El-Shahawi, M. S.; Al-Jahdali, M. S.; Bashammakh, A. S.; Al-Sibaai, A. A.; Nassef, H. M.

2013-09-01

119

Synthesis, characterization and biocidal activities of Schiff base polychelates containing polyurethane links in the main chain  

NASA Astrophysics Data System (ADS)

The concept of combining metallo-polymers with urethanes offers a versatile approach for the synthesis of new polymeric materials. Polyurethane containing transition metals was synthesized by the reaction of Schiff base metal complex with toluene 2,4 diisocyanate. The proposed structures were confirmed by elemental analysis, 1H NMR, 13C NMR and FT-IR. The geometry is determined by UV-Visible spectra and magnetic moment measurements, which reveals that the Mn(II), Co(II) and Ni(II) complexes have octahedral geometry while square planer geometry is reported for Cu(II) and tetrahedral for Zn(II) complex. The antimicrobial activities are determined using the agar well diffusion method with Staphylococcus aureus, Escherichia coli, Bacillus subtilis (bacteria), Aspergillus niger, Candida albicans and Aspergillus flavus (yeast). All the polymeric metal complexes show comparatively good biocidal activity, which is further enhanced after polymerization.

Hasnain, Sumaiya; Nishat, Nahid

120

Synthesis of Three Rimantadine Schiff Bases and Their Biological Effects on Serum Albumin  

PubMed Central

Three new rimantadine Schiff bases (RSBs) were prepared, and then the interaction of RSBs with bovine serum albumin (BSA) was investigated using fluorescence, synchronous fluorescence, UV-vis absorption spectroscopy under physiological conditions. The results showed that the three RSBs effectively quenched the intrinsic fluorescence of BSA via static quenching. Binding constant (Ka), number of binding sites (n), and the binding distance (r) between three RSBs and BSA were calculated by Stern-Volmer equation and Frsters theory in this study. According to the results of displacement experiments of site probes, it was considered that the binding sites were located in hydrophobic cavities in sub-domains IIA of BSA. What is more, synchronous fluorescence studies indicated that the hydrophobicity around tryptophan residues was increased with the addition of rimantadine-o-vanillin (ROV) and rimantadine-4-methoxy-salicylaldehyde (RMS), while there was no apparent change with the addition of rimantadine-salicylaldehyde (RS).

Liu, Bing-Mi; Ma, Ping; Wang, Xin; Kong, Yu-Mei; Zhang, Li-Ping; Liu, Bin

2014-01-01

121

First X-ray structural characterization of isatin Schiff base derivative. NMR and theoretical conformational studies  

NASA Astrophysics Data System (ADS)

Isatin (1H-indole-2,3-dione) is an endogenous natural compound under intense development in medicinal chemistry. Here, we characterize isatin Schiff base derivative by X-ray crystallography. We describe a derivative that crystallizes E-isomer form in the triclinic space group P 1bar;a = 5.9580 (4) , b = 8.4184 (7) , c = 14.1801 (14) , ? = 73.962 (8), ? = 83.184 (7), ? = 81.143 (6). NMR data show that E-conformer interconverts to the Z-conformer when dissolved, this equilibrium weakly depends on the solvent type. The Z-isomer geometry and the energetics of ?EE-Z interconversion barriers were determined by quantum chemical calculations. The isomers are further characterized by means of FT-IR and UV-Vis spectroscopy.

Davidovich, Pavel; Novikova, Daria; Tribulovich, Vyacheslav; Smirnov, Sergey; Gurzhiy, Vlad; Melino, Gerry; Garabadzhiu, Alexander

2014-10-01

122

Rhodamine-derived Schiff base for the selective determination of mercuric ions in water media  

NASA Astrophysics Data System (ADS)

A new rhodamine-derived Schiff base ( RS) was synthesized and its sensing property to metal ions was investigated by UV/vis and fluorescence spectroscopies. Addition of Hg 2+ ions to the aqueous solution of RS gave a visual color change as well as significantly fluorescent enhancement, while other ions including Pb 2+, Cd 2+, Cr 3+, Zn 2+, Cu 2+, Fe 2+, Co 3+, Ni 2+, Ca 2+, Mg 2+, K + and Na + ions did not induce any distinct color/spectral changes, which constituted a Hg 2+-selective fluorescent OFF- ON chemosensor. The Hg 2+-induced ring-opening of spirolactam of rhodamine in RS resulted in the dual chromo- and fluorogenic observation.

Quang, Duong Tuan; Wu, Jia-Sheng; Luyen, Nguyen Dinh; Duong, Tran; Dan, Nguyen Dang; Bao, Nguyen Chi; Quy, Phan Tu

2011-02-01

123

Spectroscopic, crystallographic, and docking studies of 3,4-dimethyl- N-((thiophen-2-yl)methylene)isoxazol-5-amine Schiff base  

NASA Astrophysics Data System (ADS)

A novel 3,4-dimethyl- N-((thiophen-2-yl)methylene)isoxazol-5-amine ( DMTMIA) Schiff base has been synthesized by condensation of 3,4-dimethyl-5-amine isoxazole with thiophene-2-carboxaldehyde and characterized by using elemental analysis, 1H NMR, 13C NMR, Mass, IR and UV-Visible spectroscopic techniques. The structure of DMTMIA has also been determined crystallographically. It crystallizes in the orthorhombic crystal system with Pbca space group. The unit cell dimensions of the Schiff base are a = 11.326(4), b = 12.198(4), c = 14.954(5) . The Schiff base was designed and energy minimization was carried out with the help of HyperChem software and subsequently structure activity study was employed to investigate the ability to stabilize DNA-Topoisomerase I. Docking results revealed that the Schiff base involved in van der Waals interactions.

Kumar, Ch. Vijay; Kumar, M. Pradeep; Tejaswi, S.; Shivaraj

2014-12-01

124

Design of nanostructures based on aromatic peptide amphiphiles.  

PubMed

Aromatic peptide amphiphiles are gaining popularity as building blocks for the bottom-up fabrication of nanomaterials, including gels. These materials combine the simplicity of small molecules with the versatility of peptides, with a range of applications proposed in biomedicine, nanotechnology, food science, cosmetics, etc. Despite their simplicity, a wide range of self-assembly behaviours have been described. Due to varying conditions and protocols used, care should be taken when attempting to directly compare results from the literature. In this review, we rationalise the structural features which govern the self-assembly of aromatic peptide amphiphiles by focusing on four segments, (i) the N-terminal aromatic component, (ii) linker segment, (iii) peptide sequence, and (iv) C-terminus. It is clear that the molecular structure of these components significantly influences the self-assembly process and resultant supramolecular architectures. A number of modes of assembly have been proposed, including parallel, antiparallel, and interlocked antiparallel stacking conformations. In addition, the co-assembly arrangements of aromatic peptide amphiphiles are reviewed. Overall, this review elucidates the structural trends and design rules that underpin the field of aromatic peptide amphiphile assembly, paving the way to a more rational design of nanomaterials based on aromatic peptide amphiphiles. PMID:25199102

Fleming, Scott; Ulijn, Rein V

2014-12-01

125

Spectroscopic study and PM5 semiempirical calculations of tautomeric forms of gossypol Schiff base with n-butylamine in the solid state and in the solution  

Microsoft Academic Search

The Schiff base of gossypol with n-butylamine was synthesised and its structure was studied by FT-IR and 1H NMR, 13C NMR and 15N NMR as well as PM5 semiempirical methods. It is shown that the Schiff base exists in solution and in solid state as the enamineenamine tautomer. The structure of this tautomer is discussed in detail.

Piotr Przybylski; Grzegorz Wojciechowski; Wojciech Schilf; Bogumil Brzezinski; Franz Bartl

2003-01-01

126

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

PubMed Central

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 (1H, 13C, and 29Si) 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. PMID:23983671

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

2013-01-01

127

Crystal Structures of Type I Dehydroquinate Dehydratase in Complex with Quinate and Shikimate Suggest a Novel Mechanism of Schiff Base Formation  

PubMed Central

A component of the shikimate biosynthetic pathway, dehydroquinate dehydratase (DHQD) catalyzes the dehydration of 3-dehydroquniate (DHQ) to 3-dehydroshikimate. In the type I DHQD reaction mechanism a lysine forms a Schiff base intermediate with DHQ. The Schiff base acts as an electron sink to facilitate the catalytic dehydration. To address the mechanism of Schiff base formation, we determined structures of the Salmonella enterica wild-type DHQD in complex with the substrate analogue quinate and the product analogue shikimate. In addition, we determined the structure of the K170M mutant (Lys170 being the Schiff base forming residue) in complex with quinate. Combined with nuclear magnetic resonance and isothermal titration calorimetry data that revealed altered binding of the analogue to the K170M mutant, these structures suggest a model of Schiff base formation characterized by the dynamic interplay of opposing forces acting on either side of the substrate. On the side distant from the substrate 3-carbonyl group, closure of the enzymes ?8??8 loop is proposed to guide DHQ into the proximity of the Schiff base-forming Lys170. On the 3-carbonyl side of the substrate, Lys170 sterically alters the position of DHQs reactive ketone, aligning it at an angle conducive for nucleophilic attack. This study of a type I DHQD reveals the interplay between the enzyme and substrate required for the correct orientation of a functional group constrained within a cyclic substrate. PMID:24437575

2015-01-01

128

Crystal structures of type I dehydroquinate dehydratase in complex with quinate and shikimate suggest a novel mechanism of Schiff base formation.  

PubMed

A component of the shikimate biosynthetic pathway, dehydroquinate dehydratase (DHQD) catalyzes the dehydration of 3-dehydroquniate (DHQ) to 3-dehydroshikimate. In the type I DHQD reaction mechanism a lysine forms a Schiff base intermediate with DHQ. The Schiff base acts as an electron sink to facilitate the catalytic dehydration. To address the mechanism of Schiff base formation, we determined structures of the Salmonella enterica wild-type DHQD in complex with the substrate analogue quinate and the product analogue shikimate. In addition, we determined the structure of the K170M mutant (Lys170 being the Schiff base forming residue) in complex with quinate. Combined with nuclear magnetic resonance and isothermal titration calorimetry data that revealed altered binding of the analogue to the K170M mutant, these structures suggest a model of Schiff base formation characterized by the dynamic interplay of opposing forces acting on either side of the substrate. On the side distant from the substrate 3-carbonyl group, closure of the enzyme's ?8-?8 loop is proposed to guide DHQ into the proximity of the Schiff base-forming Lys170. On the 3-carbonyl side of the substrate, Lys170 sterically alters the position of DHQ's reactive ketone, aligning it at an angle conducive for nucleophilic attack. This study of a type I DHQD reveals the interplay between the enzyme and substrate required for the correct orientation of a functional group constrained within a cyclic substrate. PMID:24437575

Light, Samuel H; Antanasijevic, Aleksandar; Krishna, Sankar N; Caffrey, Michael; Anderson, Wayne F; Lavie, Arnon

2014-02-11

129

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)

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.

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

1992-01-01

130

Detection of trace amounts of Pb(II) by schiff base-chitosan-grafted multiwalled carbon nanotubes  

NASA Astrophysics Data System (ADS)

A simple, highly sensitive, accurate and selective method for determination of trace amounts of Pb(II) in water samples is presented. A novel Schiff base-chitosan-grafted multiwalled carbon nanotubes (S-CS-MWCNTs) solid-phase extraction adsorbent was synthesized by covalently grafting a Schiff base-chitosan (S-CS) onto the surfaces of oxidized MWCNTs. The stability of a chemically (S-CS-MWCNTs) especially in concentrated hydrochloric acid which was then used as a recycling and preconcentration reagent for further uses of (S-CS-MWCNTs). The method is based on selective chelation of Pb(II) on surfactant coated C18, modified with a Schiff base-chitosan-grafted multiwalled carbon nanotubes (S-CS-MWCNTs). The retained ions were then eluted with 4 mL of 4 M nitric acid and determined by flame atomic absorption spectrometry (FAAS) at 283.3 nm for Pb. The influence of flow rates of sample and eluent solutions, pH, break-through volume, effect of foreign ions on chelation and recovery were investigated. 1.5 g of surfactant coated C18 adsorbs 40 mg of the Schiff s base which in turn can retain 15.0 0.9 mg of each of the two ions. The limit of detection (3?) for Pb(II) was found to be 3.20 ng L-1. The enrichment factor for both ions are 100. The mentioned method was successfully applied on determination of lead in different water samples. The ions were also speciated by means of three columns system.

Moghimi, Ali

2013-07-01

131

Elucidating the exact role of engineered CRABPII residues for the formation of a retinal protonated Schiff base  

SciTech Connect

Cellular Retinoic Acid Binding Protein II (CRABPII) has been reengineered to specifically bind and react with all-trans-retinal to form a protonated Schiff base. Each step of this process has been dissected and four residues (Lys132, Tyr134, Arg111, and Glu121) within the CRABPII binding site have been identified as crucial for imine formation and/or protonation. The precise role of each residue has been examined through site directed mutagenesis and crystallographic studies. The crystal structure of the R132K:L121E-CRABPII (PDB-3I17) double mutant suggests a direct interaction between engineered Glu121 and the native Arg111, which is critical for both Schiff base formation and protonation.

Vasileiou, Chrysoula; Wang, Wenjing; Jia, Xiaofei; Lee, Kin Sing Stephen; Watson, Camille T.; Geiger, James H.; Borhan, Babak; (MSU)

2010-03-04

132

Elucidating the exact role of engineered CRABPII residues for the formation of a retinal protonated Schiff base  

PubMed Central

Cellular Retinoic Acid Binding Protein II (CRABPII) has been re-engineered to specifically bind and react with alltrans-retinal to form a protonated Schiff base. Each step of this process has been dissected and four residues (Lys132, Tyr134, Arg111, Glu121) within the CRABPII binding site have been identified as crucial for imine formation and/or protonation. The precise role of each residue has been examined through site directed mutagenesis and crystallographic studies. The crystal structure of the R132K:L121E-CRABPII double mutant suggests a direct interaction between engineered Glu121 and the native Arg111, which is critical for both Schiff base formation and protonation. PMID:19603486

Vasileiou, Chrysoula; Wang, Wenjing; Jia, Xiaofei; Lee, Kin Sing Stephen; Watson, Camille T.; Geiger, James H.; Borhan, Babak

2015-01-01

133

Self-assembled nanostructures of specially designed Schiff-bases and their zinc complexes: Preparation, characterization and photoluminescence property  

NASA Astrophysics Data System (ADS)

Four specially designed Schiff bases 2-formyl-4-R-6-(3N-4-hydroxybenzoicacid)-iminomethyl-phenolato (where R = methyl/tert-butyl/chloro for L1, L2, L3 respectively) and 2-(3N-4-hydroxybenzoicacid)-iminomethyl-phenolato (L4) having ability to form hydrogen bonding and their zinc complexes (1-4) have been synthesized and characterized. These complexes gave various types of nano-sized materials via self-assembly in solid state. FE-SEM was employed to investigate their morphology. Using a variety of analytical techniques such as elemental analysis, infrared spectroscopy (FT-IR), ESI-MS and 1H NMR spectroscopy, a consistent picture of structures of these complexes are obtained. All the Schiff-bases and their zinc complexes exhibit photoluminescence property. Density functional theory calculation has been performed to rationalize the origin of the spectral bands of the ligands as well as the complexes.

Guha, Averi; Sanyal, Ria; Chattopadhyay, Tanmay; Han, YounGyu; Mondal, Tapan Kumar; Das, Debasis

2013-06-01

134

Adherence to Brgi-Dunitz stereochemical principles requires significant structural rearrangements in Schiff-base formation: insights from transaldolase complexes.  

PubMed

The Brgi-Dunitz angle (?BD) describes the trajectory of approach of a nucleophile to an electrophile. The adoption of a stereoelectronically favorable ?BD can necessitate significant reactive-group repositioning over the course of bond formation. In the context of enzyme catalysis, interactions with the protein constrain substrate rotation, which could necessitate structural transformations during bond formation. To probe this theoretical framework vis--vis biocatalysis, Schiff-base formation was analysed in Francisella tularensis transaldolase (TAL). Crystal structures of wild-type and Lys?Met mutant TAL in covalent and noncovalent complexes with fructose 6-phosphate and sedoheptulose 7-phosphate clarify the mechanism of catalysis and reveal that substrate keto moieties undergo significant conformational changes during Schiff-base formation. Structural changes compelled by the trajectory considerations discussed here bear relevance to bond formation in a variety of constrained enzymic/engineered systems and can inform the design of covalent therapeutics. PMID:24531488

Light, Samuel H; Minasov, George; Duban, Mark-Eugene; Anderson, Wayne F

2014-02-01

135

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

NASA Astrophysics Data System (ADS)

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.

Ceyhan, Gkhan; elik, Cumali; Uru?, Serhan; Demirta?, ?brahim; Elmasta?, Mahfuz; Tmer, Mehmet

2011-10-01

136

DNA interaction with octahedral and square planar Ni(II) complexes of aspartic-acid Schiff-bases  

NASA Astrophysics Data System (ADS)

Ni(II) complexes of (S,E)-2-(2-OHbenzilydene)aspartic acid; (S,E)-2-(2,3-diOHbenzilydene)aspartic acid-; (S,E)-2-(2,4-diOH-benzilydene)aspartic acid; (S,E)-2-(2,5-diOHbenzilydene)aspartic acid and (S,E)-2-((2-OHnaphthalene-1-yl)methylene)aspartic acid Schiff-bases have been synthesized by template method in ethanol or ammonia media. They were characterized by elemental analyses, conductivity measurements, magnetic moment, UV, IR and 1H nmr spectra as well as thermal analysis (TG, DTG, DTA). The Schiff-bases are dibasic tridentate or tetradentate donors and the complexes have square planar and octahedral structures. The complexes decompose in two or three steps where kinetic and thermodynamic parameters of the decomposition steps were computed. The interactions of the formed complexes with FM-DNA were monitored by UV and fluorescence spectroscopy.

Sallam, S. A.; Orabi, A. S.; Abbas, A. M.

2011-12-01

137

Synthesis of a New Heteropolytopic Cryptand Through Schiff Base Condensation in the Presence of Ba(II) Ion  

Microsoft Academic Search

A new Schiff base cryptand (L) has been prepared via [2+2] condensation of 1,3,5-tris(2-formylphenoxymethyl)benzene (1) with 1,3,5-tris(aminomethyl)benzene trishydrochloride (2) in the presence of Ba(II) ion. The analytical data show that the Ba(II) cation is not retained by the product. Thus it seems that the role of the Ba(II) ion is to organize the transition state preceding the formation of the

Hassan Keypour; Ahmad Ali Dehghani-Firouzabadi; Majid Rezaeivala; Sadegh Salehzadeh

2009-01-01

138

Aspartic acid-96 is the internal proton donor in the reprotonation of the Schiff base of bacteriorhodopsin.  

PubMed Central

Above pH 8 the decay of the photocycle intermediate M of bacteriorhodopsin splits into two components: the usual millisecond pH-independent component and an additional slower component with a rate constant proportional to the molar concentration of H+, [H+]. In parallel, the charge translocation signal associated with the reprotonation of the Schiff base develops a similar slow component. These observations are explained by a two-step reprotonation mechanism. An internal donor first reprotonates the Schiff base in the decay of M to N and is then reprotonated from the cytoplasm in the N----O transition. The decay rate of N is proportional to [H+]. By postulating a back reaction from N to M, the M decay splits up into two components, with the slower one having the same pH dependence as the decay of N. Photocycle, photovoltage, and pH-indicator experiments with mutants in which aspartic acid-96 is replaced by asparagine or alanine, which we call D96N and D96A, suggest that Asp-96 is the internal proton donor involved in the re-uptake pathway. In both mutants the stoichiometry of proton pumping is the same as in wild type. However, the M decay is monophasic, with the logarithm of the decay time [log (tau)] linearly dependent on pH, suggesting that the internal donor is absent and that the Schiff base is directly reprotonated from the cytoplasm. Like H+, azide increases the M decay rate in D96N. The rate constant is proportional to the azide concentration and can become greater than 100 times greater than in wild type. Thus, azide functions as a mobile proton donor directly reprotonating the Schiff base in a bimolecular reaction. Both the proton and azide effects, which are absent in wild type, indicate that the internal donor is removed and that the reprotonation pathway is different from wild type in these mutants. PMID:2556706

Otto, H; Marti, T; Holz, M; Mogi, T; Lindau, M; Khorana, H G; Heyn, M P

1989-01-01

139

Synthesis, characterization and experimental, theoretical, electrochemical, antioxidant and antibacterial study of a new Schiff base and its complexes.  

PubMed

A new Schiff base ligand was synthesized by reaction of salicylaldehyde with 1,6-bis(4-chloro-2-aminophenoxy)hexane. Then the Schiff base complexes were synthesized by metal salts and the Schiff base. The metal to ligand ratio of metal complexes was found to be 1:1. The Cu(II) complex is proposed to be square planar and the Co(II), Ni(II), Mn(II) and Zn(II) complexes are proposed to be tetrahedral geometry. The Ti(III) and V(III) complexes are proposed to be a capped octahedron in which a seventh ligand has been added to triangular face. The complexes are non-electrolytes as shown by their molar conductivities (?M). The structure of metal complexes is proposed from elemental analysis, FT-IR, UV-vis, magnetic susceptibility measurements, molar conductivity measurements, Mass Spectra and thermal gravimetric analysis. In addition antimicrobial and antioxidant studies, cyclic voltammetry of the complexes, theoretical 1H NMR and HOMO-LUMO energy calculations of the new di-functional ligand were done. PMID:24792202

Baykara, Haci; Ilhan, Salih; Levent, Abdulkadir; Salih Seyitoglu, M; zdemir, Sadin; Okumu?, Veysi; ztomsuk, Abdussamet; Cornejo, Mauricio

2014-09-15

140

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

PubMed Central

Novel mixed ligand bivalent copper complexes [Cu. L. A. ClO4] 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

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

2014-01-01

141

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

PubMed Central

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

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

2014-01-01

142

Unsymmetrical Schiff base (ON) ligand on complexation with some transition metal ions: Synthesis, spectral characterization, antibacterial, fluorescence and thermal studies  

NASA Astrophysics Data System (ADS)

A series of eight metal Schiff base complexes were synthesized by the thermal reaction of Cu(II), Ni(II), Fe(III), Co(II), Zn(II), Hg(II), La(III) or Sm(III) with a Schiff base "L" produced by the condensation of furfuraldehyde and 1,2-diaminobenzene. These compounds were characterized by elemental analysis, UV-Vis, FT-IR, molar conductance, mass spectrometry, thermal and fluorescence studies. The studies suggested the coordination of the ligand L to metal through azomethine imine nitrogen and furan oxygen atoms of Schiff base moiety. Thermogravimetric (TG/DTG) analyses data were studied and indicated high stability for all complexes and suggested the presence of lattice and/or coordinated water molecules in the complexes. Coats-Redfern method has been used to calculate the kinetic and thermodynamic parameters of the metal complexes. The spectral and thermal analysis reveal that all complexes have octahedral geometry except Cu(II) and Ni(II) complexes which can attain a square planner arrangements. The ligand and its complexes exhibited intraligand (?-??) fluorescence and can potentially serve as photoactive materials. Both the ligand and its complexes have been screened for antibacterial activities.

Ali, Omyma A. M.; El-Medani, Samir M.; Abu Serea, Maha R.; Sayed, Abeer S. S.

2015-02-01

143

Synthesis, Spectroscopic, Molecular Structure, and Antibacterial Studies of Dibutyltin(IV) Schiff Base Complexes Derived from Phenylalanine, Isoleucine, and Glycine  

PubMed Central

New series of organotin(IV) complexes and Schiff bases derived from amino acids have been designed and synthesized from condensation of 1H-indole-2,3-dione, 5-chloro-1H-indole-2,3-dione, and ?-amino acids (phenylalanine, isoleucine, and glycine). All compounds are characterized by elemental analyses, molar conductance measurements, and molecular weight determinations. Bonding of these complexes is discussed in terms of their UV-visible, infrared, and nuclear magnetic resonance (1H, 13C, and 119Sn NMR) spectral studies. The results suggest that Schiff bases behave as monobasic bidentate ligands and coordinate with dibutyltin(IV) in octahedral geometry according to the general formula [Bu2Sn(L)2]. Elemental analyses and NMR spectral data of the ligands with their dibutyltin(IV) complexes agree with their proposed distorted octahedral structures. Few representative compounds are tested for their in vitro antibacterial activity against Gram-positive (B. cereus, Staphylococcus spp.) and Gram-negative (E. coli, Klebsiella spp.) bacteria. The results show that the dibutyltin complexes are more reactive with respect to their corresponding Schiff base ligands. PMID:25525422

Singh, Har Lal; Singh, Jangbhadur

2014-01-01

144

Synthesis, characterization, biological and catalytic applications of transition metal complexes derived from Schiff base.  

PubMed

A novel series of Cu(II), Ni(II), Zn(II), Co(II), and Cd(II) complexes have been synthesized from the Schiff base. Structural features were determined by analytical and spectral techniques like IR, (1)H NMR, UV-vis, elemental analysis, molar electric conductibility, magnetic susceptibility and thermal studies. The complexes are found to be soluble in dimethylformamide and dimethylsulfoxide. Molar conductance values in dimethylformamide indicate the non-electrolytic nature of the complexes. Binding of synthesized complexes with calf thymus DNA (CT DNA) was studied. There is significant binding of DNA in lanes 2, 3, and 5. Lanes 4 and 6 are showing more florescence when compared to the control indicating that these molecules are strongly bound to the DNA by inserting themselves between the two stacked base pairs and exhibiting their original property of fluorescence. Angiogenesis study has revealed that the compounds B-2, B-4 and B-5 have potent antitumor efficacy and activation of antiangiogenesis could be one of the possible underlying mechanisms of tumor inhibition. PMID:24915881

Bushra Begum, A; Rekha, N D; Vasantha Kumar, B C; Lakshmi Ranganatha, V; Khanum, Shaukath Ara

2014-08-01

145

Structural, spectroscopic and DFT study of 4-methoxybenzohydrazide Schiff bases. A new series of polyfunctional ligands  

NASA Astrophysics Data System (ADS)

Five Schiff bases obtained from condensation of 4-methoxybenzohydrazide with related aldehydes, namely o-vanillin, vanillin, 5-bromovanillin, 5-chlorosalicylaldehyde and 5-bromosalicylaldehyde were prepared. A detailed structural and spectroscopic study is reported. The crystal structures of four members of the family were determined and compared with one another. The hydrazones obtained from 5-chlorosalicylaldehyde and 5-bromosalicylaldehyde resulted to be isomorphic to each other. The solid-state structures are stabilized by intra-molecular Osbnd H⋯N interactions in salicylaldehyde derivatives between the Osbnd H moiety from the aldehyde and the hydrazone nitrogen atom. All crystals are further stabilized by inter-molecular H-bonds mediated by the crystallization water molecule. A comparative analysis between experimental and theoretical results is presented. The conformational space was searched and geometries were optimized both in gas phase and including solvent effects. The structure is predicted for the compound for which the crystal structure was not determined. Infrared and electronic spectra were measured and assigned with the help of data obtained from computational methods based on the Density Functional Theory.

Ferraresi-Curotto, Vernica; Echeverra, Gustavo A.; Piro, Oscar E.; Pis-Diez, Reinaldo; Gonzlez-Bar, Ana C.

2015-02-01

146

Structural, spectroscopic and DFT study of 4-methoxybenzohydrazide Schiff bases. A new series of polyfunctional ligands.  

PubMed

Five Schiff bases obtained from condensation of 4-methoxybenzohydrazide with related aldehydes, namely o-vanillin, vanillin, 5-bromovanillin, 5-chlorosalicylaldehyde and 5-bromosalicylaldehyde were prepared. A detailed structural and spectroscopic study is reported. The crystal structures of four members of the family were determined and compared with one another. The hydrazones obtained from 5-chlorosalicylaldehyde and 5-bromosalicylaldehyde resulted to be isomorphic to each other. The solid-state structures are stabilized by intra-molecular OH?N interactions in salicylaldehyde derivatives between the OH moiety from the aldehyde and the hydrazone nitrogen atom. All crystals are further stabilized by inter-molecular H-bonds mediated by the crystallization water molecule. A comparative analysis between experimental and theoretical results is presented. The conformational space was searched and geometries were optimized both in gas phase and including solvent effects. The structure is predicted for the compound for which the crystal structure was not determined. Infrared and electronic spectra were measured and assigned with the help of data obtained from computational methods based on the Density Functional Theory. PMID:25255482

Ferraresi-Curotto, Vernica; Echeverra, Gustavo A; Piro, Oscar E; Pis-Diez, Reinaldo; Gonzlez-Bar, Ana C

2015-02-25

147

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

PubMed Central

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

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

148

Coordination geometry around copper in a Schiff-base trinuclear copper complex using EXAFS spectroscopy  

NASA Astrophysics Data System (ADS)

In the present investigation, we have studied extended X-ray absorption fine structure (EXAFS) spectra of a trinuclear Schiff-base copper complex tetraaqua-di-?3-(N-salicylidene-DL-glutamato)-tricopper(II)heptahydrate, [Cu3(C12H10NO5)2 (H2O)4]. 7H2O, in which three metal sites are present. One metal site is square-pyramidal (4+1) and other two similar metal sites are tetragonally distorted octahedral (4+2). EXAFS has been recorded at the K-edge of copper in the complex at the dispersive EXAFS beamline at 2 GeV Indus-2 synchrotron source at RRCAT, Indore, India. The analysis of EXAFS spectra of multinuclear metal complexes pose some problems due to the presence of many absorbing atoms, even when the absorbing atoms may be of the same element. Hence, using the available crystal structure of the complex, theoretical models have been generated for the different copper sites separately, which are then fitted to the experimental EXAFS data. The two coordination geometries around the copper sites have been determined. The contributions of the different copper sites to the experimental spectrum have been estimated. The structural parameters, which include bond-lengths, coordination numbers and thermal disorders, for the two types of copper sites have been reported. Further, copper has been found to be in +2 oxidation state at these metal sites.

Gaur, Abhijeet; Shrivastava, B. D.; Gaur, D. C.; Prasad, J.; Srivastava, K.; Jha, S. N.; Bhattacharyya, D.; Poswal, A.

2012-05-01

149

Modulation of amyloid-? aggregation by histidine-coordinating Cobalt(III) Schiff base complexes.  

PubMed

Oligomers of the A?42 peptide are significant neurotoxins linked to Alzheimer's disease (AD). Histidine (His) residues present at the N terminus of A?42 are believed to influence toxicity by either serving as metal-ion binding sites (which promote oligomerization and oxidative damage) or facilitating synaptic binding. Transition metal complexes that bind to these residues and modulate A? toxicity have emerged as therapeutic candidates. Cobalt(III) Schiff base complexes (Co-sb) were evaluated for their ability to interact with A? peptides. HPLC-MS, NMR, fluorescence, and DFT studies demonstrated that Co-sb complexes could interact with the His residues in a truncated A?16 peptide representing the A?42 N terminus. Coordination of Co-sb complexes altered the structure of A?42 peptides and promoted the formation of large soluble oligomers. Interestingly, this structural perturbation of A? correlated to reduced synaptic binding to hippocampal neurons. These results demonstrate the promise of Co-sb complexes in anti-AD therapeutic approaches. PMID:24961930

Heffern, Marie C; Velasco, Pauline T; Matosziuk, Lauren M; Coomes, Joseph L; Karras, Constantine; Ratner, Mark A; Klein, William L; Eckermann, Amanda L; Meade, Thomas J

2014-07-21

150

Novel Schiff-base-derived FabH inhibitors with dioxygenated rings as antibiotic agents.  

PubMed

Fatty acid biosynthesis plays a vital role in bacterial survival and several key enzymes involved in this biosynthetic pathway have been identified as attractive targets for the development of new antibacterial agents. Of these promising targets, ?-ketoacyl-acyl carrier protein (ACP) synthase III (FabH) is the most attractive target that could trigger the initiation of fatty acid biosynthesis and is highly conserved among Gram-positive and -negative bacteria. Designing small molecules with FabH inhibitory activity displays great significance for developing antibiotic agents, which should be highly selective, nontoxic and broad-spectrum. In this manuscript, a series of novel Schiff base compounds were designed and synthesized, and their biological activities were evaluated as potential inhibitors. Among these 21 new compounds, (E)-N-((3,4-dihydro-2H-benzo[b][1,4]dioxepin-7-yl)methylene)hexadecan-1-amine (10) showed the most potent antibacterial activity with a MIC value of 3.89-7.81 ?M(-1) against the tested bacterial strains and exhibited the most potent E. coli FabH inhibitory activity with an IC(50) value of 1.6 ?M. Docking simulation was performed to position compound 10 into the E. coli FabH active site to determine the probable binding conformation. PMID:23401291

Zhou, Yang; Du, Qian-Ru; Sun, Jian; Li, Jing-Ran; Fang, Fei; Li, Dong-Dong; Qian, Yong; Gong, Hai-Bin; Zhao, Jing; Zhu, Hai-Liang

2013-03-01

151

Selective Anion Binding by a Cofacial Binuclear Zinc Complex of a Schiff-Base Pyrrole Macrocycle  

PubMed Central

The synthesis of the new cofacial binuclear zinc complex [Zn2(L)] of a Schiff-base pyrrole macrocycle is reported. It was discovered that the binuclear microenvironment between the two metals of [Zn2(L)] is suited for the encapsulation of anions, leading to the formation of [K(THF)6][Zn2(?-Cl)(L)].2THF and [Bun4N][Zn2(?-OH)(L)] which were characterized by X-ray crystallography. Unusually obtuse Zn-X-Zn angles (X=Cl: 150.54(9) and OH: 157.4(3)) illustrate the weak character of these interactions and the importance of the cleft pre-organization to stabilize the host. In the absence of added anion, aggregation of [Zn2(L)] was inferred and investigated by successive dilutions and by the addition of coordinating solvents to [Zn2(L)] solutions using NMR spectroscopy as well as isothermal microcalorimetry (ITC). On anion addition, evidence for de-aggregation of [Zn2(L)], combined with the formation of the 1:1 host-guest complex, was observed by NMR spectroscopy and ITC titrations. Furthermore, [Zn2(L)] binds to Cl? selectively in THF as deduced from the ITC analyses, while other halides induce only de-aggregation. These conclusions were reinforced by DFT calculations, which indicated that the binding energies of OH? and Cl? were significantly greater than for the other halides. PMID:21391550

Devoille, Aline M. J.; Richardson, Patricia; Bill, Nathan; Sessler, Jonathan L.; Love, Jason B.

2011-01-01

152

Crystal structures, spectroscopic and theoretical study of novel Schiff bases of 2-(methylthiomethyl)anilines.  

PubMed

New Schiff bases derived from p-methoxysalicylaldehyde and 2-(methylthiomethyl)anilines (substituted with methyl, methoxy, nitro) were synthesized and characterized by elemental analyses, FT-IR, NMR, electronic spectra and quantum chemical calculations. X-ray crystallography of two compounds showed the solid structures are stabilized by intramolecular and intermolecular H-bonds. The effect of OH?N interaction between the phenolic hydrogen and imine nitrogen on the proton and carbon NMR shifts, and the role of CH?O and CH?S contacts are discussed. The bond lengths and angles, (1)H and (13)C NMR data, ELUMO-HOMO, dipole moments and polarizability of the compounds were predicted by density functional theory, DFT (B3LYP/6-31G(??)) method. The experimental geometric parameters and the NMR shifts were compared with the calculated values, which gave good correlations. The electronic effects of aryl ring substituents (methyl, methoxy and nitro) on the properties of the resulting compounds, such as the color, NMR shifts, electronic spectra and the calculated energy band gaps, dipole moments and polarizability are discussed. Increase in electron density shifted the phenolic proton resonance to lower fields. The methoxy-substituted compound has a small dipole moment and subsequent large polarizability value. Highest polarity was indicated by the nitro compound which also showed high polarizability due to its larger size. The energy gaps obtained from ELUMO-HOMO calculations suggest these compounds may have applications as organic semiconducting materials. PMID:25576935

Olalekan, Temitope E; Adejoro, Isaiah A; VanBrecht, Bernardus; Watkins, Gareth M

2015-03-15

153

Copper conjugates of nimesulide Schiff bases targeting VEGF, COX and Bcl-2 in pancreatic cancer cells.  

PubMed

Copper conjugates of Schiff base derivatives of nimesulide (1), a well-known cyclooxygenase-2 (COX-2) inhibitor, were synthesized, structurally characterized and evaluated for their COX selectivity indices and cytotoxicities on pancreatic tumor, BxPC-3 (COX-2 positive) and MiaPaCa (COX-2 negative) cell lines. Copper conjugates exhibit distorted square planar geometries as revealed by the single crystal X-ray structure determination of Cu(L1)(2) and show significant growth inhibition in both cell lines (IC50 values 3-26 microM for COX-2 positive and 5-9 microM for COX-2 negative cell line) than the parent nimesulide (35 microM for COX-2 positive and >100 microM for COX-2 negative cell line). The mechanistic pathway for the biological activity involves inhibition of vascular endothelial growth factor (VEGF) and COX inhibition, as well as down regulation of antiapoptotic Bcl-2 and Bcl-(XL) proteins. PMID:17689613

Ambike, Vinita; Adsule, Shreelekha; Ahmed, Fakhara; Wang, Zhiwei; Afrasiabi, Zahra; Sinn, Ekkehard; Sarkar, Fazlul; Padhye, Subhash

2007-10-01

154

Photoisomerization action spectrum of retinal protonated Schiff base in the gas phase  

SciTech Connect

The photophysical behaviour of the isolated retinal protonated n-butylamine Schiff base (RPSB) is investigated in the gas phase using a combination of ion mobility spectrometry and laser spectroscopy. The RPSB cations are introduced by electrospray ionisation into an ion mobility mass spectrometer where they are exposed to tunable laser radiation in the region of the S{sub 1} ? S{sub 0} transition (420680nm range). Four peaks are observed in the arrival time distribution of the RPSB ions. On the basis of predicted collision cross sections with nitrogen gas, the dominant peak is assigned to the all-trans isomer, whereas the subsidiary peaks are assigned to various single, double and triple cis geometric isomers. RPSB ions that absorb laser radiation undergo photoisomerization, leading to a detectable change in their drift speed. By monitoring the photoisomer signal as a function of laser wavelength an action spectrum, extending from 480 to 660nm with a clear peak at 615 5nm, is obtained. The photoisomerization action spectrum is related to the absorption spectrum of isolated retinal RPSB molecules and should help benchmark future electronic structure calculations.

Coughlan, N. J. A.; Catani, K. J.; Adamson, B. D.; Wille, U.; Bieske, E. J., E-mail: evanjb@unimelb.edu.au [School of Chemistry, The University of Melbourne, Victoria 3010 (Australia)

2014-04-28

155

(E)-2-[(2-hydroxybenzylidene)amino]phenylarsonic acid Schiff base: Synthesis, characterization and theoretical studies  

NASA Astrophysics Data System (ADS)

The structure of the Schiff base (E)-2-[(2-hydroxybenzylidene)amino]phenylarsonic [(E)-HBAPhAA], synthesized from salicylaldehyde and o-aminophenylarsonic acid in the presence of HCl, was characterized by FTIR, 1H NMR, EI-MS, UV-Vis spectroscopy, and X-ray crystallography. The crystal belonged to the monoclinic space group P21/c. Two molecules formed a dimer via intermolecular interactions due to the attachment of H atoms to O1, O3 and O4 with Osbnd H bond distances within reasonable ranges, ca. 0.84(3) . The structure also showed two intramolecular interactions of 2.634(2) and 3.053(2) for Nsbnd H⋯O hydrogen bonds, which caused the structures to be almost planar. We performed a theoretical analysis using DFT theory at B3LYP/6-31+G(d,p) level to determine the stability of the E and Z conformers. The geometry analysis of the E- and Z-isomers revealed an interconversion energy barrier between E/Z isomers of 22.72 kcal mol-1. We also theoretically analyzed the keto form of the E-isomer and observed a small energy barrier for the tautomerization of 6.17 kcal mol-1.

Judith Percino, M.; Cern, Margarita; Castro, Mara Eugenia; Ramrez, Ricardo; Soriano, Guillermo; Chapela, Vctor M.

2015-02-01

156

Molecular docking study, synthesis and biological evaluation of Schiff bases as Hsp90 inhibitors.  

PubMed

Heat shock protein 90 (Hsp90) is an emerging attractive target for the discovery of novel cancer therapeutic agents. Docking methods are powerful in silico tools for lead generation and optimization. In our mission to rationally develop novel effective small molecules against Hsp90, we predicted the potency of our designed compounds by Sybyl surflex Geom X docking method. The results of the above studies revealed that Schiff bases derived from 2,4-dihydroxy benzaldehyde/5-chloro-2,4-dihydroxy benzaldehyde demonstrated effective binding with the protein. Subsequently, a few of them were synthesized (1-10) and characterized by IR, (1)HNMR and mass spectral analysis. The synthesized molecules were evaluated for their potential to suppress Hsp90 ATPase activity by Malachite green assay. The anticancer studies were performed by 3-(4,5-dimethythiazol- 2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay method. The software generated results was in satisfactory agreement with the evaluated biological activity. PMID:24486109

Dutta Gupta, Sayan; Snigdha, D; Mazaira, Gisela I; Galigniana, Mario D; Subrahmanyam, C V S; Gowrishankar, N L; Raghavendra, N M

2014-04-01

157

Synthesis, molecular structure, and properties of a neutral Schiff base phenolic complex of magnesium  

SciTech Connect

Multidrug resistance (MDR) in cancer mediated by the MDR1 P-glycoprotein (Pgp), a 140--180 kDa plasma membrane protein, renders chemotherapeutic treatment ineffective by pumping a variety of natural product cytotoxic agents and xenobiotic compounds out of cancer cells. Pgp has been a major target for synthesis and development of both therapeutic antagonists that block its transport function and diagnostic radiopharmaceuticals that are transported by the protein for use in functional imaging of Pgp transport activity in tumors in vivo. Most, but not all, compounds that interact with Pgp are hydrophobic and cationic at physiological pH. To further understand the Pgp targeting properties, the authors sought to directly evaluate the effect of charge of the complex on Pgp interactions. This could be done by comparing the cytotoxicity profile of a neutral complex to that of an identical, but positively charged, complex in both drug-sensitive and multidrug-resistant cancer cells. Thus, a neutral analogue of the Ga(III) and Fe(III) complexes was desired. Herein the authors describe the synthesis and structure of a novel neutral Schiff base Mg complex and evaluate its cytotoxic potency in human drug-sensitive KB-3-1 and multi-drug-resistant KB-8-5 tumor cells.

Polyakov, V.R.; Sharma, V.; Crankshaw, C.L.; Piwnica-Worms, D. [Washington University Medical School, St. Louis, MO (United States)] [Washington University Medical School, St. Louis, MO (United States)

1998-09-07

158

Syntheses, characterization, biological activities and photophysical properties of lanthanides complexes with a tetradentate Schiff base ligand  

NASA Astrophysics Data System (ADS)

A tetradentate Schiff base ligand L (N,N'-bis(1-naphthaldimine)-o-phenylenediamine) was prepared from the condensation of 2-hydroxy-1-naphthaldehyde with o-phenylenediamine in a molar ratio of 2:1. New eight lanthanide metal complexes [Ln L(NO 3) 2(H 2O) x](NO 3) {Ln(III) = Nd, Dy, Sm, Pr, Gd, Tb, La and Er, x = 0 for Nd, Sm, 1 for La, Gd, Pr, Nd, Dy, and 2 for Tb} were prepared. The characterization and nature of bonding of these complexes were elucidated by elemental analysis, spectral analysis ( 1H NMR, FT-IR, UV-vis), molar conductivity measurements, luminescence spectra and thermogravimetric studies. Analytical and spectral data revealed that the ligand L coordinates to the central Ln(III) ions by its two imine nitrogen atoms and two phenolic oxygen atoms with 1:1 stoichiometry. Under the excitation with 329 nm at room temperature, Tb and Dy complexes exhibited characteristic luminescence of the central metal ions attributed to efficient energy transfer from the ligand to the metal center. Most of Ln(III) complexes found to exhibit antibacterial activities against a number of pathogenic bacteria. We found that the antioxident activity of Ln(III) complexes on DPPH rad is concentration dependent and higher than that of the free ligand L.

Taha, Ziyad A.; Ajlouni, Abdulaziz M.; Al Momani, Waleed; Al-Ghzawi, Abeer A.

2011-10-01

159

Syntheses, characterization, biological activities and photophysical properties of lanthanides complexes with a tetradentate Schiff base ligand.  

PubMed

A tetradentate Schiff base ligand L (N,N'-bis(1-naphthaldimine)-o-phenylenediamine) was prepared from the condensation of 2-hydroxy-1-naphthaldehyde with o-phenylenediamine in a molar ratio of 2:1. New eight lanthanide metal complexes [LnL(NO(3))(2)(H(2)O)(x)](NO(3)) {Ln(III) = Nd, Dy, Sm, Pr, Gd, Tb, La and Er, x = 0 for Nd, Sm, 1 for La, Gd, Pr, Nd, Dy, and 2 for Tb} were prepared. The characterization and nature of bonding of these complexes were elucidated by elemental analysis, spectral analysis ((1)H NMR, FT-IR, UV-vis), molar conductivity measurements, luminescence spectra and thermogravimetric studies. Analytical and spectral data revealed that the ligand L coordinates to the central Ln(III) ions by its two imine nitrogen atoms and two phenolic oxygen atoms with 1:1 stoichiometry. Under the excitation with 329 nm at room temperature, Tb and Dy complexes exhibited characteristic luminescence of the central metal ions attributed to efficient energy transfer from the ligand to the metal center. Most of Ln(III) complexes found to exhibit antibacterial activities against a number of pathogenic bacteria. We found that the antioxident activity of Ln(III) complexes on DPPH() is concentration dependent and higher than that of the free ligand L. PMID:21764359

Taha, Ziyad A; Ajlouni, Abdulaziz M; Al Momani, Waleed; Al-Ghzawi, Abeer A

2011-10-15

160

Photoisomerization action spectrum of retinal protonated Schiff base in the gas phase  

NASA Astrophysics Data System (ADS)

The photophysical behaviour of the isolated retinal protonated n-butylamine Schiff base (RPSB) is investigated in the gas phase using a combination of ion mobility spectrometry and laser spectroscopy. The RPSB cations are introduced by electrospray ionisation into an ion mobility mass spectrometer where they are exposed to tunable laser radiation in the region of the S1 ? S0 transition (420-680 nm range). Four peaks are observed in the arrival time distribution of the RPSB ions. On the basis of predicted collision cross sections with nitrogen gas, the dominant peak is assigned to the all-trans isomer, whereas the subsidiary peaks are assigned to various single, double and triple cis geometric isomers. RPSB ions that absorb laser radiation undergo photoisomerization, leading to a detectable change in their drift speed. By monitoring the photoisomer signal as a function of laser wavelength an action spectrum, extending from 480 to 660 nm with a clear peak at 615 5 nm, is obtained. The photoisomerization action spectrum is related to the absorption spectrum of isolated retinal RPSB molecules and should help benchmark future electronic structure calculations.

Coughlan, N. J. A.; Catani, K. J.; Adamson, B. D.; Wille, U.; Bieske, E. J.

2014-04-01

161

Photoisomerization action spectrum of retinal protonated Schiff base in the gas phase.  

PubMed

The photophysical behaviour of the isolated retinal protonated n-butylamine Schiff base (RPSB) is investigated in the gas phase using a combination of ion mobility spectrometry and laser spectroscopy. The RPSB cations are introduced by electrospray ionisation into an ion mobility mass spectrometer where they are exposed to tunable laser radiation in the region of the S1 ? S0 transition (420-680nm range). Four peaks are observed in the arrival time distribution of the RPSB ions. On the basis of predicted collision cross sections with nitrogen gas, the dominant peak is assigned to the all-trans isomer, whereas the subsidiary peaks are assigned to various single, double and triple cis geometric isomers. RPSB ions that absorb laser radiation undergo photoisomerization, leading to a detectable change in their drift speed. By monitoring the photoisomer signal as a function of laser wavelength an action spectrum, extending from 480 to 660nm with a clear peak at 615 5nm, is obtained. The photoisomerization action spectrum is related to the absorption spectrum of isolated retinal RPSB molecules and should help benchmark future electronic structure calculations. PMID:24784270

Coughlan, N J A; Catani, K J; Adamson, B D; Wille, U; Bieske, E J

2014-04-28

162

Effect of acids on the infrared spectra of the Schiff base of trans-retinal  

SciTech Connect

trans-Retinylidene-tert-butylamine was put into contact with a series of acids (HCl, HBr, and HI and six carboxylic acids, trichloro-, dichloro-, monochloro-, and monobromoacetic acids, and 3-chloropropionic and propionic acids) whose pK/sub a/ values vary from 0.66 to 4.87. It can be inferred from the Fourier-transform infrared spectra that in order to obtain complete protonation of the Schiff base in chloroform solution an acid having a pK/sub a/ value of at least 2 is needed. With a pK/sub a/ value of about 4, similar to that of aspartic or glutamic acid, the estimated degree of protonation is about 65%. This shows that a mechanism is required to bring about 100% or nearly 100% protonation in rhodopsins. The intensification of the C double bond C bands upon protonation shows that the positive charge is delocalized along the conjugated chain. The N/sup +/H stretching region of the spectrum could be studied to advantage but the N/sup +/H in-plane bending bands could not be identified.

Lussier, L.S.; Sandorfy, C.; Le-Thanh, H.; Vocelle, D.

1987-04-23

163

Tetradentate Schiff base ligands and their complexes: Synthesis, structural characterization, thermal, electrochemical and alkane oxidation  

NASA Astrophysics Data System (ADS)

Three Schiff base ligands (H2L1-H2L3) with N2O2 donor sites were synthesized by condensation of 1,5-diaminonapthalene with benzaldehyde derivatives. A series of Cu(II), Co(II), Ni(II), Mn(II) and Cr(III) complexes were prepared and characterized by spectroscopic and analytical methods. Thermal, electrochemical and alkane oxidation reactions of the ligands and their metal complexes were investigated. Extensive application of 1D (1H, 13C NMR) and 2D (COSY, HETCOR, HMBC and TOSCY) NMR techniques were used to characterize the structures of the ligands and establish the 1H and 13C resonance assignments of the three ligands. Ligands H2L1 and H2L3 were obtained as single crystals from THF solution and characterized by X-ray diffraction. Both molecules are centrosymmetric and asymmetric unit contains one half of the molecule. Catalytic alkane oxidation reactions with the transition metal complexes investigated using cyclohexane and cyclooctane as substrates. The Cu(II) and Cr(III) complexes showed good catalytic activity in the oxidation of cyclohexane and cyclooctane to desired oxidized products. Electrochemical and thermal properties of the compounds were also investigated.

Ceyhan, Gkhan; Kse, Muhammet; McKee, Vickie; Uru?, Serhan; Glc, Ay?egl; Tmer, Mehmet

164

Two new heterodinuclear Schiff base complexes: Synthesis, crystal structure and thermal studies  

NASA Astrophysics Data System (ADS)

Two new heterodinuclear Schiff base complexes, [Hg(L)NiCl2(DMF)2] 1, and [Zn(L)NiCl2(DMF)2] 2, where H2L = N,N?-bis(salicylidene)-1,3-diaminopropane and DMF = dimethylformamide have been synthesized and characterized using elemental analysis, IR spectroscopy, thermal analysis and X-ray diffraction. Structural studies on 1 and 2 reveal the presence of a heterodinuclear [NiIIHgII] unit and [ZnIINiII] in which the central metal ions are connected to each other by two phenolate oxygen bridges. For complex 1 the Ni(II) ion adopts an elongated octahedral geometry (NiN2O4) while the Hg(II) ion assumes a distorted tetrahedral arrangement (HgO2Cl2) whereas for complex 2 the Zn(II) ion adopts an elongated octahedral geometry (ZnN2O4) while the Ni(II) ion assumes a distorted tetrahedral arrangement (NiO2Cl2). There are intermolecular Csbnd HClsbnd M interactions among the dinuclear complexes which are interconnected for 1 and 2. These intermolecular interactions result in the formation of a three dimensional structure for 1 and one dimensional zig-zag chains for 2.

Yardan, Alper; Hopa, Cigdem; Yahsi, Yasemin; Karahan, Ahmet; Kara, Hulya; Kurtaran, Raif

2015-02-01

165

Synthesis, characterization and crystal structure of some bidentate heterocyclic Schiff base ligands of 4-toluoyl pyrazolones and its mononuclear Cu(II) complexes  

NASA Astrophysics Data System (ADS)

We depict the synthesis of a new set of six bidentate heterocyclic Schiff base ligands, formed by the condensation of three different 4-toluoyl pyrazolones with various aromatic amines in ethanolic medium. All of these ligands have been characterized on the basis of elemental analysis, IR, 1H NMR, 13C NMR and Mass spectral data. The molecular geometries of three of these ligands have been determined by single crystal X-ray study. It reveals that these ligands exist in amine-one tautomeric form in the solid state. The reaction of these ligands with copper(II) resulted in the formation of mononuclear complexes having the general composition [CuL 2(H 2O) 2] with two water molecules at axial positions. These complexes have been characterized on the basis of elemental analysis, Cu-estimation, molar conductivity, magnetic measurements, IR, UV-Visible, FAB-Mass, TG-DTA-DSC data, cyclic voltametric measurements and ESR spectral studies. ESR spectra and magnetic susceptibility measurements indicates distorted octahedral stereochemistry of Cu(II) complexes, while non-electrolytic behaviour of complexes indicates the absence of counter ion.

Vyas, Komal M.; Jadeja, R. N.; Gupta, Vivek K.; Surati, K. R.

2011-03-01

166

Synthesis, characterization and biological activity of ferrocene-based Schiff base ligands and their metal (II) complexes  

NASA Astrophysics Data System (ADS)

Metal (II) complexes derived from S-benzyl-N-(1-ferrocenyl-3-(4-methylbenzene)acrylketone) dithiocarbazate; HL1, S-benzyl-N-(1-ferrocenyl-3-(4-chlorobenzene)acrylketone)dithiocarbazate; HL2, all the compounds were characterized using various spectroscopic techniques. The molar conductance data revealed that the chelates were non-electrolytes. IR spectra showed that the Schiff bases were coordinated to the metal ions in a bidentate manner with N, S donor sites. The ligands and their metal complexes have been screened for in vitro antibacterial, antifungal properties. The result of these studies have revealed that zinc (II) complexes 6 and 13 of both the ligands and copper (II) complexes 9 of the HL2 were observed to be the most active against all bacterial strains, antifungal activity was overall enhanced after complexation of the ligands.

Liu, Yu-Ting; Lian, Gui-Dan; Yin, Da-Wei; Su, Bao-Jun

167

Co(II), Ni(II) and Cu(II) complexes with coumarin-8-yl Schiff-bases: Spectroscopic, in vitro antimicrobial, DNA cleavage and fluorescence studies  

NASA Astrophysics Data System (ADS)

A new series of Co(II), Ni(II) and Cu(II) complexes of the type ML2H 2O of Schiff-bases derived from m-substituted thiosemicarbazides and 8-acetyl-7-hydroxy-4-methylcoumarin have been synthesized and characterized by spectroscopic studies. Schiff-bases exhibit thiol-thione tautomerism wherein sulphur plays an important role in the coordination. The coordination possibility of the Schiff-bases towards metal ions have been proposed in the light of elemental analyses, spectral (IR, UV-vis, FAB-mass, ESR and fluorescence), magnetic and thermal studies. The low molar conductance values in DMF indicate that, the metal complexes are non-electrolytes. The cyclic voltammetric studies suggested that, the Cu(II) and Ni(II) complexes are of single electron transfer quasi-reversible nature. The Schiff-bases and its metal complexes have been evaluated for their in vitro antibacterial ( Escherichia coli, Staphilococcus aureus, Bascillus subtilis and Salmonella typhi) and antifungal activities ( Candida albicans, Cladosporium and Aspergillus niger) by MIC method. The Schiff-base I and its metal complexes exhibited DNA cleavage activity on isolated DNA of A. niger.

Patil, Sangamesh A.; Unki, Shrishila N.; Kulkarni, Ajaykumar D.; Naik, Vinod H.; Badami, Prema S.

2011-09-01

168

Reactivity of rhenium(V) oxo Schiff base complexes with phosphine ligands: rearrangement and reduction reactions.  

PubMed

The symmetric rhenium(V) oxo Schiff base complexes trans-[ReO(OH2)(acac2en)]Cl and trans-[ReOCl(acac2pn)], where acac2en and acac2pn are the tetradentate Schiff base ligands N,N'-ethylenebis(acetylacetone) diimine and N,N'-propylenebis(acetylacetone) diimine, respectively, were reacted with monodentate phosphine ligands to yield one of two unique cationic phosphine complexes depending on the ligand backbone length (en vs pn) and the identity of the phosphine ligand. Reduction of the Re(V) oxo core to Re(III) resulted on reaction of trans-[ReO(OH2)(acac2en)]Cl with triphenylphosphine or diethylphenylphosphine to yield a single reduced, disubstituted product of the general type trans-[Re(III)(PR3)2(acac2en)]+. Rather unexpectedly, a similar reaction with the stronger reducing agent triethylphosphine yielded the intramolecularly rearranged, asymmetric cis-[Re(V)O(PEt3)(acac2en)]+ complex. Reactions of trans-[Re(V)O(acac2pn)Cl] with the same phosphine ligands yielded only the rearranged asymmetric cis-[Re(V)O(PR3)(acac2pn)]+ complexes in quantitative yield. The compounds were characterized using standard spectroscopic methods, elemental analyses, cyclic voltammetry, and single-crystal X-ray diffraction. The crystallographic data for the structures reported are as follows: trans-[Re(III)(PPh3)2(acac2en)]PF6 (H48C48N2O2P2Re.PF6), 1, triclinic (P), a = 18.8261(12) A, b = 16.2517(10) A, c = 15.4556(10) A, alpha = 95.522(1) degrees , beta = 97.130(1) degrees , gamma = 91.350(1) degrees , V = 4667.4(5) A(3), Z = 4; trans-[Re(III)(PEt2Ph)2(acac2en)]PF6 (H48C32N2O2P2Re.PF6), 2, orthorhombic (Pccn), a = 10.4753(6) A, b =18.4315(10) A, c = 18.9245(11) A, V = 3653.9(4) A3, Z = 4; cis-[Re(V)O(PEt3)(acac2en)]PF6 (H33C18N2O3PRe.1.25PF6, 3, monoclinic (C2/c), a = 39.8194(15) A, b = 13.6187(5) A, c = 20.1777(8) A, beta = 107.7730(10) degrees , V = 10419.9(7) A3, Z = 16; cis-[Re(V)O(PPh3)(acac2pn)]PF6 (H35C31N2O3PRe.PF6), 4, triclinic (P), a = 10.3094(10) A, b =12.1196(12) A, c = 14.8146(15) A, alpha = 105.939(2) degrees , beta = 105.383(2) degrees , gamma = 93.525(2) degrees , V = 1698.0(3) A3, Z = 2; cis-[Re(V)O(PEt2Ph)(acac2pn)]PF6 (H35C23N2O3PRe.PF6), 5, monoclinic (P2(1)/n), a = 18.1183(18) A, b = 11.580(1) A, c = 28.519(3) A, beta = 101.861(2) degrees , V = 5855.9(10) A(3), Z = 4. PMID:15792474

Benny, Paul D; Green, Jenny L; Engelbrecht, Hendrik P; Barnes, Charles L; Jurisson, Silvia S

2005-04-01

169

Cadmium(II) complexes of fully condensed Schiff-base ligands derived from two different symmetrical and asymmetrical tripodal tetraamines and 2-acetylpyridine; the novel observations for heptadentate mono-capped trigonal antiprismatic Schiff-base complexes  

Microsoft Academic Search

In the presence of cadmium(II), 2-acetylpyridine condenses with tris(3-aminopropyl)amine, tpt, and bis(3-aminopropyl)(2-aminoethyl)amine, ppe, in absolute methanol to produce two fully condensed potentially heptadentate Schiff-base complexes, [Cd(py3tpt)](ClO4)2 and [Cd(py3ppe)](ClO4)2. X-ray structure analysis of the former complex shows mono-capped distorted trigonal antiprism geometry wherein the Cd?unique nitrogen distance is 2.486 . In comparison with the weighted mean of other Cd?N distances, 2.425

Hassan Keypour; Sadegh Salehzadeh; Robin G. Pritchard; R. V. Parish

2000-01-01

170

Synthesis and characterization of Schiff base octaazamacrocyclic complexes and their biological studies.  

PubMed

A condensation reaction between 1,2-diphenylethane-1,2-dione dihydrazone (DPEDDH) and dimethyl or diethyloxalate in methanol resulted in a novel Schiff base octaazamacrocyclic ligand, (L): (6,7,14,15-tetraoxa-2,3,10,11-tetraphenyl-1,4,5,8,9,12,13,16-octaazacyclohexadecane-1,3,9,11-tetraene). Subsequently metal complexes of the type [MLX2] and [CuL]X2; (M=Mn(II), Co(II), Ni(II) and Zn(II); X=Cl or NO3) were synthesized by the reaction of the free macrocyclic ligand (L) with the corresponding metal salts in 1:1 molar ratio. These complexes were characterized on the basis of analytical data, molar conductivity and magnetic susceptibility measurements, ESI-mass, IR, NMR ((1)H and (13)C), EPR and electronic spectral studies. The thermal stability of the complexes was also studied by TGA and DTA analyses. These studies show that all the complexes have octahedral arrangement around the metal ions except copper complexes which are square planar. The ligand and its complexes were screened for their antibacterial activity in vitro against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and were also studied for their anticancer activity against the human cancer cells lines: HeLa (Human cervical carcinoma), MCF7 (Human breast adenocarcinoma) and Hep3B (Human Hepatocellular carcinoma). The recorded IC50 values for the tested compounds show moderate to good cytotoxicity against these cancer cell lines. The copper complex, [CuL]Cl2, showed excellent antimicrobial activity against tested microorganisms which is almost equivalent to the standard drug ciprofloxacin. PMID:25490374

Zafar, Hina; Kareem, Abdul; Sherwani, Asif; Mohammad, Owais; Ansari, Mohammad Azam; Khan, Haris M; Khan, Tahir Ali

2014-10-24

171

Synthesis, crystal structure and nuclease activity of a Schiff base copper(II) complex.  

PubMed

A new Schiff base copper(II) complex, Cu(o-VANAHE)(2) (o-VANAHE = 2-(o-vanillinamino)-1-hydroxyethane), has been synthesized and characterized. Single crystal X-ray diffraction results suggest that this complex structure belongs to triclinic crystal system, space group P1 with the following crystallographic parameters: a = 8.819(4) angstroms, b = 10.794(5) angstroms, c = 11.350(5) angstroms, alpha = 70.262(6) degrees, beta = 70.816(6) degrees, gamma = 78.360(6) degrees, V = 955.4(7) angstroms3, Z = 2, D(c) = 1.571 Mg x m(-3), and the final R1 = 0.0393, wR2 = 0.0994 for the observed reflections 2620(I > 2sigma(I)). The molecular geometry is almost coplanar. Viscosity, fluorescence spectroscopy and cyclic voltammetry have been conducted to assess their interaction between this complex and DNA. Results showed that the copper(II) complex can increase DNA's relative viscosity and quench the fluorescence intensity of EB bound to DNA. The adding of DNA to the solution of Cu(o-VANAHE)2 causes a slight decrease in the voltammetric current, as well as a slight shift in the E(1/2) to less negative potential. The interaction between the complex and DNA has also been investigated by submarine gel electrophoresis, interestingly, we found that the copper(II) complex can cleave circular plasmid pBR322 DNA to nicked and linear forms. PMID:15833330

Li, Lian-Zhi; Zhao, Chao; Xu, Tao; Ji, Hai-Wei; Yu, Yan-Hong; Guo, Guang-Qiang; Chao, Hui

2005-05-01

172

Spectroscopic, thermal analysis and DFT computational studies of salen-type Schiff base complexes.  

PubMed

A new series of metal(II) complexes of Co(II), Ni(II), Cu(II), Zn(II), and Pb(II) have been synthesized from a salen-type Schiff base ligand derived from o-vanillin and 4-methyl-1,2-phenylenediamine and characterized by elemental analysis, spectral (IR, UV-Vis, (1)H NMR, (13)C NMR and EI-mass), molar conductance measurements and thermal analysis techniques. Coats-Redfern method has been utilized to calculate the kinetic and thermodynamic parameters of the metal complexes. The molecular geometry, Mulliken atomic charges of the studied compounds were investigated theoretically by performing density functional theory (DFT) to access reliable results to the experimental values. The theoretical (13)C chemical shift results of the studied compounds have been calculated at the B3LYP, PBEPBE and PW91PW91 methods and standard 6-311+G(d,p) basis set starting from optimized geometry. The comparison of the results indicates that B3LYP/6-311+G(d,p) yields good agreement with the observed chemical shifts. The measured low molar conductance values in DMF indicate that the metal complexes are non-electrolytes. The spectral and thermal analysis reveals that all complexes have octahedral geometry except Cu(II) complex which can attain the square planner arrangement. The presence of lattice and coordinated water molecules are indicated by thermograms of the complexes. The thermogravimetric (TG/DTG) analyses confirm high stability for all complexes followed by thermal decomposition in different steps. PMID:24021948

Ebrahimi, Hossein Pasha; Hadi, Jabbar S; Abdulnabi, Zuhair A; Bolandnazar, Zeinab

2014-01-01

173

Spectroscopic, thermal analysis and DFT computational studies of salen-type Schiff base complexes  

NASA Astrophysics Data System (ADS)

A new series of metal(II) complexes of Co(II), Ni(II), Cu(II), Zn(II), and Pb(II) have been synthesized from a salen-type Schiff base ligand derived from o-vanillin and 4-methyl-1,2-phenylenediamine and characterized by elemental analysis, spectral (IR, UV-Vis, 1H NMR, 13C NMR and EI-mass), molar conductance measurements and thermal analysis techniques. Coats-Redfern method has been utilized to calculate the kinetic and thermodynamic parameters of the metal complexes. The molecular geometry, Mulliken atomic charges of the studied compounds were investigated theoretically by performing density functional theory (DFT) to access reliable results to the experimental values. The theoretical 13C chemical shift results of the studied compounds have been calculated at the B3LYP, PBEPBE and PW91PW91 methods and standard 6-311+G(d,p) basis set starting from optimized geometry. The comparison of the results indicates that B3LYP/6-311+G(d,p) yields good agreement with the observed chemical shifts. The measured low molar conductance values in DMF indicate that the metal complexes are non-electrolytes. The spectral and thermal analysis reveals that all complexes have octahedral geometry except Cu(II) complex which can attain the square planner arrangement. The presence of lattice and coordinated water molecules are indicated by thermograms of the complexes. The thermogravimetric (TG/DTG) analyses confirm high stability for all complexes followed by thermal decomposition in different steps.

Ebrahimi, Hossein Pasha; Hadi, Jabbar S.; Abdulnabi, Zuhair A.; Bolandnazar, Zeinab

2014-01-01

174

Chloroform-soluble schiff-base Zn(II) or Cd(II) complexes from a dynamic combinatorial library.  

PubMed

A dynamic combinatorial library of metal ion Schiff-base complexes have been studied for the extraction of Zn(II) or Cd(II) from aqueous solution into chloroform. Library components consist of different aminophenols and 2-pyridinecarboxaldehyde. Extraction of both Zn(II) and Cd(II) into chloroform was observed from aqueous solutions containing 0.0500 mM M(NO3)2, 0.100 M aminophenol, 0.100 M 2-pyridinecarboxaldehyde, 0.100 M NaCl, and 5.00 mM buffer at pH 8.5. Extraction was dependent on pH but not on counterions including Cl-, Br-, or NO3-. Studies showed that equilibrium was attained between the Schiff-base complexes across the two-phase chloroform-water system after 24 h of stirring. Analysis of the extracted species by use of 1H NMR spectroscopy and mass spectrometry as well as solubility studies on characterized complexes suggested that the major extracted species is the neutral bis-Schiff-base metal ion complex. In libraries containing mixtures of two different aminophenols and 2-pyridinecarboxaldehyde, an enhanced extent of extraction of Zn(II) into chloroform is observed. Studies suggest that a Zn(II) complex, which is likely the mixed Schiff-base complex, has superior extraction properties compared to simple libraries with a single aminophenol component. The structures of two bis-Schiff-base complexes of Zn(II) and one of Cd(II) have been determined by X-ray crystallography. The geometries of the two Zn(II) complexes, which differ only by a methyl substituent on the Schiff-base ligand, are markedly different, supporting the use of combinatorial methods in coordination chemistry. Zn(SB14)2 crystallized as the sesquihydrate (C24H18N4O2Zn.1.5 H2O) in the space group C2/c, with cell dimensions a = 23.219(15) A, b = 11.299(7) A, c = 16.822(11) A, beta = 102.91(5) degrees, V = 4302(5) A3, and Z = 8. Zn(SB15)2 crystallized as a 1:1 methanol solvate (C26H22N4O2Zn.CH3OH) in the space group P2(1)/c with cell dimensions a = 13.981(5) A, b = 7.978(3) A, c = 22.568(8) A, beta = 104.53(3) degrees, V = 2436.8(15) A3, and Z = 4. Cd(SB14)2 crystallized as a 1:1 ethanol solvate (C24H18N4O2Cd.CH3CH2OH) in the space group R3 with unit cell dimensions of a = 36.423(2) A, c = 9.2930(10) A, V = 10678(2) A3, and Z = 18. PMID:11261969

Epstein, D M; Choudhary, S; Churchill, M R; Keil, K M; Eliseev, A V; Morrow, J R

2001-03-26

175

A theoretical investigation into the luminescent properties of d8-transition-metal complexes with tetradentate Schiff base ligands.  

PubMed

A theoretical investigation on the luminescence efficiency of a series of d(8) transition-metal Schiff base complexes was undertaken. The aim was to understand the different photophysics of [M-salen](n) complexes (salen = N,N'-bis(salicylidene)ethylenediamine; M = Pt, Pd (n = 0); Au (n = +1)) in acetonitrile solutions at room temperature: [Pt-salen] is phosphorescent and [Au-salen](+) is fluorescent, but [Pd-salen] is nonemissive. Based on the calculation results, it was proposed that incorporation of electron-withdrawing groups at the 4-position of the Schiff base ligand should widen the (3)MLCT-(3)MC gap (MLCT = metal-to-ligand charge transfer and MC = metal centered, that is, the dd excited state); thus permitting phosphorescence of the corresponding Pd(II) Schiff base complex. Although it is experimentally proven that [Pd-salph-4E] (salph = N,N'-bis(salicylidene)-1,2-phenylenediamine; 4E means an electron-withdrawing substituent at the 4-position of the salicylidene) displays triplet emission, its quantum yield is low at room temperature. The corresponding Pt(II) Schiff base complex, [Pt-salph-4E], is also much less emissive than the unsubstituted analogue, [Pt-salph]. Thus, a detailed theoretical analysis of how the substituent and central metal affected the photophysics of [M-salph-X] (X is a substituent on the salph ligand, M = Pt or Pd) was performed. Temperature effects were also investigated. The simple energy gap law underestimated the nonradiative decay rates and was insufficient to account for the temperature dependence of the nonradiative decay rates of the complexes studied herein. On the other hand, the present analysis demonstrates that inclusions of low-frequency modes and the associated frequency shifts are decisive in providing better quantitative estimates of the nonradiative decay rates and the experimentally observed temperature effects. Moreover, spin-orbit coupling, which is often considered only in the context of radiative decay rate, has a significant role in determining the nonradiative rate as well. PMID:24715418

Tong, Glenna So Ming; Chow, Pui Keong; To, Wai-Pong; Kwok, Wai-Ming; Che, Chi-Ming

2014-05-19

176

Surfactant-copper(II) Schiff base complexes: synthesis, structural investigation, DNA interaction, docking studies, and cytotoxic activity.  

PubMed

A series of surfactant-copper(II) Schiff base complexes (1-6) of the general formula, [Cu(sal-R2)2] and [Cu(5-OMe-sal-R2)2], {where, sal?=?salicylaldehyde, 5-OMe-sal?=?5-methoxy- salicylaldehyde, and R2?=?dodecylamine (DA), tetradecylamine (TA), or cetylamine (CA)} have been synthesized and characterized by spectroscopic, ESI-MS, and elemental analysis methods. For a special reason, the structure of one of the complexes (2) was resolved by single crystal X-ray diffraction analysis and it indicates the presence of a distorted square-planar geometry in the complex. Analysis of the binding of these complexes with DNA has been carried out adapting UV-visible-, fluorescence-, as well as circular dichroism spectroscopic methods and viscosity experiments. The results indicate that the complexes bind via minor groove mode involving the hydrophobic surfactant chain. Increase in the length of the aliphatic chain of the ligands facilitates the binding. Further, molecular docking calculations have been performed to understand the nature as well as order of binding of these complexes with DNA. This docking analysis also suggested that the complexes interact with DNA through the alkyl chain present in the Schiff base ligands via the minor groove. In addition, the cytotoxic property of the surfactant-copper(II) Schiff base complexes have been studied against a breast cancer cell line. All six complexes reduced the visibility of the cells but complexes 2, 3, 5, and 6 brought about this effect at fairly low concentrations. Analyzed further, but a small percentage of cells succumbed to necrosis. Of these complexes (6) proved to be the most efficient aptotoxic agent. PMID:24854148

Lakshmipraba, Jagadeesan; Arunachalam, Sankaralingam; Solomon, Rajadurai Vijay; Venuvanalingam, Ponnambalam; Riyasdeen, Anvarbatcha; Dhivya, Rajakumar; Akbarsha, Mohammad Abdulkader

2015-04-01

177

The role of a Schiff base scaffold, N-(2-hydroxy acetophenone) glycinate-in overcoming multidrug resistance in cancer.  

PubMed

Drug resistance is a problem that hinders the numerous successes of chemotherapeutic intervention of cancer and continues to be a major obstacle for cures. Till date, several attempts have been made to develop suitable multidrug resistance (MDR) reversing agents. But, throughout the clinical development of MDR reversing agents, patients repeatedly suffer from toxicities. So far, some anticancer activity of Schiff bases which are the condensation products of carbonyl compounds and primary amines and their metal complexes has been described. But, overcoming multidrug resistance, by the use of such small molecules still remain unexplored. Under this backdrop, in search of less toxic and more effective MDR reversing agents our laboratory has developed the different metal chelates of Schiff base N-(2-hydroxy acetophenone)glycinate (NG) which is structurally similar to azatyrosine [L-?-(5-hydroxy-2-pyridyl)-alanine] that inhibits tumor formation by deactivating the c-Raf-1 kinase and c-Ha-ras signalling pathway. A decade-long research proposes possible strategies to overcome MDR by exploiting the chemical nature of such metal chelates. In this review we have catalogued the success of metal chelates of NG to overcome MDR in cancer. The review depict that the problem of MDR can be circumvent by synchronized activation of immunogenic cell death pathways that utilize the components of a host's immune system to kill cancer cells in combination with other conventional strategies. The current wealth of preclinical information promises better understanding of the cellular processes underlying MDR reversing activity of metal derivatives of NG and thus exposes several cellular targets for rational designing of new generation of Schiff base metal chelates as MDR reversing agents. PMID:24044945

Ganguly, Avishek; Chakraborty, Paramita; Banerjee, Kaushik; Choudhuri, Soumitra Kumar

2014-01-23

178

NH-type of chiral Ni(II) complexes of glycine Schiff base: design, structural evaluation, reactivity and synthetic applications.  

PubMed

The work being reported here deals with the design of a new type of "N-H" Ni(II) complexes of glycine Schiff bases and study general aspects of their reactivity. It was confirmed that the presence of NH function in these Ni(II) complexes does not interfere with the homologation of the glycine residue, rendering these derivatives of high synthetic value for the general synthesis of ?-amino acids. In particular, the practical application of these NH-type complexes was demonstrated by asymmetric synthesis of various ?-substituted pyroglutamic acids via Michael addition reactions with chiral Michael acceptors. PMID:24424805

Bergagnini, Mackenzie; Fukushi, Kazunobu; Han, Jianlin; Shibata, Norio; Roussel, Christian; Ellis, Trevor K; Acea, Jos Luis; Soloshonok, Vadim A

2014-02-28

179

Schiff bases attached L-glutamine and L-asparagine: first investigation on antimutagenic and antimicrobial analyses.  

PubMed

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 B? (AFB?) using micronuclei (MN) assay in human lymphocyte cell culture in vitro. The protective role of these compounds against AFB?-induced MN is probably related to its doses. PMID:23687951

Sakiyan, Iffet; Anar, Mustafa; O?tc, Hatice; Agar, Guleray; Sar?, Nur?en

2014-06-01

180

Synthesis, characterization, and antibacterial activity of new rare-earth ion complexes with unsymmetrical Schiff base ligand  

Microsoft Academic Search

A new unsymmetrical Schiff base ligand (H2LLi) was synthesized using L-lysine, salicylaldehyde, and 2-hydroxy-1-naphthaldehyde. Three rare-earth ion complexes of this\\u000a ligand, [REE(H2L)(NO3)]NO3 ? 2H2O (REE = La, Sm, Ho), have been prepared and characterized by elemental analyses, IR spectra, UV spectra, TG-DTG, and molar conductance. The antibacterial activity of the ligand and its complexes are also studied. The antibacterial experiments

Y. H. Fan; X. T. He; C. F. Bi; F. Guo; Y. Bao; R. Chen

2007-01-01

181

Synthesis, characterization, cytotoxic activities, and DNA-binding properties of the La(III) complex with Naringenin Schiff-base  

Microsoft Academic Search

A new Naringenin Schiff-base ligand (H3L) and its complex, [La(H2L)2(NO3)3H2O], have been synthesized and characterized on the basis of elemental analyses, molar conductivities, mass spectra, 1H NMR, thermogravimetry\\/differential thermal analysis (TGDTA), UV spectra, and IR spectra. Spectrometric titrations, ethidium bromide displacement experiments, and viscosity measurements indicate that the two compounds, especially the La(III) complex, strongly bind with calf-thymus DNA, presumably

Bao-dui Wang; Zheng-Yin Yang; Qin Wang; Ti-kuan Cai; Patrick Crewdson

2006-01-01

182

Schiff base addition to cyclic dicarboxylic anhydrides: an unusual concerted reaction. An MO and DFT theoretical study.  

PubMed

The existing controversy as to whether dicarboxylic anhydride iminolysis by Schiff bases is a concerted [4 + 2] addition or a stepwise reaction following either a Perkin-like route or occurs as iminolysis via zwitterionic intermediates is solved computationally by DFT and MO theory. Both types of theory favor a concerted mechanism starting as bimolecular addition of imine to the carbonyl carbon of anhydride monoenol, accompanied by simultaneous elimination of carboxylate. The reaction proceeds further without forming any intermediate and completes as intramolecular charge transfer from enol HOMO to imine LUMO with ring closure. PMID:12919059

Kaneti, Jose; Bakalova, Snezhana M; Pojarlieff, Ivan G

2003-08-22

183

Homo dinuclear lanthanide(III) complexes of a mesogenic Schiff-base, N, N'-di-(4-decyloxysalicylidene)-1',6'-diaminohexane: Synthesis and characterization  

NASA Astrophysics Data System (ADS)

A mesogenic Schiff-base, N, N'-di-(4-decyloxysalicylidene)-1',6'-diaminohexane, H 2ddsdh (abbreviated as H 2L 2) that exhibits smectic-B ( SmB) mesophase, was synthesized and its structure studied by elemental analysis, mass spectrometry, NMR & IR spectral techniques. The Schiff-base, H 2L 2, upon condensation with hydrated lanthanide(III) nitrates, yields Ln III complexes of the general composition [Ln 2(L 2H 2) 3(NO 3) 4](NO 3) 2, where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho. IR and NMR spectral data imply a bi-dentate bonding of the Schiff-base in its zwitterionic form (as L 2H 2) to the Ln III ions through two phenolate oxygens. The POM and DSC studies reveal that none of the Ln III complexes exhibits mesomorphism. Fluorescence studies show that the Tb III complex displays characteristic metal-centered fluorescence (solution state).

Shakya, Pawan Raj; Singh, Angad Kumar; Rao, T. R.

2011-09-01

184

A novel Schiff base bearing dopamine groups with tripodal structure. Synthesis and its salen/salophen-bridged Fe/Cr(III) capped complexes  

NASA Astrophysics Data System (ADS)

This work presents the synthesis of a novel Schiff base and its complexation properties with Fe(III) and Cr(III). A Schiff base bearing dopamine (TRDPA) was synthesized using dopamine hydrochloride and 1,3,5-tris (formylphenoxymethyl)benzene in methanol media. The prepared TRDPA was then reacted with four new trinuclear Fe(III) and Cr(III) complexes involving tetradenta Schiff bases N,N-bis(salicylidene)ethylenediamine-(salenH2) or bis(salicylidene)-o-phenylenediamine-(salophenH2). The structures of these compounds were characterized through 1H NMR, 13C NMR, FT-IR, thermal analysis (TG), elemental analysis, and magnetic susceptibility measurements. The complexes were also characterized as low-spin distorted octahedral Fe(III) and Cr(III) bridged by a catechol group.

Kocyigit, Ozcan

2013-02-01

185

Analysis of the factors that influence the C=N stretching frequency of polyene Schiff bases. Implications for bacteriorhodopsin and rhodopsin.  

PubMed Central

In this study quantum mechanical calculations of force constants and normal mode analysis are used to elucidate the factors that influence the C=C and C=N stretching frequencies in polyenes and in protonated Schiff bases. The C=N stretching frequency is found to depend on both the C=N stretching force constant and the C=N-H bending force constant. Due to the contributions of these two modes, the C=N stretching frequency is particularly sensitive to the magnitude of the Schiff base counterion interactions and to the hydrogen bonding environment of the Schiff base nitrogen. Models for chromophore-protein interactions in the retinal binding site and for the photochemical transformations of bacteriorhodopsin and rhodopsin are evaluated in light of these results. PMID:3345334

Gilson, H S; Honig, B H; Croteau, A; Zarrilli, G; Nakanishi, K

1988-01-01

186

New insights into the mechanism of the Schiff base hydrolysis catalyzed by type I dehydroquinate dehydratase from S. enterica: a theoretical study.  

PubMed

The reaction pathway of Schiff base hydrolysis catalyzed by type I dehydroquinate dehydratase (DHQD) from S. enterica has been studied by performing molecular dynamics (MD) simulations and density functional theory (DFT) calculations and the corresponding potential energy profile has also been identified. On the basis of the results, the catalytic hydrolysis process for the wild-type enzyme consists of three major reaction steps, including nucleophilic attack on the carbon atom involved in the carbon-nitrogen double bond of the Schiff base intermediate by a water molecule, deprotonation of the His143 residue, and dissociation between the product and the Lys170 residue of the enzyme. The remarkable difference between this and the previously proposed reaction mechanism is that the second step here, absent in the previously proposed reaction mechanism, plays an important role in facilitating the reaction through a key proton transfer by the His143 residue, resulting in a lower energy barrier. Comparison with our recently reported results on the Schiff base formation and dehydration processes clearly shows that the Schiff base hydrolysis is rate-determining in the overall reaction catalyzed by type I DHQD, consistent with the experimental prediction, and the calculated energy barrier of ?16.0 kcal mol(-1) is in good agreement with the experimentally derived activation free energy of ?14.3 kcal mol(-1). When the imidazole group of His143 residue is missing, the Schiff base hydrolysis is initiated by a hydroxide ion in the solution, rather than a water molecule, and both the reaction mechanism and the kinetics of Schiff base hydrolysis have been remarkably changed, clearly elucidating the catalytic role of the His143 residue in the reaction. The new mechanistic insights obtained here will be valuable for the rational design of high-activity inhibitors of type I DHQD as non-toxic antimicrobials, anti-fungals, and herbicides. PMID:22847490

Yao, Yuan; Li, Ze-Sheng

2012-09-21

187

Synthesis, characterization, spectroscopic and thermodynamic studies of charge transfer interaction of a new water-soluble cobalt(II) Schiff base complex with imidazole derivatives  

NASA Astrophysics Data System (ADS)

The water-soluble cobalt(II) tetradentate Schiff base complex [Co(II)L](ClO 4) 2, L: ( N, N'-bis{5-[(triphenylphosphonium)-methyl]salicylidine}- o-phenylenediamineperchlorate has been synthesized and characterized. This complex forms charge transfer (CT) complexes with imidazole and 1-methylimidazole. The formation constant, molar absorptivity ( ?'), and thermodynamic parameters for charge transfer complexes formation of cobalt(II) Schiff base complexes with imidazole derivatives were determined by using UV-vis spectrophotometric method in aqueous solutions at constant ionic strength ( I = 0.2 mol dm -3 KNO 3) at pH 6.0 and various temperatures between 292 and 315 K.

Boghaei, Davar M.; Askarizadeh, Elham; Bezaatpour, Abolfazl

2008-02-01

188

Efficient in situ three-component formation of chiral oxazoline-Schiff base copper(II) complexes: towards combinatorial library of chiral catalysts for asymmetric Henry reaction.  

PubMed

A combinatorial in situ three-component chiral oxazoline-Schiff base copper(II) complex catalyst formation method was developed. This simple combinatorial chiral catalyst approach provided a modular library of chiral oxazoline-Schiff base copper(II) complex catalysts. The catalytic activity of these in situ generated catalysts can be rapidly and conveniently evaluated in the asymmetric Henry reaction. Moderate to good yields and enantioselectivities (up to 92% ee) were obtained under the optimized condition. The combination of modular three-component catalyst formation and in situ asymmetric reaction provides a new technology in asymmetric catalysis. PMID:20458398

Yang, Wen; Liu, Han; Du, Da-Ming

2010-06-28

189

Affinity to bovine serum albumin and anticancer activity of some new water-soluble metal Schiff base complexes  

NASA Astrophysics Data System (ADS)

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 Frster 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.

Asadi, Mozaffar; Asadi, Zahra; Zarei, Leila; Sadi, Somaye Barzegar; Amirghofran, Zahra

2014-12-01

190

Synthesis, structure, DNA binding and cleavage properties of ternary amino acid Schiff base-phen/bipy Cu(II) complexes.  

PubMed

Ternary Cu(II) complexes [Cu(II)(saltrp)(B)] (1,2), (saltrp=salicylidene tryptophan, B=1,10 phenathroline (1) or 2,2' bipyridine (2)) were synthesized and characterized. Complex 2 was structurally characterized by single crystal X-ray crystallography. The molecular structure shows a distorted square pyramidal coordination geometry (CuN(3)O(2)) in which the ONO donor Schiff base is bonded to the Cu(II) in the basal plane. The N,N donor heterocyclic base displays an axial-equatorial binding mode. CT-DNA binding studies revealed that the complexes show good binding propensity (Intrinsic binding constant, K(b)=3.3210(5) M(-1) for 1 and K(b)=3.1010(5) M(-1) for 2). The catalytic role of these complexes in the oxidative and hydrolytic cleavage of DNA was studied in detail. Complex 1 binds and cleaves DNA more efficiently as compared to 2. From the kinetic experiments, rate constants for the hydrolysis of phosphodiester bond of DNA backbone were determined as 1.94 h(-1) and 1.05 h(-1) for 1 and 2 respectively. It amounts to (2.93-5.41)10(7) fold rate enhancement compared to uncatalyzed double stranded DNA, which is impressive as compared to related Cu(II) Schiff base complexes. PMID:22071085

Reddy, Pulimamidi Rabindra; Shilpa, Addla; Raju, Nomula; Raghavaiah, Pallepogu

2011-12-01

191

Immobilization of cobalt(III) Schiff base complexes onto Montmorillonite-K10: Synthesis, experimental and theoretical structural determination  

NASA Astrophysics Data System (ADS)

The [Co(naphophen)(PPh3)(OH2)]ClO4 and [Co(naphophen)(PBu3)(OH2)]BF4 (where naphophen = bis(naphthaldehyde)1,2-phenylenediimine) complexes were synthesized and chracterized by FT-IR, UV-Vis, 1H NMR, 13C NMR spectroscopy and elemental analysis techniques. The coordination geometry of the synthesized complexes were determined by X-ray crystallography. Cobalt (III) complexes have six-coordinated pseudo-octahedral geometry in which the O(1), O(2), N(1) and N(2) atoms of the Schiff base forms the equatorial plane. These complexes showed a dimeric structure via hydrogen bonding between the phenolate oxygen and the hydrogens of the coordinated H2O molecule. The theoretical calculations were also performed to optimize the structure of the complexes in the gas phase to confirm the structures proposed by X-ray crystallography. In addition, UV-Visible and IR spectra of complexes were calculated and compared with the corresponding experimental spectra to complete the experimental structural identification. The synthesized complexes were incorporated onto the Montmorillonite-K10 nanoclay via simple ion-exchange reaction. The structure and morphology of the obtained nanohybrids were identified by FT-IR, XRD, TGA/DTA, SEM and TEM techniques. Based on the XRD results of the new nanohybrid materials, the Schiff base complexes were intercalated in the interlayer spaces of clay. SEM and TEM micrographs of the clay/complex shows that the resulting hybrid nanomaterials has layer structures.

Kianfar, Ali Hossein; Kamil Mahmood, Wan Ahmad; Dinari, Mohammad; Farrokhpour, Hossein; Enteshari, Majid; Azarian, Mohammad Hossein

2015-02-01

192

Synthesis, spectral, electrochemical and catalytic properties of Ru(III) Schiff base complexes containing N, O donors  

NASA Astrophysics Data System (ADS)

A series of new hexa coordinated ruthenium(III) complexes of the type [RuY2(EPh3)2(X-DPMP)] (where Y = Br or Cl; E = P or As; DPMP = 2-[(2,6-Diisopropyl-phenylimino)-methyl]-phenol, X = H, Br, Cl, I and Ph) have been synthesized by equimolar [RuY3(EPh3)3] and the Schiff base ligands in benzene. The bidentate Schiff base ligands (X-DPMP) have been derived from condensation of 2,6-diisopropylaniline with mono and multisubstituted salicylaldehyde derivatives. The complexes have been characterized by elemental analysis, magnetic susceptibility, UV-Vis., IR and EPR spectral and electrochemical measurements. All the ruthenium(III) complexes are found to be stable, paramagnetic, low spin, redox active and display either quasi reversible or irreversible redox couples based on metal centre. They have exhibited catalytic activity for the oxidation of wide range of primary and secondary alcohols to corresponding aldehydes or ketones with moderate to high conversion in the presence of N-methylmorpholine-N-oxide (NMO) as co-oxidant.

Raja, K. Kanmani; Indra Gandhi, N.; Lekha, L.; Easwaramoorthy, D.; Rajagopal, G.

2014-02-01

193

pH-metric and spectroscopic properties of new 4-hydroxysalicylidene-2-aminopyrimidine Schiff-base transition metal complexes  

NASA Astrophysics Data System (ADS)

The new complexes, cis-[WO 2(Hsap) 2], [Ru(PPh 3) 2(Hsap) 2], [Pd(Hsap)Cl(H 2O)], [Pd(PPh 3) 2(Hsap)]Cl, [Ag(Hsap)(H 2O) 2], [Ni(Hsap)(AcO)(H 2O) 2], [Ni(Hsap) 2] and [Cu(Hsap)Cl(H 2O)] are reported, where H 2sap is 4-hydroxysalicylidene-2-amino pyrimidine Schiff-base. The complexes were characterized by elemental analyses, spectroscopic (IR, NMR, UV-vis, ESR and mass) and physical techniques (conductivity, magnetic and thermal measurements). The Schiff-base H 2sap behaves as a bidentate chelate with the deprotonated 2-hydroxy and azomethine nitrogen centers with the pendant pyrimidine cyclic nitrogen functionality playing no role in coordination. The dissociation constants of H 2sap and the stability constants of the metal complexes have been determined pH-metrically at various temperatures, and the thermodynamic activation parameters (? S*, ? G*, ? H*) calculated.

Ouf, Abd El-Fatah; Ali, Mayada S.; Saad, Eman M.; Mostafa, Sahar I.

2010-06-01

194

Spectral characterization, electrochemical and anticancer studies on some metal(II) complexes containing tridentate quinoxaline Schiff base.  

PubMed

Co(II), Ni(II), Cu(II) and Zn(II) complexes of a tridentate ONO donor Schiff base ligand derived from 3-(2-aminoethylamino)quinoxalin-2(1H)-one were synthesized. The ligand and its metal complexes were characterized using elemental analysis, molar conductance, IR, (1)H NMR, mass, magnetic susceptibility, electronic spectra and ESR spectral studies. Electrochemical behavior of the synthesized compounds was studied using cyclic voltammetry. The grain size of the synthesized compounds was determined by powder XRD. The Schiff base and its complexes have been screened for their antimicrobial activities against the bacterial species E. coli, K. pneumoniae, P. aeruginosa and S. aureus; fungal species include, A. niger, and C. albicans by disc diffusion method. The results show that the complexes have higher activity than the free ligand. The interaction of the complexes with calf thymus DNA (CT DNA) has been investigated by electronic absorption method. Furthermore, the DNA cleavage activity of the complexes was studied using agarose gel electrophoresis. In vitro anticancer studies of the ligand and its complexes using MTT assay was also done. PMID:24637276

Chellaian, Justin Dhanaraj; Johnson, Jijo

2014-06-01

195

Synthesis of metal complexes involving Schiff base ligand with methylenedioxy moiety: spectral, thermal, XRD and antimicrobial studies.  

PubMed

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. PMID:24820326

Sundararajan, M L; Jeyakumar, T; Anandakumaran, J; Karpanai Selvan, B

2014-10-15

196

Modern spectroscopic technique in the characterization of biosensitive macrocyclic Schiff base ligand and its complexes: inhibitory activity against plantpathogenic fungi.  

PubMed

Complexes of the type [M(L)Cl2], where M = Co(II), Ni(II) and Cu(II) have been synthesized with a macrocyclic Schiff base ligand (1,4,5,7,10,11,12,15-octaaza,5,11,16,18-tetraphenyl, 3,4,12,13-tetramethyl cyclo-octadecane) derived from Schiff base (obtained by the condensation of 4-aminoantipyrine and dibenzoyl methane) and ethylenediamine. The ligand was characterized on the basis of elemental analysis, IR, (1)H NMR, EI Mass and molecular modeling studies while the complexes were characterized by elemental analysis, molar conductance measurements, magnetic susceptibility measurements, IR, electronic and EPR spectral studies. All the complexes are non-electrolyte in nature. The covalency factor (?) and coefficient factor (?) suggest the covalent nature of the complexes. The ligand and its metal complexes have shown antifungal activity with their LD50 values determined by probit analysis against two economically important fungal plant pathogens i.e. Macrophomina phaseolina and Fusarium solani. PMID:24161868

Tyagi, Monika; Chandra, Sulekh; Akhtar, Jameel; Chand, Dinesh

2014-01-24

197

Synthesis, crystal structure and theoretical studies of a Schiff base 2-[4-hydroxy benzylidene]-amino naphthalene  

NASA Astrophysics Data System (ADS)

The molecular structure of a new Schiff base, 2-[4-hydroxy benzylidene]-amino naphthalene (HBAN) has been examined by HF and B3LYP/6-311++G(d,p) calculations. The X-ray structure was determined in order to establish the conformation of the molecule. The compound, C17H13NO, crystallizes in the orthorhombic, P212121 space group with the cell dimension, a = 6.2867(2), b = 10.2108(3), c = 19.2950(6) , ? = ? = ? = 90 and z = 4. The asymmetric unit contains a molecule of a Schiff base. A strong intermolecular Osbnd H⋯N and a weak Csbnd H⋯O hydrogen bonds stabilized the crystal structure. The vibrational spectra of HBAN have been calculated using density functional theoretical computation and compared with the experimental. The study is extended to the HOMO-LUMO analysis to calculate the energy gap (?), Ionization potential (I), Electron Affinity (A), Global Hardness (?), Chemical Potential (?) and Global Electrophilicity (w). The calculated HOMO and LUMO energy reveals that the charge transfer occurs within the molecule.

Arunagiri, C.; Subashini, A.; Saranya, M.; Thomas Muthiah, P.; Thanigaimani, K.; Abdul Razak, I.

2015-01-01

198

Synthesis, crystal structure and theoretical studies of a Schiff base 2-[4-hydroxy benzylidene]-amino naphthalene.  

PubMed

The molecular structure of a new Schiff base, 2-[4-hydroxy benzylidene]-amino naphthalene (HBAN) has been examined by HF and B3LYP/6-311++G(d,p) calculations. The X-ray structure was determined in order to establish the conformation of the molecule. The compound, C17H13NO, crystallizes in the orthorhombic, P212121 space group with the cell dimension, a=6.2867(2), b=10.2108(3), c=19.2950(6) , ?=?=?=90 and z=4. The asymmetric unit contains a molecule of a Schiff base. A strong intermolecular O-H?N and a weak C-H?O hydrogen bonds stabilized the crystal structure. The vibrational spectra of HBAN have been calculated using density functional theoretical computation and compared with the experimental. The study is extended to the HOMO-LUMO analysis to calculate the energy gap (?), Ionization potential (I), Electron Affinity (A), Global Hardness (?), Chemical Potential (?) and Global Electrophilicity (w). The calculated HOMO and LUMO energy reveals that the charge transfer occurs within the molecule. PMID:25084236

Arunagiri, C; Subashini, A; Saranya, M; Thomas Muthiah, P; Thanigaimani, K; Abdul Razak, I

2015-01-25

199

Preparation and Characterization of Di-, Tri-, and Tetranuclear Schiff Base Complexes Derived from Diamines and 3,4-Dihydroxybenzaldehyde  

PubMed Central

A series of new di-, tri-, and tetranuclear Co(II) and Cu(II) complexes of three new diSchiff base ligands were synthesized by two different methods. The first method involved the synthesis of the three ligands from condensation reaction of 3,4-dihydroxybenzaldehyde (L?H2) with ethylenediamine (en), o-phenylenediamine (o-PD), or 4,5-dimethyl-1,2-phenylendiamine (DMPD) in a mole ratio of 2?:?1 followed by the reaction of the resulting Schiff bases ligands with Cu(II) or Co(II) ions in the presence of 2,2?-bipyridyl (L) to form the di- and trinuclear metal complexes. The second method involved the condensation of the copper complex LCu(II)L? (L = 2,2?-bipyridyl, L? = 4-formylbenzene-1,2-bis(olate)) with en, o-PD, or DMPD in a mole ratio of 2?:?1, respectively, followed by reaction with CuCl2 or Cu(ClO4)2 to form di-, tri-, and tetranuclear copper (II) complexes, respectively. The structures of the ligands and metal complexes were characterized by elemental analyses, NMR, and FTIR spectra. The geometries of metal complexes were suggested according to elemental analysis, electronic spectra, thermal analyses, atomic absorption, and magnetic moments and conductivity measurements. PMID:24453995

Abdulghani, Ahlam Jameel; Khaleel, Asmaa Mohammed Noori

2013-01-01

200

Synthesis of metal complexes involving Schiff base ligand with methylenedioxy moiety: Spectral, thermal, XRD and antimicrobial studies  

NASA Astrophysics Data System (ADS)

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, 1H NMR, 13C 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, 1H NMR, 13C 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.

Sundararajan, M. L.; Jeyakumar, T.; Anandakumaran, J.; Karpanai Selvan, B.

2014-10-01

201

Co(II) and Cd(II) Complexes Derived from Heterocyclic Schiff-Bases: Synthesis, Structural Characterisation, and Biological Activity  

PubMed Central

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

Ahmed, Riyadh M.; Yousif, Enaam I.; Al-Jeboori, Mohamad J.

2013-01-01

202

In vitro activity of taurine-5-bromosalicylaldehyde Schiff base against planktonic and biofilm cultures of methicillin-resistant Staphylococcus aureus.  

PubMed

Staphylococcus aureus is a major human pathogen, implicated in both community and hospital acquired infections. The therapy for methicillin-resistant Staphylococcus aureus (MRSA) infections is becoming more difficult because of multidrug resistance and strong biofilmforming properties. Schiff bases have attracted attention as promising antibacterial agents. In this study, we investigated the in vitro activity of taurine-5-bromosalicylaldehyde Schiff base (TBSSB) against MRSA. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentration (MBC) were determined using a microtiter broth dilution method. TBSSB effectively inhibited planktonic MRSA, with an MIC of 32 ?g/ml. The time-kill curve confirmed that TBSSB exhibited bactericidal activity against MRSA. TBSSB was also found to significantly inhibit MRSA biofilm formation at 24 h, especially at 1MIC and sub-MIC levels. Furthermore, scanning electron microscopy and transmission electron microscopy showed remarkable morphological and ultrastructural changes on the MRSA cell surface, due to exposure to TBSSB. This study indicated that TBSSB may be an effective bactericidal agent against MRSA. PMID:24759427

Yuan, Ruqiang; Diao, Yunpeng; Zhang, Wenli; Lin, Yuan; Huang, Shanshan; Zhang, Houli; Ma, Li

2014-08-28

203

Spectral characterization, electrochemical and anticancer studies on some metal(II) complexes containing tridentate quinoxaline Schiff base  

NASA Astrophysics Data System (ADS)

Co(II), Ni(II), Cu(II) and Zn(II) complexes of a tridentate ONO donor Schiff base ligand derived from 3-(2-aminoethylamino)quinoxalin-2(1H)-one were synthesized. The ligand and its metal complexes were characterized using elemental analysis, molar conductance, IR, 1H NMR, mass, magnetic susceptibility, electronic spectra and ESR spectral studies. Electrochemical behavior of the synthesized compounds was studied using cyclic voltammetry. The grain size of the synthesized compounds was determined by powder XRD. The Schiff base and its complexes have been screened for their antimicrobial activities against the bacterial species E. coli, K. pneumoniae, P. aeruginosa and S. aureus; fungal species include, A. niger, and C. albicans by disc diffusion method. The results show that the complexes have higher activity than the free ligand. The interaction of the complexes with calf thymus DNA (CT DNA) has been investigated by electronic absorption method. Furthermore, the DNA cleavage activity of the complexes was studied using agarose gel electrophoresis. In vitro anticancer studies of the ligand and its complexes using MTT assay was also done.

Chellaian, Justin Dhanaraj; Johnson, Jijo

2014-06-01

204

Comparative experimental and theoretical studies of N-(4-Methylbenzylidene)-N?-(2-carboxyphenyl) hydrazine novel Schiff base  

NASA Astrophysics Data System (ADS)

In this work, N-(4-Methylbenzylidene)-N?-(2-carboxyphenyl) hydrazine, C15H14N2O2, Schiff base molecule has been synthesized and characterized by elemental analyses, UV-Vis and IR spectroscopy and single crystal X-ray determination. The molecule of the title compound adopt an E configuration about the azomethine Cdbnd N double bond. The benzene and phenyl rings are planar and the dihedral angle between the planes is 7.2(2). The crystal structure is stabilized by intermolecular Osbnd H⋯O and intramoleculer Nsbnd H⋯O hydrogen bonding interactions. X-ray diffraction analyses show that, N-(4-Methylbenzylidene)-N?-(2-carboxyphenyl) hydrazine Schiff base molecule crystallizes in the monoclinic system, P21/c space group, a = 4.392(5) , b = 22.340(5) , c = 13.528(5) , ? = 92.882(5), V = 1325.7(16) 3, Z = 4. The conformational analysis of N-(4-Methylbenzylidene)-N?-(2-carboxyphenyl) hydrazine was performed by the density functional theory (DFT) B3LYP method using the 6-311++G(d,p) basis set. Also, theoretical values of FTIR and UV-Vis were performed by the same method. The calculated geometry parameters, IR and UV-Vis results were compared with experimental results.

Tun, Tuncay; Tezcan, Habibe; Sa?lam, Semran; Dilek, Nefise

2014-06-01

205

Spectrophotometric study on the binding of two water soluble Schiff base complexes of Mn(III) with ct-DNA.  

PubMed

In this work, binding of two water soluble Schiff base complexes: Bis sodium (5-sulfosalicylaldehyde) o-phenylendiiminato) Manganese (III) acetate (Salophen complex) and Bis sodium (5-sulfosalicylaldehyde) 1, 2 ethylendiiminato) Manganese (III) acetate (Salen complex) with calf thymus (ct) DNA were investigated by using different spectroscopic and electrometric techniques including UV-vis, Circular dichroism (CD) and fluorescence spectroscopy, viscommetry and cyclic voltammetry (CV). Both complexes have shown a hyperchromic and a small bathochromic shift in the visible region spectra. A competitive binding study showed that the enhanced emission intensity of ethidium bromide (EB) in the presence of DNA was quenched by the addition of the two Schiff base complexes indicating that they displace EB from its binding site in DNA. Moreover structural changes in the CD spectra and an increase in the CV spectra with addition of DNA were observed. The results show that both complexes bind to DNA. The binding constants have been calculated using fluorescence data for two complexes also K(b) was calculated with fluorescence Scatchard plot for Salophen. Ultimately, the experimental results show that the dominant interactions are electrostatic while binding mode is surface binding then followed by hydrophobic interactions in grooves in high concentration of complexes. PMID:21365249

Dehkordi, Maryam Nejat; Bordbar, Abdol-Khlegh; Mehrgardi, Masood Ayatolahi; Mirkhani, Valiolah

2011-07-01

206

A highly sensitive and selective fluorescent chemosensor for detection of Zn(2+) based on a Schiff base.  

PubMed

A Schiff-base fluorescent probe - 2-((E)-(quinolin-8-ylimino)methyl)quinolin-8-ol (H7L) was synthesized and evaluated as a chemoselective Zn(2+) sensor. Upon treatment with Zn(2+), the complexation of H7L with Zn(2+) resulted in a red shift with a pronounced enhancement in the fluorescence emission intensity in ethanol solution. Moreover, other common alkali, alkaline earth and transition metal ions failed to induce response or minimal spectral changes. Notably, this chemosensor could distinguish clearly Zn(2+) from Cd(2+). Fluorescence studies on H7L and H7L-Zn(2+) 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. This chemosensor exhibits a very good fluorescence sensing ability to Zn(2+) over a wide range of pH. PMID:25590829

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

2015-04-01

207

Synthesis, characterization and electrochemical study of synthesis of a new Schiff base (H?cddi(t)butsalen) ligand and their two asymmetric Schiff base complexes of Ni(II) and Cu(II) with NN'OS coordination spheres.  

PubMed

A novel Schiff base (H(2)cddi(t)butsalen) ligand was prepared via condensation of Methyl-2-{N-(2'-aminoethane)}-amino-1-cyclopentenedithiocarboxylate(Hcden) and 3,5-di-tert-butyl-2-hydroxybenzaldehyde. The ligand and Ni(II) and Cu(II) complexes were characterized based on elemental analysis, IR, (1)H NMR, (13)C NMR, UV-Vis spectrometry and cyclic voltammetry. The structure of copper{methyl-2-{N-[2-(3,5-di-tert-butyl-2-hydroxyphenyl)methylidynenitrilo]ethyl}amino-1-cyclopentedithiocarboxylate has been determined by X-ray crystallography. The X-ray results confirm that the geometry of the complex is slightly distorted square-planar structure. The copper(II) ion coordinates to two nitrogen atoms from the imine moiety of the ligand, a sulfur atom the methyl dithiocarboxylate moiety and phenolic oxygen atom. PMID:22925979

Menati, Saeid; Azadbakht, Azadeh; Taeb, Abbas; Kakanejadifard, Ali; Khavasi, Hamid Reza

2012-11-01

208

Antimicrobial efficacy of phenanthrenequinone based Schiff base complexes incorporating methionine amino acid: structural elucidation and in vitro bio assay.  

PubMed

This work focuses the synthesis and characterization of few novel mixed ligand Schiff base metal complexes and their biological activities. For deriving the structural aspects, spectral techniques such as FT-IR, UV-Vis., (1)H NMR, Raman, EPR and the physicochemical characterizations including elemental analysis, molar conductance and magnetic susceptibility method have been involved. All the complexes adopt square planar geometry. DNA binding ability of these complexes has been explored using diverse techniques viz. UV-Vis. absorption, fluorescence spectroscopy, viscometry and cyclic voltammetry. These studies prove that CT-DNA binding of the complexes follows the intercalation mode. Comparative DNA oxidative cleavage ability of the complexes has been done under ultraviolet photo radiation on pUC19 DNA. In addition, the biocidal action of the complexes has been investigated against few pathogenic bacteria and fungi by disc diffusion method. Importantly, the amylase inhibition activity of Cu(II) complex has been explored. The amylase inhibition property has been found to be increased upon increasing the complex concentration. PMID:24632238

Arun, Thesingu Rajan; Raman, Natarajan

2014-06-01

209

Nickel analysis in real samples by Ni2+ selective PVC membrane electrode based on a new Schiff base.  

PubMed

A newly synthesized Schiff base 3-aminoacetophenonesemicarbazone (AAS) has been used for the preparation of Ni(2+) selective PVC membrane electrode. The proposed electrode exhibits a Nernstian response over the nickel concentration range of 1.010(-7) to 1.010(-2)mol L(-1) with a slope of 30.00.3 mV/decade of concentration. The limit of detection as determined from the intersection linear segment of the calibration plot is 5.110(-8) mol L(-1). The electrode shows good selectivity towards nickel with respect to several alkali, alkaline earth, transition and heavy metal ions. The response time of the electrode is very fast (?10 s) and can be used for 17 weeks in the pH range of 2.0-9.8. The electrode can also be used in partially non-aqueous media having up to 20% (v/v) methanol, ethanol or acetone content with no significant change in the value of slope or working concentration range. To investigate the analytical applicability of the electrode, it was successfully applied as an indicator electrode in Ni(2+) ion potentiometric titration with EDTA, and in direct determination of nickel(II) in real samples. PMID:24094213

Tomar, Praveen Kumar; Chandra, Sulekh; Malik, Amrita; Kumar, Ankit

2013-12-01

210

Antimicrobial efficacy of phenanthrenequinone based Schiff base complexes incorporating methionine amino acid: Structural elucidation and in vitro bio assay  

NASA Astrophysics Data System (ADS)

This work focuses the synthesis and characterization of few novel mixed ligand Schiff base metal complexes and their biological activities. For deriving the structural aspects, spectral techniques such as FT-IR, UV-Vis., 1H NMR, Raman, EPR and the physicochemical characterizations including elemental analysis, molar conductance and magnetic susceptibility method have been involved. All the complexes adopt square planar geometry. DNA binding ability of these complexes has been explored using diverse techniques viz. UV-Vis. absorption, fluorescence spectroscopy, viscometry and cyclic voltammetry. These studies prove that CT-DNA binding of the complexes follows the intercalation mode. Comparative DNA oxidative cleavage ability of the complexes has been done under ultraviolet photo radiation on pUC19 DNA. In addition, the biocidal action of the complexes has been investigated against few pathogenic bacteria and fungi by disc diffusion method. Importantly, the amylase inhibition activity of Cu(II) complex has been explored. The amylase inhibition property has been found to be increased upon increasing the complex concentration.

Arun, Thesingu Rajan; Raman, Natarajan

2014-06-01

211

Metal based photosensitizers of tetradentate Schiff base: Promising role in anti-tumor activity through singlet oxygen generation mechanism  

NASA Astrophysics Data System (ADS)

In the present investigation, a Schiff base N?1,N?3-bis[(Z)-(2-hydroxynapthyl)methylidene]benzene-1,3-dicarbodihydrazide (L1) and its Co(II), Ni(II) and Cu(II) complexes have been synthesized and characterized as novel photosensitizing agents for photodynamic therapy (PDT). The interaction of these complexes with calf thymus DNA (CT DNA) has been explored using absorption, thermal denaturation and viscometric studies. The experimental results revealed that Co(II) and Ni(II) complexes on binding to CT DNA imply a covalent mode, most possibly involving guanine N7 nitrogen of DNA, with an intrinsic binding constant Kb of 4.5 104 M-1 and 4.2 104 M-1, respectively. However, interestingly, the Cu(II) complex is involved in the surface binding to minor groove via phosphate backbone of DNA double helix with an intrinsic binding constant Kb of 5.7 104 M-1. The Co(II), Ni(II) and Cu(II) complexes are active in cleaving supercoiled (SC) pUC19 DNA on photoexposure to UV-visible light of 365 nm, through 1O2 generation with quantum yields of 0.28, 0.25 and 0.30, respectively. Further, these complexes are cytotoxic in A549 lung cancer cells, showing an enhancement of cytotoxicity upon light irradiation.

Pradeepa, S. M.; Bhojya Naik, H. S.; Vinay Kumar, B.; Indira Priyadarsini, K.; Barik, Atanu; Ravikumar Naik, T. R.; Prabhakara, M. C.

2013-11-01

212

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

PubMed

A new unsymmetrical tridentate Schiff base ligand was derived from the 1:1M 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 2:1M 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, (1)H NMR, UV/Vis, elemental analyses and conductometry. The crystal structure of nickel complex has been determined by single crystal X-ray diffraction. PMID:24681321

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

2014-07-15

213

Synthesis of new Schiff base-camphorsulfonyl amide ligands and in situ screening in the asymmetric additions of organozinc reagents to aldehydes  

Microsoft Academic Search

We have designed and synthesized a new library of highly modular Schiff base-camphorsulfonyl amide ligands from readily available starting materials. These ligands have been used in the asymmetric addition of diethyl zinc to aldehydes in good yields (up to 91%) and high enantioselectivities (up to 93%). Moreover, when the ligands were used in the asymmetric addition of phenylacetylene to aldehydes,

Jiangtao Sun; Xu Pan; Zhenya Dai; Chengjian Zhu

2008-01-01

214

Synthesis, spectral characterization and biological activity of zinc(II) complexes with 3-substituted phenyl-4-amino-5-hydrazino-1, 2, 4-triazole Schiff bases  

NASA Astrophysics Data System (ADS)

New Zn(II) complexes have been synthesized by the reactions of zinc(II) acetate with Schiff bases derived from 3-substituted phenyl-4-amino-5-hydrazino-1, 2, 4-triazole and benzaldehyde, 2-hydroxyacetophenone or 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 1:1 stoichiometry of the type [ZnL(H 2O) 2], [ZnL'(OAc) 2(H 2O) 2] (L = dianionic Schiff bases derived from 3-(substituted phenyl)-4-amino-5-hydrazino-1, 2, 4-triazole and 2-hydroxyacetophenone or indoline-2,3-dione; L' = neutral Schiff bases derived from 3-(substituted phenyl)-4-amino-5-hydrazino-1, 2, 4-triazole and benzaldehyde) and they were characterized by FT-IR, 1H NMR, 13C NMR and FAB mass. All these Schiff bases and their complexes have also been screened for their antibacterial activities against Bacillus subtilis, Escherichia coli and antifungal activities against Colletotrichum falcatum, Aspergillus niger, Fusarium oxysporium and Carvularia pallescence by petriplates methods.

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

215

A novel copper(II)-Schiff base complex containing pyrrole ring: Synthesis, characterization and its modified electrodes applied in oxidation of aliphatic alcohols  

E-print Network

1 A novel copper(II)-Schiff base complex containing pyrrole ring: Synthesis, characterization 35042 Rennes Cedex, France. Abstract A new copper(II) complex Cu(II)-L containing N2O2 donor atoms has of copper acetate monohydrate. It was characterized by spectroscopic methods such as FT-IR, UV­vis, mass

Boyer, Edmond

216

Structural properties of schiff bases of 4-aminophenol in DMSO solutions on the data density, viscosity and ultrasound speed at 308.15 K  

NASA Astrophysics Data System (ADS)

Density, ultrasonic velocity and viscosity of some Schiff bases of 4-aminophenol have been measured in dimethyl sulfoxide solutions over a wide range of concentration at 308.15 K. From these experimental data, some acoustical parameters have been evaluated, which helps in understanding the molecular interactions occurring in these solutions.

Baluja, Shipra; Vaishnani, K. P.

2013-08-01

217

Synthesis of copper/nickel nanoparticles using newly synthesized Schiff-base metals complexes and their cytotoxicity/catalytic activities.  

PubMed

Transition metal complexes compounds with Schiff bases ligand representing an important class of compounds that could be used to develop new metal-based anticancer agents and as precursors of metal NPs. Herein, 2,3-bis-[(3-ethoxy-2-hydroxybenzylidene)amino]but-2-enedinitrile Schiff base ligand and its corresponding copper/nickel complexes were synthesized. Also, we reported a facile and rapid method for synthesis nickel/copper nanoparticles based on thermal reduction of their complexes. Free ligand, its metal complexes and metals nanoparticles have been characterized based on elemental analysis, transmission electron microscopy, powder X-ray diffraction, magnetic measurements and by various spectroscopic (UV-vis, FT-IR, (1)H NMR, GC-MS) techniques. Additionally, the in vitro cytotoxic activity of free ligand and its complexes compounds were assessed against two cancer cell lines (HeLa and MCF-7 cells)and one healthy cell line (HEK293 cell). The copper complex was found to be active against these cancer cell lines at very low LD50 than the free ligand, while nickel complex did not show any anticancer activity against these cell lines. Also, the antibacterial activity of as-prepared copper nanoparticles were screened against Escherichia coli, which demonstrated minimum inhibitory concentration and minimum bactericidal concentration values lower than those values of the commercial Cu NPs as well as the previous reported values. Moreover, the synthesized nickel nanoparticles demonstrated remarkable catalytic performance toward hydrogenation of nitrobenzene that producing clean aniline with high selectivity (98%). This reactivity could be attributed to the high degree of dispersion of Ni nanoparticles. PMID:25159596

Aazam, Elham S; El-Said, Waleed Ahmed

2014-12-01

218

FTIR studies on protonation of selected aromatic polyimines  

NASA Astrophysics Data System (ADS)

Protonation of selected aromatic polyazomethines by methanesulfonic acid and p-chlorophenol were investigated using FTIR spectroscopy. The influence of the protonation agent on the conjugation effect in polymers is discussed. To explain the observed differences in the protonation effects, geometry optimization was performed for systems of model compounds and protonation agents. For the model compounds the appropriate bis-Schiff bases consisting of two imine groups placed between three phenyl rings were used for calculations.

Kaczmarczyk, Bozena

2013-12-01

219

Schiff base formation and recognition of amino sugars, aminoglycosides and biological polyamines by 2-formyl phenylboronic acid in aqueous solution.  

PubMed

Interactions of 2-, 3- and 4-formyl phenylboronic acids (FPBAs) with sugars, amino sugars, aminoglycosides and various poly- and monoamines have been studied by UV-vis, (1)H and (11)B NMR titrations in water at variable pH. Behavior of 2-FPBA was anomalous in several aspects. Transformation of the acid into its conjugate base was slow in NMR time scale and was accompanied by intramolecular cyclization affording the respective benzoboroxole. The equilibrium constants for imine formation (K(imine)) between 2-FPBA and simple monoamines including amino sugars were ca. 2 orders of magnitude larger than those with other isomers. Still one order of magnitude larger K(imine) values were observed for 2-FPBA with aminoglycosides (kanamycin, amikacin, gentamicin, neomycin) and polyamines (spermine, spermidine). The examination of UV-vis and (11)B NMR spectra of imines formed with 2-FPBA showed that formally neutral Schiff bases in fact were zwitterionic species containing a protonated imine group and an anionic B(OH)(3)(-) group. The enhanced stability of imines with monoamines can therefore be attributed to the electrostatic stabilization provided by the zwitterionic structure and further increased stability of imines with antibiotics and polyamines is explicable by additional stabilization of the borate anionic group by ion paring with ammonium groups not involved in Schiff base formation. Thanks to high molar absorptivity of protonated imines interaction of 2-FPBA with aminoglycosides allows detecting them spectrophotometrically in a ?M concentration range in neutral aqueous solutions in the presence of sugars, amino sugars and amino acids. PMID:22842531

Gutirrez-Moreno, Nini J; Medrano, Felipe; Yatsimirsky, Anatoly K

2012-09-14

220

Immobilization of cobalt(III) Schiff base complexes onto Montmorillonite-K10: Synthesis, experimental and theoretical structural determination.  

PubMed

The [Co(naphophen)(PPh3)(OH2)]ClO4 and [Co(naphophen)(PBu3)(OH2)]BF4 (where naphophen=bis(naphthaldehyde)1,2-phenylenediimine) complexes were synthesized and chracterized by FT-IR, UV-Vis, (1)H NMR, (13)C NMR spectroscopy and elemental analysis techniques. The coordination geometry of the synthesized complexes were determined by X-ray crystallography. Cobalt (III) complexes have six-coordinated pseudo-octahedral geometry in which the O(1), O(2), N(1) and N(2) atoms of the Schiff base forms the equatorial plane. These complexes showed a dimeric structure via hydrogen bonding between the phenolate oxygen and the hydrogens of the coordinated H2O molecule. The theoretical calculations were also performed to optimize the structure of the complexes in the gas phase to confirm the structures proposed by X-ray crystallography. In addition, UV-Visible and IR spectra of complexes were calculated and compared with the corresponding experimental spectra to complete the experimental structural identification. The synthesized complexes were incorporated onto the Montmorillonite-K10 nanoclay via simple ion-exchange reaction. The structure and morphology of the obtained nanohybrids were identified by FT-IR, XRD, TGA/DTA, SEM and TEM techniques. Based on the XRD results of the new nanohybrid materials, the Schiff base complexes were intercalated in the interlayer spaces of clay. SEM and TEM micrographs of the clay/complex shows that the resulting hybrid nanomaterials has layer structures. PMID:25459719

Kianfar, Ali Hossein; Kamil Mahmood, Wan Ahmad; Dinari, Mohammad; Farrokhpour, Hossein; Enteshari, Majid; Azarian, Mohammad Hossein

2014-11-01

221

(E)3-2-(1-(2,4-Dihydroxyphenyl)ethyldeneamino)phenyl)-2-methylquinazoline-4(3H)-one Schiff Base and Its Metal Complexes: A New Drug of Choice against Methicillin-Resistant Staphylococcus aureus  

PubMed Central

The 3-(2-aminophenyl) quinazolin-2-methyl-4(3H)-one and 2,4-dihydroxyacetophenone undergo condensation to afford (E)3-2-(1-(2,4-dihydroxyphenyl)ethyldeneamino)phenyl)-2-methylquinazoline-4(3H)-one Schiff base (DHPEAPMQ). The newly synthesized Schiff base (DHPEAPMQ) and its metal complexes were evaluated for their antimicrobial activity against methicillin-resistant Staphylococcus aureus isolated from the Gulbarga region in India. The Cu(II), Ni(II), and Zn(II) complexes of Schiff base (DHPEAPMQ) showed good antimicrobial activity. So, this could be a new drug of choice. PMID:24733996

Siddappa, K.; Mane, Sunilkumar B.; Manikprabhu, Deene

2014-01-01

222

Synthesis and characterization of metal complexes of Schiff base ligand derived from imidazole-2-carboxaldehyde and 4-aminoantipyrine.  

PubMed

The Co(II), Ni(II), Cu(II) and Zn(II) complexes of the Schiff base derived from imidazole-2-carboxaldehyde and 4-aminoantipyrine were synthesized. These compounds were characterized by elemental analysis, IR, mass, (1)H NMR, electronic spectra, magnetic moment, molar conductance, thermal analysis, powder XRD and SEM. The analytical data show that the metal to ligand ratio is 1:1. The IR results show that the ligand acts as a bidentate donor coordinating through the azomethine nitrogen and imidazole nitrogen atoms. From the electronic spectra and magnetic moment value predicts the geometry of the complexes. The surface morphology of the compounds was studied by SEM. The compounds were screened for their antibacterial activity and antifungal activity using Kirby Bayer disc diffusion method. The DNA cleavage and superoxide dismutase activities of the compounds were investigated. The anticancer activities of the complexes have been carried out towards HeLa and HCT116 cancer cells. PMID:24934973

Selwin Joseyphus, R; Shiju, C; Joseph, J; Justin Dhanaraj, C; Arish, D

2014-12-10

223

Synthesis, Spectral Characterization, and Biological Evaluation of Transition Metal Complexes of Bidentate N, O Donor Schiff Bases  

PubMed Central

New series of three bidentate N, O donor type Schiff bases (L1)(L3) were prepared by using ethylene-1,2-diamine with 5-methyl furfural, 2-anisaldehyde, and 2-hydroxybenzaldehyde in an equimolar ratio. These ligands were further complexed with Co(II), Cu(II), Ni(II), and Zn(II) metals to produce their new metal complexes having an octahedral geometry. These compounds were characterized on the basis of their physical, spectral, and analytical data. Elemental analysis and spectral data of the uncomplexed ligands and their metal(II) complexes were found to be in good agreement with their structures, indicating high purity of all the compounds. All ligands and their metal complexes were screened for antimicrobial activity. The results of antimicrobial activity indicated that metal complexes have significantly higher activity than corresponding ligands. This higher activity might be due to chelation process which reduces the polarity of metal ion by coordinating with ligands. PMID:25147493

Sumrra, Sajjad Hussain; Ambreen, Sabahat; Imran, Muhammad; Danish, Muhammad; Rehmani, Fouzia Sultana

2014-01-01

224

Molecular engineering of Schiff-base linked covalent polymers with diverse topologies by gas-solid interface reaction  

NASA Astrophysics Data System (ADS)

The design and construction of molecular nanostructures with tunable topological structures are great challenges in molecular nanotechnology. Herein, we demonstrate the molecular engineering of Schiff-base bond connected molecular nanostructures. Building module construction has been adopted to modulate the symmetry of resulted one dimensional (1D) and two dimensional (2D) polymers. Specifically, we have designed and constructed 1D linear and zigzag polymers, 2D hexagonal and chessboard molecular nanostructures by varying the number of reactive sites and geometry and symmetry of precursors. It is demonstrated that high-quality conjugated polymers can be fabricated by using gas-solid interface reaction. The on-demanding synthesis of polymeric architectures with diverse topologies paves the way to fabricate molecular miniature devices with various desired functionalities.

Liu, Xuan-He; Guan, Cui-Zhong; Zheng, Qing-Na; Wang, Dong; Wan, Li-Jun

2015-03-01

225

Synthesis, analgesic, anti-inflammatory and anti-ulcerogenic activities of certain novel Schiff's bases as fenamate isosteres.  

PubMed

A series of certain novel Schiff bases as fenamate isosteres (VI:a-k) were synthesized to locate analgesic, anti-inflammatory agent with minimal ulcerogenic potential. The structures of the newly synthesized compounds were elucidated on the basis of their elemental analysis as well as IR, and NMR and mass spectroscopic data. All the compounds were evaluated for their anti-inflammatory activity by carrageenan induced paw oedema method. The compounds possessing good anti-inflammatory activity were further tested for analgesic, ulcerogenic, lipid peroxidation potentials and liver toxicity. Compounds (VI-c), (VI-f), (VI-h) and (VI-i) showed the best anti-inflammatory and significant analgesic activities at doses comparable to that of the standard drug Indomethacin. However, compounds (VI-c) and (VI-f) could be considered the most potent anti-inflammatory and analgesic molecules with maximum reduction in gastro-intestinal ulceration with no hepatocyte necrosis or liver degeneration. PMID:25522819

Alafeefy, Ahmed M; Bakht, Mohammed A; Ganaie, Majid A; Ansarie, Mohd N; El-Sayed, Nahed N; Awaad, Amani S

2015-01-15

226

Schiff's base derivatives bearing nitroimidazole and quinoline nuclei: new class of anticancer agents and potential EGFR tyrosine kinase inhibitors.  

PubMed

New Schiff's base derivatives 5a-j have been synthesized by reaction between 2-phenoxyquinoline-3-carbaldehydes 3a-j and 2-(2-methyl-5-nitro-1H-imidazol-1-yl)acetohydrazide 4 in presence of nickel(II) nitrate as a catalyst in ethanol under reflux in good yield (78-92%). All compounds were tested for anticancer and inhibition of EGFR. Of the compounds studied, majority of the compounds showed effective antiproliferation and inhibition of EGFR and HER-2 activities. Compound 5h showed most effective inhibition (IC50=0.120.05 ?M) by binding in to the active pocket of EGFR receptor with minimum binding energy (?Gb=-58.3691 kcal/mol). The binding was stabilized by two hydrogen bonds, two ?-cation and one ?-sigma interactions. Compound 5d showed most effective inhibition (IC50=0.370.04 ?M). PMID:24630412

Makawana, Jigar A; Sangani, Chetan B; Lin, Lin; Zhu, Hai-Liang

2014-04-01

227

Binuclear ruthenium(III) Schiff base complexes bearing N 4O 4 donors and their catalytic oxidation of alcohols  

NASA Astrophysics Data System (ADS)

An interesting series of binuclear ruthenium(III) Schiff base complexes bearing bis-salophen/bis-naphophen units of the general composition [(EPh 3)(X)Ru-L-Ru(X)(EPh 3)] (where E = P or As; X = Cl or Br; L = binucleating dianionic tetradentate ligands) have been synthesized and characterized by analytical (elemental analysis, magnetic susceptibility measurements), spectral (FT-IR, UV-vis and EPR) and electrochemical methods. These ruthenium(III) complexes have two N 2O 2 metal binding sites, which are linked to each other with a biphenyl bridge and acts as potential catalyst for oxidation of wide range of primary and secondary alcohols to corresponding aldehydes or ketones with moderate to high conversion in the presence of N-methylmorpholine- N-oxide (NMO). The formation of high-valent Ru V = O species as a catalytic active intermediate is proposed for the catalytic processes.

Venkatachalam, G.; Raja, N.; Pandiarajan, D.; Ramesh, R.

2008-12-01

228

Synthesis, characterization and biological activity of transition metal complexes with Schiff bases derived from 2-nitrobenzaldehyde with glycine and methionine  

NASA Astrophysics Data System (ADS)

Schiff bases derived from 2-nitrobenzaldehyde with amino acids (glycine, methionine) and their Co(II), Ni(II) and Cu(II) complexes have been synthesized and characterized by various physico-chemical techniques. From spectral studies, it has been concluded that the ligands acts as bidentate molecule, coordinates metal through azomethine nitrogen and carboxylate oxygen. Mass spectrum explains the successive degradation of the molecular species in solution and justifies ML2 complexes. X-ray powder diffraction helps to determine the cell parameters of the complexes. Molecular structure of the complexes has been optimized by MM2 calculations and suggests a square planar geometry. The ligands and their metal complexes have been tested in vitro against Streptococcus, Staph, Staphylococcus aureus and Escherchia coli bacteria in order to assess their antibacterial potential. The results indicate that the biological activity increases on complexation.

Singh, Bibhesh K.; Rajour, Hemant K.; Prakash, Anant

229

Synthesis and characterization of metal complexes of Schiff base ligand derived from imidazole-2-carboxaldehyde and 4-aminoantipyrine  

NASA Astrophysics Data System (ADS)

The Co(II), Ni(II), Cu(II) and Zn(II) complexes of the Schiff base derived from imidazole-2-carboxaldehyde and 4-aminoantipyrine were synthesized. These compounds were characterized by elemental analysis, IR, mass, 1H NMR, electronic spectra, magnetic moment, molar conductance, thermal analysis, powder XRD and SEM. The analytical data show that the metal to ligand ratio is 1:1. The IR results show that the ligand acts as a bidentate donor coordinating through the azomethine nitrogen and imidazole nitrogen atoms. From the electronic spectra and magnetic moment value predicts the geometry of the complexes. The surface morphology of the compounds was studied by SEM. The compounds were screened for their antibacterial activity and antifungal activity using Kirby Bayer disc diffusion method. The DNA cleavage and superoxide dismutase activities of the compounds were investigated. The anticancer activities of the complexes have been carried out towards HeLa and HCT116 cancer cells.

Selwin Joseyphus, R.; Shiju, C.; Joseph, J.; Justin Dhanaraj, C.; Arish, D.

2014-12-01

230

Schiff's base derivatives bearing nitroimidazole moiety: new class of antibacterial, anticancer agents and potential EGFR tyrosine kinase inhibitors.  

PubMed

New Schiff's base derivatives 5a-5h have been synthesized by reaction between 1-(4-bromophenyl)-2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethanone 3 and various benzohydrazide 4a-4h in presence of nickel (II) nitrate as a catalyst in ethanol at room temperature in good yield (54-88%). All compounds were tested for antibacterial as well as anticancer and inhibition of EGFR. Of the compounds studied, compounds 5d, 5f and 5g in the case of antiproliferation and inhibition of EGFR as well as compounds 5b, 5c, 5e and 5h in the case of antibacterial activity were found to be most effective compounds in the series. Compound 5f shows effective inhibition (IC50=0.210.02 ?M) by binding in to the active pocket of EGFR receptor with minimum binding energy (?Gb=-49.4869 kcal/mol). PMID:24144854

Makawana, Jigar A; Sun, Juan; Zhu, Hai-Liang

2013-12-01

231

Synthesis and crystal structure of hydroxyacetophenone Schiff bases containing propargyl moiety: Solvent effects on UV-visible spectra  

NASA Astrophysics Data System (ADS)

Four tetradentate (N2O2) and tridentate (NO2) Schiff base compounds (L1-L4) with propargyl moiety were prepared by the condensation of 1-[2-hydroxy-4-(prop-2-yn-1-yloxy)phenyl]ethanone with various aliphatic amines. The newly synthesized compounds (L1-L4) were characterized on the basis of the results of elemental analysis, thermal analysis, FT-IR, 1H NMR spectroscopic studies and single crystal X-ray crystallography. The different bands observed in the electronic spectra of the compounds in various organic solvents have been assigned to the proper electronic transitions. The hydrogen bonding and tautomeric equilibria in both of solution and the solid state are explained. The solvatochromism of the synthesized compounds in different solvents in the UV-visible spectra are discussed.

Selvarani, V.; Annaraj, B.; Neelakantan, M. A.; Sundaramoorthy, S.; Velmurugan, D.

2012-06-01

232

Synthesis and biodistribution of six novel 99mTc complexes of 2-hydroxybenzaldehyde-amino acid Schiff bases.  

PubMed

For the purpose of developing novel diagnostic pharmaceuticals of 99mTc-labeled small-size complexes, six novel complexes of 99mTc-2-hydroxybenzaldehyde-amino acid Schiff bases were designed and synthesized, and their biodistributions in mice were investigated. All the compounds were obtained in radiochemical yields higher than 90% at optimal conditions, and poor uptakes in muscle, brain, heart and tumor were commonly observed with rapid blood clearance. Potentiality was revealed of good kidney imaging by 2-hydroxybenzaldehyde-alanine (L2) complex within 40 min post-injection. Good bone uptake of 2-hydroxybenzaldehyde-histidine (L4) and 2-hydroxybenzaldehyde-aspartic acid (L5) complexes, high spleen accumulation of 2-hydroxybenzaldehyde-glycine (L1) and 2-hydroxybenzaldehyde-cysteine (L3) complexes, and non-specific biodistribution of 2-hydroxybenzaldehyde-glutamic acid (L6) complex were demonstrated. PMID:16309915

Wang, Mingzhao; Meng, Zhaoxing; Fu, Jisheng

2006-02-01

233

A novel dinuclear Schiff-base copper(II) complex modified electrode for ascorbic acid catalytic oxidation and determination.  

PubMed

A new dinuclear copper salicylaldehyde-glycine Schiff-base complex [Cu(2)(Sal-Gly)(2)(H(2)O)(2)] was synthesized and structurally characterized. [Cu(2)(Sal-Gly)(2)(H(2)O)(2)] crystallized in the monoclinic system in the P2(1)/c space group. The molecule is a dinuclear complex, formed by two [Cu(Sal-Gly)(H(2)O)] units. The electropolymerization properties of the copper complex on a glass carbon electrode were studied at different potential ranges. The electropolymerization occurred when the high scan potential reached 1.4 V. The modified electrode exhibited good electrocatalytic oxidation properties to ascorbic acid and showed a sensitivity of 22.9 nA ?M(-1) (r(2) = 0.9998) and detection limit of 0.39 ?M (S/N = 3) in the amperometric determination of ascorbic acid. The designed determination method can be used to analyze vitamin C tablets. PMID:22124199

Zhang, Zhijun; Li, Xi; Wang, Chenggang; Zhang, Chaocan; Liu, Peng; Fang, Tingting; Xiong, Yan; Xu, Wenjing

2012-01-28

234

Synthesis and catalytic activity of heterogeneous rare-earth metal catalysts coordinated with multitopic Schiff-base ligands.  

PubMed

Four multitopic Schiff-base ligand precursors were synthesized via condensation of 4,4'-diol-3,3'-diformyl-1,1'-diphenyl or 1,3,5-tris(4-hydroxy-5-formylphenyl)benzene with 2,6-diisopropylaniline or 2,6-dimethylaniline. Amine elimination reactions of Ln[N(SiMe(3))(2)](3) (Ln = La, Nd, Sm or Y) with these multitopic ligand precursors gave ten heterogeneous rare-earth metal catalysts. These heterogeneous rare-earth metal catalysts are active for intramolecular hydroalkoxylation of alkynols, and the catalytic activities are influenced by the ligand and metal ion. The recycling experiment on the most active heterogeneous catalyst showed the catalyst has a good reusability. PMID:22782285

Sun, Yilin; Wu, Guangming; Cen, Dinghai; Chen, Yaofeng; Wang, Limin

2012-08-28

235

Construction of 1-D 4f and 3d-4f coordination polymers with flexible Schiff base ligands.  

PubMed

Three new lanthanide 1-D coordination polymers ({[Ln(2)(H(2)L)(OAc)(6)]EtOH2H(2)O}(n) (Ln = Eu (1), Er (2)) and {YbNiLCl(OAc)(2)(H(2)O)}(n) (3)) and a heterobinuclear complex [YbNiLCl(3)(H(2)O)(3)] (4) are reported which are formed from salen type Schiff-base ligands H(2)L (H(2)L = N,N'-bis(3-methoxysalicylidene)butane-1,4-diamine). The polymeric structures are formed by bridging H(2)L units in the case of 1 and 2, and by acetate groups in 3. The structures of 1-4 were determined by single crystal X-ray crystallographic studies and their luminescence properties in MeCN solution were determined. PMID:21874186

Yang, Xiaoping; Lam, Daniel; Chan, Christopher; Stanley, Julie M; Jones, Richard A; Holliday, Bradley J; Wong, Wai-Kwok

2011-10-14

236

N-1 and C-3 substituted indole Schiff bases as selective COX-2 inhibitors: synthesis and biological evaluation.  

PubMed

A group of N-1 and C-3 disubstituted-indole Schiff bases bearing an indole N-1 (R'=H, CH(2)Ph, COPh) substituent in conjunction with a C-3 -C=HN-C(6)H(4)-4-X (X=F, Me, CF(3), Cl) substituent were synthesized and evaluated as inhibitors of cyclooxygenase (COX) isozymes (COX-1/COX-2). Within this group of Schiff bases, compounds 15 (R(1)=CH(2)Ph, X=F), 17 (R(1)=CH(2)Ph, X=CF(3)), 18 (R(1)=COPh, X=F) and 20 (R(1)=COPh, X=CF(3)) were identified as effective and selective COX-2 inhibitors (COX-2 IC(50)'s=0.32-0.84 ?M range; COX-2 selectivity index (SI)=113 to >312 range). 1-Benzoyl-3-[(4-trifluoromethylphenylimino)methyl]indole (20) emerged as the most potent (COX-1 IC(50) >100 ?M; COX-2 IC(50)=0.32 ?M) and selective (SI >312) COX-2 inhibitor. Furthermore, compound 20 is a selective COX-2 inhibitor in contrast to the reference drug indomethacin that is a potent and selective COX-1 inhibitor (COX-1 IC(50)=0.13 ?M; COX-2 IC(50)=6.9 ?M, COX-2 SI=0.02). Molecular modeling studies employing compound 20 showed that the phenyl CF(3) substituent attached to the CN spacer is positioned near the secondary pocket of the COX-2 active site, the CN nitrogen atom is hydrogen bonded (NNH=2.85 ) to the H90 residue, and the indole N-1 benzoyl is positioned in a hydrophobic pocket of the COX-2 active site near W387. PMID:22361134

Kaur, Jatinder; Bhardwaj, Atul; Huang, Zhangjian; Knaus, Edward E

2012-03-15

237

Structural investigation of oxovanadium(IV) Schiff base complexes: X-ray crystallography, electrochemistry and kinetic of thermal decomposition.  

PubMed

A series of new VO(IV) complexes of tetradentate N2O2 Schiff base ligands (L(1)-L(4)), were synthesized and characterized by FT-IR, UV-vis and elemental analysis. The structure of the complex VOL(1)?DMF was also investigated by X-ray crystallography which revealed a vanadyl center with distorted octahedral coordination where the 2-aza and 2-oxo coordinating sites of the ligand were perpendicular to the "-yl" oxygen. The electrochemical properties of the vanadyl complexes were investigated by cyclic voltammetry. A good correlation was observed between the oxidation potentials and the electron withdrawing character of the substituents on the Schiff base ligands, showing the following trend: MeO5-H>5-Br>5-Cl. Furthermore, the kinetic parameters of thermal decomposition were calculated by using the Coats-Redfern equation. According to the Coats-Redfern plots the kinetics of thermal decomposition of studied complexes is of the first-order in all stages, the free energy of activation for each following stage is larger than the previous one and the complexes have good thermal stability. The preparation of VOL(1)?DMF yielded also another compound, one kind of vanadium oxide [VO]X, with different habitus of crystals, (platelet instead of prisma) and without L(1) ligand, consisting of a V10O28 cage, diaminium moiety and dimethylamonium as a counter ions. Because its crystal structure was also new, we reported it along with the targeted complex. PMID:25448962

Asadi, Mozaffar; Asadi, Zahra; Savaripoor, Nooshin; Dusek, Michal; Eigner, Vaclav; Shorkaei, Mohammad Ranjkesh; Sedaghat, Moslem

2015-02-01

238

Structural investigation of oxovanadium(IV) Schiff base complexes: X-ray crystallography, electrochemistry and kinetic of thermal decomposition  

NASA Astrophysics Data System (ADS)

A series of new VO(IV) complexes of tetradentate N2O2 Schiff base ligands (L1-L4), were synthesized and characterized by FT-IR, UV-vis and elemental analysis. The structure of the complex VOL1?DMF was also investigated by X-ray crystallography which revealed a vanadyl center with distorted octahedral coordination where the 2-aza and 2-oxo coordinating sites of the ligand were perpendicular to the '-yl' oxygen. The electrochemical properties of the vanadyl complexes were investigated by cyclic voltammetry. A good correlation was observed between the oxidation potentials and the electron withdrawing character of the substituents on the Schiff base ligands, showing the following trend: MeO < H < Br < Cl. We also studied the thermodynamics of formation of the complexes and kinetic aspects of their thermal decomposition. The formation constants with various substituents on the aldehyde ring follow the trend 5-OMe > 5-H > 5-Br > 5-Cl. Furthermore, the kinetic parameters of thermal decomposition were calculated by using the Coats-Redfern equation. According to the Coats-Redfern plots the kinetics of thermal decomposition of studied complexes is of the first-order in all stages, the free energy of activation for each following stage is larger than the previous one and the complexes have good thermal stability. The preparation of VOL1?DMF yielded also another compound, one kind of vanadium oxide [VO]X, with different habitus of crystals, (platelet instead of prisma) and without L1 ligand, consisting of a V10O28 cage, diaminium moiety and dimethylamonium as a counter ions. Because its crystal structure was also new, we reported it along with the targeted complex.

Asadi, Mozaffar; Asadi, Zahra; Savaripoor, Nooshin; Dusek, Michal; Eigner, Vaclav; Shorkaei, Mohammad Ranjkesh; Sedaghat, Moslem

2015-02-01

239

Enhanced catalytic activity of zeolite encapsulated Fe(III)-Schiff-base complexes for oxidative coupling of 2-napthol.  

PubMed

Iron(III) Schiff-base complexes of general formula [Fe(L)(2)Cl]2H(2)O, where L = N,?-bis(salicylidene)ethylenediamine and N,N?-disalicylidene-1,2-phenylenediamine have been encapsulated within various alkali exchanged zeolites viz. LiY, NaY, and KY by flexible ligand method. The encapsulated complexes are characterized by EDX, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), FT-IR, UV-vis, diffuse reflectance spectroscopy (DRS), electron spin resonance spectroscopy (ESR) and cyclic voltammetry studies. The diffuse reflectance UV-vis spectra of encapsulated complexes show a dramatic red shift of the charge transfer band with increasing electropositivity of the exchangeable cations. The electrochemical analysis predicts the shifting of the reduction potential toward negative values with increasing size of the alkali exchanged cations. The zeolite encapsulated Schiff-base complexes of iron are found to be catalytically active toward the oxidative coupling of 2-napthol. Metal complexes incorporated in potassium exchanged zeolite-Y are found to be more effective for catalytic conversion of 2-naphthol to binaphthol and induces higher selectivity toward the R-conformation. The catalytic conversion of 2-napthol to BINOL is found to depend on the reduction potential of the catalyst, with a more negative reduction potential being better for the catalytic conversion. Density functional calculation is being carried out on both the neat Fe-Salen and Fe-Salophen complexes and those encapsulated in NaY zeolite to investigate change in structural parameters, energies of the HOMO and LUMO, and global hardness and softness. Fukui functions, as local descriptors, are used to analyze the hard-hard interaction at a particular site of the complexes. PMID:22256783

Bania, Kusum K; Bharali, Dipsikha; Viswanathan, B; Deka, Ramesh C

2012-02-01

240

Rational design of two bpy-bridged 3D and 2D Co(II) open frameworks with similar amino-acid-based Schiff bases.  

PubMed

Two novel bpy-bridged Co(II) Schiff base complexes have been synthesized by the hydro(solvo)thermal reactions of corresponding amino-acid-based Schiff bases, bpy and Co(NO(3))(2)6H(2)O. The following formulae identify the two complexes: {[Co(napala)(bpy)(0.5)]H(2)O}(n) (1) and [Co(napgly)(bpy)(0.5)](n) (2) [H(2)napala = N-(2-hydroxy-1-naphthylmethylidene)-D/L-alanine, H(2)napgly = N-(2-hydroxy-1-naphthylmethylidene)-glycine and bpy = 4,4'-bipyridine]. These two compounds have been characterized using single-crystal X-ray diffraction, infrared, powder X-ray diffraction, thermogravimetric analysis, optical spectra analysis, and magnetic measurement. Complex 1 features an unprecedented threefold interpenetrated diamond network based on the fan-shaped Co(II)(4)(?(2)-napala)(4) molecular square node and bpy linker, which represents the first example of 3D framework among the amino-acid-based Schiff base complexes with salicylaldehyde or its derivatives. In 2, adjacent Co(II) ions are bridged by ?(2)-napgly(2-) to form left- and right-handed [Co(II)(?(2)-napgly)](n) helical chains. These two types of helical chains are sustained alternately by a symmetrical bpy co-ligand into a 2D grid-based layer. The solid-state fluorescence of complexes 1 and 2 are quenched almost completely compared with free mixed-ligands at room temperature. Moreover, magnetic studies show the dominant antiferromagnetic coupling between the Co(II) centers mediated by the syn-anti-COO(-)-bridges in both complexes. PMID:23064659

Li, Zong-Ze; Du, Lin; Zhou, Jie; Zhu, Ming-Rong; Qian, Fen-Hua; Liu, Jing; Chen, Peng; Zhao, Qi-Hua

2012-12-21

241

Catalytic formation of ethylene carbonate from supercritical carbon dioxide\\/ethylene oxide mixture with tetradentate Schiff-base complexes as catalyst  

Microsoft Academic Search

Various tetradentate Schiff-base aluminum complexes (designated as SalenAlX) were prepared and used as catalysts for the synthesis of ethylene carbonate from supercritical carbon dioxide\\/ethylene oxide mixture. Their catalytic activities can be markedly enhanced in the presence of a Lewis base or quaternary salt. With SalenAlCl\\/n-Bu4NBr as catalyst, the formation rate of ethylene carbonate is up to 2220 turnovers\\/h and about

Xiao-Bing Lu; Xiou-Juan Feng; Ren He

2002-01-01

242

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

NASA Astrophysics Data System (ADS)

Four Schiff base ligands and their corresponding organotin(IV) complexes have been synthesized and characterized by elemental analyses, IR, 1H 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.

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

2011-10-01

243

Synthesis of gadolinium(III) and samarium(III) complexes of new potentially heptadentate (N 4O 3) tripodal Schiff base ligands, and a theoretical study  

Microsoft Academic Search

Two new potentially heptadentate N4O3 Schiff base ligands {N[(CH2)3NCH(2-OH-3,5-t-Bu2C6H2)]3} (H3L1) and {N[(CH2)3NCH(2-OH-3,5-t-Bu2C6H2)]2 [(CH2)2NCH(2-OH-3,5-t-Bu2C6H2)]} (H3L2) were synthesized and characterized by various spectroscopic methods. The heptadentate N4O3 Schiff bases, H3L1 and H3L2, were derived from the condensation reaction of two tripodal tetraamine ligands, tris(3-aminopropyl)amine and (2-aminoethyl)-bis(3-aminopropyl)amine with 3 equiv. of 3,5-di-tert-butylsalicylaldehyde, respectively. The neutral gadolinium(III) and samarium(III) complexes, [Ln(L)], of these bulky

Sadegh Salehzadeh; Seyedeh Mahnaz Nouri; Hassan Keypour; Mojtaba Bagherzadeh

2005-01-01

244

Novel tandem synthesis of bis(?-NN'-tetrazolate) bridged dinuclear nickel(ii) Schiff base complex via [3 + 2] cyclo-addition at ambient condition.  

PubMed

A novel bis(?-NN'-tetrazolate) bridged centrosymmetric dinuclear nickel(ii) Schiff base complex [Ni2(L)2(PTZ)2]2H2O2CH3CN (HL is a tridentate Schiff base, 2-((2-(ethylamino)ethylimino)methyl)-6-methoxyphenol and HPTZ is 5-pyrazinyltetrazole) has been synthesized via [3 + 2] cyclo-addition reaction of 2-cyanopyrazine and sodium azide in presence of nickel(ii) acetate tetrahydrate and HL. The structure of the complex is confirmed by single crystal X-ray diffraction analysis. The combination of H-bonding and C-H? interactions creates a 3(6)-hxl topological supramolecular network. The acetonitrile molecules are encapsulated as a hydrophobic guest within the 2D supramolecular network. PMID:24577138

Das, Mithun; Harms, Klaus; Chattopadhyay, Shouvik

2014-04-21

245

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)

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.

?ahin, Mustafa; Koak, Nuriye; Erdenay, Damla; Arslan, U?ur

2013-02-01

246

L-Ornithine Schiff base-copper and -cadmium complexes as new proteasome inhibitors and apoptosis inducers in human cancer cells.  

PubMed

Ubiquitin-proteasome system (UPS) plays a crucial role in many cellular processes such as cell cycle, proliferation and apoptosis. Aberrant activation of UPS may result in cellular transformation or other altered pathological conditions. Previous studies have shown that metal-based complexes could inhibit proteasome activity and induce apoptosis in certain human cancer cells. In the current study, we report that the cadmium and copper complexes with heterocycle-ornithine Schiff base are potent inhibitors of proteasomal chymotrypsin-like (CT-like) activity, leading to induction of apoptosis in cancer cells. Two novel copper-containing complexes and two novel cadmium-containing complexes with different heterocycle-ornithine Schiff base structures as ligands were synthesized and characterized. We found that complexes Cu1, Cd1 and Cd2 show proteasome-inhibitory activities in human breast cancer MDA-MB-231 and human prostate cancer LNCaP cells, resulting in the accumulation of p27, a natural proteasome substrate and other ubiquitinated proteins, followed by the induction of apoptosis. Our results suggest that metal complexes with heterocycle-ornithine Schiff base have proteasome-inhibitory capabilities and have the potential to be developed into novel anticancer drugs. PMID:25467055

Zhang, Zhongyu; Bi, Caifeng; Fan, Yuhua; Zhang, Nan; Deshmukh, Rahul; Yan, Xingchen; Lv, Xiuwen; Zhang, Pengfei; Zhang, Xia; Dou, Q Ping

2014-12-01

247

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

NASA Astrophysics Data System (ADS)

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 N2O2 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 H2O2. 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.

Sobha, S.; Mahalakshmi, R.; Raman, N.

248

Aspartate-Histidine Interaction in the Retinal Schiff Base Counterion of the Light-Driven Proton Pump of Exiguobacterium sibiricum  

PubMed Central

One of the distinctive features of eubacterial retinal based proton pumps, proteorhodopsins, xanthorhodopsin and others, is hydrogen bonding of the key aspartate residue, the counterion to the retinal Schiff base, to a histidine. We describe properties of the recently found eubacterium proton pump from Exiguobacterium sibiricum (named ESR) expressed in E. coli, especially features that depend on Asp-His interaction, the protonation state of the key aspartate, Asp85, and its ability to accept proton from the Schiff base during the photocycle. Proton pumping by liposomes and E. coli cells containing ESR occurs in a broad pH range above pH 4.5. Large light-induced pH changes indicate that ESR is a potent proton pump. Replacement of His57 with methionine or asparagine strongly affects the pH dependent properties of ESR. In the H57M mutant a dramatic decrease in the quantum yield of chromophore fluorescence emission and a 45 nm blue shift of the absorption maximum upon raising the pH from 5 to 8 indicates deprotonation of the counterion with a pKa of 6.3, which is also the pKa at which the M intermediate is observed in the photocycle of the protein solubilized in detergent (DDM). This is in contrast with the wild type protein, in which the same experiments show that the major fraction of Asp85 is deprotonated at pH > 3 and that it protonates only at low pH, with a pKa of 2.3. The M intermediate in the wild type photocycle accumulates only at high pH, with an apparent pKa of 9 from deprotonation of a residue interacting with Asp85, presumably His57. In liposomes reconstituted with ESR the pKas for M formation and spectral shifts are 23 pH units lower than in DDM. The distinctively different pH dependencies of the protonation of Asp85 and the accumulation of the M intermediate in the wild type protein vs. the H57M mutant indicate that there is strong Asp-His interaction, which substantially lowers the pKa of Asp85 by stabilizing its deprotonated state. PMID:22738070

Balashov, S.P.; Petrovskaya, L.E.; Lukashev, E.P.; Imasheva, E.S.; Dioumaev, A.K.; Wang, J.M.; Sychev, S.V.; Dolgikh, D.A.; Rubin, A.B.; Kirpichnikov, M.P.; Lanyi, J.K.

2012-01-01

249

Aspartate-histidine interaction in the retinal schiff base counterion of the light-driven proton pump of Exiguobacterium sibiricum.  

PubMed

One of the distinctive features of eubacterial retinal-based proton pumps, proteorhodopsins, xanthorhodopsin, and others, is hydrogen bonding of the key aspartate residue, the counterion to the retinal Schiff base, to a histidine. We describe properties of the recently found eubacterium proton pump from Exiguobacterium sibiricum (named ESR) expressed in Escherichia coli, especially features that depend on Asp-His interaction, the protonation state of the key aspartate, Asp85, and its ability to accept a proton from the Schiff base during the photocycle. Proton pumping by liposomes and E. coli cells containing ESR occurs in a broad pH range above pH 4.5. Large light-induced pH changes indicate that ESR is a potent proton pump. Replacement of His57 with methionine or asparagine strongly affects the pH-dependent properties of ESR. In the H57M mutant, a dramatic decrease in the quantum yield of chromophore fluorescence emission and a 45 nm blue shift of the absorption maximum with an increase in the pH from 5 to 8 indicate deprotonation of the counterion with a pK(a) of 6.3, which is also the pK(a) at which the M intermediate is observed in the photocycle of the protein solubilized in detergent [dodecyl maltoside (DDM)]. This is in contrast with the case for the wild-type protein, for which the same experiments show that the major fraction of Asp85 is deprotonated at pH >3 and that it protonates only at low pH, with a pK(a) of 2.3. The M intermediate in the wild-type photocycle accumulates only at high pH, with an apparent pK(a) of 9, via deprotonation of a residue interacting with Asp85, presumably His57. In liposomes reconstituted with ESR, the pK(a) values for M formation and spectral shifts are 2-3 pH units lower than in DDM. The distinctively different pH dependencies of the protonation of Asp85 and the accumulation of the M intermediate in the wild-type protein versus the H57M mutant indicate that there is strong Asp-His interaction, which substantially lowers the pK(a) of Asp85 by stabilizing its deprotonated state. PMID:22738070

Balashov, S P; Petrovskaya, L E; Lukashev, E P; Imasheva, E S; Dioumaev, A K; Wang, J M; Sychev, S V; Dolgikh, D A; Rubin, A B; Kirpichnikov, M P; Lanyi, J K

2012-07-24

250

Dicopper(II) complexes of a new pyrazolate-containing Schiff-base macrocycle and related acyclic ligand.  

PubMed

Dicopper(II) complexes of two new 3,5-disubstituted-pyrazole-based ligands, bis(quadridentate) macrocyclic ligand (L1)(2-) and bis(terdentate) acyclic ligand (L2)(-), were synthesised by Schiff base condensation of 3,5-diformylpyrazole and either one equivalent of 1,3-diaminopropane or two equivalents of 2-(2-aminoethyl)pyridine in the presence of one or two equivalents of copper(II) ions, respectively. Copper(II) acetate monohydrate was employed in the synthesis of [Cu(2)(L1)(OAc)(2)], [Cu(2)(L2)(H(2)O)(2)(OAc)(3)] and [Cu(II)(2)(L1)(NCS)(2)]; in the last of these one equivalent of NaNCS per copper(II) ion was also added. The fourth complex, [Cu(2)(L2)(NCS)(2)(DMF)]BF(4), was prepared using copper(II) tetrafluoroborate hexahydrate, along with two equivalents of NaOH and six of NaSCN. All four of these dimetallic complexes have been characterised by single crystal X-ray diffraction: the two macrocyclic complexes are the first such Schiff base complexes to be so characterised. A feature common to all four of the structures is bridging of the two copper(II) centres by the pyrazolate moiety/moieties. The structure determinations show that the coordination mode of the acetate groups in both [Cu(2)(L1)(OAc)(2)].2MeOH.H(2)O and [Cu(2)(L2)(H(2)O)(2)(OAc)(3)] is unidentate as had been tentatively predicted by analysis of the infrared spectra (DeltaOCO of 199 and 208 cm(-1), respectively). The magnetochemical studies of the macrocyclic complexes, over the temperature range 4-300 K, revealed strong antiferromagnetic coupling with J = -169 and -213 cm(-1) for [Cu(2)(L1)(OAc)(2)].2H(2)O and [Cu(II)(2)(L1)(NCS)(2)].DMF respectively. The J values have been discussed in relation to a published correlation involving the CuN(pyrazolate)N(pyrazolate) angles. PMID:17213932

de Geest, Duncan J; Noble, Andy; Moubaraki, Boujemaa; Murray, Keith S; Larsen, David S; Brooker, Sally

2007-01-28

251

Nickel(II) complexes of fully and partially condensed Schiff-base ligands derived from tris(3aminopropyl)amine and acetylpyridine  

Microsoft Academic Search

In the presence of nickel(II), 2acetylpyridine condenses with tris(3aminopropyl)amine in absolute MeOH to give the fully condensed Schiff-base complex [Ni(tptpy3)]2+. Although the ligand is potentially heptadentate, the metal atom is effectively six-coordinate, interaction with the bridgehead nitrogen being rather weak. However, when aqueous MeOH is used, the condensation is limited to a single step, and a complex of the pentadentate

Hassan Keypour; Sadegh Salehzadeh; Robin G. Pritchard; R. V. Parish

1998-01-01

252

A N,N'-dioxide-copper(II) complex as an efficient catalyst for the enantioselective and diastereoselective Mannich-type reaction of glycine Schiff bases with aldimines.  

PubMed

Mild mannered! A highly diastereo- and enantioselective Mannich-type reaction of glycine Schiff base 1 has been developed by using the N,N'-dioxide L-Cu(II) complex as a catalyst. Various optically active anti-alpha,beta-diamino acid esters were obtained in good yields with up to 96:4 d.r. and 97% ee. This straightforward method features a low catalyst loading and mild reaction conditions. PMID:19229921

Shang, Deju; Liu, Yanling; Zhou, Xin; Liu, Xiaohua; Feng, Xiaoming

2009-01-01

253

Activation of C-H Bonds via the Merger of Photoredox and Organocatalysis: A Coupling of Benzylic Ethers with Schiff Bases.  

PubMed

The photoredox-mediated coupling of benzylic ethers with Schiff bases has been accomplished. Direct benzylic C-H activation by a combination of a thiol catalyst with an iridium photocatalyst and subsequent radical-radical coupling with secondary aldimines affords a variety of ?-amino ether products in good to excellent yields. Mechanistic studies suggest that a reductive quenching pathway of the photocatalyst is operable. PMID:25457231

Hager, Dominik; MacMillan, David W C

2014-12-10

254

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

PubMed

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. PMID:24858353

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

2014-11-11

255

Synthesis, Characterization, Antimicrobial, DNA Cleavage, and In Vitro Cytotoxic Studies of Some Metal Complexes of Schiff Base Ligand Derived from Thiazole and Quinoline Moiety  

PubMed Central

A novel Schiff base ligand N-(4-phenylthiazol-2yl)-2-((2-thiaxo-1,2-dihydroquinolin-3-yl)methylene)hydrazinecarboxamide (L) obtained by the condensation of N-(4-phenylthiazol-2-yl)hydrazinecarboxamide with 2-thioxo-1,2-dihydroquinoline-3-carbaldehyde and its newly synthesized Cu(II), Co(II), Ni(II), and Zn(II) complexes have been characterized by elemental analysis and various spectral studies like FT-IR, 1H NMR, ESI mass, UV-Visible, ESR, TGA/DTA, and powder X-ray diffraction studies. The Schiff base ligand (L) behaves as tridentate ONS donor and forms the complexes of type [ML(Cl)2] with square pyramidal geometry. The Schiff base ligand (L) and its metal complexes have been screened in vitro for their antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The DNA cleavage activity of ligand and its metal complexes were studied using plasmid DNA pBR322 as a target molecule by gel electrophoresis method. The brine shrimp bioassay was also carried out to study the in vitro cytotoxicity properties for the ligand and its metal complexes against Artemia salina. The results showed that the biological activities of the ligand were found to be increased on complexation. PMID:24729778

Yernale, Nagesh Gunvanthrao; Bennikallu Hire Mathada, Mruthyunjayaswamy

2014-01-01

256

Synthesis and Biological Evaluation of Novel 6-Hydroxy-benzo[d][1,3]oxathiol-2-one Schiff Bases as Potential Anticancer Agents.  

PubMed

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 ?M. This class of compounds can be considered as a good starting point for the development of new lead molecules in the fight against cancer. PMID:25633329

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

2015-01-01

257

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)

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.

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

2014-11-01

258

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

PubMed

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, (1)H-(13)C 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(2)O, 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(2)O)(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. PMID:17904895

Keskio?lu, Eren; Gndzalp, Ayla Balaban; Cete, Servet; Hamurcu, Fatma; Erk, Birgl

2008-08-01

259

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)

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.

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

2014-02-01

260

Pd(II) and Zn(II) Based Complexes with Schiff Base Ligands: Synthesis, Characterization, Luminescence, and Antibacterial and Catalytic Activities  

PubMed Central

Two new metal complexes involving Schiff base ligands, namely, [Pd(L1)2] (1) and [Zn(L2)2] (2), [HL1: 2,4-dibromo-6-((E)-(mesitylimino)methyl)phenol and HL2: 2-((E)-(2,6-diisopropylphenylimino)methyl)-4,6-dibromophenol], have been solvothermally synthesized and characterized by elemental analysis, IR-spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. Both 1 and 2 are mononuclear cyclometalated complexes with square planar and tetrahedral coordination geometry, respectively. 1 and 2 display photoluminescence in the solid state at 298?K (fluorescence lifetimes ? = 5.521??s at 508?nm for 1; ? = 3.697??s at 506?nm for 2). These Schiff base ligands and their metal complexes have been screened for antibacterial activity against several bacteria strains, and the results are compared with the activity of penicillin. Moreover, the Suzuki reaction of 4-bromoanisole with phenylboronic acid by 1 has also been studied. PMID:24307886

Feng, Zhi-Qiang; Yang, Xiao-Li; Ye, Yuan-Feng

2013-01-01

261

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

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 (1.210(-8)molL(-1)), near Nernstian slope (29.80.4mV decade(-1) of activity), wide working concentration range (6.410(-8)-1.010(-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. PMID:24268244

Bandi, Koteswara Rao; Singh, Ashok Kumar; Upadhyay, Anjali

2014-01-01

262

2-Hydroxynaphthalene-1-carbaldehyde- and 2-(aminomethyl)pyridine-based Schiff base Cu(II) complexes for DNA binding and cleavage.  

PubMed

Three mononuclear Cu(II) complexes, [CuCl(naph-pa)] (1), [Cu(bipy)(naph-pa)]Cl (2), and [Cu(naph-pa)(phen)]Cl (3) ((naph-pa)=Schiff base derived from the condensation of 2-hydroxynaphthalene-1-carbaldehyde and 2-picolylamine (=2-(aminomethyl)pyridine), bipy=2,2'-bypiridine, and phen=1,10-phenanthroline) were synthesized and characterized. Complex 1 exhibits square-planar geometry, and 2 and 3 exhibit square pyramidal geometry, where Schiff base and bipy/phen act as NNO and as NN donor ligands, respectively. CT (Calf thymus)-DNA-binding studies revealed that the complexes bind through intercalative mode and show good binding propensity (intrinsic binding constant K(b): 0.9810(5), 2.2210(5), and 2.6710(5) M(-1) for 1-3, resp.). The oxidative and hydrolytic DNA-cleavage activity of these complexes has been studied by gel electrophoresis: all the complexes displayed chemical nuclease activity in the presence and absence of H(2)O(2). From the kinetic experiments, hydrolytic DNA cleavage rate constants were determined as 2.48, 3.32, and 4.10 h(-1) for 1-3, respectively. It amounts to (0.68-1.14)10(8)-fold rate enhancement compared to non-catalyzed DNA cleavage, which is impressive. The complexes display binding and cleavage propensity to DNA in the order of 3>2>1. PMID:23081926

Reddy, Pulimamidi Rabindra; Shilpa, Addla

2012-10-01

263

Surface tectonics of nanoporous networks of melamine-capped molecular building blocks formed through interface Schiff-base reactions.  

PubMed

Control over the assembly of molecules on a surface is of great importance for the fabrication of molecule-based miniature devices. Melamine (MA) and molecules with terminal MA units are promising candidates for supramolecular interfacial packing patterning, owing to their multiple hydrogen-bonding sites. Herein, we report the formation of self-assembled structures of MA-capped molecules through a simple on-surface synthetic route. MA terminal groups were successfully fabricated onto rigid molecular cores with 2-fold and 3-fold symmetry through interfacial Schiff-base reactions between MA and aldehyde groups. Sub-molecular scanning tunneling microscopy (STM) imaging of the resultant adlayer revealed the formation of nanoporous networks. Detailed structural analysis indicated that strong hydrogen-bonding interactions between the MA groups persistently drove the formation of nanoporous networks. Herein, we demonstrate that functional groups with strong hydrogen-bond-formation ability are promising building blocks for the guided assembly of nanoporous networks and other hierarchical 2D assemblies. PMID:23868669

Liu, Xuan-He; Wang, Dong; Wan, Li-Jun

2013-10-01

264

New ruthenium(II) carbonyl complexes bearing disulfide Schiff base ligands and their applications as catalyst for some organic transformations.  

PubMed

Schiff base disulfide ligands (H2L(1-6)) were synthesized from the condensation of cystamine with salicylaldehyde(H2L(1)), 5-chlorosalicylaldehyde(H2L(2)), o-vanillin(H2L(3)), 2-hydroxyacetophenone(H2L(4)), 3-methyl-2-hydroxyacetophenone(H2L(5)), and 2-hydroxy-1-naphthaldehyde(H2L(6)). H2L(1-6) reacts with the ruthenium precursor complex [RuHCl(CO)(PPh3)3] in benzene giving rise to six new ruthenium(II) complexes of general formula [Ru(CO)L(1-6)]. Characterization of the new complexes was carried out by using elemental and spectral (IR, UV-Vis, NMR ((1)H and (13)C) and Mass) techniques. An octahedral geometry was assigned for all the complexes based on the spectral data obtained. The catalytic efficiency of the new complexes in aldehyde to amide conversion in the presence of NaHCO3, N-alkylation of aniline in the presence of t-BuOK, and transfer hydrogenation of ketones in the presence of iPrOH/KOH reactions were studied. Furthermore, the effect of solvents and catalyst/substrate ratio on the catalytic aldehyde to amide conversion were also discussed. PMID:24747860

Prakash, Govindan; Viswanathamurthi, Periasamy

2014-08-14

265

Synthesis, spectroscopic (electronic, IR, NMR and ESR) and theoretical studies of transition metal complexes with some unsymmetrical Schiff bases  

NASA Astrophysics Data System (ADS)

Two unsymmetrical Schiff bases, glyoxal salicylaldehyde oxalic acid dihydrazone (gsodh) and glyoxal salicylaldehyde malonic acid dihydrazone (gsmdh) and their Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized. The structures of metal complexes are elucidated on the basis of elemental analyses, molar conductance, magnetic susceptibility measurements, electronic, ESR, IR and NMR (1H and 13C) spectral studies. Both ligands show monobasic tetra-dentate behaviour, bonding through CO, two CN and a phenolate group. The electronic spectral studies in solid state indicate a square planar geometry for Ni(II) and Cu(II) complexes and a tetrahedral geometry for Co(II) complexes. However, Co(II) and Cu(II) complexes adopt octahedral geometry in DMSO solution. The ESR spectra of Cu(II) complexes in DMSO solution at 77 K predict an elongated tetragonal distorted octahedral geometry around metal ion and presence of unpaired electron in d orbital. Further, the structures of ligands and their Ni(II) complexes have been satisfactorily modelled by calculations based on density functional theory (DFT). The electronic spectra of Ni(II) complexes are also analyzed in depth with the help of time dependent-DFT (TD-DFT). The theoretical analyses of electronic structure and molecular orbitals have demonstrated that the high-energy absorption bands are M ? L charge transfer and low energy transitions are d-d transitions.

Singh, Vinod P.; Singh, Shweta; Singh, Divya P.; Tiwari, K.; Mishra, Monika

2014-01-01

266

Triaryl-substituted Schiff bases are high-affinity subtype-selective ligands for the estrogen receptor.  

PubMed

We have explored the isoelectronic replacement of the C?C double bond found at the core of many nonsteroidal estrogen ligands with a simple Schiff base (C?N). Di- and triaryl-substituted imine derivatives were conveniently prepared by the condensation of benzophenones with various anilines without the need for phenolic hydroxy protection. Most of these imines demonstrated high affinity for the estrogen receptors, which, in some cases exceeded that of estradiol. In cell-based assays, these imines profiled as ER? agonists but as ER? antagonists, showing preferential reliance on the N-terminal activation function (AF1), which is more active in ER?. X-ray analysis revealed that the triaryl-imines distort the ligand-binding pocket in a new way: by controlling the separation of helices 3 and 11, which appears to alter the C-terminal AF2 surface that binds transcriptional coactivators. This work suggests that C?N for C?C substitution might be more widely considered as a general strategy for preparing drug analogues. PMID:24708493

Liao, Zong-Quan; Dong, Chune; Carlson, Kathryn E; Srinivasan, Sathish; Nwachukwu, Jerome C; Chesnut, Robert W; Sharma, Abhishek; Nettles, Kendall W; Katzenellenbogen, John A; Zhou, Hai-Bing

2014-04-24

267

Nad(P)H vs. Schiff base fluorescence by spectroscopy, imaging, and maximum sensitivity micrographs at the convergence of cellular detoxification, senescence, and transformation  

NASA Astrophysics Data System (ADS)

Two intracellular fluorochromes, NAD(P)H and Schiff Bases, provide monitoring of energy metabolism and photoperoxidations. Fluorochrome spectra and topographic distribution are measured in a microspectrofluorometer, pixel by pixel using a CCD. The mitochondrial arrangement of Saccharomyces cerevisie and metabolic activity at nuclear kidney epithelial sites is revealed. A kind of accelerated photoaging results in the accumulation of Schiff pigment. Schiff base emission is red-shifted, and it may be preceded by photo-oxidation of NAD(P)H. UVA production of oxygen radicals and peroxides may influence detoxification, senescence and/or transformation. Besides lysosomes, mitochondrial energy metabolism and ER and Golgi detoxification are open to study as multi-organelle complexes with fluorescent xenobiotics and probes. Melanocytes vs. melanoma cells in culture will be investigated using a new compact interferometer for Fourier coding of both emission and excitation spectra. Surprisingly, the photographic method, using the highest sensitivity films, may sometimes produce excellent structural detail. However, for kinetic studies, the CCD, or equivalent, is required. There is good potential for applications in diagnostics and prognostics plus the evaluation of new biopharmeceuticals.

Kohen, Elli; Hirschberg, Joseph G.; Kohen, Cahide; Monti, Marco

1999-05-01

268

Mechanism of isomerization of 11-cis-retinal in lipid dispersions by aromatic amines  

Microsoft Academic Search

It has previously been shown that retinotoxic, primary aromatic amines catalyze the isomerization of 11-cis-retinal to its all-trans congener after Schiff base formation. This process led to the short-circuiting of the visual cycle and the observed retinotoxicity when it occurred in vivo. The catalysis was also observed to occur in vitro in phosphatidylcholine-based vesicles but not in hydrocarbon solutions. The

Brian S. Fulton; Robert R. Rando

1987-01-01

269

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)

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.

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

2012-01-01

270

DNA damage induced by a chromium(III) Schiff base complex is reversible under physiological condition.  

PubMed

[Cr(naphen)(H2O)(2)]+, where naphen is 1,2-bis(naphthylideneamino)ethane having the basic salen moiety, has been characterized structurally. [Cr(naphen)(H2O)(2)]+, which has an extended aromatic system and binds with calf thymus DNA (CT DNA) intercalatively, has been found to promote DNA cleavage in the presence of biological reductant such as ascorbate and oxidant like hydrogen peroxide. Results of electron paramagnetic resonance (EPR) experiments suggest involvement of hydroxyl radicals in the oxidative cleavage of DNA in the presence of the Cr(III) complex and hydrogen peroxide. The cell viability study on nicked DNA by [Cr(naphen)(H2O)(2)]+ has shown that the damage brought about to DNA could be repaired by Escherichia coli DNA repair enzymes. PMID:16202452

Vaidyanathan, V G; Weyhermuller, T; Nair, Balachandran Unni; Subramanian, J

2005-11-01

271

Synthesis and characterization of water soluble O-carboxymethyl chitosan Schiff bases and Cu(II) complexes.  

PubMed

In this study, mono-imine was synthesized (3a and 4a) via a condensation reaction between 2,4-pentadion and aminobenzoic acid (meta or para) in alcohol (1:1). The second-imine (CS-3a and CS-4a) was obtained as a result of the reaction of the free oxo groups of mono-imine (3a and 4a) with the amino groups on the chitosan (CS). Their structures were characterized with FTIR and (13)C CP-MAS. Then, the water soluble forms of CS-3a and CS-4a were obtained through oxidation of the hydroxide groups on the chitosan to carboxymethyl groups using monochloracetic acid ([O-CMCS-3a]2H2O and [O-CMCS-4a]2H2O). Thus, the solubility problem of chitosan in an aqueous media was overcome and Cu(II) complexes could be synthesized more easily. Characterization of the synthesized O-carboxymethyl chitosan Schiff base derivatives and their metal complexes, [O-CMCS-3a-Cu(OAc)2]2H2O and [O-CMCS-4a-Cu(OAc)2]2H2O, was conducted using FTIR, UV-Vis, TG/DTA, XRD, SEM, elemental analysis, conductivities and magnetic susceptibility measurements. PMID:25128824

Baran, Talat; Mente?, Ayfer; Arslan, Hlya

2015-01-01

272

The oxidation of Schiff bases of pyridoxal and pyridoxal phosphate with amino acids by manganous ions and peroxidase  

PubMed Central

1. Oxygen was taken up rapidly when pyridoxal or pyridoxal phosphate was added to mixtures of pea-seedling extracts and Mn2+ ions. 2. The increases in total oxygen uptake were proportional to the pyridoxal or pyridoxal phosphate added and were accompanied by the disappearance of these compounds. 3. In addition to Mn2+ ions, the reactions depended on two factors in the extracts, a thermolabile one in the non-diffusible material and a thermostable one in the diffusate; these factors could be replaced in the reactions by horse-radish peroxidase (donorhydrogen peroxide oxidoreductase, EC 1.11.1.7) and amino acids respectively. 4. When pyridoxal phosphate was added to mixtures of amino acids and Mn2+ ions oxygen uptake was rapid after a lag period of 3090min.; the lag period was shortened to a few minutes by peroxidase, particularly in the presence of traces of p-cresol, or by light. 5. When pyridoxal replaced pyridoxal phosphate relatively high concentrations were required and peroxidase had only a small activating effect. 6. Pyridoxal or pyridoxal phosphate disappeared during the reactions and carbon dioxide and ammonia were formed. 7. With phenylalanine as the amino acid present, benzaldehyde was identified as a reaction product. 8. It is suggested that the reactions are oxidations of the Schiff bases formed between pyridoxal or pyridoxal phosphate and amino acids, mediated by a manganese oxidationreduction cycle, and resulting in oxidative decarboxylation and deamination of the amino acids. PMID:5947150

Hill, J. M.; Mann, P. J. G.

1966-01-01

273

Direct QM/MM Excited-State Dynamics of Retinal Protonated Schiff Base in Isolation and Methanol Solution.  

PubMed

We use the full multiple spawning (FMS) dynamics approach with a hybrid quantum mechanics/molecular mechanics (QM/MM) reparameterized semiempirical method to investigate the excited-state dynamics of retinal protonated Schiff base (RPSB) in isolation, in neat methanol solution, and in methanol solution with a Cl(-) counterion. The excited-state lifetime is dramatically affected by MeOH solvent, which slows down the photoisomerization by an order of magnitude. We show that this is due to charge migration in the RPSB chromophore and the concomitant solvent friction in polar media. Simulation results are compared to experiments where available, with good agreement for excited-state lifetimes, bond selectivity of isomerization, and the time/energy-resolved fluorescence spectrum. We find that the inclusion of a Cl(-) counterion in the simulations has little effect on lifetimes, mechanism, or bond selectivity. In contrast to previous studies limited to RPSB and a surrounding counterion, we find that the placement of the counterion has little effect on bond selectivity. This suggests that dielectric screening can spoil the effect of a counterion in directing excited-state reactivity. PMID:25178510

Punwong, Chutintorn; Owens, Jane; Martnez, Todd J

2015-01-22

274

Structure investigation of three hydrazones Schiff's bases by spectroscopic, thermal and molecular orbital calculations and their biological activities.  

PubMed

Three Schiff's bases AI (2(1-hydrazonoethyl)phenol), AII (2, 4-dibromo 6-(hydrazonomethyl)phenol) and AIII (2(hydrazonomethyl)phenol) were prepared as new hydrazone compounds via condensation reactions with molar ratio (1:1) of reactants. Firstly by reaction of 2-hydroxy acetophenone solution and hydrazine hydrate; it gives AI. Secondly condensation between 3,5-dibromo-salicylaldehyde and hydrazine hydrate gives AII. Thirdly condensation between salicylaldehyde and hydrazine hydrate gives AIII. The structures of AI-AIII were characterized by elemental analysis (EA), mass (MS), FT-IR and (1)H NMR spectra, and thermal analyses (TG, DTG, and DTA). The activation thermodynamic parameters, such as, ?E(?), ?H(?), ?S(?) and ?G(?) were calculated from the TG curves using Coats-Redfern method. It is important to investigate their molecular structures to know the active groups and weak bond responsible for their biological activities. Consequently in the present work, the obtained thermal (TA) and mass (MS) practical results are confirmed by semi-empirical MO-calculations (MOCS) using PM3 procedure. Their biological activities have been tested in vitro against Escherichia coli, Proteus vulgaris, Bacillissubtilies and Staphylococcus aurous bacteria in order to assess their anti-microbial potential. PMID:25437844

Belal, Arafa A M; Zayed, M A; El-Desawy, M; Rakha, Sh M A H

2015-03-01

275

Potential bioactive Schiff base compounds: Synthesis, characterization, X-ray structures, biological screenings and interaction with Salmon sperm DNA  

NASA Astrophysics Data System (ADS)

Three Schiff base compounds ofN?-substituted benzohydrazide and sulfonohydrazide derivatives: N?-(2-hydroxy-3-methoxybenzylidene)-4-tert-butyl- benzohydrazide (1), N?-(5-bromo-2-hydroxybenzylidene)-4-tert-butylbenzohydrazide (2) and N?-(2-hydroxy-3-methoxybenzylidene)-4-methylbenzenesulfonohydrazide (3) were synthesized and characterized by elemental analysis, FT-IR, 1H, 13C NMR spectroscopy and single crystal analysis. The title compounds have been screened for their biological activities including, antibacterial, antifungal, antioxidant, cytotoxic, enzymatic activities as well as interaction with SS-DNA which showed remarkable activities in each area of research. The DNA binding of the compounds 1-3 with SS-DNA has been carried out with absorption spectroscopy, which reveals the binding propensity towards SS-DNA via intercalation mode of interaction. The intercalative mode of interaction is also supported by viscometric results. The synthesized compounds were also found to be effective against alkaline phosphatase enzyme. They also show significant to good antimicrobial activity against six bacterial and five fungal strains. The MIC (minimum inhibitory concentration) for antibacterial activity ranges from 1.95-500 ?g/mL. Compounds 1-3 show cytotoxic activity comparable to the control. At higher conc. (100 ?g/L) compound 3 shows 100% activity means that it has killed all brine shrimps. They were also found to be effective antioxidant of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and show almost comparable antioxidant activity to that of the standard and known antioxidant, ascorbic acid.

Sirajuddin, Muhammad; Uddin, Noor; Ali, Saqib; Tahir, Muhammad Nawaz

2013-12-01

276

Biofilm inhibition of linezolid-like Schiff bases: Synthesis, biological activity, molecular docking and in silico ADME prediction.  

PubMed

Herein, we report the synthesis and screening of linezolid-like Schiff bases as inhibitors of biofilm formation. The result of biofilm inhibition of Pseudomonas aeruginosa suggested that compounds 5h (IC50 value=12.970.33?M) and 5i (IC50 value=15.630.20?M) had more inhibitory activity when compared with standard linezolid (IC50=15.930.18?M) without affecting the growth of cells (and thus behave as anti-quorum sensing agents). The compounds 5h (MIC range=2.5-10?g/mL) and 5i (MIC range=3.5-10?g/mL) with 2-chloroquinolinyl and 2-chloro-8-methylquinolinyl motif, respectively, showed antibacterial activity in comparable range of linezolid (MIC range=2-3?g/mL) and were more potent when compared with ciprofloxacin (MIC range=25-50?g/mL). Thus, the active derivatives were not only potent inhibitors of P. aeruginosa biofilm growth but also efficient antibacterial agents. The docking study of most active compounds 5h and 5i against PqsD enzyme of P. aeruginosa exhibited good binding properties. In silico ADME properties of synthesized compounds were also analyzed and showed potential to develop as good oral drug candidates. PMID:25592714

Sangshetti, Jaiprakash N; Khan, Firoz A Kalam; Patil, Rajendra H; Marathe, Sayali D; Gade, Wasudev N; Shinde, Devanand B

2015-02-15

277

Emissive bis-salicylaldiminato Schiff base ligands and their zinc(II) complexes: Synthesis, photophysical properties, mesomorphism and DFT studies  

NASA Astrophysics Data System (ADS)

Bis-salicylaldiminato Schiff base ligands and their Zn(II) complexes derived from 2,3-Diaminomaleonitrile (DAMN) were synthesized. Their molecular structures, photophysical properties and mesogenic behaviors were investigated. The ligands and their Zn(II) complexes were characterized by using elemental analysis, FT-IR, 1H NMR and molar conductivity measurements. Photophysical properties of ligands and their Zn(II) complexes were investigated in different polar solvents by using UV-visible and fluorescence spectroscopic studies. Ligands emit green light whereas complexes emit orange light upon irradiation with UV-visible light. The liquid crystalline phases of ligands and their Zn(II) complexes were characterized by polarizing optical microscopy and differential scanning calorimetry. The ligand having longer 4-n-octadecyloxy chain (n = 18) displays columnar phase whereas the lower homologues (n = 16, 12) did not show mesophase. The Zn(II) complexes having 4-n-octadecyloxy end chain display smectic B like phase whereas other lower homologues are non mesogenic in nature. The thermal stability of the compounds were studied by using thermo gravimetric analysis. The density functional theory was carried out to obtain the stable molecular conformation, dipole moment, molecular orbitals and polarizability of the ligands and their Zn(II) complexes.

Paul, Manoj Kr.; Dilipkumar Singh, Y.; Bedamani Singh, N.; Sarkar, Utpal

2015-02-01

278

Synthesis, spectral, antitumor and antimicrobial studies on Cu(II) complexes of purine and triazole Schiff base derivatives  

NASA Astrophysics Data System (ADS)

A series of copper (II) complexes of Schiff bases derived from 7H-2,6-diaminopurine and 4H-3,5-diamino-1,2,4-triazole with 2-pyridinecarbaldehyde, salicylaldehyde, 2,4-dihydroxybenzaldehyde and 2-hydroxy-1-naphthaldehyde have been prepared. The donor atoms and the possible geometry of the complexes were investigated by means of elemental and thermal analyses, molar conductance, magnetic moment, UV-Vis, IR, ESR and mass spectra. The ligands behaved as tetradentate, coordinating through the nitrogen atom of the azomethine group and the nearest nitrogen atom to it or oxygen atom of ?-hydroxyl group. The results of simultaneous DTA & TGA analyses of the complexes showed the final degradation product for these complexes is CuO. The spectral studies confirmed a four coordinate environment around the metal ion. The obtained results were supported by 3D molecular modeling of complexes using molecular mechanics (MM+) and semiempirical molecular orbital calculations (PM3). These complexes were also tested for their in vitro antimicrobial activities against some bacterial and fungal strains. Complex 2 was investigated for its cyctotoxic effect against human breast cancer (MCF7), liver carcinoma (HEPG2) and colon carcinoma cell lines (HCT116). This compound exhibited a moderate activity against the tested cell lines with IC50 of 10.3, 9.8 and 8.7 ?g/ml against MCF7, HCT116 and HEPG2, respectively.

Amer, Said; El-Wakiel, Nadia; El-Ghamry, Hoda

2013-10-01

279

Effects of tryptophan mutation on the deprotonation and reprotonation kinetics of the Schiff base during the photocycle of bacteriorhodopsin.  

PubMed Central

The rates of deprotonation and reprotonation of the protonated Schiff base (PSB) are determined during the photocycle of nine bacteriorhodopsin mutants in which Trp-10, 12, 80, 86, 137, 138, 182 and 189 are individually substituted by either phenylalanine or cysteine. Of all the mutants, the replacement of Trp-86, Trp-182, and Trp-189 by phenylalanine and Trp-137 by cysteine is found to significantly alter the rate of the deprotonation, but not that of the reprotonation process. As compared with ebR, the Trp-86 mutation dramatically increases the rate of deprotonation of the PSB while the Trp-182 mutation greatly decreases this rate. Temperature dependence studies on the rate constants of the deprotonation demonstrate that the different energetic and entropic effects of the mutation are responsible for the observed different kinetic behavior of the Trp-86 and Trp-182 mutants as compared with that of ebR. In the case of Trp-86 mutant, a large decrease in both energy and entropy of activation suggests that the mutation of this tryptophan residue opens up the protein structure as a result of eliminating the hydrogen-bonding group on its side chain by a phenylalanine substitution. A correlation is observed between the proton pumping yield and the relative amplitudes of the slow deprotonation component but not with rate constants of the rise or decay process at constant pH. These results are best discussed in terms of the heterogeneity model (with parallel cycle) rather than back reaction model. PMID:1318094

Wu, S; Chang, Y; el-Sayed, M A; Marti, T; Mogi, T; Khorana, H G

1992-01-01

280

Spectroscopic, electrochemical DNA binding and in vivo anti-inflammatory studies on newly synthesized Schiff bases of 4-aminophenazone.  

PubMed

4-Aminophenazone (Ap-1) Schiff bases i.e., 4-{(3,4,5-trimethoxybenzylidine) amino}phenazone (Ap-2), 4-{(2-chlorobenzylidine) amino}phenazone (Ap-3) and 4-{(4-chlorobenzylidine)amino} phenazone (Ap-4) were synthesized and characterized by different spectroscopic techniques. Interaction of these compounds with ds.DNA was investigated through UV-Visible spectroscopy, fluorescence spectroscopy and cyclic voltammetry at stomach (4.7) and blood (7.4) pH under 37 C (human body temperature). Instrumental findings were further quantified both kinetically and thermodynamically. Results obtained through these techniques inferred intercalative mode of binding of all the compounds with DNA. The binding constant data, "Kb", and free energy change, ?G, indicated comparatively greater binding affinity and more spontaneity of binding of compounds with DNA at stomach pH (4.7), respectively. However, among these compounds, Ap-4 showed comparatively greater binding at both the pH. Formation of compound-DNA complex was further confirmed through the decrease in diffusion rates after the addition of DNA. The in vivo anti-inflammatory activity of the compounds was evaluated using the carrageenan-induced hind paw edema method. The results revealed that among all the compounds, Ap-4 showed greater percentage of edema inhibition compared to standard drug. PMID:25036662

Arshad, Nasima; Ahmad, Mukhtar; Ashraf, Muhammad Zaman; Nadeem, Humaira

2014-09-01

281

Synthesis, Characterization, DNA Interaction, and Antitumor Activities of La (III) Complex with Schiff Base Ligand Derived from Kaempferol and Diethylenetriamine  

PubMed Central

A novel La (III) complex, [LaL(H2O)3]NO33H2O, with Schiff base ligand L derived from kaempferol and diethylenetriamine, has been synthesized and characterized by elemental analysis, IR, UV-visible, 1H NMR, thermogravimetric analysis, and molar conductance measurements. The fluorescence spectra, circular dichroism spectra, and viscosity measurements and gel electrophoresis experiments indicated that the ligand L and La (III) complex could bind to CT-DNA presumably via intercalative mode and the La (III) complex showed a stronger ability to bind and cleave DNA than the ligand L alone. The binding constants (Kb) were evaluated from fluorescence data and the values ranged from 0.454 to 0.659 105 L mol?1 and 1.71 to 17.3 105 L mol?1 for the ligand L and La (III) complex, respectively, in the temperature range of 298310?K. It was also found that the fluorescence quenching mechanism of EB-DNA by ligand L and La (III) complex was a static quenching process. In comparison to free ligand L, La (III) complex exhibited enhanced cytotoxic activities against tested tumor cell lines HL-60 and HepG-2, which may correlate with the enhanced DNA binding and cleaving abilities of the La (III) complex. PMID:25371657

Wang, Qin; Huang, Yu; Zhang, Jin-Sheng; Yang, Xin-Bin

2014-01-01

282

Syntheses, structures, and properties of two luminous mercury(II) halide compounds containing a tetradentate N-donor Schiff base  

NASA Astrophysics Data System (ADS)

A 1D coordination polymer [Hg2(L)Br4]n (1) and one dinuclear compound [Hg2(L)I4] (2) [L = N,N'-(bis(pyridin-2-yl)benzylidene)ethane-1,2-diamine] are isolated using a 2:1 M ratio of HgBr2/HgI2 and Schiff base (L) in methanol-acetonitrile solution mixture and X-ray crystallographically characterized. Structural analyses show that in 1 1D chain is formed through binucleating bis(bidentate) bridging behavior of L and asymmetric Hg-(?-Br)2-Hg bridges in an alternate fashion; one terminal bromide unit completes the distorted square pyramidal geometry around each mercury(II). In 2, two mercury(II) centers are connected by bis(bidentate) bridging behavior of L and two iodides bound to each metal(II) center remain as terminal resulting in a discrete dinuclear entity with distorted tetrahedral geometry. Weak intermolecular Hg⋯I and I⋯I interactions in 2 promote dimensionality. In DMF solutions, 1 and 2 display intraligand 1(?-??) fluorescence.

Satapathi, Smita; Chattopadhyay, Soumi; Roy, Subhasis; Bhar, Kishalay; Mitra, Partha; Ghosh, Barindra Kumar

2012-12-01

283

Synthesis, structural characterization, catalytic, thermal and electrochemical investigations of bidentate Schiff base ligand and its metal complexes  

NASA Astrophysics Data System (ADS)

In this study, we prepared the Schiff base ligand (L) and its Cu(II), Co(II) and Ni(II) complexes. The compounds were characterized by the analytical and spectroscopic methods. The ligand (L) behaves as a bidentate ligand and coordinates to the metal ions via the nitrogen atoms. The complexes have the mononuclear structures. The analytical and spectroscopic results indicated that the chloride ions coordinate to the metal ions. The complexes have the general formulae [M(L)(Cl) 2] (M: Cu(II), Co(II) and Ni(II) metal ions). Electrochemical properties were investigated as ligand and metal centres in the different solvents and at the scan rates, respectively. The thermal properties of the metal complexes were studied in the N 2 atmosphere. We investigated the improved catalytic activity of the Cu(II), Co(II) and Ni(II) complexes on the cyclohexane as a substrate. Obtained data showed that the best catalyst is the Cu(II) complex. The single crystal of the ligand (L) was obtained from CH 3CN solution. There is a C-HN H-bond linking the molecules into chains (C6)N(2) 3.4415(18) under symmetry operation ( x + 1, y, z) as well as ?-? stacking on the outside of the "V" shape - nothing on the inside.

Dolaz, Mustafa; McKee, Vickie; Uru?, Serhan; Demir, Necmettin; Sabik, Ali E.; Glc, Ay?egl; Tmer, Mehmet

2010-07-01

284

Synthesis, structural characterization, catalytic, thermal and electrochemical investigations of bidentate Schiff base ligand and its metal complexes.  

PubMed

In this study, we prepared the Schiff base ligand (L) and its Cu(II), Co(II) and Ni(II) complexes. The compounds were characterized by the analytical and spectroscopic methods. The ligand (L) behaves as a bidentate ligand and coordinates to the metal ions via the nitrogen atoms. The complexes have the mononuclear structures. The analytical and spectroscopic results indicated that the chloride ions coordinate to the metal ions. The complexes have the general formulae [M(L)(Cl)(2)] (M: Cu(II), Co(II) and Ni(II) metal ions). Electrochemical properties were investigated as ligand and metal centres in the different solvents and at the scan rates, respectively. The thermal properties of the metal complexes were studied in the N(2) atmosphere. We investigated the improved catalytic activity of the Cu(II), Co(II) and Ni(II) complexes on the cyclohexane as a substrate. Obtained data showed that the best catalyst is the Cu(II) complex. The single crystal of the ligand (L) was obtained from CH(3)CN solution. There is a C-H...N H-bond linking the molecules into chains (C6)...N(2) 3.4415(18)A under symmetry operation (x+1,y,z) as well as pi-pi stacking on the outside of the "V" shape--nothing on the inside. PMID:20409747

Dolaz, Mustafa; McKee, Vickie; Uru?, Serhan; Demir, Necmettin; Sabik, Ali E; Glc, Ay?egl; Tmer, Mehmet

2010-07-01

285

Environmental Dependence of Artifact CD Peaks of Chiral Schiff Base 3d-4f Complexes in Soft Mater PMMA Matrix  

PubMed Central

Four chiral Schiff base binuclear 3d-4f complexes (NdNi, NdCu, GdNi, and GdCu) have been prepared and characterized by means of electronic and CD spectra, IR spectra, magnetic measurements, and X-ray crystallography (NdNi). A so-called artifact peak of solid state CD spectra, which was characteristic of oriented molecules without free molecular rotation, appeared at about 470 nm. Magnetic data of the complexes in the solid state (powder) and in PMMA cast films or solutions indicated that only GdCu preserved molecular structures in various matrixes of soft maters. For the first time, we have used the changes of intensity of artifact CD peaks to detect properties of environmental (media solid state (KBr pellets), PMMA cast films, concentration dependence of PMMA in acetone solutions, and pure acetone solution) for chiral 3d-4f complexes (GdCu). Rigid matrix keeping anisotropic orientation exhibited a decrease in the intensity of the artifact CD peak toward negative values. The present results suggest that solid state artifact CD peaks can be affected by environmental viscosity of a soft mater matrix. PMID:22072930

Okamoto, Yu; Nidaira, Keisuke; Akitsu, Takashiro

2011-01-01

286

Structure investigation of three hydrazones Schiff's bases by spectroscopic, thermal and molecular orbital calculations and their biological activities  

NASA Astrophysics Data System (ADS)

Three Schiff's bases AI (2(1-hydrazonoethyl)phenol), AII (2, 4-dibromo 6-(hydrazonomethyl)phenol) and AIII (2(hydrazonomethyl)phenol) were prepared as new hydrazone compounds via condensation reactions with molar ratio (1:1) of reactants. Firstly by reaction of 2-hydroxy acetophenone solution and hydrazine hydrate; it gives AI. Secondly condensation between 3,5-dibromo-salicylaldehyde and hydrazine hydrate gives AII. Thirdly condensation between salicylaldehyde and hydrazine hydrate gives AIII. The structures of AI-AIII were characterized by elemental analysis (EA), mass (MS), FT-IR and 1H NMR spectra, and thermal analyses (TG, DTG, and DTA). The activation thermodynamic parameters, such as, ?E?, ?H?, ?S? and ?G? were calculated from the TG curves using Coats-Redfern method. It is important to investigate their molecular structures to know the active groups and weak bond responsible for their biological activities. Consequently in the present work, the obtained thermal (TA) and mass (MS) practical results are confirmed by semi-empirical MO-calculations (MOCS) using PM3 procedure. Their biological activities have been tested in vitro against Escherichia coli, Proteus vulgaris, Bacillissubtilies and Staphylococcus aurous bacteria in order to assess their anti-microbial potential.

Belal, Arafa A. M.; Zayed, M. A.; El-Desawy, M.; Rakha, Sh. M. A. H.

2015-03-01

287

Synthesis, structural characterization, fluorescence, antimicrobial, antioxidant and DNA cleavage studies of Cu(II) complexes of formyl chromone Schiff bases  

NASA Astrophysics Data System (ADS)

Cu(II) complexes have been synthesized from different Schiff bases, such as 3-((2-hydroxy phenylimino)methyl)-4H-chromen-4-one (HL1), 2-((4-oxo-4H-chromen-3-yl)methylneamino) benzoicacid (HL2), 3-((3-hydroxypyridin-2-ylimino)methyl)-4H-chromen-4-one (HL3) and 3-((2-mercaptophenylimino)methyl)-4H-chromen-4-one (HL4). The complexes were characterized by analytical, molar conductance, IR, electronic, magnetic, ESR, thermal, powder XRD and SEM studies. The analytical data reveal that metal to ligand molar ratio is 1:2 in all the complexes. Molar conductivity data indicates that all the Cu(II) complexes are neutral. On the basis of magnetic and electronic spectral data, distorted octahedral geometry is proposed for all the Cu(II) complexes. Thermal behaviour of the synthesized complexes illustrates the presence of lattice water molecules in the complexes. X-ray diffraction studies reveal that all the ligands and their Cu(II) complexes have triclinic system with different unit cell parameters. Antimicrobial, antioxidant and DNA cleavage activities indicate that metal complexes exhibited greater activity as compared with ligands.

Kavitha, P.; Saritha, M.; Laxma Reddy, K.

2013-02-01

288

Selective recognition of sulfate anions in a 95% ethanol solvent with a simple neutral salicylaldehyde dansyl hydrazine Schiff base tuned by Brnsted-Lowry acid-base reaction  

NASA Astrophysics Data System (ADS)

A new Schiff base compound, 5-(dimethylamino)-N?-(2-hydroxybenzylidene)naphthalene-1-sulfonohydrazide (R), has been synthesized, characterized, and employed as a selective fluorescence receptor for the recognition of sulfate anions. UV-vis absorption, fluorescence emission, 1H NMR spectra and DFT calculation studies on the system have been carried out to determine the nature of the interactions between R and anions. The results reveal that the deprotonation of the phenol without the need of a strong base leads to the formation of a hydrogen-bonding complex with a sbnd SO2sbnd NHsbnd group, which is responsible for the spectra changes. The deprotonation process for the selectivity recognition of sulfate can be tuned by the Brnsted-Lowry acid-base reaction in nonaqueous solutions, revealing that suitable phenolic hydroxyl acidity is the key factor for anion recognition selectivity.

Wei, Gao-Ning; Zhang, Jing-Li; Jia, Cang; Fan, Wei-Zhen; Lin, Li-Rong

2014-07-01

289

Oxidation of phenyl propyne catalyzed by copper(II) complexes of a benzimidazolyl schiff base ligand: Effect of acid/base, oxidant, surfactant and morphology  

NASA Astrophysics Data System (ADS)

Copper(II) complexes with a new N-Substituted benzimidazolyl schiff base ligand are used as catalyst for the oxidation of 1-phenyl propyne. The oxidation is carried out under mild conditions using stoichiometric amounts of oxidant and catalytic amounts of Cu(II) complex as catalyst. Effect of acid/base, oxidant, morphology and surfactant has been studied. Two major products of phenyl propyne oxidation are the ?-diketonic product and a terminal aldehyde. Diketone is the major product under acidic conditions while aldehyde formation is highest under basic conditions. The maximum conversion is found with the NO3- bound complex. GC-MS is used to find the percentage yields of products. SEM and PXRD of the reused complexes as catalyst suggest that morphology affects the catalytic efficiency.

Kumar, Ravinder; Mathur, Pavan

2015-02-01

290

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)

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.

Keypour, Hassan; Shayesteh, Maryam; Rezaeivala, Majid; Chalabian, Firoozeh; Elerman, Yalcin; Buyukgungor, Orhan

2013-01-01

291

Photo- and electroluminescent properties of zinc(II) complexes with tetradentate Schiff bases, derivatives of salicylic aldehyde  

NASA Astrophysics Data System (ADS)

It is studied how the introduction of various substituents into the composition of organic ligands affects the photoluminescence spectra of new zinc(II) complexes with tetradentate Schiff bases H2L (derivatives of salicylic aldehyde (H2SAL1, H2SAL2) and o-vanillin (H2MO1, H2MO2) with ethylenediamine and o-phenylenediamine) in the form of bulk solids and thin films. It is demonstrated that the emission spectra of bulk solid complexes without o-phenylenediamine bridges (ZnSAL1 and ZnMO1) contain additional long-wavelength bands compared to the spectra of corresponding thin films. In the case of films obtained from [ZnSAL1]2 dimer complexes, the long-wavelength band is dominant. At the same time, the photoluminescence spectra of ZnSAL2 and ZnMO2 complexes with o-phenylenediamine bridges are similar in the case of solid samples and thin films. The electroluminescent properties of organic light-emitting diodes (OLEDs) with the ITO/?-NPD/ZnL/Ca:Al structure are studied. The bathochromic shift of the electroluminescence peaks of OLEDs with respect to the photoluminescence spectra of bulk solid samples and thin films is probably related to the formation of exciplexes at the ?-NPD/ZnL interface. The electroluminescence spectra of OLEDs based on [ZnSAL1]2 show a hypsochromic shift of the emission maximum, which can be caused by a shift of the recombination region into the ?-NPD layer.

Vashchenko, A. A.; Lepnev, L. S.; Vitukhnovskii, A. G.; Kotova, O. V.; Eliseeva, S. V.; Kuz'mina, N. P.

2010-03-01

292

Remarkable photocytotoxicity in hypoxic HeLa cells by a dipyridophenazine copper(II) Schiff base thiolate.  

PubMed

Copper(II) complexes [Cu(satp)(L)] (1-3) of a Schiff base thiolate (salicylidene-2-aminothiophenol, H2satp) and phenanthroline bases (L), viz. 1,10-phenanthroline (phen in 1), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 2) and dipyrido[3,2-a:2',3'-c]phenazine (dppz in 3), were prepared, characterized and their anaerobic DNA photocleavage activity and hypoxic photocytotoxicity studied. The redox active complexes show the Cu(II)-Cu(I) couple near -0.5 V for 1 and near 0.0 V vs. SCE (saturated calomel electrode) for 2 and 3. The one-electron paramagnetic complexes (~1.85 ?B) are avid DNA binders giving Kb values within 1.010(5)-8.010(5) M(-1). Thermal melting and viscosity data along with molecular docking calculations suggest DNA groove and/or partial intercalative binding of the complexes. The complexes show anaerobic DNA cleavage activity in red light under argon via type-I pathway, while DNA photocleavage in air proceeds via hydroxyl radical pathway. The DFT (density functional theory) calculations reveal a thyil radical pathway for the anaerobic DNA photocleavage activity and suggest the possibility of generation of a transient copper(I) species due to bond breakage between the copper and sulfur to generate the thyil radical. An oxidation of the copper(I) species is likely by oxygen in an aerobic medium or by the buffer medium in an anaerobic condition. Complex 3 exhibits significant photocytotoxicity in HeLa cells (IC50=8.3(1.0) ?M) in visible light, while showing lower dark toxicity (IC50=17.2(1.0) ?M). A significant reduction in the dark toxicity is observed under hypoxic cellular conditions (IC50=30.0(1.0) ?M in dark), while retaining its photocytotoxicity (IC50=8.0(1.0) ?M). PMID:21726772

Lahiri, Debojyoti; Majumdar, Ritankar; Mallick, Dibyendu; Goswami, Tridib K; Dighe, Rajan R; Chakravarty, Akhil R

2011-08-01

293

La(III) complex involving the O,N-donor environment of quinazoline-4(3H)-one Schiff's base and their antimicrobial attributes against methicillin-resistant Staphylococcus aureus (MRSA).  

PubMed

The incidence of methicillin-resistant Staphylococcus aureus increased during the past few decades, so there is an urgent need of new antimicrobial agents if public health is concerned. Though the Schiff's bases and La(III) complex have enormous biological activity, but less attention was given in their synthesis. In the present investigation, we synthesized a new (E)-3-((2-hydroxynaphthalen-1-yl) methyleneamino)-2-methylquinazoline-4(3H)-one HNMAMQ Schiff's base by the condensation of 3-(2-aminophenyl) quinazolin-2-methyl-4(3H)-one and 2-hydroxy-1-naphthaldehyde. The Schiff's base HNMAMQ and its La(III) complex were characterized by elemental analyses, IR, NMR, mass spectra, and thermal studies. The newly synthesized Schiff's base HNMAMQ and its La(III) complex were evaluated for their antimicrobial activity against methicillin-resistant Staphylococcus aureus isolated from the Gulbarga region in India. The Schiff's base HNMAMQ and its La(III) complex showed good antimicrobial activity and thus represents a potential new drug of choice. PMID:24813293

Siddappa, K; Mane, Sunilkumar B; Manikprabhu, Deene

2014-09-15

294

DFT study on second-order nonlinear optical properties of a series of mono Schiff-base M(II) (M = Ni, Pd, Pt) complexes  

NASA Astrophysics Data System (ADS)

A series of mono Schiff-base M(II) (M = Ni, Pd, Pt) complexes based on the crystal data are designed. Density Functional Theory (DFT) method was employed to investigate the second-order nonlinear optical (NLO) properties of all metal complexes. The results show that the second-order NLO properties of metal complexes are intensively sensitive to the exchange of donor/acceptor because of the differences of the extent of charge separation and the intraligand charge transfer (ILCT) processes. The metal ions do not offer direct contributions to second-order NLO responses because they are as electron bridges for transferring electrons in CT processes.

Liu, Chun-Guang; Qiu, Yong-Qing; Sun, Shi-Ling; Chen, Hui; Li, Na; Su, Zhong-Min

2006-10-01

295

Catalytic asymmetric 1,4-additions of beta-keto esters to nitroalkenes promoted by a bifunctional homobimetallic Co2-Schiff base complex.  

PubMed

Catalytic asymmetric 1,4-addition of beta-keto esters to nitroalkenes is described. 2.5 mol % of a homobimetallic Lewis acid/Brnsted base bifunctional Co2-Schiff base complex smoothly promoted the reaction in excellent yield (up to 99%), diastereoselectivity, and enantioselectivity (up to >30:1 dr and 98% ee). Catalyst loading was successfully reduced to 0.1 mol %. Mechanistic studies suggested that intramolecular cooperative functions of the two Co-metal centers are important for high catalytic activity and stereoselectivity. PMID:20110907

Furutachi, Makoto; Chen, Zhihua; Matsunaga, Shigeki; Shibasaki, Masakatsu

2010-01-01

296

Mononuclear and Tetranuclear Compounds of Yttrium and Dysprosium Ligated by a Salicylic Schiff-Base Derivative: Synthesis, Photoluminescence, and Magnetism.  

PubMed

The Schiff-base (2-aminoethyl)hydroxybenzoic acid (H2L) as a proligand was prepared in situ from 3-formylsalicylic acid and ethanolamine (ETA). The mononuclear {[Y(HL)4][ETAH]H2O} (1) and {[Dy(HL)4] [ETAH]3MeOHH2O} (2) and tetranuclear {[Y4(HL)2(L)4(?3-OH)2]4MeOH4H2O} (3), {[Dy4(HL)2(L)4(?3-OH)2]5(MeOH)27H2O (4), and {[Dy4(HL)8(L)2]4MeOH2H2O}(5) rare-earth metal complexes of this ligand could be obtained as single-crystalline materials by the treatment of H2L in the presence of the metal salts [Ln(NO3)3(H2O)m] (Ln = Y, Dy). In the solid state, the tetranuclear compounds 3 and 4 exhibit butterfly structures, whereas 5 adopts a rectangular arrangement. Electrospray ionization mass spectrometry data of the ionic compounds 1 and 2 support single-crystal X-ray analysis. The yttrium compounds 1 and 3 show fluorescence with 11.5% and 13% quantum yield, respectively, whereas the quantum yield of the dysprosium complex 4 is low. Magnetic studies on the dysprosium compounds 4 and 5 suggest the presence of weak antiferromagnetic interactions between neighboring metal centers. Compound 4 shows single-molecule-magnet behavior with two relaxation processes, one with the effective energy barrier Ueff = 84 K and the preexponential factor ?0 = 5.1 10(-9) s. PMID:25238652

Yadav, Munendra; Mereacre, Valeriu; Lebedkin, Sergei; Kappes, Manfred M; Powell, Annie K; Roesky, Peter W

2014-09-19

297

Switching and redox isomerism in first-row transition metal complexes containing redox active Schiff base ligands.  

PubMed

The reversible redox isomerisms in first row transition metal complexes of the type ML2 were studied. The six ML2 complexes (M = Mn(III) (), Fe(II) (), Co(III) (), Ni(II) (), Cu(II) () and Zn(II) ()) were synthesized with a redox active Schiff base ligand [2-(3,5-di-tert-butyl-2-hydroxyphenylamino)-4-chlorophenol] (H3L) presenting different oxidation states from -2 to 0 (L(2-), L(-) and L(0)). EPR spectra and magnetic susceptibility measurements indicate the presence of complexes of the type [Mn(III)(L(2-))(L(-))] () with S = 1/2, [Fe(II)(L(-))2] () with S = 2, [Co(III)(L(2-))(L(-))] () with S = 1/2, [Ni(II)(L(-))2] () with S = 1, [Cu(II)(L(-))2] () with S = 1/2 and [Zn(II)(L(-))2] () with S = 0 at high temperatures. Temperature and solvents influence the electronic structures of the species and give several valence tautomers. At low temperatures these complexes present thermally induced metal-to-ligand (, , ) or ligand-to-ligand (in , ) electron transfer (partial or total), resulting in compounds of the type [Mn(IV)(L(2-))2] () with S = 1/2, [Fe(III)(L(-))(L(2-))] () with S = 1, [Ni(III)(L(2-))(L(-))] () with S = 0, [Cu(II)(L(2-))(L(0))] () with S = 1/2 and [Zn(II)(L(2-))(L(0))] () with S = 1. This electron transfer is in agreement with the general trend in the redox potentials of the first row transition metal ions from Mn(ii) to Zn(ii), and it allows us to prepare and stabilize reversibly switchable tautomeric forms in transition metal complexes with redox-active ligands. PMID:25233051

Sasmal, Ashok; Garribba, Eugenio; Gmez-Garca, Carlos J; Desplanches, Cdric; Mitra, Samiran

2014-11-14

298

Effect of the Schiff base complex diaqua-(N-salicylidene-l-glutamato)copper(II) monohydrate on human tumor cells.  

PubMed

The aim of our study was to estimate cytostatic/cytotoxic activity of the copper(II) Schiff base complex of the composition [Cu(N-salicylidene-l-glutamato)(H2O)2]H2O, further Cu(SG-L)H2O, against human colon carcinoma cell line HT-29, as well as to determine type of cell death and to find out the molecular mechanism of apoptosis induced by this complex. Two highest concentrations (50, 100 mol/l) of the complex showed a strong cytotoxic activity against human colon carcinoma cells HT-29 after 72 h of influence. Other concentrations had a cytostatic activity. Unchelated copper(II) ions and free ligands had no effect on the cell growth. Cu(SG-L)H2O preferentially reduced cancer cell viability compared to healthy cells (NIH-3T3). Cu(SG-L)H2O induced apoptosis of cells HT-29 at all concentrations used (1-100 mol/l) after 48 h of influence. Apoptosis was carried out by the mitochondrial pathway with active caspases 3 and 9. By the spin-trapping technique combined with electron paramagnetic resonance we found that our complex is photochemically stable in aqueous systems and does not exhibit radical-scavenging activity when 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) cation radical was used as an oxidant. The complex exhibits a strong prooxidant property in the initial stages of thermal decomposition of K2S2O8 in water solutions leading to the massive production of ()OH radicals. Therefore, this complex could strongly participate in anticancer action via a free radical mechanism. PMID:24113525

Konarikova, Katarina; Andrezalova, Lucia; Rapta, Peter; Slovakova, Marianna; Durackova, Zdenka; Laubertova, Lucia; Gbelcova, Helena; Danisovic, Lubomir; Bohmer, Daniel; Ruml, Tomas; Sveda, Martin; Zitnanova, Ingrid

2013-12-01

299

Some new nano-structure zinc(II) coordination compounds of an imidazolidine Schiff base: spectral, thermal, antimicrobial properties and DNA interaction.  

PubMed

Some novel nano-sized structure zinc complexes of a new Schiff base ligand entitled as (3-nitro-benzylidene)-{2-[2-(3-nitro-phenyl)-imidazolidine-1-yl]-ethyl}-amine(L) with general formula of ZnLX2 wherein X=Cl(-), Br(-), I(-), SCN(-) and N3(-) have been synthesized under ultrasonic conditions. The ligand and its complexes have been characterized by elemental analysis, molar conductance measurements, FT-IR, (1)H and (13)C NMR and UV-Visible spectroscopy. The resulting data from spectral investigation especially (1)H and (13)C NMR well confirmed formation of an imidazolidine ring in the ligand structure. Transmission electron microscopy (TEM) showed nano-size structures with average particle sizes of 21.80-78.10nm for the zinc(II) Schiff base complexes. The free Schiff base and its Zn(II) complexes have been screened in vitro both for antibacterial activity against some gram-positive and gram-negative bacteria and also for antifungal activity. The metal complexes were found to be more active than the free Schiff base ligand. The results showed that ZnL(N3)2 is the most effective inhibitor against Escherichia coli, Pseudomonas aereuguinosa, Staphylococcus aureus and Candida albicans while ZnLBr2 was found to be more effective against Bacillus subtillis than other compounds. Moreover, DNA cleavage potential of all compounds with plasmid DNA was investigated. The results showed that the ligand and ZnLCl2 complex cleave DNA more efficiently than others. In final, thermal analysis of ligand and its complexes revealed that they are decomposed via 2-3 thermal steps in the range of room temperature to 1000C. Furthermore some activation kinetic parameters such as A, E(*), ?H(*), ?S(*) and ?G(*) were calculated based on TG/DTA plots by use of coats - Redfern relation. Positive values of activation energy evaluated for the compounds confirmed the thermal stability of them. In addition to, the positive ?H(*), and ?G(*) values suggested endothermic character for the thermal decomposition steps. PMID:24747864

Montazerozohori, Morteza; Musavi, Sayed Alireza; Naghiha, Asghar; Zohour, Mostafa Montazer

2014-08-14

300

Preparation and structure investigation of novel Schiff bases using spectroscopic, thermal analyses and molecular orbital calculations and studying their biological activities  

NASA Astrophysics Data System (ADS)

Two novel Schiffs bases (EB1 and L1) as new macrocyclic compounds were prepared via condensation reactions between bisaldehyde (2,2?-(ethane-1,2-diylbis(oxy))dibenzaldehyde): firstly with hydrazine carbothioamide to give (EB1), secondly with 4,6-diaminopyrimidine-2-thiol to give (L1). EB1 has a general formula C18H20N6O2S2 of mole mass = 416.520, and IUPAC name ((N,N?Z,N,N?E)-N,N?-(((ethane1,2diylbis(oxy))bis(2,1phenylene))bis(methanylylidene))bis(1hydrazinylmethanethioamide). L1 has a general formula C20H16N4O2S of mole mass = 376.10; and IUPAC name 1,2-bis(2-vinylphenoxy)ethane4,6-diaminopyrimidine-2-thiol). The structures of the compounds obtained were characterized based on elemental analysis, FT-IR and 1H NMR spectra, mass, and thermogravimetric analysis (TG, DTG). The activation thermodynamic parameters, such as, ?E*, ?H*, ?S* and ?G* were calculated from the TG curves using Coats-Redfern method. It is important to investigate their structures to know the active groups and weak bond responsible for their biological activities. The obtained thermal (TA) and mass (MS) practical results are confirmed by semi-empirical MO-calculation using PM3 procedure, on the neutral and positively charged forms of these novel Schiff bases. Therefore, comparison between MS and TA helps in selection of the proper pathway representing the decomposition of these compounds to give indication about their structures and consequently their biological activities. Their biological activities have been tested in vitro against Escherichia coli, Proteus vulgaris, Bacillissubtilies and Staphylococcus aurous bacteria in order to assess their antimicrobial potential.

Zayed, Ehab M.; Zayed, M. A.; El-Desawy, M.

2015-01-01

301

A series of transition and non-transition metal complexes from a N?O? hexadentate Schiff base ligand: Synthesis, spectroscopic characterization and efficient antimicrobial activities.  

PubMed

Some transition and non-transition metal complexes of the hexadentate N?O? donor Schiff base ligand 1,8-N-bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine, abbreviated to H?fsatrien, have been synthesized. All the 14 metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic (UV-Vis, IR, NMR, ESR) data. The analytical data helped to elucidate the structures of the metal complexes. The Schiff base, H?fsatrien, is found to act as a dibasic hexadentate ligand using N?N?O? donor set of atoms (leaving the COOH group uncoordinated) leading to an octahedral geometry for the complexes around all the metal ions except VO(+) and UO?(+). However, surprisingly the same ligand functions as a neutral hexadentate and neutral tetradentate one towards UO?(+) and VO(+), respectively. In case of divalent metal complexes they have the general formula [M(H?fsatrien)] (where M stands for Cu, Co, Hg and Zn); for trivalent metal complexes it is [M(H?fsatrien)]XnH?O (where M stands for Cr, Mn, Fe, Co and X stands for CH?COO, Cl, NO?, ClO?) and for the complexes of VO(+) and UO?(+), [M(H?fsatrien)]Y (where M=VO and Y=SO?); M=UO? and Y=2 NO?). The Schiff base ligand and most of the complexes have been screened in vitro to judge their antibacterial (Escherichia coli and Staphylococcus aureus) and antifungal (Aspergillus niger and Pencillium chrysogenum) activities. PMID:20801711

Sarkar, Saikat; Dey, Kamalendu

2010-11-01

302

Metal complexes of a new potentially heptadentate(N 7) tripodal Schiff base ligand. Synthesis, NMR studies and ab initio calculations  

Microsoft Academic Search

Tris(3-aminopropyl)amine, 2-pyridinecarboxaldehyde and a number of metal ions were used to prepare metal complexes of a new fully condensed potentially heptadentate(N7) tripodal Schiff base ligand (L333). The resulting complexes, [M(L333)](ClO4)2 {M= Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II); L333=[N(CH2CH2CH2NCH(C5H4N))3]}, were characterized by microanalysis, IR and electronic spectra in all cases and by NMR spectra in the case of Zn(II)

Sadegh Salehzadeh; Seyed Amrollah Javarsineh; Hassan Keypour

2006-01-01

303

Synthesis, characterization, and X-ray crystal structure analysis of Cd(??) and Cu(II) complexes of an acyclic pentadentate Schiff base  

Microsoft Academic Search

Cd(??) and Cu(II) complexes of an acyclic pentadentate Schiff base were prepared by template condensation of two equivalents of 2-acetylpyridine with one equivalent of bis(3-aminopropyl)amine in methanol. The resulting complexes [CdL(NO3)]ClO4 (1) and [CuL](ClO4)2 CH3CN (2) were characterized by X-ray crystallography, elemental analysis, IR and mass spectrometry in both cases and by NMR in the case of 1. The

Sadegh Salehzadeh; Reza Golbedaghi; Allan G. Blackman

2010-01-01

304

Computational evidence of preferred energy and preferred binding energy in the formation of 1 + 1 versus 2 + 2 macrocyclic Schiff base complexes  

Microsoft Academic Search

This work reports a theoretical study on 1+1 versus 2+2 cyclocondensation reactions between 2,6-diacetylpyridine and 3,6-dioxaoctane-l,8-diamine in the presence of Mg(II) and Pb(II) metal ions. The results of calculations at DFT(B3LYP) level of theory using LanL2DZ, SDD and CEP-121G basis sets were consistent with the experimental observations and all showed that 1+1 and 2+2 macrocyclic Schiff base complexes are preferred

Sadegh Salehzadeh; Mehdi Bayat

2011-01-01

305

A theoretical study on the formation of 1 + 1 versus 2 + 2 macrocyclic Schiff base complexes in the absence of coordinated anions  

Microsoft Academic Search

This work reports a theoretical study on 1+1 against 2+2 cyclocondensation reactions between 2,6-diacetylpyridine and 3,6-dioxaoctane-l,8-diamine in the presence of Mg(II) and Pb(II) metal ions. The results of calculations at DFT(B3LYP) level of theory using LanL2DZ, SDD and CEP-121G basis sets indicate that in the absence of a coordinated anion the 1+1 macrocyclic Schiff base complexes are the preferred products

Sadegh Salehzadeh; Mehdi Bayat

2011-01-01

306

Synthesis, characterization, and crystal structure of a Ni(II) complex of an acyclic pentadentate Schiff base; an agreement between the experimental and theoretical results  

Microsoft Academic Search

A Ni(II) complex of an acyclic pentadentate Schiff base was prepared by template condensation of two equivalents of 2-acetylpyridine with one equivalent of bis(3-aminopropyl)amine in the presence of Ni(II) in methanol. The resulting complex, [NiL33(MeOH)](ClO4)2 CH3OH, was characterized by X-ray crystallography, elemental analysis, and IR spectrophotometry. The X-ray crystallographic structure revealed a six-coordinate, distorted octahedral geometry in which the

Sadegh Salehzadeh; Reza Golbedaghi; Hamid Reza Khavasi

2009-01-01

307

A novel chelate-assisted C?C bond formation on a Cd(II) complex of an asymmetric heptadentate(N 7) tripodal Schiff base ligand  

Microsoft Academic Search

Cadmium(II) complexes of some potentially heptadentate tripodal Schiff base ligands with the general formula N{(CH2)nNCHC5H4N}2{(CH2)mNCHC5H4N}) (where n=m=2, L222; n=2, m=3, L322; n=3, m=2, L332) have been studied. These ligands are products of the full condensation of a number of tripodal tetraamines with 2-pyridinecarboxaldehyde. An unusual reaction of an additional 2-pyridine-carboxaldehyde with a methylene group adjacent to the imine bond only

Sadegh Salehzadeh; Michael D. Ward; Harry Adams

2009-01-01

308

Synthesis of novel p-tert-butylcalix[4]arene Schiff bases and their complexes with C60, potential HIV-Protease inhibitors  

NASA Astrophysics Data System (ADS)

Some p-tert-butylcalix[4]arene Schiff base crown ethers were synthesized, characterized using 1H, 13C-NMR, DEPT 135 and Mass spectrometry. Their complexes with C60 were isolated and characterized. The inhibition effect of these complexes on HIVP was studied and found that complexes of 9 and 10 have comparable Ki values to Pepstatine which is known as HIVP inhibitor and used as a control. The synthesis of the ligands, complexes and the inhibition behavior are discussed in this article.

Khadra, Khalid Abu; Mizyed, Shehadeh; Marji, Deeb; Haddad, Salim F.; Ashram, Muhammad; Foudeh, Ayat

2015-02-01

309

Synthesis and Crystal Structure of a Dibridged Dinuclear Cadmium(II) Complex with Schiff Base 2-[(2-Dimethylaminoethylimino)methyl]-6-methoxyphenol  

Microsoft Academic Search

A tetradentate Schiff base compound 2-[(2-dimethylaminoethylimino)methyl]-6-methoxyphenol (HL) reacts with cadmium nitrate and ammonium thiocyanate in a methanol solution to give a dinuclear complex [Cd2L2(?1,1-NCS)(NCS)(OH2)]. The complex was characterized by physico-chemical and spectroscopic methods. X-ray crystallography indicates that each Cd(II) atom is in a distorted octahedral coordination. The two metal atoms are bridged by one phenolate O and one end-on thiocyanate

San-Jun Peng; Hai-Yun Hou; Qiong Wang; Tao Yang; Cong-Shan Zhou

2008-01-01

310

Infrared and DNA-binding on ultraviolet and fluorescence spectra of new copper and zinc complexes with a naringenin Schiff-base ligand  

NASA Astrophysics Data System (ADS)

A naringenin Schiff-base ligand (H 3L) and its copper(II) and zinc(II) complexes have been synthesized and characterized by elemental analyses, molar conductivities, 1H NMR, IR spectra, UV spectra and thermal analyses. The DNA-binding properties of the Cu(II) and Zn(II) complexes have been investigated by fluorescence spectroscopy, ultraviolet spectroscopy and by viscosity measurements. The results indicate that complexes and ligand may bind to DNA by intercalation modes, but the binding affinity of the complexes is much higher than that of the ligand.

Li, Yan-hua; Wang, Bao-dui; Yang, Zheng-yin

2007-06-01

311

Cu(II) Schiff base complex as a highly efficient catalyst for the synthesis of polyhydroquinoline derivatives via Hantzsch condensation in water.  

PubMed

In the present study, Cu(II) Schiff-base complex is introduced as a highly efficient and green solid catalyst for the unsymmetrical Hantzsch condensation through a four-component coupling of various aldehydes, dimedone, ethyl acetoacetate and ammonium acetate to form polyhydroquinoline derivatives in good to excellent yields. This reaction was carried out in the presence of 1 mol% of catalysts in water at room temperature. The reusability of the catalysts was demonstrated by a five-run test. Remarkable features of this new procedure are cleaner reaction profiles, shorter reactiontimes, simple experimental and work-up procedures. PMID:23701007

Vahdat, Seyed Mohammad

2013-12-01

312

A Schiff Base-Derived Copper (II) Complex Is a Potent Inducer of Apoptosis in Colon Cancer Cells by Activating the Intrinsic Pathway  

PubMed Central

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??g/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??g/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

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

313

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)

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.

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

2013-09-01

314

Potency of photoinduced electron transfer and antioxidant efficacy of pyrrole and pyridine based Cu(II)-Schiff complexes while binding with CT-DNA.  

PubMed

Here we report a systematic and comparative study to define a correlation between the structure and function of a series of simple, biologically active small inorganic Schiff base copper complexes for the occurrence of charge transfer phenomenon in calf thymus DNA (CT-DNA) using transient absorption spectroscopy corroborated with magnetic field effect. Four copper(II) Schiff base complexes with differently substituted heterocyclic ligands with antioxidant activity have been used. The binding constants of the order of ? 10(4) support the moderate binding affinity of the complexes towards CT-DNA. The methyl-substituted pyrrole complex shows maximum binding affinity (Kb: 8.33 10(4)) compared to others. The occurrence of photoinduced electron transfer (PET) from CT-DNA to pyrrole containing complexes has been confirmed by identifying the corresponding transient radical ions whereas the extent of PET with pyridine substituted complexes is too small to be observed. The increase of the yield of radical ions in presence of magnetic field depicts that the initial spin correlation in geminate radical ion pair is triplet. The difference between experimental and calculated B values, the measure of hyperfine interactions (HFI) present in the system, arises due to hole hopping through intrastrand and interstrand DNA bases. The unsubstituted pyrrole complexes cleave DNA much more than the methyl-substituted one. Therefore, the probability of intrastrand superexchange increases with methyl-substituted complexes, that reduces the rate of hole hopping and hence the B value. PMID:24602815

Koley Seth, Banabithi; Ray, Aurkie; Saha, Arpita; Saha, Partha; Basu, Samita

2014-03-01

315

Palladium(II) and zinc(II) complexes of neutral [N2O2] donor Schiff bases derived from furfuraldehyde: synthesis, characterization, fluorescence and corrosion inhibitors of ligands.  

PubMed

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)2H2O. 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. PMID:24858346

Ali, Omyma A M

2014-11-11

316

A novel highly selective colorimetric sensor for aluminum (III) ion using Schiff base derivative  

NASA Astrophysics Data System (ADS)

A novel colorimetric sensor, 2-hydroxy naphthaldehyde isonicotinoyl hydrazone (HINH), was easily synthesized by the condensation of isoniazid and 2-hydroxy-1-naphthaldehyde. The as-prepared compound showed effective colorimetric single selectivity and high sensitivity for aluminum cation in CH3CN/H2O (1:3) binary solutions. The detection limit is 1.0 10-8 M Al3+ based on UV-vis changes.

Wang, Dong-Fang; Ke, Ying-Chang; Guo, Hong-Xu; Chen, Jianhua; Weng, Wen

2014-03-01

317

Construction and NIR luminescent property of hetero-bimetallic Zn Nd complexes from two chiral salen-type Schiff-base ligands  

NASA Astrophysics Data System (ADS)

Two new near-infrared (NIR) luminescent Zn-Nd complexes [ZnL 1Nd(OAc)(NO 3) 2] ( 3) and [ZnL 2Nd(DMF) 2(NO 3) 3] ( 4) have been obtained with two salen-type Schiff-base ligands H 2L 1 and H 2L 2, ( H 2L 1 = N, N'-bis(3-methoxysalicylidene)-(1s, 2s)-(-)1,2-dipheneylethylenediamine and H 2L 2 = N, N'-bis(3-methoxysalicylidene)-(s)-2,2-diamine-1,1'-binaphthyl) from the reaction of different chiral diamines with o-vanillin. The X-ray crystal structure analysis reveals that both of them crystallize in the chiral space groups with P2(1), a = 10.1669(6), b = 19.3775(11), c = 17.4639(10) , ? = 94.8710(10), V = 3428.1(3) 3, Z = 4 for 3, and C2, a = 22.1914(13), b = 9.7886(6), c = 22.0138(13) , ? = 118.9590(10), V = 4372.5(4) 3, Z = 4 for 4. Complexes 3- 4 are both dinuclear Zn-Nd structures, while suitable choice of chiral Schiff-base ligands could induce the different complexions of ligands and metal ions, and the functional control of ligand character shows a potentially effective way to the fine-tuning properties of NIR luminescence from Nd ions.

Bi, Wei-Yu; L, Xing-Qiang; Chai, Wen-Li; Song, Ji-Rong; Wong, Wai-Yeung; Wong, Wai-Kwok; Jones, Richard A.

2008-11-01

318

Synthesis, characterization and electrochemical behaviour of cobalt(II) and cobalt(III):O 2- complexes, respectively, with linear and tripodal tetradentate ligands derived from Schiff bases  

NASA Astrophysics Data System (ADS)

New octahedral cobalt complexes with linear and tripodal tetradentate ligands derived from Schiff bases have been synthesized and characterized using elemental analysis, molar conductance, IR spectra, magnetic measurements, electronic and ESR spectra. The experimental results support the binding of linear ligands with two N and two O donor sites to cobalt ion. They show a square planar geometry and tripodal ligands coordinated to the metal ion by only one nitrogen atom, giving an arrangement of NO 3 donor groups, the other axial sites being occupied by the molecular oxygen and/or the aquo molecules. From the results of cyclic voltammetry it is shown that chelate structure and ligand geometry and electron donating effect of the ligand substituents are among the factors influencing the redox potentials of the complexes. Linear ligands lead to high-spin cobalt(II) complexes. They do not interact with dioxygen and stabilize the Co(II) state counter to their related Schiff-base complexes. The low-spin complexes with tripodal ligands are O 2 adducts and the configuration in these complexes is best formulated as [Co IIIO 2-].

Djebbar-Sid, S.; Benali-Baitich, O.; Deloume, J. P.

2001-07-01

319

Synthesis, spectroscopy and biological investigations of manganese(III) Schiff base complexes derived from heterocyclic ?-diketone with various primary amine and 2,2'-bipyridyl  

NASA Astrophysics Data System (ADS)

The mixed ligand mononuclear complex [Mn(bipy)(HPMFP)(OAc)]ClO 4 was synthesized by reaction of Mn(OAc) 32H 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 ? S*, enthalpy change ? 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.

Surati, Kiran R.

2011-06-01

320

Synthesis and characterization of Ni(II), Cu(II) and Zn(II) complexes with new macrocyclic Schiff base ligands containing piperazine moiety  

NASA Astrophysics Data System (ADS)

Two new macrocyclic Schiff base ligands L 1 and L 2 from [1 + 1] and [2 + 2] condensation reaction, respectively, have been obtained in a one-pot synthesis starting from 1,4-bis(2-formylphenyl)piperazine and 2,2-dimethyl-propylendiamine. Unfortunately, because of the low solubility of two products, we were unable to separate them effectively. Macrocyclic Schiff base complexes [NiL 1](ClO 4) 2, [CuL 1](ClO 4) 2 and [ZnL 1](ClO 4) 2 were prepared from the reaction of a mixture of L 1 and L 2 in the presence of nickel(II), copper(II) and zinc(II) metal ions, respectively. In all cases, only [1 + 1] condensation products were obtained and no metal complexes were isolated with the L 2 macrocycle. All of complexes have been characterized by elemental analysis, IR spectra, FAB-MS, conductivity measurements and in the case of Zn(II) complex by 1H and 13C NMR spectroscopy. Crystal structures of [NiL 1](ClO 4) 2 and [NiL 1'](ClO 4) 2 complexes have been also determined. The Ni(II) is coordinated to the ligand L 1 and L 1' by two nitrogen atoms of piperazine group and two nitrogen atoms of the imine groups, in a slightly distorted square-planar geometry.

Keypour, Hassan; Arzhangi, Parisa; Rahpeyma, Nasibeh; Rezaeivala, Majid; Elerman, Yalcin; Bykgngr, Orhan; Valencia, Laura; Khavasi, Hamid Reza

2010-08-01

321

Spectral characterization, optical band gap calculations and DNA binding of some binuclear Schiff-base metal complexes derived from 2-amino-ethanoic acid and acetylacetone  

NASA Astrophysics Data System (ADS)

Bi-nuclear metal complexes derived from the 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-ethanoic acid (glycine) and acetylacetone have been synthesized and characterized by elemental analyses, Raman spectra, FT-IR, ES-MS, UV-Vis., 1H NMR, ESR, thermal analyses (TG, DTG and DTA) and magnetic measurements. The results showed that, the Schiff base ligand can bind two metal ions in the same time. It coordinates to the first metal ion as mono-negative bi-dentate through azomethine nitrogen and enolic carbonyl after deprotonation. At the same time, it binds to the second metal ion via carboxylate oxygen after deprotonation. The thermodynamic parameters E?, ?H?, ?G? and ?S? have been calculated by Coats-Redfern (CR) and Horowitz-Metzger (HM) methods. The optical band gaps of the isolated complexes have been calculated from absorption spectra and the results indicated semi-conducting nature of the investigated complexes. The interactions between the copper (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.

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

2015-01-01

322

Substitutional group dependent colori/fluorimetric sensing of Mn2+, Fe3+ and Zn2+ ions by simple Schiff base chemosensor  

NASA Astrophysics Data System (ADS)

Schiff base is one of the easiest synthesizable chemosensor and exhibit strong coordination with metal ions; the property that has been vastly exploited for metal ions sensing. Simple Schiff base chemosensors (1a-d and 2a-d) were synthesized and demonstrated substitutional group dependent colorimetric sensing of metal ions. Chemosensor without (1a, 2a) and OCH3 substitution (1b, 2b) did not show any significant colour change for metal ions. However, a highly selective colorimetric change (colourless to pink) for Mn2+ ions (10-6 M) was observed with diethylamine substituted 1c, 2c. Hydroxyl substitution (1d, 2d) leads to selective colorimetric sensing (colourless to orange) of Fe3+ ions (10-6 M). PVA thin films of 2c/2d were fabricated and demonstrated selective colorimetric sensing of Mn2+ and Fe3+ ions. The practical applicability of the synthesized chemosensors were also demonstrated by performing selective colorimetric sensing of Mn2+ and Fe3+ ions in real samples such as tap, ground, pond and river water. Effect of substitution on the fluorescence selectivity of Zn2+ has also been investigated.

Hariharan, P. S.; Anthony, Savarimuthu Philip

2015-02-01

323

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)

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.

Emara, Adel A. A.

2010-09-01

324

Spin Crossover Properties of Iron(ii) Complexes with a N4O2 Donor Set by Extended ?-CONJUGATED Schiff-Base Ligands  

NASA Astrophysics Data System (ADS)

The preparation and magnetic properties of three Fe(II) Schiff-base complexes, [Fe(qnal-21)2]CH2Cl2 (1), [Fe(qnal-12)2]2C6H6 (2) and [Fe(Hqsalc)2] (3), (Hqnal-21 = N-(8'-quinolyl)-2-hydroxy-1-naphthaldimine, Hqnal-12 = N-(8'-quinolyl)-1-hydroxy-2-naphthaldimine, H2qsalc = 4-hydroxy-3-[(8-quinolinylimino)methyl]benzoic acid) are reported. X-ray single crystal structure analyses of 1 and 2 reveal that an Fe(II) ion in each complex is coordinated by two Schiff-base ligands, qnal-21 or qnal-12, in a meridional fashion. Molecular packing of 2 shows that a qnal-12 interacts with neighboring two qnal-12's through ?-? interactions, which results in the formation of one-dimensional chain. Although the magnetic property of 2 shows a high-spin state at all the temperature range measured, the ?T-T plot of 3 shows abrupt spin crossover behavior with a wide hysteresis of 21 K, probably due to the hydrogen-bond network originated by carboxyl groups.

Kuroda, Takayoshi

2013-09-01

325

DNA binding, cytotoxicity and apoptosis induction activity of a mixed-ligand copper(II) complex with taurine Schiff base and imidazole  

NASA Astrophysics Data System (ADS)

A novel binuclear copper(II) complex (complex 1) with taurine Schiff base and imidazole has been synthesized and structurally characterized by single crystal X-ray diffraction, elemental analysis, ESI-MS spectrometry, UV-vis and IR spectroscopy. Single-crystal analysis revealed that 1 displays the sulfonate-bridged dinuclear copper(II) centers. Both copper atoms are five-coordinated and exhibit slightly distorted square pyramidal geometries. Each of copper atom is surrounded by three oxygen atoms and one nitrogen atom from different taurine Schiff base ligands, and one nitrogen atom from one imidazole ligand. The interaction between 1 and calf thymus DNA (CT-DNA) was investigated by UV-vis, fluorescence, circular dichroism (CD) spectra and agarose gel electrophoresis. The experimental results indicated that 1 could bind to CT-DNA via an intercalative mode and show efficient cleavage activity. In addition, 1 showed an antitumor effect on cell cycle and apoptosis. Flow cytometric analysis revealed that MGC-803 cells were arrested in the S phase after treatment with 1. Fluorescence microscopic observation indicated that 1 could induce apoptosis of MGC-803 cells.

Li, Mei; kong, Lin Lin; Gou, Yi; Yang, Feng; Liang, Hong

2014-07-01

326

Distinguishable Zn(II) and Pb(II) template effects on forming pendant-armed Schiff-base macrocyclic complexes including a remarkable Pb(II)-? macrocyclic complex.  

PubMed

36-Membered [2 + 2] half-fold Schiff-base macrocyclic dinuclear Zn(II) complexes (1a and 1b) and 18-membered [1 + 1] Schiff-base macrocyclic mononuclear Pb(II) complexes (2 and 3) are produced from the condensation between 1,3-propanediamine and a pair of extended dialdehydes with different functional pendant arms (H2hpdd and H2pdd) because of the distinguishable cationic template effects. It is very interesting to mention that a unique intramolecular Pb(II)-? macrocyclic complex 2 with an uncommon ?(3)-coordination type is achieved under ambient conditions and it can remain stable both in the solid state and in solution. The subtle variations of pendant-arms in the macrocyclic ligands H2hpdd and H2pdd yield different Pb(II) complexes, where the competition between Pb(II)-? and Pb(II)-NO3(-) electrostatic interactions as well as the combination of steric and electronic effects of pendant arms are believed to play important roles. PMID:25188754

Zhang, Kun; Geng, Jiao; Jin, Chao; Huang, Wei

2014-11-01

327

Synthesis, spectroscopy and biological investigations of manganese(III) Schiff base complexes derived from heterocyclic ?-diketone with various primary amine and 2,2'-bipyridyl.  

PubMed

The mixed ligand mononuclear complex [Mn(bipy)(HPMFP)(OAc)]ClO(4) was synthesized by reaction of Mn(OAc)(3)2H(2)O 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 (1)H and (13)C 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 ?S*, enthalpy change ?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. PMID:21458364

Surati, Kiran R

2011-06-01

328

[Mn(III)(Schiff base)]?[Re(IV)(CN)?], highly anisotropic 3D coordination framework: synthesis, crystal structure, magnetic investigations, and theoretical analysis.  

PubMed

A new highly anisotropic coordination heterobimetallic polymer [Mn(III)(Schiff-base)]3[Re(IV)(CN)7] was synthesized and characterized structurally and magnetically. The single crystal X-ray analysis has revealed that this is the first framework among the complexes composed of homoleptic cyanometallate and Mn(III) complex of the tetradentate Schiff base ligand. A formation of 3D assembly is possible due to both the pentagonal bipyrimidal geometry of the cyanometallate unit and suitable size of constituents: [Re(CN)7](3-) and [Mn(III)(acacen)](+), where acacen = N,N'-ethylenebis(acetylacetoneiminato). The powder and crystal magnetic studies show that the compound undergoes an antiferromagnetic ordering of a complicated character below Neel temperature of 13 K, and exhibits a metamagnetic behavior and strong magnetic anisotropy similar to those observed in related 3D Mn(II)-[Mo(CN)7](4-) systems. Unusual magnetic properties of [Mn(III)(acacen)]3[Re(IV)(CN)7] (1) originate from an interplay of Re-Mn anisotropic spin coupling and ZFS effect of Mn(III) ions with a noncollinear orientation of the local magnetic axes in the cyano-bridged 3D network. A theoretical model of anisotropic spin coupling between orbitally degenerate [Re(IV)(CN)7](3-) complexes and Mn(III) ions is developed, and specific microscopic mechanisms of highly anisotropic spin coupling in Re(IV)-CN-Mn(III) linkages in complex 1 are analyzed in detail. PMID:25250555

Samsonenko, Denis G; Paulsen, Carley; Lhotel, Elsa; Mironov, Vladimir S; Vostrikova, Kira E

2014-10-01

329

Synthesis, spectroscopic and catalytic studies of Cu(II), Co(II) and Ni(II) complexes immobilized on Schiff base modified chitosan  

NASA Astrophysics Data System (ADS)

A new class of bidentate (N, O) Schiff base ligand (L) has been derived from the functional biopolymer (chitosan) and 1,2-diphenylethanedione in 1:1 M ratio. This ligand has been used to synthesise the new first row transition metal complexes of Cu(II), Co(II) and Ni(II). The structural properties of the ligand and the synthesized tetra-coordinated complexes have been investigated by elemental analysis, magnetic study, molar conductance measurement and spectroscopic methods viz. FT-IR, UV-Vis., 1H NMR, 13C NMR and XRD. The spectral evidences strongly suggested the square planar geometry to the complexes. The XRD studies proved that crystallinity of chitosan has been diminished after Schiff base formation and metal complexation of L. Thermal and surface properties of the complexes have been also discussed from the investigation of their TG-DTG curves and SEM images, respectively. In addition, the catalytic efficiency of these complexes has been studied in the cyclohexane oxidation reaction using H2O2 as oxidant at 70 C.

Antony, R.; Theodore David Manickam, S.; Saravanan, K.; Karuppasamy, K.; Balakumar, S.

2013-10-01

330

Synthesis, experimental and theoretical characterization of N,N'-dipyridoxyl (1,4-butanediamine) Schiff-base ligand and its Cu(II) complex.  

PubMed

A new N,N'-dipyridoxyl(1,4-butanediamine) [=H(2)BS] Schiff-base ligand and its Cu(II) salen complex, [Cu(BS)(H(2)O)(CH(3)OH)], were synthesized and characterized by IR, UV-vis, (1)H NMR, mass spectrometry and elemental analysis. Also, full optimization of the geometries, (1)H NMR chemical shifts (for the H(2)BS) and vibrational frequencies were calculated by using density functional theory (DFT) method. Structure of the H(2)BS ligand is not planar, i.e. two pyridine rings are not in the same plane. In the structure of the Cu complex, the Schiff-base ligand acts as a dianionic tetradentate ligand in N, N, O(-), O(-) manner. The coordinating atoms of BS(2-) occupy equatorial positions of the octahedral complex, where the H(2)O and CH(3)OH ligands locate at axial positions. The calculated results are in good agreement with the experimental data, confirming the suitability of the proposed and optimized structures for the H(2)BS ligand and its Cu complex. PMID:21233009

Eshtiagh-Hosseini, Hossein; Housaindokht, Mohammad R; Beyramabadi, S Ali; Tabatabaei, S Hamid Mir; Esmaeili, Abbas Ali; Khoshkholgh, Malihe Javan

2011-03-01

331

Anion receptors based on highly fluorinated aromatic scaffolds.  

PubMed

Mono-, di-, and tri-pentafluorobenzyl-substituted hexafluorobenzene (HFB) scaffolds, viz., R(I), R(II), and R(III) are proposed as promising receptors for molecules of chemical, biological, and environmental relevance, viz., N2, O3, H2O, H2O2, F(-), Cl(-), BF4(-), NO3(-), ClO(-), ClO2(-), ClO3(-), ClO4(-), and SO4(2-). The receptor-guest complexes modeled using M06L/6-311++G(d,p) DFT show a remarkable increase in the complexation energy (E(int)) with an increase in the number of fluorinated aromatic moieties in the receptor. Electron density analysis shows that fluorinated aromatic moieties facilitate the formation of large number of lone pair-? interactions around the guest molecule. The lone pair strength of the guest molecules quantified in terms of the absolute minimum (V(min)) of molecular electrostatic potential show that E(int) strongly depends on the electron deficient nature of the receptor as well as strength of lone pairs in the guest molecule. Compared to HFB, R(I) exhibits 1.1-2.5-fold, R(II) shows 1.6-3.6-fold, and the bowl-shaped R(III) gives 1.8-4.7-fold increase in the magnitude of E(int). For instance, in the cases of HFBF(-), R(I)F(-), R(II)F(-), and R(III)F(-) the E(int) values are -21.1, -33.7, -38.1, and -50.5 kcal/mol, respectively. The results strongly suggest that tuning lone pair-? interaction provides a powerful strategy to design receptors for small molecules and anions. PMID:24869653

Mohan, Neetha; Suresh, Cherumuttathu H

2014-06-19

332

Hydrolysis of Letrozole catalyzed by macrocyclic Rhodium (I) Schiff-base complexes.  

PubMed

Ten mononuclear Rhodium (I) complexes were synthesized by macrocyclic ligands having N4 and N2O2 donor sites. Square planar geometry is assigned based on the analytical and spectral properties for all complexes. Rh(I) complexes were investigated as catalysts in hydrolysis of Nitrile group containing pharmaceutical drug Letrozole. A comparative study showed that all the complexes are efficient in the catalysis. The percent yields of all the catalytic reaction products viz. drug impurities were determined by spectrophotometric procedures and characterized by spectral studies. PMID:25554950

Reddy, P Muralidhar; Shanker, K; Srinivas, V; Krishna, E Ravi; Rohini, R; Srikanth, G; Hu, Anren; Ravinder, V

2015-03-15

333

Preparation and antitubercular activities in vitro and in vivo of novel Schiff bases of isoniazid.  

PubMed

Structural modification of the frontline antitubercular isonicotinic acid hydrazide (INH) provides lipophilic adaptations (3-46) of the drug in which the hydrazine moiety of the parent compound has been chemically blocked from the deactivating process of N(2)-acetylation by N-arylaminoacetyl transferases. As a class, these compounds show high levels of activity against Mycobacterium tuberculosis in vitro and in tuberculosis-infected macrophages. They provide strong protection in tuberculosis-infected mice and have low toxicity. With some representatives of this class achieving early peak plasma concentrations approximately three orders of magnitude above minimum inhibitory concentration, they may serve as tools for improving our understanding of INH-based treatment modalities, particularly for those patients chronically underdosed in conventional INH therapy. PMID:19524330

Hearn, Michael J; Cynamon, Michael H; Chen, Michaeline F; Coppins, Rebecca; Davis, Jessica; Joo-On Kang, Helen; Noble, Abigail; Tu-Sekine, Becky; Terrot, Marianne S; Trombino, Daniella; Thai, Minh; Webster, Eleanor R; Wilson, Rebecca

2009-10-01

334

Preparation and antitubercular activities in vitro and in vivo of novel Schiff bases of isoniazid  

PubMed Central

Structural modification of the frontline antitubercular isonicotinic acid hydrazide (INH) provides lipophilic adaptations (3-46) of the drug in which the hydrazine moiety of the parent compound has been chemically blocked from the deactivating process of N2-acetylation by N-arylaminoacetyl transferases. As a class, these compounds show high levels of activity against Mycobacterium tuberculosis in vitro and in tuberculosis-infected macrophages. They provide strong protection in tuberculosis-infected mice and have low toxicity. With some representatives of this class achieving early peak plasma concentrations approximately three orders of magnitude above minimum inhibitory concentration, they may serve as tools for improving our understanding of INH-based treatment modalities, particularly for those patients chronically underdosed in conventional INH therapy. PMID:19524330

Hearn, Michael J.; Cynamon, Michael H.; Chen, Michaeline F.; Coppins, Rebecca; Davis, Jessica; Kang, Helen Joo-On; Noble, Abigail; Tu-Sekine, Becky; Terrot, Marianne S.; Trombino, Daniella; Thai, Minh; Webster, Eleanor R.; Wilson, Rebecca

2009-01-01

335

Synthesis, characterization and antimicrobial activities of mixed ligand transition metal complexes with isatin monohydrazone Schiff base ligands and heterocyclic nitrogen base  

NASA Astrophysics Data System (ADS)

Mixed ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II) with various uninegative tridentate ligands derived from isatin monohydrazone with 2-hydroxynapthaldehyde/substituted salicylaldehyde and heterocyclic nitrogen base 8-hydroxyquinoline have been synthesized and characterized by elemental analysis, conductometric studies, magnetic susceptibility and spectroscopic techniques (IR, UV-VIS, NMR, mass and ESR). On the basis of these characterizations, it was revealed that Schiff base ligands existed as monobasic tridentate ONO bonded to metal ion through oxygen of carbonyl group, azomethine nitrogen and deprotonated hydroxyl oxygen and heterocyclic nitrogen base 8-hydroxyquinoline existed as monobasic bidentate ON bonded through oxygen of hydroxyl group and nitrogen of quinoline ring with octahedral or distorted octahedral geometry around metal ion. All the compounds have been tested in vitro against various pathogenic Gram positive bacteria, Gram negative bacteria and fungi using different concentrations (25, 50, 100, 200 ?g/mL) of ligands and their complexes. Comparative study of antimicrobial activity of ligands, and their mixed complexes indicated that complexes exhibit enhanced activity as compared to free ligands and copper(II) Cu(LIV)(Q)?H2O complex was found to be most potent antimicrobial agent.

Devi, Jai; Batra, Nisha

2015-01-01

336

Sandwich complexes based on the "all-metal" Al4 2- aromatic ring.  

PubMed

We report on novel sandwichlike structures [Al(4)MAl(4)](q-) (q=0-2 and M=Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W) based on the recently synthesized all-metal aromatic Al(4)(2-) square ring. The sandwichlike structures have two aromatic tetraaluminum square rings which trap a transition-metal cation from either the first, second, or third row. The stability of the anionic sandwichlike complexes towards electron detachment is discussed, and addition of alkali cations is found to stabilize the 2- charged complexes, preventing spontaneous electron detachment. Once the sandwichlike complexes are formed, the Al(4)(2-) square properties remain nearly unchanged; this fact strongly supports the hypothesis that in these complexes the Al(4)(2-) square rings remain aromatic. PMID:16683278

Mercero, Jose M; Formoso, Elena; Matxain, Jon M; Eriksson, Leif A; Ugalde, Jesus M

2006-06-01

337

Coal-tar-based pavement sealcoat, polycyclic aromatic Hydrocarbons (PAHs), and environmental health  

USGS Publications Warehouse

Studies by the U.S. Geological Survey (USGS) have identified coal-tar-based sealcoat-the black, viscous liquid sprayed or painted on asphalt pavement such as parking lots-as a major source of polycyclic aromatic hydrocarbon (PAH) contamination in urban areas for large parts of the Nation. Several PAHs are suspected human carcinogens and are toxic to aquatic life.

Mahler, B.J.; Van Metre, P.C.

2011-01-01

338

Surface-confined crystalline two-dimensional covalent organic frameworks via on-surface Schiff-base coupling.  

PubMed

We performed a co-condensation reaction between aromatic aldehyde and aromatic diamine monomers on a highly oriented pyrolytic graphite surface either at a solid/liquid interface at room temperature or in low vacuum with moderate heating. With this simple and moderate methodology, we have obtained surface-confined 2D covalent organic frameworks (COFs) with few defects and almost entire surface coverage. The single crystalline domain can extend to more than 1 ?m(2). By varying the backbone length of aromatic diamines the pore size of 2D surface COFs is tunable from ?1.7 to 3.5 nm. In addition, the nature of the surface COF can be modified by introducing functional groups into the aromatic amine precursor, which has been demonstrated by introducing methyl groups to the backbone of the diamine. Formation of small portions of bilayers was observed by both scanning tunneling microscopy (STM) and AFM, which clearly reveals an eclipsed stacking manner. PMID:23924203

Xu, Lirong; Zhou, Xin; Yu, Yanxia; Tian, Wei Quan; Ma, Jun; Lei, Shengbin

2013-09-24

339

Biological activity of palladium(II) and platinum(II) complexes of the acetone Schiff bases of S-methyl- and S-benzyldithiocarbazate and the X-ray crystal structure of the [Pd(asme) 2] (asme=anionic form of the acetone Schiff base of S-methyldithiocarbazate) complex  

Microsoft Academic Search

Palladium(II) and platinum(II) complexes of general empirical formula, [M(NS)2] (NS=uninegatively charged acetone Schiff bases of S-methyl- and S-benzyldithiocarbazate; M=PtII and PdII) have been prepared and characterized by a variety of physicochemical techniques. Based on conductance, IR and electronic spectral evidence, a square-planar structure is assigned to these complexes. The crystal and molecular structure of the [Pd(asme)2] complex (asme=anionic form of

Mohammad Akbar Ali; Aminul Huq Mirza; Raymond J Butcher; M. T. H Tarafder; Tan Boon Keat; A. Manaf Ali

2002-01-01

340

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

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. PMID:23747379

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

2013-09-01

341

Synthesis, characterization and antimicrobial evaluation of some new schiff, mannich and acetylenic Mannich bases incorporating a 1,2,4-triazole nucleus.  

PubMed

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. PMID:25412038

Aouad, Mohamed R

2014-01-01

342

Synthesis, spectral and antimicrobial studies of bis(cyclopentadienyl)titanium(IV) derivatives with Schiff bases derived from 2-amino-5-phenyl-1,3,4-thiadiazole.  

PubMed

The reactions of bis(cyclopentadienyl)titanium(IV) dichloride with Schiff bases derived by condensing 2- amino-5-phenyl-1,3,4-thiadiazole with benzaldehyde (SPT), 4-nitrobenzaldehyde (SNT), 4-methoxybenzaldehyde (SMT), 2-hydroxybenzaldehyde (SSTH) or 2-hydroxyacetophenone (SATH) have been studied in refluxing tetrahydrofuran and complexes of types [Cp(2)TiCl(SB)]Cl (SB= SPT, SNT or SMT) and [Cp(2)Ti(SB')]Cl (SB'H= SSTH or SATH) have been isolated. Tentative structural conclusions are drawn for these reaction products based upon elemental analyses, electrical conductance, magnetic moment and spectral (UV-vis, IR and (1)H NMR) data. Studies were conducted to assess the growth-inhibiting potential of the complexes synthesized, and the ligands, against various fungal and bacterial strains. PMID:18365105

Srivastava, A K; Pandey, O P; Sengupta, S K

2005-01-01

343

Oxophily of gadolinium(III) and synthesis of dissymmetric di(Schiff bases) and dissymmetric dinuclear compounds. Crystal structure of [Cu[sub 2]L[prime](OH)](ClO[sub 4])[sub 2][center dot]H[sub 2]O with L[prime] = 2-[N-(2-pyridylethyl)formimidoyl]-6-[N-((dimethylamino)propyl)formimidoyl]phenolato  

SciTech Connect

The strong oxophilic character of the Gd(III) ion has been utilized to protect one of the carbonyl functions of 2,6-diformyl-4-methylphenol, which has allowed the quantitative synthesis of mono(Schiff bases), then dissymmetric di(Schiff bases). The synthetic process is as follows: the reaction of 2,6-diformyl-4-methylphenol with a primary amine RNH[sub 2] in the presence of Gd(III) affords a complex in which Gd(III) is coordinated to two mono(Schiff bases) through their carbonyl and phenolic oxygen atoms. The mono(Schiff base) may be isolated by precipitation of Gd(III) in the form of gadolinium(III) oxalate. The reaction of another primary amine, R[prime]NH[sub 2], on this mono(Schiff base) affords a dissymmetric di(Schiff base), from which dissymmetric dinuclear compounds can be synthesized. For example, this reaction has been carried out with RNH[sub 2] = 2-(2-aminoethyl)pyridine and R[prime]NH[sub 2] = N,N-dimethylpropylenediamine. The mono(Schiff base) 2-formyl-6-(N-(2-pyridylethyl)formimidoyl)-4-methylphenol (HL) and the di(Schiff base) 2-[N-(2-pyridylethyl)formimidoyl]-6-[N-((dimethylamino)propyl)formimidoyl]-4-methylphenol (HL[prime]) have been unambiguously characterized from their [sup 1]H NMR spectra. The copper(II) dinuclear compound [CuL[prime](OH)](ClO[sub 4])[sub 2][center dot]H[sub 2]O obtained from this di(Schiff base) has been synthesized, and its crystal structure has been solved. 36 refs., 2 figs., 5 tabs.

Andruh, M.; Kahn, O.; Sainton, J. (Universite de Paris Sud, Orsay (France)); Dromzee, Y.; Jeannin, S. (Universite Pierre et Marie Curie, Paris (France))

1993-04-28

344

Biological activity of palladium(II) and platinum(II) complexes of the acetone Schiff bases of S-methyl- and S-benzyldithiocarbazate and the X-ray crystal structure of the [Pd(asme)2] (asme=anionic form of the acetone Schiff base of S-methyldithiocarbazate) complex.  

PubMed

Palladium(II) and platinum(II) complexes of general empirical formula, [M(NS)(2)] (NS=uninegatively charged acetone Schiff bases of S-methyl- and S-benzyldithiocarbazate; M=Pt(II) and Pd(II)) have been prepared and characterized by a variety of physicochemical techniques. Based on conductance, IR and electronic spectral evidence, a square-planar structure is assigned to these complexes. The crystal and molecular structure of the [Pd(asme)(2)] complex (asme=anionic form of the acetone Schiff base of S-methyldithiocarbazate) has been determined by X-ray diffraction. The complex has a distorted cis-square planar structure with the ligands coordinated to the palladium(II) ions as uninegatively charged bidentate NS chelating agents via the azomethine nitrogen and the mercaptide sulfur atoms. The distortion from a regular square-planar geometry is attributed to the restricted bite angles of the ligands. Antimicrobial tests indicate that the Schiff bases exhibit strong activities against the pathogenic bacteria, Bacillus subtilis (mutant defective DNA repair), methicillin-resistant Staphylococcus aureus, B. subtilis (wild type) and Pseudomonas aeruginosa and the fungi, Candida albicans (CA), Candida lypotica (2075), Saccharomyces cerevisiae (20341) and Aspergillus ochraceous (398)-the activities exhibited by these compounds being greater than that of the standard antibacterial and antifungal drugs, streptomycin and nystatin, respectively. The palladium(II) and platinum(II) complexes are inactive against most of these organisms but, the microbe, Pseudomonas aeruginosa shows strong sensitivity to the platinum(II) complexes. Screening of the compounds for their cytotoxicities against T-lymphoblastic leukemia cancer cells has shown that the acetone Schiff base of S-methyldithiocarbazate (Hasme) exhibits a very weak activity, whereas the S-benzyl derivative (Hasbz) is inactive. However, the palladium(II) complexes exhibit strong cytotoxicities against this cancer; their activities being more than that of the standard anticancer drug, tamoxifen. The [Pt(asme)(2)] complex exhibits a very weak cytotoxicity, whereas [Pt(asbz)(2)] is inactive against leukemic cells. PMID:12433421

Akbar Ali, Mohammad; Mirza, Aminul Huq; Butcher, Raymond J; Tarafder, M T H; Keat, Tan Boon; Ali, A Manaf

2002-11-25

345

Preparation and structure investigation of novel Schiff bases using spectroscopic, thermal analyses and molecular orbital calculations and studying their biological activities.  

PubMed

Two novel Schiff's bases (EB1 and L1) as new macrocyclic compounds were prepared via condensation reactions between bisaldehyde (2,2'-(ethane-1,2-diylbis(oxy))dibenzaldehyde): firstly with hydrazine carbothioamide to give (EB1), secondly with 4,6-diaminopyrimidine-2-thiol to give (L1). EB1 has a general formula C??H??N?O?S? of mole mass=416.520, and IUPAC name ((N,N'Z,N,N'E)-N,N'-(((ethane1,2diylbis(oxy))bis(2,1phenylene))bis(methanylylidene))bis(1hydrazinylmethanethioamide). L1 has a general formula C??H??N?O?S of mole mass=376.10; and IUPAC name 1,2-bis(2-vinylphenoxy)ethane4,6-diaminopyrimidine-2-thiol). The structures of the compounds obtained were characterized based on elemental analysis, FT-IR and (1)H NMR spectra, mass, and thermogravimetric analysis (TG, DTG). The activation thermodynamic parameters, such as, ?E(*), ?H(*), ?S(*) and ?G(*) were calculated from the TG curves using Coats-Redfern method. It is important to investigate their structures to know the active groups and weak bond responsible for their biological activities. The obtained thermal (TA) and mass (MS) practical results are confirmed by semi-empirical MO-calculation using PM3 procedure, on the neutral and positively charged forms of these novel Schiff bases. Therefore, comparison between MS and TA helps in selection of the proper pathway representing the decomposition of these compounds to give indication about their structures and consequently their biological activities. Their biological activities have been tested in vitro against Escherichia coli, Proteus vulgaris, Bacillissubtilies and Staphylococcus aurous bacteria in order to assess their antimicrobial potential. PMID:25016203

Zayed, Ehab M; Zayed, M A; El-Desawy, M

2015-01-01

346

Anion-dependent assembly of four sensitized near-infrared luminescent heteronuclear Zn(II)-Yb(III) Schiff base complexes from a trinuclear Zn(II) complex.  

PubMed

Four anion-dependent 0D Zn(II)-Yb(III) heterometallic Schiff base complexes, [YbZn2L2(OAc)4]ClO4 (2), YbZnL2(NO3)3 (3), [(YbL)2(H2O)Cl(OAc)]2[ZnCl4]2 (4), and YbZnL(OAc)4 (5), were assembled through central metal substitution or reconstruction from homotrinuclear Zn(II) complex {[(Zn(OAc)(H2O)L]2Zn}(ClO4)24H2O [1; HL = 2-ethoxy-6-[(pyridin-2-ylmethylimino)methyl]phenol] with different Yb(III)X3 salts [X = ClO4 (2), NO3 (3), Cl (4), and OAc (5)], in which the Zn(II)-sensitized near-infrared luminescent performances in the four complexes 2-5 are closely related to their structural models. PMID:25158297

Zheng, Zhi-Peng; Ou, Yan-Jun; Hong, Xu-Jia; Wei, Lei-Ming; Wan, Lin-Tao; Zhou, Wo-Hua; Zhan, Qing-Guang; Cai, Yue-Peng

2014-09-15

347

Grafting of a rhenium-oxo complex on Schiff base functionalized graphene oxide: an efficient catalyst for the oxidation of amines.  

PubMed

A rhenium-oxo complex such as methyltrioxorhenium (MTO) has been homogeneously immobilized on a Schiff base modified graphene oxide (GrO) support via covalent bonding. The loading of MTO on GrO nanosheets was monitored by FTIR, TG-DTA, and elemental analyses. The developed heterogeneous catalyst is found to be efficient for the oxidation of various amines to the corresponding N-oxides using hydrogen peroxide as an oxidant in high to excellent yields. At the end of the reaction, the catalyst is readily recovered by filtration and reused for subsequent runs. After the third run, the catalyst showed a marginal decrease in catalytic activity owing to the leaching of the MTO complex from the support. PMID:24718600

Khatri, Praveen K; Choudhary, Shivani; Singh, Raghuvir; Jain, Suman L; Khatri, Om P

2014-06-01

348

Synthesis, crystal structure and spectroscopic properties of some cadmium(II) complexes with three polyamine and corresponding macroacyclic Schiff base ligands  

Microsoft Academic Search

Three Cd(II) macroacyclic Schiff base complexes [CdL4(NO3)2] (4), [CdL5(NO3)2] (5), [CdL6(NO3)2] (6) were prepared by template condensation of 2-pyridinecarboxaldehyde with N1-(2-nitrobenzyl)-N1-(2-aminoethyl)ethane-1,2-diamine (L1), N1-(2-nitrobenzyl)-N1-(2-aminoethyl)propane-1,3-diamine (L2) or N1-(2-nitrobenzyl)-N1-(3-aminopropyl)propane-1,3-diamine (L3), in the presence of cadmium metal ion, respectively. Three Cd(II) complexes with L1, L2 and L3 were also synthesized. All complexes have been studied with IR, 1H NMR, 13C NMR, DEPT, COSY, HMQC

Hassan Keypour; Reza Azadbakht; Sadegh Salehzadeh; Hamid Khanmohammadi; Hamidreza Khavasi; Harry Adams

2008-01-01

349

Immobilized molybdenum-thiosemicarbazide Schiff base complex on the surface of magnetite nanoparticles as a new nanocatalyst for the epoxidation of olefins  

NASA Astrophysics Data System (ADS)

In this work, a new magnetically recoverable nanocatalyst was developed by immobilization of thiosemicarbazide ligand on the surface of silica coated magnetite nanoparticles (SCMNPs) through Schiff base condensation and followed complexation with MoO2(acac)2. Characterization of the prepared nanocatalyst was performed with different physicochemical methods such as Fourier transform infrared (FT-IR) and atomic absorption spectroscopies, X-ray diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The prepared catalyst catalyzed the epoxidation of olefins and allyl alcohols with tert-butyl hydroperoxide (TBHP) and cumene hydroperoxide (CHP) quantitatively with excellent selectivity toward the corresponding epoxides under mild reaction conditions.

Mohammadikish, M.; Masteri-Farahani, M.; Mahdavi, S.

2014-03-01

350

Spectra and DNA-binding affinities of Copper(II), Nickel(II) complexes with a novel glycine Schiff base derived from chromone  

NASA Astrophysics Data System (ADS)

New [CuL(H 2O) 3]NO 3H 2O and [NiLH 2O]NO 32H 2O complexes with Schiff base (LNa) derived from 6-hydroxy-3-carbaldehyde chromone (CDC) and glycine are reported. Two complexes have been characterized by elemental analysis, IR data, TG/DTA and molar conductivity. The binding of these two complexes to calf thymus DNA (CT-DNA) has been investigated, respectively, with UV-vis spectroscopy, fluorescence spectroscopy and viscosity measurements. The experiment results indicate that the two complexes may bind to CT-DNA through an intercalative mode and [CuL(H 2O) 3]NO 3H 2O intercalates into DNA more deeply than [NiLH 2O]NO 32H 2O. Their intrinsic binding constants ( K) with DNA are 6.08 10 5 and 2.76 10 5 M -1.

Qin, Dong-dong; Yang, Zheng-yin; Wang, Bao-dui

2007-11-01

351

A novel 1D chain of azido bridged copper(II) with a salen-type di-Schiff base ligand  

NASA Astrophysics Data System (ADS)

One new complex of Cu(II), [(CuL)2Cu3(N3)6]n (1) has been synthesized by reacting the "ligand complex", [CuL] with copper acetate and sodium azide (NaN3) in methanol-water where the di-Schiff base ligand H2L = N,N'-bis(?-methylsalicylidene)-1,3-propanediamine. The X-ray single crystal structural analysis shows that complex 1 consists of an incomplete face-sharing double cube of four Cu(II) ions with the formula of [(CuL)2Cu2(N3)2]2+ which are connected by [Cu(N3)4]2- unit to form a novel 1D chain.

Biswas, Saptarshi; Ghosh, Ashutosh

2012-07-01

352

Photoinduced electron transfer from PbS quantum dots to cobalt(III) Schiff base complexes: light activation of a protein inhibitor  

PubMed Central

This paper describes the activation of a biologically inert Co(III) Schiff base (SB) complex to its protein inhibitor form by photoinduced electron transfer (PET) from a colloidal PbS quantum dot (QD, radii = 1.5 1.7 nm) to the cobalt center, with a charge separation time constant of 125 ns. Reduction of the Co(III)-SB initiates release of the native axial ligands, promoting replacement with the histidine mimic 4-methylimidazole. The rate of ligand displacement increases by approximately a factor of eight upon exposure of the PbS QD/Co(III)-SB mixture to light of energy greater than the energy of the first excitonic state of the QDs, from which PET occurs. These results suggest an approach for the preparation of inorganic therapeutic agents that can be specifically coupled to a biologically active site by cooperative redox-binding ligation. PMID:23931454

Peterson, Mark D.; Holbrook, Robert J.; Meade, Thomas J.; Weiss, Emily A.

2013-01-01

353

Proton transfer reaction of a new orthohydroxy Schiff base in some protic and aprotic solvents at room temperature and 77 K.  

PubMed

The ground and excited state proton transfer reactions of a new orthohydroxy Schiff base, salicylidine-3,4,7-methyl amine (SMA) has been studied by means of absorption, emission and time resolved fluorescence spectroscopy in some polar protic and aprotic solvents at room temperature and 77K. The spectral behavior of SMA has been investigated both in neutral and basic conditions. The intramolecularly hydrogen bonded enol and zwitterion have been detected in pure methanol and ethanol, the anion is detected in basic condition. At 77K, SMA shows phosphorescence in pure methanol and ethanol. From nanosecond measurements and quantum yields of fluorescence, we have estimated the decay rates of proton transfer reaction in methanol and ethanol. PMID:16257703

Mukhopadhyay, M; Banerjee, D; Koll, A; Filarowski, A; Mukherjee, S

2005-11-01

354

Synthesis and characterization of bioactive zinc(II) and cadmium(II) complexes with new Schiff bases derived from 4-nitrobenzaldehyde and acetophenone with ethylenediamine.  

PubMed

The new Schiff bases N,N'-bis (4-nitro benzaldehyde) ethylenediamine (L(1)) and N,N'-bis (acetophenone) ethylenediamine (L(2)) and its Zn(II), Cd(II) complexes were synthesized and characterized by different physicochemical studies. Vibrational spectra indicate coordination of metal ion through azomethine nitrogen and acetate/nitrate ions. The presence of water molecule in all the complexes has been supported by TG/DTA studies. Mass spectrum explains the successive degradation of the molecular species in solution and justifies ML complexes. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. The bioefficacy of the ligands and their complexes have been examined against the growth of bacteria in vitro to evaluate their antimicrobial potential. The results indicate that the ligand and their metal complexes possess notable antimicrobial properties. X-ray powder diffraction determines the cell parameters of the complexes. PMID:20418153

Prakash, Anant; Singh, Bibhesh K; Bhojak, Narendar; Adhikari, Devjani

2010-08-01

355

Synthesis, Structural Elucidation, and In Vitro Antitumor Activities of Some Pyrazolopyrimidines and Schiff Bases Derived from 5-Amino-3-(arylamino)-1H-pyrazole-4-carboxamides.  

PubMed

The reaction of 5-amino-3-(arylamino)-1H-pyrazole-4-carboxamides 1a,b with acetylacetone 2 and arylidenemalononitriles 5a-c yielded the pyrazolo[1,5-a]-pyrimidine derivatives 4a,b and 7a-f respectively. On the other hand, Schiff bases 9a,b and 12a-j were obtained upon treatment of carboxamides 1a,b with isatin 8 and some selected aldehydes 11a-e. The newly synthesized compounds were characterized by analytical and spectroscopic data. Representative examples of the synthesized products 4a,b, 7e, 7f, 9b, 12b-f, 12h, and 12j were screened for their in vitro antitumor activities against different human cancer cell lines and the structure-activity relationship (SAR) was discussed. PMID:23833708

Hafez, Taghrid S; Osman, Souad A; Yosef, Hisham Abdallah A; El-All, Amira S Abd; Hassan, Ashraf S; El-Sawy, Abdallah A; Abdallah, Mohamed M; Youns, Mahmoud

2013-06-01

356

Synthesis, characterization and biological studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes with bidentate Schiff bases derived by heterocyclic ketone.  

PubMed

A series of metal complexes of Co(II), Ni(II), Cu(II) and Zn(II) have been synthesized with newly prepared biologically active ligands. These ligands were prepared by the condensation of 4-amino-5-mercapto-3-methyl-s-triazole (AMMT), 4-Amino-3-ethyl-5-mercapto-s-triazole (AEMT) with 2-acetylpyridine. The structure of the complexes have been proposed by elemental analyses, spectroscopic data i.e. IR, 1H NMR, electronic and magnetic measurements. Thermal studies of the complexes are also reported. Antibacterial activities of 10 complexes have been studied in vitro. Heterocyclic bidentate Schiff bases were associated with substantially higher antibacterial activities than some commercial antibiotics. PMID:16271421

Singh, Kiran; Barwa, Manjeet Singh; Tyagi, Parikshit

2006-01-01

357

Synthesis, Structural Elucidation, and In Vitro Antitumor Activities of Some Pyrazolopyrimidines and Schiff Bases Derived from 5-Amino-3-(arylamino)-1H-pyrazole-4-carboxamides  

PubMed Central

The reaction of 5-amino-3-(arylamino)-1H-pyrazole-4-carboxamides 1a,b with acetylacetone 2 and arylidenemalononitriles 5ac yielded the pyrazolo[1,5-a]-pyrimidine derivatives 4a,b and 7af respectively. On the other hand, Schiff bases 9a,b and 12aj were obtained upon treatment of carboxamides 1a,b with isatin 8 and some selected aldehydes 11ae. The newly synthesized compounds were characterized by analytical and spectroscopic data. Representative examples of the synthesized products 4a,b, 7e, 7f, 9b, 12bf, 12h, and 12j were screened for their in vitro antitumor activities against different human cancer cell lines and the structure-activity relationship (SAR) was discussed. PMID:23833708

Hafez, Taghrid S.; Osman, Souad A.; Yosef, Hisham Abdallah A.; El-All, Amira S. Abd; Hassan, Ashraf S.; El-Sawy, Abdallah A.; Abdallah, Mohamed M.; Youns, Mahmoud

2013-01-01

358

Comparing photochemistry of n- and tert-butylamine all-trans retinal protonated Schiff-base: Effects of C dbnd N configurational inhomogeneity  

NASA Astrophysics Data System (ADS)

Photochemistry of all-trans tert-butylamine retinal protonated Schiff-base (TB-RPSB) is investigated by femtosecond pump-hyperspectral probe spectroscopy. Unlike the n-butyl analogue (NB-RPSB) no shifting of the transient spectral bands is observed upon tuning the excitation pulses from 395 to 475 nm. The 15 nm shift observed for NB-RPSB in similar experiments was assigned to unspecified ground state structural inhomogeneity. Present results indicate that is most likely due to the coexistence of C 15dbnd N double bond isomers in NB-RPSB. Elimination of this inhomogeneity in TB-RPSB makes it a more appropriate model for appreciating protein effects on RPSB photochemistry in retinal proteins.

Zhu, Jingyi; Bismuth, Oshrat; Gdor, Itay; Wand, Amir; Friedman, Noga; Sheves, Mordechai; Ruhman, Sanford

2009-09-01

359

An Efficient Sonochemical Synthesis of Novel Schiff's Bases, Thiazolidine, and Pyrazolidine Incorporating 1,8-Naphthyridine Moiety and Their Cytotoxic Activity against HePG2 Cell Lines  

PubMed Central

Novel Schiff's bases 4ae, 5a, 5b, and 6, thiazolidine 7ad, and pyrazolidine 8 have been synthesized using the versatile synthon 4-hydroxy-2,7-dimethyl-1,8-naphthyridine 1. Reactions carried out under ultrasound irradiation showed higher rates and yields than those done under silent conditions. The newly synthesized compounds were evaluated for HepG2 cell growth inhibition. The results obtained revealed that the tested compounds possess inhibitory effect on the growth of HepG2 liver cancer cells. The results were compared to doxorubicin as a reference drug (IC50: 0.04). Compounds 4a and 7b showed the highest inhibition activity against the HepG2 cell line (IC50: 0.047 and 0.041?M, resp.) among all the tested compounds. PMID:24723815

Ahmed, N. S.; Alfooty, K. O.; Khalifah, S. S.

2014-01-01

360

An efficient sonochemical synthesis of novel Schiff's bases, thiazolidine, and pyrazolidine incorporating 1,8-naphthyridine moiety and their cytotoxic activity against HePG2 cell lines.  

PubMed

Novel Schiff's bases 4a-e, 5a, 5b, and 6, thiazolidine 7a-d, and pyrazolidine 8 have been synthesized using the versatile synthon 4-hydroxy-2,7-dimethyl-1,8-naphthyridine 1. Reactions carried out under ultrasound irradiation showed higher rates and yields than those done under silent conditions. The newly synthesized compounds were evaluated for HepG2 cell growth inhibition. The results obtained revealed that the tested compounds possess inhibitory effect on the growth of HepG2 liver cancer cells. The results were compared to doxorubicin as a reference drug (IC50: 0.04). Compounds 4a and 7b showed the highest inhibition activity against the HepG2 cell line (IC50: 0.047 and 0.041 M, resp.) among all the tested compounds. PMID:24723815

Ahmed, N S; Alfooty, K O; Khalifah, S S

2014-01-01

361

An unexpected Schiff base-type Ni(II) complex: Synthesis, crystal structures, fluorescence, electrochemical property and SOD-like activities  

NASA Astrophysics Data System (ADS)

An unexpected Schiff base-type Ni(II) complex, [Ni(L2)2]?CH3OH (HL2 = 1-(2-{[(E)-3, 5-dibromo-2-hydroxybenzylidene]amino}phenyl)ethanone oxime), has been synthesized via complexation of Ni(II) acetate tetrahydrate with HL1 (2-(3,5-dibromo-2-hydroxyphenyl)-4-methyl-1,2-dihydroquinazoline 3-oxide) originally. HL1 and its corresponding Ni(II) complex were characterized by IR, 1H NMR spectra, as well as by elemental analysis, UV-Vis and emission spectroscopy, respectively. Crystal structures of the ligand and complex have been determined by single-crystal X-ray diffraction. Each complex links two other molecules into an infinite 1-D chain via intermolecular hydrogen bonding interactions. Moreover, the electrochemical property of the nickle complex was studied by cyclic voltammetry. In addition, SOD-like activities of HL1 and Ni(II) complex were also investigated.

Chai, Lan-Qin; Zhang, Hong-Song; Huang, Jiao-Jiao; Zhang, Yu-Li

2015-02-01

362

Synthesis and characterization of bioactive zinc(II) and cadmium(II) complexes with new Schiff bases derived from 4-nitrobenzaldehyde and acetophenone with ethylenediamine  

NASA Astrophysics Data System (ADS)

The new Schiff bases N, N' -bis (4-nitro benzaldehyde) ethylenediamine (L 1) and N, N' -bis (acetophenone) ethylenediamine (L 2) and its Zn(II), Cd(II) complexes were synthesized and characterized by different physicochemical studies. Vibrational spectra indicate coordination of metal ion through azomethine nitrogen and acetate/nitrate ions. The presence of water molecule in all the complexes has been supported by TG/DTA studies. Mass spectrum explains the successive degradation of the molecular species in solution and justifies ML complexes. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. The bioefficacy of the ligands and their complexes have been examined against the growth of bacteria in vitro to evaluate their antimicrobial potential. The results indicate that the ligand and their metal complexes possess notable antimicrobial properties. X-ray powder diffraction determines the cell parameters of the complexes.

Prakash, Anant; Singh, Bibhesh K.; Bhojak, Narendar; Adhikari, Devjani

2010-08-01

363

Response surface optimized peroxyoxalate chemiluminescence of octahydro-Schiff base derivative as new luminophor and study of the quenching effect of some cations, amino acids and cholesterol.  

PubMed

We report the first detailed study of the characteristics of an octahydro-Schiff base derivative as a new luminophor in the peroxyoxalate chemiluminescence (POCL) system. The effect of reagents on this new POCL system was investigated. In addition, the response surface methodology was used for evaluating the relative significance of variables in this POCL system, establishing models and determining optimal conditions. The quenching effect of some cations and compounds such as Cu(2+), Fe(3+), Hg(2+), imidazole, histidine and cholesterol on an optimized POCL reaction were studied. The dynamic ranges were up to approximaterly 100 and 175 10(-6) M for Cu(2+) and cholesterol respectively. The detection limits were 3.3 10(-6) m and 2.58 10(-6) m for Cu(2+) and histidine, respectively. In all cases the relative standard deviations were 4-5% (n = 4). PMID:24723462

Yeganeh Faal, Ali; Jamalyan, Bahare; Bordbar, Maryam; Shayeste, Tavakol Heidary; Salavati-Niasari, Masoud

2014-12-01

364

Synthesis, spectroscopic characterization and magnetic properties of homo- and heterodinuclear complexes of transition and non-transition metal ions with a new Schiff base ligand.  

PubMed

Four homodinuclear complexes of Ni(II)-Ni(II), Cu(II)-Cu(II), Co(II)-Co(II) and Co(III)-Co(II) and five heterodinuclear complexes of Co(III)-Zn(II), Co(III)-Cu(II), Co(III)-Ni(II), Cu(II)-Zn(II) and Zn(II)-Cu(II) with the octadentate Schiff base compartmental ligand 1,8-N-bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine (H4fsatrien) have been synthesized. The complexes have been characterized with the help of elemental analyses, molecular weights, molar conductances, magnetic susceptibilities and spectroscopic (UV-vis, IR, ESR) data. Cryomagnetic data also helped to elucidate the structural features of the Cu(II) complexes. PMID:18650125

Sarkar, Saikat; Biswas, Susobhan; Dey, Kamalendu

2008-12-15

365

Highly polarizable metallic complexes for nonlinear optics copper(II) and nickel(II) complexes of bis(salicylaldiminato) Schiff base  

NASA Astrophysics Data System (ADS)

In this study highly polarizable metallic complexes of Cu2+, Ni2+, and Cr3+ of Bis(salicylaldiminato) Schiff base have been synthesized. These nonlinear optical materials showed second harmonic generation (SHG) when they were pumped 1.06 micrometers Nd:YAG laser. The intensity of the SH signal varied between the metal complexes, being strongest for Ni-salen complex. An extensive study for these materials has been done to characterize their optical quality and chemical stability. We report here the synthesis, nonlinear optical characterization, electron paramagnetic resonance, FTIR, thermogravimetric measurements and the second order nonlinear response of thermally robust series of donor- acceptor substituted Bis(salicylaldiminato) Ni2+, Cu2+, and Cr3+ complexes.

Darwish, Abdalla M.; Copeland, Robert R.; Sliz, R.; Venkateswarlu, Putcha; Aggarwal, Mohan D.; Williams, Alton; Bhat, Kamala N.; Thompson, James M.; Laxmeshwar, N. B.

1996-11-01

366

Solid state NMR spectroscopy as a precise tool for assigning the tautomeric form and proton position in the intramolecular bridges of o-hydroxy Schiff bases.  

PubMed

Two analogous Schiff bases, (S,E)-2-((1-hydroxy-3-methyl-1,1-diphenylbutan-2-ylimino)methyl)phenol (1) and (S,Z)-2-hydroxy-6-((1-hydroxy-3-methyl-1,1-diphenylbutan-2-ylamino)methylene)cyclohexa-2,4-dienone (2), exist in the solid state as phenol-imine and keto-amine tautomers, respectively. Their crystal structures were solved using the X-ray diffraction method. Sample 1 forms orthorhombic crystals of space group P2(1)2(1)2(1), while 2 forms monoclinic crystals of space group P2(1). In each sample, one molecule is in the asymmetric unit of the crystal structure. One-dimensional and two-dimensional solid state NMR techniques were used for structure assignment and for inspection of the (13)C and (15)N ?(ii) of the chemical shift tensor (CST) values. NMR study indicates that the span (? = ?(11)-?(33)) and the skew (? = 3(?(22)-?(iso)/?) are extremely sensitive to change in the tautomeric form of the Schiff bases. Theoretical calculations of NMR shielding parameters for 1 and 2 and a model compound with reduced aliphatic residue were performed using the GIAO method with B3LYP functional and 6-311++g(d,p) basis sets. From comparative analysis of the experimental and theoretical parameters, it was concluded that the position of hydrogen in the intramolecular bridge has tremendous influence on (13)C and (15)N CST parameters. Inspection of ? and ? parameters allowed for the establishment of the nature of the hydrogen bonding and the assignment of the equilibrium proton position in the intramolecular bridges in the solid state. PMID:21049987

Jaworska, Magdalena; Hrynczyszyn, Pawe? B; We?niak, Miros?aw; Wojtczak, Andrzej; Nowicka, Katarzyna; Krasi?ski, Grzegorz; Kassassir, Hassan; Ciesielski, W?odzimierz; Potrzebowski, Marek J

2010-12-01

367

Weakly-bridged dimeric diorganotin(IV) compounds derived from pyruvic acid hydrazone Schiff base ligands: Synthesis, characterization and crystal structures  

NASA Astrophysics Data System (ADS)

We report the synthesis of four diorganotin(IV) compounds of Schiff base pyruvic acid hydrazone derivatives formulated as [R 2SnLY] 2, where L 1 is 2-SC 4H 3CON 2C(CH 3)CO 2 with Y = CH 3CH 2CH 2CH 2OH, R = n-Bu ( 1); L 2 is C 6H 5CON 2C(CH 3)CO 2 with Y = CH 3CH 2OH, R = p-F-Bz ( 2); L 3 is 2-HOC 6H 4CON 2C(CH 3)CO 2 with Y dbnd H 2O, R = p-CN -Bz ( 3); and L 4 is 4-NO 2-C 6H 4CON 2C(CH 3)CO 2 with Y dbnd CH 3CH 2OH, R = Bz ( 4). The structures of all compounds have been established by a combination of single-crystal X-ray diffraction analysis, 1H and 119Sn NMR spectroscopy, IR spectroscopy, and elemental analysis. Studies reveal that four ligands present the same coordination mode with tin center, which all present tridentate ONO donor Schiff bases and coordinate to the tin center in an enolic form. In compounds 1- 4, each tin atom is seven-coordinated and exhibits a distorted pentagonal bipyramid with a planar SnO 4N unit and two apical alkyl carbon atoms, thus forming a weakly-bridged dimeric molecule. Additionally, the distance of Sn⋯O bridge in each compound is obviously affected by the choice of different alkyl groups and coordination solvent molecules, which fluctuates in the range of 2.571(5)-2.839(4) . Furthermore, the supramolecular structure analysis show that there are two types of supramolecular infrastructures, 1D chain or 2D network, which are formed by intermolecular O-HN or C-H⋯X (X = O, N or F) hydrogen bonds.

Hong, Min; Yin, Han-Dong; Cui, Ji-Chun

2011-03-01

368

Asymmetric C-C Bond Formation between Chiral N-Phosphonyl Imines and Ni(II)-Complex of Glycine Schiff Base Provides a GAP Synthesis of ?,?-syn-Diamino Acid Derivatives.  

PubMed

The GAP asymmetric synthesis of ?,?-diamino acid derivatives has been achieved by reacting chiral N-phosphonyl imines with Ni(II)-complex of glycine ester-based enolate without the use of traditional purifications of chromatography and recrystallization. The successful control of synstereochemistry of vicinal diamino products complements our previous methods which afforded anti stereoisomers and enables all four individual isomers to be synthesized by simply changing enolate geometry. In contrast to our previous synthesis where required at least 5 equiv of glycine Schiff base enolate for complete conversion, the new synthesis only needs 1.1 equiv of glycine Schiff base enolate to give complete diastereoselectivity (>99% de) and yields (91% - 97%). The absolute stereochemistry has been unambiguously determined by X-ray structural analysis. PMID:25309122

Sun, Hao; Zhang, Haowei; Han, Jianlin; Pan, Yi; Li, Guigen

2013-08-01

369

Batch and hydrodynamic monitoring of vitamin C using novel periodate selective sensors based on a newly synthesized Ni(II)-Schiff bases complexes as a neutral receptors.  

PubMed

A highly selective membrane electrodes based on a two newly synthesized nickel (II) Schiff bases, [NiL(1)] and [NiL(2)] where L(1) and L(2) are N,N/bis(salicylaldehyde)4,5-dimethyl-1,2-phenylenediamine (H(2)L(1)) and N,N/bis(salicylaldehyde)4,5-dichloro-1,2-phenylenediamine (H(2)L(2)) were used as a neutral carrier ionophores for static and hydrodynamic potentiometric mode of operations for the determination of periodate. Under static mode of operation, the sensors displayed a near-Nernstian slope of -66.1+/-0.8 and -59.9+/-1.1mV decade(-1) of activity and detection limits to 5.2x10(-6) and 7.3x10(-6)molL(-1) for the sensors based on [NiL(1)] and [NiL(2)], respectively. Under hydrodynamic mode of operation (FIA), the slope of the calibration plot, limit of detection, and working linear range were -71.1mV decade(-1) of activity, 7.3x10(-6) and 1.0x10(-5) to 1.0x10(-3)molL(-1), respectively. The response time of the sensors in whole concentration ranges was very short (<10s). The response of the sensors was independent on the pH range of 3-8. A tubular version was further developed and coupled to a flow injection system for ascorbic acid (AA) determination in beverages and pharmaceutical preparations. This approach was achieved by selecting a 50-cm reactor and an overall flow of 3mLmin(-1), and injecting volume 100microL of AA standards in a 1.0x10(-4)molL(-1) IO(4)(-) solution. Under these conditions, a linearity range of 2-13microgmL(-1), with a slope of 4.97mV (mg/L)(-1) (r(2)=0.9995), detection limit 0.9mgL(-1) and a reproducibility of +/-1.1mV (n=5) was recorded. This simple and inexpensive flow injection analysis manifold, with a good potentiometric detector, enabled the analysis of approximately 50 samples h(-1) without requiring pretreatment procedures. An average recovery of 98.8% and a mean standard deviation of 1.3% were obtained. PMID:20006099

Aziz, Ayman A Abdel; Kamel, Ayman H

2010-01-15

370

Spectral, magnetic, biocidal screening, DNA binding and photocleavage studies of mononuclear Cu(II) and Zn(II) metal complexes of tricoordinate heterocyclic Schiff base ligands of pyrazolone and semicarbazide/thiosemicarbazide based derivatives  

NASA Astrophysics Data System (ADS)

We depict the synthesis and characterization of copper(II) and zinc(II) coordination compounds of 4-(3',4'-dimethoxybenzaldehydene)2-3-dimethyl-1-phenyl-3-pyrazolin-5-semicarbazone ( 1a), 4-(3',4'-dimethoxybenzaldehydene)2-3-dimethyl-1-phenyl-3-pyrazolin-5-thiosemicarbazone ( 1b), 4-(3'-hydroxy-4'-nitrobenzaldehydene)2-3-dimeth yl-1-phenyl-3-pyrazolin-5-semicarbazone ( 1c) and 4-(3'-hydroxy-4'-nitrobenzal dehydene)2-3-dimethyl-1-phenyl-3-pyrazolin-5-thiosemicarbazone ( 1d). All the remote compounds have the general composition [ML 2] (M = Cu(II) and Zn(II)); L = Schiff base ( 1a- 1d). All the complexes were characterized by elemental analysis, molar conductivity, IR, 1H NMR, UV-vis, ESI-Mass, magnetic susceptibility measurements, cyclic voltammetric measurements, and EPR spectral studies. It has been originated that the Schiff bases with Cu(II) and Zn(II) ions form mononuclear complexes on 1:2 (metal:ligand) stoichiometry. Distorted octahedral environment is suggested for the metal complexes. The conductivity data confirm the non-electrolytic nature of the complexes. The interaction of CuL 21a- 1d complexes with CT DNA was investigated by spectroscopic, electrochemical and viscosity measurements. Results suggest that the copper complexes bind to DNA via an intercalative mode. Moreover, the complexes have been found to promote the photocleavage of plasmid DNA pBR322 under irradiation at 365 nm. The Schiff bases and their metal complexes were screened for their antifungal and antibacterial activities against different species of pathogenic fungi and bacteria and their biopotency has been discussed.

Raman, N.; Selvan, A.; Manisankar, P.

2010-07-01

371

Affinity-based elimination of aromatic VOCs by highly crystalline multi-walled carbon nanotubes.  

PubMed

Carbon nanotubes (CNTs) are capable of adsorbing pollutant chemicals. Their adsorptive capacities and adsorbing mechanisms, however, are not fully understood. As-grown CNTs often contain both crystalline and amorphous carbon, and the ratio of carbon types can affect adsorption. In this study, highly crystalline multi-walled carbon nanotubes (HC-MWCNTs) were used as the adsorbent for volatile organic compounds (VOCs) in contaminated air samples. Air containing 23 added VOCs (1,1-dichloroethylene, dichloromethane, trans-1,2-dichloroethylene, cis-1,2-dichloroethylene, chloroform, 1,1,1-trichloroethane, carbon tetrachloride, 1,2-dichloroethane, benzene, trichloroethylene, 1,2-dichloropropane, bromodichloromethane, cis-1,3-dichloropropene, toluene, trans-1,3-dichloropropene, 1,1,2-trichloroethane, tetrachloroethylene, dibromochloromethane, m-xylene, p-xylene, o-xylene, bromoform, and p-dichlorobenzene) was used for model samples. Adsorptive experiments were carried out by passing the air samples through a cartridge packed with HC-MWCNTs. Initial results showing high selectivity and high affinity for adsorbing aromatic VOCs (benzene, toluene, m-xylene, p-xylene, o-xylene, and p-dichlorobenzene) have provided new insight into the adsorption mechanisms. Data suggest that the HC-MWCNTs, unlike conventional carbon materials, adsorb aromatic compounds according to Fukui's frontier theory, which is based on the interactions between the HOMO and LUMO of the aromatic VOCs and those of the HC-MWCNTs. PMID:18371779

Sone, Hiroaki; Fugetsu, Bunshi; Tsukada, Takayuki; Endo, Morinobu

2008-02-15

372

Synthesis, characterization of N,N?-bis(2-hydroxynaphthalidene)phenylene-1,2-diamine with M(II)(M = Ni, Zn and Fe) Schiff-base complexes and their non-linear optical studies by z-scan technique  

NASA Astrophysics Data System (ADS)

Schiff-base complexes of N, N'-bis(2-hydroxynaphthalidene)phenylene-1,2-diamine ligand with metal M (M = Ni(II), Zn(II) and Fe(II)) have been synthesized and characterized by their UV, FT-IR, NMR, elemental analysis and magnetic susceptibility measurements. Non-linear optical measurements carried out using nanosecond laser pulses at 532 nm show that these complexes can be used for optical limiting applications.

Sampath Kumar, H. C.; Ramachandra Bhat, B.; Rudresha, B. J.; Ravindra, R.; Philip, Reji

2010-07-01

373

Synthesis, characterization and X-ray crystal structures of Vanadium(IV), Cobalt(III), Copper(II) and Zinc(II) complexes derived from an asymmetric bidentate Schiff-base ligand at ambient temperature  

NASA Astrophysics Data System (ADS)

An asymmetric bidentate Schiff-base ligand (HL: 2-((allylimino)methyl)phenol) was prepared from reaction of salicylaldehyde and Allylamine. Vanadium(IV), Cobalt(III), Copper(II) and Zinc(II) complexes, VOL2, CoL3, CuL2 and ZnL2 were synthesized from the reaction of VO(acac)2, CoCl26H2O, CuCl22H2O and Zn(NO3)26H2O with the bidentate Schiff base ligand (HL: 2-allyliminomethyl-phenol) in methanol at ambient temperature. The ligand and its metal complexes were characterized by elemental analysis (CHN), FT-IR spectroscopy. In addition, 1H and 13C NMR techniques were employed for characterization of the ligand (HL) and diamagnetic complex ZnL2. The molecular structures of all complexes were determined by single crystal X-ray diffraction technique. In the ZnL2 and CuL2 complexes, the metal ion is coordinated by two nitrogen and two oxygen atoms from two Schiff base ligands in an approximately square planar trans-[MN2O2] coordination geometry. In the Vanadium(IV) complex, VOL2, the vanadium center in this structure has a distorted tetragonal pyramidal N2O3 coordination sphere and for Cobalt(III) complex, CoL3, the CoIII ion is six coordinated by three bidentate Schiff base ligands in a distorted octahedral environment.

Khorshidifard, Mahsa; Amiri Rudbari, Hadi; Kazemi-Delikani, Zahra; Mirkhani, Valiollah; Azadbakht, Reza

2015-02-01

374

Synthesis, characterization of N, N?-bis(2-hydroxynaphthalidene)phenylene-1,2-diamine with M(II)(M = Ni, Zn and Fe) Schiff-base complexes and their non-linear optical studies by z-scan technique  

Microsoft Academic Search

Schiff-base complexes of N,N?-bis(2-hydroxynaphthalidene)phenylene-1,2-diamine ligand with metal M (M=Ni(II), Zn(II) and Fe(II)) have been synthesized and characterized by their UV, FT-IR, NMR, elemental analysis and magnetic susceptibility measurements. Non-linear optical measurements carried out using nanosecond laser pulses at 532nm show that these complexes can be used for optical limiting applications.

H. C. Sampath Kumar; B. Ramachandra Bhat; B. J. Rudresha; R. Ravindra; Reji Philip

2010-01-01

375

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  

SciTech Connect

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 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.

Otto, H.; Marti, T.; Holz, M.; Mogi, T.; Stern, L.J.; Engel, F.; Khorana, H.G.; Heyn, M.P. (Freie Universitaet Berlin (Germany, F.R.))

1990-02-01

376

Discovery and investigation of anticancer ruthenium-arene Schiff-base complexes via water-promoted combinatorial three-component assembly.  

PubMed

The structural diversity of metal scaffolds makes them a viable alternative to traditional organic scaffolds for drug design. Combinatorial chemistry and multicomponent reactions, coupled with high-throughput screening, are useful techniques in drug discovery, but they are rarely used in metal-based drug design. We report the optimization and validation of a new combinatorial, metal-based, three-component assembly reaction for the synthesis of a library of 442 Ru-arene Schiff-base (RAS) complexes. These RAS complexes were synthesized in a one-pot, on-a-plate format using commercially available starting materials under aqueous conditions. The library was screened for their anticancer activity, and several cytotoxic lead compounds were identified. In particular, [(?6-1,3,5-triisopropylbenzene)RuCl(4-methoxy-N-(2-quinolinylmethylene)aniline)]Cl (4) displayed low micromolar IC50 values in ovarian cancers (A2780, A2780cisR), breast cancer (MCF7), and colorectal cancer (HCT116, SW480). The absence of p53 activation or changes in IC50 value between p53+/+ and p53-/- cells suggests that 4 and possibly the other lead compounds may act independently of the p53 tumor suppressor gene frequently mutated in cancer. PMID:25023617

Chow, Mun Juinn; Licona, Cynthia; Yuan Qiang Wong, Daniel; Pastorin, Giorgia; Gaiddon, Christian; Ang, Wee Han

2014-07-24

377

Detection of glycoproteins in polyacrylamide gels and on electroblots using Pro-Q Emerald 488 dye, a fluorescent periodate Schiff-base stain.  

PubMed

Pro-Q Emerald 488 glycoprotein stain reacts with periodic acid-oxidized carbohydrate groups, generating a bright green-fluorescent signal on glycoproteins. The stain permits detection of less than 5-18 ng of glycoprotein per band, depending upon the nature and the degree of protein glycosylation, making it roughly 8-16-fold more sensitive than the standard colorimetric periodic acid-Schiff base method using acidic fuchsin dye (pararosaniline). The green-fluorescent signal from Pro-Q Emerald 488 stain may optimally be visualized using charge-coupled device/xenon arc lamp-based imaging systems or 470-488 nm laser-based gel scanners. Though glycoprotein detection may be performed on transfer membranes, direct detection in gels avoids electroblotting and the specificity of staining is better in gels. After detecting glycoproteins with Pro-Q Emerald 488 dye, total protein profiles may subsequently be detected using SYPRO Ruby protein gel stain. Using computer-assisted registration techniques, images may then be merged to generate differential display maps. PMID:12601726

Hart, Courtenay; Schulenberg, Birte; Steinberg, Thomas H; Leung, Wai-Yee; Patton, Wayne F

2003-02-01

378

Synthesis and DNA binding studies of Ni(II), Co(II), Cu(II) and Zn(II) metal complexes of N 1,N 5-bis[pyridine-2-methylene]-thiocarbohydrazone Schiff-base ligand  

NASA Astrophysics Data System (ADS)

The thiocarbohydrazone Schiff-base ligand with a nitrogen and sulphur donor was synthesized through condensation of pyridine-2-carbaldehyde and thiocarbohydrazide. Schiff-base ligands have the ability to conjugate with metal salts. A series of metal complexes with a general formula [MCl 2(H 2L)] nH 2O (M dbnd Ni, Co, Cu and Zn) were synthesized by forming complexes of the N 1,N 5-bis[pyridine-2-methylene]-thiocarbohydrazone (H 2L) Schiff-base ligand. These metal complexes and ligand were characterized by using ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FT-IR), 1H and 13C NMR spectroscopy and mass spectroscopy, physicochemical characterization, CHNS and conductivity. The biological activity of the synthesized ligand was investigated by using Escherichia coli DNA as target. The DNA interaction of the synthesized ligand and complexes on E. coli plasmid DNA was investigated in the aqueous medium by UV-Vis spectroscopy and the binding constant ( Kb) was calculated. The DNA binding studies showed that the metal complexes had an improved interaction due to trans-geometrical isomers of the complexes than ligand isomers in cis-positions.

Tiwari, A. D.; Mishra, A. K.; Mishra, S. B.; Mamba, B. B.; Maji, B.; Bhattacharya, S.

2011-09-01

379

Synthesis, spectroscopic, antimicrobial and DNA cleavage studies of new Co(II), Ni(II), Cu(II), Cd(II), Zn(II) and Hg(II) complexes with naphthofuran-2-carbohydrazide Schiff base  

NASA Astrophysics Data System (ADS)

A series of Co(II), Ni(II), Cu(II), Cd(II), Zn(II) and Hg(II) complexes have been synthesized with newly synthesized Schiff base derived from naphthofuran-2-carbohydrazide and cinnamaldehyde. The elemental analyses of the complexes are confined to the stoichiometry of the type MLCl2 [M = Co(II) and Cu(II)], ML2Cl2 [M = Ni(II), Cd(II), Zn(II) and Hg(II)] respectively, where L is Schiff base ligand. Structures have been proposed from elemental analyses, IR, electronic, mass, 1H NMR, ESR spectral data, magnetic, and thermal studies. The measured low molar conductance values in DMF indicate that the complexes are non-electrolytes. Spectroscopic studies suggest coordination occurs through azomethine nitrogen and carbonyl oxygen of the ligand with the metal ions. The Schiff base and its complexes have been screened for their antibacterial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Salmonella typhi) and antifungal (Aspergillus niger, Aspergillus flavus, Cladosporium and Candida albicans) activities by minimum inhibitory concentration (MIC) method. The DNA cleavage studies by agarose gel electrophoresis method was studied for all the complexes.

Halli, Madappa B.; Sumathi, R. B.

2012-08-01

380

DNA cleavage, antibacterial, antifungal and anthelmintic studies of Co(II), Ni(II) and Cu(II) complexes of coumarin Schiff bases: Synthesis and spectral approach  

NASA Astrophysics Data System (ADS)

The metal complexes of Co(II), Ni(II) and Cu(II) have been synthesized from 6-formyl-7,8-dihydroxy-4-methylcoumarin with o-toluidine/3-aminobenzotrifluoride. The synthesized Schiff bases and their metal complexes were structurally characterized based on IR, 1H NMR, 13C NMR, UV-visible, ESR, magnetic, thermal, fluorescence, mass and ESI-MS studies. The molar conductance values indicate that complexes are non-electrolytic in nature. Elemental analysis reveals ML22H2O [M = Co(II), Ni(II) and Cu(II)] stoichiometry, where 'L' stands for a singly deprotonated ligand. The presence of co-ordinated water molecules were confirmed by thermal studies. The spectroscopic studies suggest the octahedral geometry. Redox behavior of the complexes were confirmed by cyclic voltammetry. All the synthesized compounds were screened for their antibacterial (Escherichia coli, Pseudomonas auregenosa, klebsiella, Proteus, Staphylococcus aureus and salmonella) antifungal (Candida, Aspergillus niger and Rhizopus), anthelmintic (Pheretima posthuma) and DNA cleavage (Calf Thymus DNA) activity.

Patil, Sangamesh A.; Prabhakara, Chetan T.; Halasangi, Bhimashankar M.; Toragalmath, Shivakumar S.; Badami, Prema S.

2015-02-01

381

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 Central

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. Images PMID:2153966

Otto, H; Marti, T; Holz, M; Mogi, T; Stern, L J; Engel, F; Khorana, H G; Heyn, M P

1990-01-01

382

Synthesis, antibacterial, antiurease, and antioxidant activities of some new 1,2,4-triazole schiff base and amine derivatives.  

PubMed

The acylhydrazone compound named ethyl N'-furan-2-carbonylbenzohydrazonate was synthesized by the condensation of ethyl benzimidate hydrochloride with furan-2-carbohydrazide. The treatment of the acylhydrazone with hydrazine hydrate afforded 4-amino-3-furan-2-yl-5-phenyl-1,2,4-triazole. The usage of this compound with various aromatic aldehydes resulted in the formation of 4-arylidenamino-3-furan-2-yl-5-phenyl-1,2,4-triazoles. Sodium borohydride reduction of 4-arylidenamino derivatives afforded 4-alkylamino-3-furan-2-yl-5-phenyl-1,2,4-triazoles. The obtained products were identified by FT-IR, (1)H-NMR, (13)C-NMR. A series of compounds were evaluated for their antibacterial, antiurease, and antioxidant activities. The results showed that the synthesized new compounds had effective antiurease and antioxidant activities. PMID:25342259

Sokmen, Bahar Bilgin; Gumrukcuoglu, Nurhan; Ugras, Serpil; Sahin, Huseyin; Sagkal, Yasemin; Ugras, Halil Ibrahim

2015-01-01

383

Microwave assisted synthesis, characterization and biocidal activities of some new chelates of carbazole derived Schiff bases of cadmium and tin metals.  

PubMed

This study is planned to report the advancement of green microwave approach in the fabrication of a new series of biologically potent (N^X, where X=O/S) donor Schiff bases and their cadmium(II) and tin(II) complexes. The ligands and their metal complexes have been characterized in terms of elemental analysis, molar ionic conductance, magnetic moment and spectral (IR, UV-Vis, NMR ((1)H, (119)Sn), FAB-mass, thermal and XRD) data. The data revealed that the ligands coordinated to the metal center via nitrogen and oxygen/sulfur atoms and form an octahedral arrangement of the ligands around central metal atom. All compounds were evaluated for their in vitro antimicrobial activities against two pathogenic bacteria Bacillus subtilis and Escherichia coli and two fungi Aspergillus niger and Aspergillus flavus by standard disc diffusion method. The discs were stored in an incubator at 37C. The compounds were dissolved in DMF at 500 and 1000 ppm concentrations for screening biocidal activity. The compounds were dissolved in DMF to get the 100 and 200 ppm concentration of test solutions for screening fungicidal activity. The inhibition zone around each disc was measured (in mm) after 24 h and 96 h for biocidal and fungicidal activities respectively. PMID:24929756

Yadav, Manju; Mishra, Neelima; Sharma, Nutan; Chandra, Sulekh; Kumar, Dinesh

2014-11-11

384

Influence of inductive effects and steric encumbrance on the catecholase activities of copper(II) complexes of reduced Schiff base ligands.  

PubMed

A series of copper(ii) complexes derived from reduced Schiff base ligands has been synthesized and characterized by single-crystal X-ray diffraction and spectroscopic analyses. With the exception of [Cu(Ala5NO2)(H2O)] (), which crystallized as a mononuclear repeating unit, [Cu2L2(H2O)x(DMSO)y]solvent (L = Ala5H (), Ala5OMe (), Ala5Cl (), Ala5Br (), Gly5Br (), Val5Br () and Leu5Br (), x = 1 or 2, y = 0 or 1, solvent = MeOH or DMSO and H2O) crystallized as phenoxo-bridged dinuclear building units containing Cu2O2 cores. In , , , and , the axial positions are occupied by solvent ligands and carboxylate oxygen atoms from adjacent dimers, resulting in the formation of 1D helical coordination polymers. In , a 2D network is constructed by utilizing weak CuO interactions (?2.7 ) with carboxylate groups. All complexes have been investigated for their catecholase activities with 3,5-DTBC, and they show significant catalytic activities except for . The catalytic activities are also observed to increase with increasing +I effects, as well as increase with increasing steric bulkiness on the ?-carbon of the carboxylate group. PMID:24435550

Thio, Yude; Yang, Xiandong; Vittal, Jagadese J

2014-03-01

385

Synthesis, spectroscopic studies, antimicrobial activities and antitumor of a new monodentate V-shaped Schiff base and its transition metal complexes.  

PubMed

Reaction of 4-aminoacetophenone and 4-bromobenzaldehyde in ethanol resulted in the formation of the monodentate V-shaped Schiff base (E)-1-(4-((4-bromo-benzylidene)amino)phenyl)ethanone (L). Interaction of L with different di- and trivalent metal ions revealed disubstituted derivatives. The ligand and its complexes were characterized by elemental analysis, mass, IR and NMR spectrometry. Biological activities of the ligand and complexes against the Escherchia coli and Staphylococcus aureus bacterias, and the two fungus Aspergillus flavus and Candida albicans were screened. The cytotoxicity of the compounds were checked as antitumor agents on liver carcinoma cell line (HepG2). They exhibited in vitro broad range of antitumor activities towards the cell line; the [ZnL2(H2O)2](NO3)2 complex was stronger antitumor towards HepG2 cell line as well as two breast cancer cell lines (MCF7 and T47D) relative to cis-platin. PMID:24887503

Ramadan, Ramadan M; Abu Al-Nasr, Ahmad K; Noureldeen, Amani F H

2014-11-11

386

Enhanced catalytic performances by surface silylation of Cu(II) Schiff base-containing SBA-15 in epoxidation of styrene with H 2O 2  

NASA Astrophysics Data System (ADS)

Schiff base functionalized SBA-15 mesoporous materials were synthesized by post-grafting of salicylaldehyde onto silylated and non-silylated amino-modified SBA-15 and followed by the introduction of Cu(II) ions via a ligand exchange reaction. Both hybrid materials prepared were characterized by XRD, FT-IR, UV-vis spectroscopy, N 2 adsorption/desorption, TG/DTA and ICP-AES techniques and comparatively examined as catalysts in epoxidation of styrene with 30 wt.% aqueous hydrogen peroxide as oxidant. It was found that the silylated material was more active and selective to styrene oxide than the non-silylated one in CH 3CN. The considerably improved activity (86.1%) and styrene oxide selectivity (95.2%) were achieved after 30 min when adding sodium hydroxide to maintain a pH of 7.5-8.0 in reaction medium. Moreover, the silylated catalyst showed good recoverability and relatively high stability against leaching of active copper species. These superior effects were attributed to the high hydrophobic character of the solid surface produced by the silanol neutralization.

Yang, Ying; Guan, Jingqi; Qiu, Pengpeng; Kan, Qiubin

2010-03-01

387

Experimental (XRD, FT-IR and UV-Vis) and theoretical modeling studies of Schiff base (E)-N'-((5-nitrothiophen-2-yl)methylene)-2-phenoxyaniline.  

PubMed

The Schiff base compound (E)-N'-((5-nitrothiophen-2-yl)methylene)-2-phenoxyaniline has been synthesized and characterized by IR, UV-Vis, and X-ray diffraction (XRD) methods. The molecular geometry from X-ray experiment in the ground state has been compared using the density functional theory (DFT) with the 6-311++G(d,p) basis set. The calculated results show that the optimized geometry can well reproduce the crystal structure, and the theoretical vibrational frequency values show good agreement with experimental values. By using TD-DFT method, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD-DFT method and the experimental one is determined. The energetic behavior of the title compound in solvent media has been examined using B3LYP method with the 6-311++G(d,p) basis set by applying the Onsager and the integral equation formalism polarizable continuum model (IEF-PCM). The predicted nonlinear optical properties of the title compound are greater than ones of urea. In addition, DFT calculations of the title compound, molecular electrostatic potential (MEP), natural bond orbital (NBO) and thermodynamic properties were performed at B3LYP/6-311++G(d,p) level of theory. PMID:24096063

Tanak, Hasan; A?ar, Ay?en Alaman; Bykgngr, Orhan

2014-01-24

388

The interaction of taurine-salicylaldehyde Schiff base copper(II) complex with DNA and the determination of DNA using the complex as a fluorescence probe  

NASA Astrophysics Data System (ADS)

The interaction of taurine-salicylaldehyde Schiff base copper(II) (Cu(TSSB) 22+) complex with DNA was explored by using UV-vis, fluorescence spectrophotometry, and voltammetry. In pH 7.4 Tris-HCl buffer solution, the binding constant of the Cu(TSSB) 22+ complex interaction with DNA was 3.49 10 4 L mol -1. Moreover, due to the fluorescence enhancing of Cu(TSSB) 22+ complex in the presence of DNA, a method for determination of DNA with Cu(TSSB) 22+ complex as a fluorescence probe was developed. The fluorescence spectra indicated that the maximum excitation and emission wavelength were 389 nm and 512 nm, respectively. Under optimal conditions, the calibration graphs are linear over the range of 0.03-9.03 ?g mL -1 for calf thymus DNA (CT-DNA), 0.10-36 ?g mL -1 for yeast DNA and 0.01-10.01 ?g mL -1 for salmon DNA (SM-DNA), respectively. The corresponding detection limits are 7 ng mL -1 for CT-DNA, 3 ng mL -1 for yeast DNA and 3 ng mL -1 for SM-DNA. Using this method, DNA in synthetic samples was determined with satisfactory results.

Zhang, Xiaoyan; Wang, Yong; Zhang, Qianru; Yang, Zhousheng

2010-09-01

389

Synthesis, structural characterization and magnetic properties of new tripeptide Schiff base heterotrinuclear Cu(II) M(II) Cu(II) (M=Ni and Mn) complexes  

NASA Astrophysics Data System (ADS)

Two novel heterotrinuclear Cu(II)-M(II)-Cu(II) (M=Ni and Mn) complexes, [Ni(H 2O) 4(CuL) 2]7H 2O ( 1), [Mn(H 2O) 4(CuL) 2]8H 2O ( 2), have been obtained by the self-assembly of the mononuclear tripeptide Schiff base complexes [CuL] - with bivalent metal ion M 2+, where H 3L= N-salicylideneglycylglycylglycine. Single crystal X-ray diffraction experiments indicate that the structures both 1 and 2, are made up of centrosymmetric trinuclear units with the M atom lying on an inversion center, formed the 1D supramolecular chain structures via hydrogen bondings and M⋯O weak interactions. The magnetic susceptibility data (2-300 K) revealed antiferromagnetic interactions between copper(II) ions and the central metal. The magnetic susceptibility data were quantitatively analyzed using the theoretical expressions deduced from the spin Hamiltonian for a symmetrical three-spin system H=-2JS(S+S) to give the coupling parameters JCuNi=-0.46 cm -1 and JCuMn=-0.15 cm -1.

Liu, Wen-Long; Zou, Yang; Ni, Chun-Lin; Li, Yi-Zhi; Meng, Qing-Jin

2005-09-01

390

Density functional theory and molecular dynamics simulation study on corrosion inhibition performance of mild steel by mercapto-quinoline Schiff base corrosion inhibitor  

NASA Astrophysics Data System (ADS)

Corrosion inhibition mechanism of two mercapto-quinoline Schiff bases, eg., 3-((phenylimino)methyl)quinoline-2-thiol (PMQ) and 3-((5-methylthiazol-2-ylimino)methyl) quinoline-2-thiol (MMQT) on mild steel surface is investigated by quantum chemical calculation and molecular dynamics simulation. Quantum chemical parameters such as EHOMO, ELUMO, energy gap (?E), dipolemoment (?), electronegativity (?), global hardness (?) and fraction of electron transfers from the inhibitor molecule to the metallic atom surface (?N) have been studied to investigate their relative corrosion inhibition performance. Parameters like local reactive sites of the present molecule have been analyzed through Fukui indices. Moreover, adsorption behavior of the inhibitor molecules on Fe (1 1 0) surface have been analyzed using molecular dynamics simulation. The binding strength of the concerned inhibitor molecules on mild steel surface follows the order MMQT>PMQ, which is in good agreement with the experimentally determined inhibition efficiencies. In view of the above, our approach will be helpful for quick prediction of a potential inhibitor from a lot of similar inhibitors and subsequently in their rational designed synthesis for corrosion inhibition application following a wet chemical synthetic route.

Saha, Sourav Kr.; Ghosh, Pritam; Hens, Abhiram; Murmu, Naresh Chandra; Banerjee, Priyabrata

2015-02-01

391

Synthesis, biological and computational study of new Schiff base hydrazones bearing 3-(4-pyridine)-5-mercapto-1,2,4-triazole moiety  

NASA Astrophysics Data System (ADS)

A series of new Schiff base hydrazones (compounds 1- 16) were synthesized by condensation reaction of 4-amino-3-(4-pyridine)-5-mercapto-1,2,4-triazole with various aldehydes and/or dialdehydes. The structure of the prepared compounds was confirmed by means of 1H NMR, 13C NMR, UV-vis, IR and elemental analyses. The all prepared compounds were assayed for antibacterial ( Escherichia coli and Staphylococcus aureus) and antifungal ( Candida albicans) activities by disc diffusion method. The results indicate that all tested compounds did not show any antibacterial activity against E. coli, as gram negative bacteria, and antifungal activity against C. albicans. But the compounds 2, 3, 4, 6 and 8 containing 4-Cl, 4-Me, 4-MeO, 2,4-di-Cl and 2-OH substituted phenyl moiety, respectively, showed good inhibition against S. aureus as compare to standard drugs. The structure of all biologically active compounds has also been theoretically studied by ab initio Hartree-Fock (HF) methods.

Khanmohammadi, Hamid; Abnosi, Mohammad H.; Hosseinzadeh, Ali; Erfantalab, Malihe

2008-12-01

392

Synthesis, spectroscopic, antimicrobial, DNA binding and cleavage studies of some metal complexes involving symmetrical bidentate N, N donor Schiff base ligand.  

PubMed

The Schiff base ligand, N,N'-bis-(4-isopropylbenzaldimine)-1,2-diaminoethane (L), obtained by the condensation of 4-isopropylbenzaldehyde and 1,2-diaminoethane, has been used to synthesize the complexes of the type [ML(2)X(2)] [M = Co(II), Ni(II) and Zn(II); X = Cl and OAc]. The newly synthesized ligand (L) and its complexes have been characterized on the basis of elemental analyses, mass, (1)H and (13)C-NMR, molar conductance, IR, UV-vis, magnetic moment, CV and thermal analyses, powder XRD and SEM. IR spectral data show that the ligand is coordinated to the metal ions in a bidentate manner. The geometrical structures of these complexes are found to be octahedral. Interestingly, reaction with Cu(II) ion with this ligand undergoes hydrolytic cleavage to form ethylenediamine copper(II) complex and the corresponding aldehyde. The antimicrobial results indicate that the chloro complexes exhibit more activity than the acetato complexes. The complexes bind to CT-DNA by intercalation modes. Novel chloroform soluble ZnL(2)Cl(2) complex exhibits tremendous antimicrobial, DNA binding and cleaving properties. PMID:21855399

Arish, D; Nair, M Sivasankaran

2011-11-01

393

A new Schiff base, (E)-4-((4-chlorophenylimino) methyl)-2-methoxyphenol: Crystal structure, thermal behavior, solid-state fluorescence, DFT calculations and FT NMR spectral analysis  

NASA Astrophysics Data System (ADS)

A new Schiff base, (E)-4-((4-chlorophenylimino) methyl)-2-methoxyphenol (4CMP), was synthesized and grown as single crystal by slow evaporation solution growth technique. The crystal structure of the compound, elucidated from single crystal X-ray diffraction analysis, was in good agreement with the calculated structure using Density functional theory (DFT) with B3LYP/6-311G(d,p) basis set of Gaussian 03 program. The physicochemical characterization of the title compound was further performed by modern spectroscopic techniques like FT-IR, FT-Raman, FT-NMR (both 1D and 2D), UV-Vis-NIR, and fluorescence analysis. UV-Vis-NIR spectrum showed the transparent nature of 4CMP crystal in the region 500-1200 nm. Solid state fluorescence of the crystal indicate that the title compound can serve as a photoactive material. Thermogravimetric analysis revealed that the grown crystal is thermally stable up to a temperature of 225 C. From DSC, the phase transition of the compound was found to be at 131 C. The dependence of both dielectric constant and dielectric loss with frequency was measured. Microscopic nonlinear optical properties like dipole moment (?) and first order hyperpolarizability (?) were also measured using DFT.

Nagapandiselvi, P.; Baby, C.; Gopalakrishnan, R.

2014-01-01

394

Antioxidant, antimicrobial, and theoretical studies of the thiosemicarbazone derivative Schiff base 2-(2-imino-1-methylimidazolidin-4-ylidene)hydrazinecarbothioamide (IMHC)  

PubMed Central

Background Adverse antimicrobial activities of thiosemicarbazone (TSC) and Schiff base derivatives have widely been studied by using different kinds of microbes, in addition different methods were used to assay the antioxidant activities using DPPH, peroxids, or ntrosyl methods. However, there are no studies describing the synthesis of TSC derived from creatinine. Results In this study, 2-(2-imino-1-methylimidazolidin-4-ylidene)hydrazinecarbothioamide (IMHC) was synthesized by the reaction of creatinine with thiosemicarbazide. The novel molecule was characterized by FT-IR, UV-VIS, and NMR spectra in addition of the elemental analysis. The free radical scavenging ability of the IMHC was determined by it interaction with the stable-free radical 2,2"-diphenyl-1-picrylhydrazyl (or nitric oxide or hydrogen peroxide) and showed encouraging antioxidant activities. Density functional theory calculations of the IMHC performed using molecular structures with optimized geometries. Molecular orbital calculations provide a detailed description of the orbitals, including spatial characteristics, nodal patterns, and the contributions of individual atoms. Highest occupied molecular orbital-lowest unoccupied molecular orbital energies and structures are shown. Conclusions IMHC shows considerable antibacterial and antifungal activities. The free radical scavenging activity of synthesized compound was screened for in vitro antioxidant activity. PMID:22373542

2012-01-01

395

Field-induced ferromagnetism and multiferroic behavior in end-on pseudohalide-bridged dinuclear copper(II) complexes with tridentate Schiff base blocking ligands.  

PubMed

Four new end-on pseudohalide-bridged dinuclear copper(II) complexes, [Cu2(L(1))2(N3)2]DMF (1), [Cu2(L(2))2(N3)2] (2), [Cu2(L(3))2(NCS)2] (3), and [Cu2(L(4))2(N3)2] (4) {where HL(1), HL(2), HL(3), and HL(4) are tridentate N2O donor Schiff bases}, are synthesized and characterized. Complexes 1, 2, and 3 possess ?? stacking interactions, while in addition hydrogen-bonding interactions are present in 1 and 3. However, by contrast, complex 4 contains neither type of interaction. Field-induced long-range ferromagnetic ordering beyond 0.9 T is observed in complexes 1 and 2 due to ?? stacking interactions, while ferroelectric ordering is observed in complexes 1 and 3 due to hydrogen-bonding interactions. Most interestingly, complex 1, which contains both ?? stacking and hydrogen-bonding interactions, shows multiferroic behavior as a result of coupling between the dielectric and magnetic fields with 8% change in the magneto-dielectric effect at room temperature. We believe that from this study will emerge a new class of multiferroic materials. PMID:25083947

Jana, Subrata; Shaw, Bikash Kumar; Bhowmik, Prasanta; Harms, Klaus; Drew, Michael G B; Chattopadhyay, Shouvik; Saha, Shyamal Kumar

2014-08-18

396

Synthesis, characterization, X-ray crystallography, acetyl cholinesterase inhibition and antioxidant activities of some novel ketone derivatives of gallic hydrazide-derived Schiff bases.  

PubMed

Alzheimer's disease (AD) is the most common form of dementia among older people and the pathogenesis of this disease is associated with oxidative stress. Acetylcholinesterase inhibitors with antioxidant activities are considered potential treatments for AD. Some novel ketone derivatives of gallic hydrazide-derived Schiff bases were synthesized and examined for their antioxidant activities and in vitro and in silico acetyl cholinesterase inhibition. The compounds were characterized using spectroscopy and X-ray crystallography. The ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays revealed that all the compounds have strong antioxidant activities. N-(1-(5-bromo-2-hydroxyphenyl)-ethylidene)-3,4,5-trihydroxybenzohydrazide (2) was the most potent inhibitor of human acetyl cholinesterase, giving an inhibition rate of 77% at 100 ?M. Molecular docking simulation of the ligand-enzyme complex suggested that the ligand may be positioned in the enzyme's active-site gorge, interacting with residues in the peripheral anionic subsite (PAS) and acyl binding pocket (ABP). The current work warrants further preclinical studies to assess the potential for these novel compounds for the treatment of AD. PMID:22374313

Gwaram, Nura Suleiman; Ali, Hapipah Mohd; Abdulla, Mahmood Ameen; Buckle, Michael J C; Sukumaran, Sri Devi; Chung, Lip Yong; Othman, Rozana; Alhadi, Abeer A; Yehye, Wageeh A; Hadi, A Hamid A; Hassandarvish, Pouya; Khaledi, Hamid; Abdelwahab, Siddig Ibrahim

2012-01-01

397

Electronic structure of the nickel(II) complex of the Schiff base of (S)-N-(2-benzoylphenyl)-1-benzylprolinamide and glycine.  

PubMed

The experimental charge density of the Ni(II) complex of the Schiff base of (S)-N-(2-benzoylphenyl)-1-benzylprolinamide and glycine was derived from high-resolution single-crystal X-ray diffraction data (lambda = 0.5604 A) at low temperature (100 K) with synchrotron radiation at the beamline F1 using a CCD area detector. The central Ni atom is pseudo-square-planar coordinated by three N atoms [1.9414 (3), 1.8559 (3) and 1.8533 (3) A] and by one O atom [1.8620 (4) A]. The N(1) atom is 0.359 A above the plane defined by the atoms Ni(1), N(2) and N(3). The d-orbital population analysis reveals an oxidation state for the Ni atom of +2 with the configuration d(8) and a hole mainly in the d(x(2)-y(2)) orbital, located in the plane of the four ligating atoms. The prochiral reaction centre was examined by topological analysis. PMID:15477692

Kozsek, Jozef; Fronc, Marek; Skubk, Pavol; Popkov, Alexander; Breza, Martin; Fuess, Hartmut; Paulmann, Carsten

2004-09-01

398

Synthesis and characterization of xanthene-bridged Schiff-base dimanganese(III) complexes: bimetallic catalysts for asymmetric oxidation of sulfides.  

PubMed

Dimanganese(III) complexes of salen-type ligands anchored by 9,9-dimethylxanthene-4,5-diyl spacers were synthesized. Two types of structures, cyclic and acyclic forms, are presented. The 2 + 2 Schiff-base condensation of 5,5'-(9,9-dimethylxanthene-4,5-diyl)bis(salicylaldehyde) and 1,2-diaminobenzene gave a macrocyclic ligand, from which a cyclic dimanganese(III) complex was synthesized. A similar dimanganese(III) complex with stereogenic centers was synthesized by the metal-assisted condensation reaction using (1R,2R)-1,2-diaminocyclohexane. Acyclic dimanganese(III) complexes anchored by one xanthene spacer were obtained by metal-assisted stepwise condensation reactions using the xanthene-bridged bis(salicylaldehyde), (1R,2R)-1,2-diaminocyclohexane monohydrochloride, and salicylaldehydes. X-Ray crystal structure analysis confirmed that both cyclic and acyclic complexes have two cofacially oriented salen-type manganese(III) units in a complex cation, showing an Mn...Mn distance of ca. 5.1 A. Asymmetric oxidation of sulfides was performed by using the chiral dimeric complexes as catalysts, which showed enantiomeric excesses ranging from 5 to 19%. The addition of 4-(dimethylamino)pyridine to the reaction system improved the enantioselectivity up to 39% ee. This effect was not observed for the corresponding mononuclear catalyst. PMID:20023944

Hirotsu, Masakazu; Ohno, Naoki; Nakajima, Takashi; Kushibe, Chie; Ueno, Keiji; Kinoshita, Isamu

2010-01-01

399

Synthesis and characterization of VO(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of chromone based azo-linked Schiff base ligand  

NASA Astrophysics Data System (ADS)

Azo-Schiff-base complexes of VO(II), Co(II), Ni(II), Cu(II) and Zn(II) have been synthesized and characterized by elemental analysis, IR, UV-Vis, 1H NMR, mass spectra, molar conductance, magnetic susceptibility measurement, electron spin resonance (EPR), CV, fluorescence, NLO and SEM. The conductance data indicate the nonelectrolytic nature of the complexes, except VO(II) complex which is electrolytic in nature. On the basis of electronic spectra and magnetic susceptibility octahedral geometry has been proposed for the complexes. The EPR spectra of copper and oxovanadium complexes in DMSO at 300 and 77 K were recorded and its salient features are reported. The redox behavior of the copper(II) complex was studied using cyclic voltammetry. The in vitro antimicrobial activity against Staphylococcus aureus, Escherichia coli, Salmonella enterica typhi, Bacillus subtilis and Candida strains was studied and compared with that of free ligand by well-diffusion technique. The azo Schiff base exhibited fluorescence properties originating from intraligand (?-??) transitions and metal-mediated enhancement is observed on complexation and so the synthesized complexes can serve as potential photoactive materials as indicated from their characteristic fluorescence properties. On the basis of the optimized structures, the second-order nonlinear optical properties (NLO) are calculated by using second-harmonic generation (SHG) and also the surface morphology of the complexes was studied by SEM.

Anitha, C.; Sheela, C. D.; Tharmaraj, P.; Johnson Raja, S.

2012-12-01

400

Semi-aromatic polyesters based on a carbohydrate-derived rigid diol for engineering plastics.  

PubMed

New carbohydrate-based polyesters were prepared from isoidide-2,5-dimethanol (extended isoidide, XII) through melt polymerization with dimethyl esters of terephthalic acid (TA) and furan-2,5-dicarboxylic acid (FDCA), yielding semi-crystalline prepolymers. Subsequent solid-state post-condensation (SSPC) gave high molecular weight (Mn =30?kg?mol(-1) for FDCA) materials, the first examples of high Mn , semi-aromatic homopolyesters containing isohexide derivatives obtained via industrially relevant procedures. NMR spectroscopy showed that the stereo-configuration of XII was preserved under the applied conditions. The polyesters are thermally stable up to 380?C. The TA- and FDCA-based polyesters have high Tg (105?C and 94?C, resp.) and Tm (284?C and 250?C, resp.) values. Its reactivity, stability, and ability to afford high Tg and Tm polyesters make XII a promising diol for the synthesis of engineering polymers. PMID:25382180

Wu, Jing; Eduard, Pieter; Thiyagarajan, Shanmugam; Noordover, Bart A J; van Es, Daan S; Koning, Cor E

2015-01-01

401

Structurally diverse copper complexes bearing NNO-tridentate Schiff-base derivatives as efficient catalysts for copolymerization of carbon dioxide and cyclohexene oxide.  

PubMed

Structurally diverse copper acetate complexes based on NNO-tridentate Schiff-base ligands were synthesized and characterized as mono-, di-, and trinuclear complexes with respect to varied ancillary ligands. Treatment of the ligand precursors (L(1)-H = 2-(1-((2-(dimethylamino)ethyl)imino)ethyl)-4-methylphenol, L(2)-H = 4-chloro-2-(1-((2-(dimethylamino)ethyl)imino)ethyl)phenol, and L(3)-H = 2-(1-((2-(dimethylamino)ethyl)imino)ethyl)-5-methylphenol) with Cu(OAc)2H2O (1 equiv) in refluxing ethanol afforded five-coordinate mono- or bimetallic copper complexes ([(L(1))Cu(OAc)(H2O)] (1); [(L(2))Cu(OAc)(H2O)] (2); [(L(3))2Cu2(OAc)2] (3)) in high yields. Dinuclear copper acetate analogue [(L(1))2Cu2(OAc)2] (4) resulted from treatment of L(1)-H as the ligand precursor in refluxing anhydrous MeOH with equimolar proportions of metal acetate salt under a dry nitrogen atmosphere. However, a trinuclear complex, [(L(4))2Cu3(OAc)4] (5), was obtained on utilizing 2-(1-((2-(dimethylamino)ethyl)imino)ethyl)-5-methoxyphenol (L(4)-H) as the proligand under the same synthetic route of 1-3; this complex was also synthesized in the reaction of L(4)-H and copper(II) acetate monohydrate in the ratio of 2:3, giving a quantitative yield. All complexes are active catalysts for copolymerization of cyclohexene oxide (CHO) and CO2 without cocatalysts. In particular, dinuclear Cu complex 3 performed satisfactorily to produce polycarbonates with controllable molecular weights and high carbonate linkages. These copper complexes are the first examples that are effective for both CO2/CHO copolymerization and formation of polymers in a controlled fashion. PMID:24802071

Tsai, Chen-Yen; Huang, Bor-Hunn; Hsiao, Mon-Wei; Lin, Chu-Chieh; Ko, Bao-Tsan

2014-05-19

402

Nano structure zinc (II) Schiff base complexes of a N3-tridentate ligand as new biological active agents: Spectral, thermal behaviors and crystal structure of zinc azide complex.  

PubMed

In this work, synthesis of some new five coordinated zinc halide/pseudo-halide complexes of a N3-tridentate ligand is presented. All complexes were subjected to spectroscopic and physical methods such as FT-IR, UV-visible, (1)H and (13)C NMR spectra, thermal analyses and conductivity measurements for identification. Based on spectral data, the general formula of ZnLX2 (X=Cl(-), Br(-), I(-), SCN(-) and N3(-)) was proposed for the zinc complexes. Zinc complexes have been also prepared in nano-structure sizes under ultrasonic irradiation. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied for confirmation of nano-structure character for the complexes. Among the complexes, zinc azide complex structure was analyzed by X-ray crystallography. This complex crystallizes as a triplet in trigonal system with space group of P31. The coordination sphere around the zinc center is well shown as a distorted trigonal bipyramidal with three nitrogen atoms from Schiff base ligand and two terminal azide nitrogen atoms attached to zinc ion. Various intermolecular interactions such as NH?N, CH?N and CH?? hydrogen bonding interactions stabilize crystalline lattice so that they causes a three dimensional supramolecular structure for the complex. In vitro screening of the compounds for their antimicrobial activities showed that ZnLI2, ZnL(N3)2, ZnLCl2 and ZnL(NCS)2 were found as the most effective compound against bacteria of Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli respectively. Also ZnLI2 and ZnLCl2 complexes were found more effective against two selected fungi than others. Finally, thermal behaviors of the zinc complexes showed that they are decomposed via 2-4 thermal steps from room temperature up to 1000C. PMID:25528511

Montazerozohori, M; Mojahedi Jahromi, S; Masoudiasl, A; McArdle, P

2015-03-01

403

Influence of the geometry around the manganese ion on the peroxidase and catalase activities of Mn(III)-Schiff base complexes.  

PubMed

The peroxidase and catalase activities of eighteen manganese-Schiff base complexes have been studied. A correlation between the structure of the complexes and their catalytic activity is discussed on the basis of the variety of systems studied. Complexes 1-18 have the general formulae [MnL(n)(D)(2)](X)(H(2)O/CH(3)OH)(m), where L(n)=L(1)-L(13); D=H(2)O, CH(3)OH or Cl; m=0-2.5 and X=NO(3)(-), Cl(-), ClO(4)(-), CH(3)COO(-), C(2)H(5)COO(-) or C(5)H(11)COO(-). The dianionic tetradentate Schiff base ligands H(2)L(n) are the result of the condensation of different substituted (OMe-, OEt-, Br-, Cl-) hydroxybenzaldehyde with diverse diamines (1,2-diaminoethane for H(2)L(1)-H(2)L(2); 1,2-diamino-2-methylethane for H(2)L(3)-H(2)L(4); 1,2-diamino-2,2-dimethylethane for H(2)L(5); 1,2-diphenylenediamine for H(2)L(6)-H(2)L(7); 1,3-diaminopropane for H(2)L(8)-H(2)L(11); 1,3-diamino-2,2-dimethylpropane for H(2)L(12)-H(2)L(13)). The new Mn(III) complexes [MnL(1)(H(2)O)Cl](H(2)O)(2.5) (2), [MnL(2)(H(2)O)(2)](NO(3))(H(2)O) (4), [MnL(6)(H(2)O)(2)][MnL(6)(CH(3)OH)(H(2)O)](NO(3))(2)(CH(3)OH) (8), [MnL(6)(H(2)O)(OAc)](H(2)O) (9) and [MnL(7)(H(2)O)(2)](NO(3))(CH(3)OH)(2) (12) were isolated and characterised by elemental analysis, magnetic susceptibility and conductivity measurements, redox studies, ESI spectrometry and UV, IR, paramagnetic (1)H NMR, and EPR spectroscopies. X-ray crystallographic studies of these complexes and of the ligand H(2)L(6) are also reported. The crystal structures of the rest of the complexes have been previously published and herein we have only revised their study by those techniques still not reported (EPR and (1)H NMR for some of these compounds) and which help to establish their structures in solution. Complexes 1-12 behave as more efficient mimics of peroxidase or catalase in contrast with 13-18. The analysis between the catalytic activity and the structure of the compounds emphasises the significance of the existence of a vacant or a labile position in the coordination sphere of the catalyst. PMID:22071076

Vzquez-Fernndez, M ngeles; Bermejo, Manuel R; Fernndez-Garca, M Isabel; Gonzlez-Riopedre, Gustavo; Rodrguez-Doutn, M Jess; Maneiro, Marcelino

2011-12-01

404

Synthesis, structure and magnetism of new polynuclear transition metal aggregates assembled with Schiff-base ligand and anionic N-donor ligands  

NASA Astrophysics Data System (ADS)

Three new polynuclear aggregates [Co 6(sae) 4(N 3) 6(MeO) 2(MeOH) 2]0.5H 2O ( 1), [Mn 4O(sae) 4(C(CN) 3)(MeOH) 3](NO 3)MeOH ( 2) and [NaFe 6(sae) 6(MeO) 6] (N(CN) 2)H 2O ( 3) have been synthesized with mixed ligands of Schiff-base (salicylidene-2-ethanolamine, H 2sae) and various anionic N-donor ligands (N 3-, N(CN) 2- or C(CN) 3-) and transition metal salts in methanol solution. Crystallographic data for 1: trigonal, R3, a = 26.113(4) , b = 26.113(4) , c = 20.689(4) , ? = 120, V = 12,218(3) 3, Z = 9, R1( wR2) = 0.0753(0.2176); for 2: orthorhombic, Pna2 1, a = 20.746(4) , b = 13.357(3) , c = 17.992(4) , V = 4985.6(2) 3, Z = 4, R1( wR2) = 0.0357(0.0969); for 3: monoclinic, C2/ c, a = 30.311(6) , b = 12.452(3) , c = 20.789(4) , ? = 94.75(3), V = 7820(3) 3, Z = 4, R1( wR2) = 0.0773(0.2299). Compound 1 exhibits a new rod-like [Co III4Co II2] structural feature. Compound 2 contains an unusual tetranuclear [Mn III4] cationic core. Compound 3 possesses a well-known circle-like [Fe III6] unit encapsulated a central sodium cation. Magnetic properties of these compounds have been studied revealing the presence of (i) intra-molecular antiferromagnetic interactions in 2 and 3 that induce an overall ST = 0 ground state and (ii) Co II-Co II ferromagnetic interactions in complex 1.

Li, Yangguang; Wu, Qiong; Lecren, Lollita; Clrac, Rodolphe

2008-11-01

405

Trinuclear heterometallic Cu(II)-Mn(II) complexes of a salen type Schiff base ligand: anion dependent variation of phenoxido bridging angles and magnetic coupling.  

PubMed

Five new trinuclear heterometallic Cu(II)-Mn(II) complexes [(CuL)2Mn(O2CPh)2] (1), [(CuL)2Mn(N3)2] (2), [(CuL)2Mn(NCO)2] (3), [(CuL)2Mn(NO3)2] (4) and [(CuL)2Mn(Sal)2]CH2Cl2 (5) have been synthesized with the di-Schiff base ligand H2L (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine and Sal = salicylate). These complexes with different anionic co-ligands have been synthesized to attain a large variation in phenoxido bridging angles and to investigate its consequence on magnetic properties. Single crystal X-ray diffraction analyses reveal that complexes 1, 2, 4 and 5 are linear, whereas 3 has an angular geometry. Variable temperature magnetic susceptibility measurements suggest that all five complexes possess an overall antiferromagnetic interaction between Cu(II) and Mn(II) ions, which results in a final ferrimagnetic ground state with spin 3/2 in the Cu(II)-Mn(II)-Cu(II) trinuclear structure. The weakest antiferromagnetic interaction (J(Cu-Mn) = -7.0 cm(-1)) is observed for 2 having the lowest value of the Cu-O-Mn angle (92.0), while the strongest antiferromagnetic interaction (J(Cu-Mn) = -26.5 cm(-1)) is observed for 3 having the largest Cu-O-Mn angle (101.4). Complexes 1, 4 and 5 show average Cu-O-Mn angles of 98.2, 97.6 and 97.7, respectively, that lead to intermediate antiferromagnetic interactions (J(Cu-Mn) = -9.6, -9.7, -9.3 cm(-1) respectively). PMID:24162065

Seth, Piya; Ghosh, Soumavo; Figuerola, Albert; Ghosh, Asutosh

2014-01-21

406

cis-{MoO2}(2+) assisted Mannich-type addition of acetylacetonate methine to the azomethine of tridentate Schiff bases: racemic complexes with chiral transformed ligands.  

PubMed

Reactions of [MoO2(acac)2] (acac(-) = acetylacetonate) with the potential N2O-donor 5,5-membered fused chelate rings forming Schiff bases 2-(2-pyridylaldimine)ethanol (HL(1)) and 4/5-R-2-(2-pyridylaldimine)phenols (HL(n); n = 2-5 for R = H, 4-Cl, 4-Me and 5-Me, respectively) lead to the facile formation of racemic complexes of the general formula cis-[MoO2(acacL(1-5))] () in 80-85% yield. Here, (acacL(n))(2-) represents a chiral N2O2-donor ligand system formed by a novel Mannich-type reaction that involves acetylacetonate and the azomethine fragment of HL(n) both coordinated to the cis-{MoO2}(2+) unit. The characterization of has been performed with the help of microanalytical (CHN), spectroscopic (ESI-MS, IR, UV-Vis and (1)H- and (13)C-NMR) and electrochemical measurements. The molecular structures of all the complexes except for are authenticated by single crystal X-ray crystallography. The Mo(vi) center in each of these analogous complexes is in a distorted octahedral N2O4 coordination sphere assembled by the chiral N2O2-donor transformed ligand (acacL(n))(2-) and the two mutually cis-oriented oxo ligands. In the crystal lattice, each of exists as a centrosymmetric discrete dimer via a pair of reciprocal N-HO hydrogen bonds between its enantiomeric pairs. PMID:25554121

Kurapati, Sathish Kumar; Pal, Samudranil

2015-01-20

407

Synthesis of alpha-amino acids via asymmetric phase transfer-catalyzed alkylation of achiral nickel(II) complexes of glycine-derived Schiff bases.  

PubMed

Achiral, diamagnetic Ni(II) complexes 1 and 3 have been synthesized from Ni(II) salts and the Schiff bases, generated from glycine and PBP (7) and PBA (11), respectively, in MeONa/MeOH solutions. The requisite carbonyl-derivatizing agents pyridine-2-carboxylic acid(2-benzoyl-phenyl)-amide 7 (PBP) and pyridine-2-carboxylic acid(2-formyl-phenyl)-amide 11 (PBA) were readily prepared from picolinic acid and o-aminobenzophenone or picolinic acid and methyl o-anthranilate, respectively. The structure of 1 was established by X-ray crystallography. Complexes 1 and 3 were found to undergo C-alkylation with alkyl halides under PTC conditions in the presence of beta-naphthol or benzyltriethylammonium bromide as catalysts to give mono- and bis-alkylated products, respectively. Decomposition of the complexes with aqueous HCl under mild conditions gave the required amino acids, and PBP and PBA were recovered. Alkylation of 1 with highly reactive alkyl halides, carried out under the PTC conditions in the presence of 10% mol of (S)- or (R)-2-hydroxy-2'-amino-1,1'-binaphthyl 31a (NOBIN) and/or its N-acyl derivatives and by (S)- or (R)-2-hydroxy-8'-amino-1,1'-binaphthyl 32a (iso-NOBIN) and its N-acyl derivatives, respectively, gave rise to alpha-amino acids with high enantioselectivities (90-98.5% ee) in good-to-excellent chemical yields at room temperature within several minutes. An unusually large positive nonlinear effect was observed in these reactions. The Michael addition of acrylic derivatives 37 to 1 was conducted under similar conditions with up to 96% ee. The (1)H NMR and IR spectra of a mixture of the sodium salt of NOBIN and 1 indicated formation of a complex between the two components. Implications of the association and self-association of NOBIN for the observed sense of asymmetric induction and nonlinear effects are discussed. PMID:14558835

Belokon, Yuri N; Bespalova, Natalia B; Churkina, Tatiana D; Csarov, Ivana; Ezernitskaya, Marina G; Harutyunyan, Syuzanna R; Hrdina, Radim; Kagan, Henri B; Kocovsk, Pavel; Kochetkov, Konstantin A; Larionov, Oleg V; Lyssenko, Konstantin A; North, Michael; Polsek, Miroslav; Peregudov, Alexander S; Prisyazhnyuk, Vladimir V; Vyskocil, Stepn

2003-10-22

408

Spectroscopic Elucidation of the Inhibitory Mechanism of Cys2His2 Zinc Finger Transcription Factors by CobaltIII Schiff Base Complexes  

PubMed Central

Transcription factors are key regulators in both normal and pathological cell processes. Affecting the activity of these proteins is a promising strategy for understanding gene regulation and developing effective therapeutics. CoIII Schiff base complexes ([Co(acacen)(L)2]+ where L = labile axial ligands) have been shown to be potent inhibitors of a number of zinc metalloproteins including Cys2His2 zinc finger transcription factors. Inhibition by [Co(acacen)(L)2]+ of the target protein is believed to occur through a dissociative exchange of the labile axial ligands for histidine (His) residues essential for function. Here, we report a series of spectroscopic investigations with model peptides of zinc fingers that elucidate the interaction between [Co(acacen)(L)2]+ complexes and zinc finger transcription factors. Observed changes in NMR chemical shifts and 2D 1H-1H NOESY NMR spectra demonstrate the preference of [Co(acacen)(L)2]+ complexes to coordinate His residues over other amino acids. The conformation of [Co(acacen)(L)2]+ upon His-coordination was characterized by 1H NMR, near-UV circular dichroism, and electronic absorption. These studies reveal that the resulting His-coordinated [Co(acacen)(L)2]+ complex possesses an octahedral structure. The effects of [Co(acacen)(L)2]+ complexes on the zinc finger structure were assessed by the degree of hydrogen bonding (probed by 2D NMR) and secondary structure profiles measured by far-UV circular dichroism. These structural studies demonstrate the ability of [Co(acacen)(L)2]+ complexes to disrupt the ??? structure of zinc fingers, resulting in primarily random coil conformations. A mechanism is described wherein [Co(acacen)(L)2]+ complexes inhibit zinc finger transcription factor activity through selectively coordinating His residues in the zinc finger via dissociative ligand exchange and disrupting the ??? structural motif required for gene regulation. PMID:24203451

Heffern, Marie C.; Kurutz, Josh

2014-01-01

409

Spectroscopic studies of bimetallic complexes derived from tridentate or tetradentate Schiff bases of some di- and tri-valent transition metals.  

PubMed

Two series of new binuclear complexes with Schiff base ligands, H(4)L(a) or H(2)L(b), derived from the reaction of 4,6-diacetylresorcinol and ethylenediamine, in the molar ratio 1:1 and 1:2 have been prepared, respectively. The two ligands react with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Cr(III) and Fe(III)-nitrates to get binuclear complexes. The ligands were characterized by elemental analysis, IR, UV-vis, (1)H NMR and mass spectra. The complexes were synthesized by direct and template methods. Different types of products were obtained for the same ligand and metal salts according to the method of preparation. The H(4)L(a) ligand behaves as a macrocyclic tetrabasic with two N(2)O(2) sits, while the H(2)L(b) ligand behaves as a dibasic with two N(2)O sites. The H(4)L(a) ligand is a compartmental ligand which hosts the two metal ions at the centers of two cis-N(2)O(2) sites, while the metal complexes of H(2)L(b) ligand are binuclear, where the ligand hosts two metal ions at the centers of two N(2)O sites. In both cases, deprotonation of the hydrogen atoms of the phenolic OH groups occur except in the case of the Ni(II), Fe(III) and Cr(III) complexes. Electronic spectra and magnetic moments of the complexes indicate that the geometries of the metal centers are either octahedral or tetrahedral. The structures are consistent with the IR, UV-vis, ESR, (1)H NMR, mass spectra, and thermal gravimetric analysis (TGA/DTA) as well as conductivity and magnetic moment measurements. PMID:16332449

Emara, Adel A A; Abou-Hussen, Azza A A

2006-07-01

410

Cocomplexation of urea and UO/sub 2//sup 2 +/ in a Schiff base macrocycle: a mimic of an enzyme binding site  

SciTech Connect

As part of the authors work on the complexation of neutral molecules by macrocyclic ligands, they are particularly interested in the complexation of urea. They have shown that urea can form complexes with (aza-)18-crown but the association constants of these complexes in water are very small (18-crown-6-urea, log K/sub s/ = 0.1). Protonation of urea effects stronger binding especially when the crown ether is sufficiently large to form an encapsulated complex (e.g., the complex benzo-27-crown-9-urea-HClO/sub 4/). Protonation of the weakly basic urea (pK/sub a/ = 0.1, water, 25 /sup 0/C) requires strongly acidic conditions and to avoid this they have introduced a covalently linked carboxylic group in the cavity of the macrocycle. A strong hydrogen bond of urea with 2-carboxyl-1,3-xylyl-30-crown-9 results in an encapsulated complex. The concept of using an electrophilic center to bind urea in the cavity of a crown ether proved to be a more general concept. A metal cation can serve as the electrophile as was shown by the isolation and single-crystal X-ray analysis of the 2,6-pyrido-27-crown-9-urea-LiClO/sub 4/ (1:2:1) complex in which one of the urea molecules is encapsulated. In an effort to bind an electrophilic metal ion in the crown ethers irreversibly they have concentrated their work on macrocycles of type 1, since the strong binding of quadridentate (salen type) Schiff bases with soft metal ions is well-known.

van Staveren, C.J.; Fenton, D.E.; Reinhoudt, D.N.; van Eerden, J.; Harkema, S.

1987-05-27

411

Determination of Quantum Chemistry Based Force Fields for Molecular Dynamics Simulations of Aromatic Polymers  

NASA Technical Reports Server (NTRS)

Ab initio quantum chemistry calculations for model molecules can be used to parameterize force fields for molecular dynamics simulations of polymers. Emphasis in our research group is on using quantum chemistry-based force fields for molecular dynamics simulations of organic polymers in the melt and glassy states, but the methodology is applicable to simulations of small molecules, multicomponent systems and solutions. Special attention is paid to deriving reliable descriptions of the non-bonded and electrostatic interactions. Several procedures have been developed for deriving and calibrating these parameters. Our force fields for aromatic polyimide simulations will be described. In this application, the intermolecular interactions are the critical factor in determining many properties of the polymer (including its color).

Jaffe, Richard; Langhoff, Stephen R. (Technical Monitor)

1995-01-01

412

Aromatic superhalogens.  

PubMed

No organic molecules with electron affinities near or above those of halogens are known. We show for the first time that aromaticity rules can be used to design molecules with electron affinities far exceeding those of halogen atoms either by tailoring the ligands of cyclopentadienyl or by multiple benzoannulations of cyclopentadienyl in conjunction with the substitution of CH groups with isoelectronic N atoms. Results based on density functional theory revealed that the electron affinities of some of these organic molecules can reach as high as 5.59?eV, thus opening the door to new class of superhalogens that contain neither a metal nor a halogen atom. PMID:24644250

Child, Brandon Z; Giri, Santanab; Gronert, Scott; Jena, Puru

2014-04-14

413

Copper(II) complexes of asymmetrical and symmetrical acyclic pentadentate (N 5 ) mono-Schiff-base ligands. The X-ray structure of [Cu(ppe-py)](ClO 4 ) 2  

Microsoft Academic Search

In the presence of copper(II) ion, two asymmetrical tripodal tetraamine ligands N{(CH2)3NH2}{(CH2)2NH2}2 (pee), N{(CH2)3NH2}2{(CH2)2NH2} (ppe) and one symmetrical ligand, N{(CH2)3NH2}3 (tpt), were condensed with 2-acetylpyridine. In EtOHH2O solutions the reaction stops after the first condensation stage, and complexes of acyclic pentadentate(N5) mono-Schiff-base ligands were obtained. With asymmetrical tetraamines there are two possible condensation sites: the primary amine of the propylene,

Hassan Keypour; Sadegh Salehzadeh; Robin G. Pritchard; Richard V. Parish

2002-01-01