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1

Mossbauer spectra of iron carbonyl complexes of aromatic azines and schiff bases  

SciTech Connect

An analysis is presented for the Mossbauer spectral data for a series of new iron carbonal complexes of aromatic azines and Schiff bases. The Mossbauer spectra were obtained on an electrodynamic instrument with a source consisting of Co 57 in chromium. The isomer shifts were related to the center of the sodium nitroprusside doublet. The nature of the substituents at the methylenimino group carbon a tom does not have a significant effect on the Mossbauer spectral parameters of binuclear complexes of iron with nitrogen bridges not containing a nitrogen-nitrogen bond. The ortho-metallated complexes obtained from Schiff bases and aromatic azines have two structurally nonequivalent iron atom positions.

Trusov, V.V.; Maksimov, Y.V.; Nekhaev, A.I.; Tyorin, V.D.

1986-02-01

2

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 O–O bond cleavage and C–O bond formation, followed finally by a proton transfer to an alpha aromatic carbon that immediately yields the product [CuII 2(bsH2m-O)(?-OH)]2+.

Sola, Miquel

2013-01-01

3

Synthesis, Spectral, and Biological Properties of Copper(II) Complexes of Thiosemicarbazones of Schiff Bases Derived from 4-Aminoantipyrine and Aromatic Aldehydes  

PubMed Central

We have synthesized a novel series of Schiff bases by condensation of 4-aminoantipyrine and various aromatic aldehydes followed by reaction with thiosemicarbazide. These thiosemicarbazones are potential ligands toward transition metal ions. The reaction of copper(II) salts with 4[N-(benzalidene)amino]antipyrinethiosemicarbazone (BAAPTS), 4[N-(4?-methoxybenzalidene) amino] antipyrinethiosemicarbozone (MBAAPTS), 4[N-(4?-dimethylamino benzalidene) amino] antipyrinethiosemicarbazone (DABAAPTS), and 4[N-(cinnamalidene) amino] antipyrinethiosemicarbazone (CAAPTS) resulted in the formation of solid complexes with the general composition CuX2 · (H2O)(L)(X = Cl, Br,NO3,NCS, or CH3COO; L = BAAPTS, MBAAPTS, DABAAPTS, or CAAPTS). These complexes were characterized through elemental analysis, molecular weight, electrical conductance, infrared, electronic spectra, and magnetic susceptibilities at room temperature. Copper(II) complexes with BAAPTS and MBAAPTS were screened for antibacterial and antifungal properties and have exhibited potential activity. Thermal stabilities of two representative complexes were also investigated.

Agarwal, Ram K.; Singh, Lakshman; Sharma, Deepak Kumar

2006-01-01

4

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

5

Unprecedented ?···? interaction between an aromatic ring and a pseudo-aromatic ring formed through intramolecular H-bonding in a bidentate Schiff base ligand: crystal structure and DFT calculations.  

PubMed

A combination of a single crystal X-ray diffraction study and density functional theory calculations has been applied to a bidentate Schiff base compound to elucidate different cooperative non-covalent interactions involved in the stabilization of the keto form over the enol one in the solid state. The single crystal X-ray structure reveals a remarkable supramolecular assembly of the keto form through a cyclic hydrogen bonded dimeric motif. The most interesting feature in the supramolecular assembly is the formation of a 'dimer of dimer' motif by ?···?, CH···? and N···O/O···O interactions in which the ?···? interaction involving the aromatic phenyl ring and the intramolecularly hydrogen bonded pseudo-aromatic ring of the keto form lying just above or below the phenyl ring of the other dimer seems to be unprecedented. The optimized geometry of the hydrogen bonded dimeric motif of the keto form of the organic molecule has been obtained by DFT calculations and agrees very well with that found within the crystalline state. The X-ray crystallographic geometry of the 'dimer of dimer' has also been computed, which shows that in the HOMO, the ? electrons are localized in the phenyl rings away from each other, while in the LUMO, there is a strong ?-? interaction between the phenyl ring of one dimer with the pseudo-aromatic ring of another dimer with an energy estimated to be 7.95 kJ mol(-1). Therefore, on HOMO ? LUMO excitation there is localization of ? electrons in the central part of the complex moiety which plays a stabilizing role of the dimer of dimer motif in the solid state. PMID:21818495

Dutta, Arpan; Jana, Atish Dipankar; Gangopadhyay, Sumana; Das, Kalyan Kumar; Marek, Jaromir; Marek, Radek; Brus, Jiri; Ali, Mahammad

2011-09-21

6

Synthesis, crystal structures and magnetic properties of dinuclear copper(II) compounds with NNO tridentate Schiff base ligands and bridging aliphatic diamine and aromatic diimine linkers.  

PubMed

The synthesis and the characterization of new dinuclear copper(II) compounds of general formula [(L(a-d))(2)Cu(2)(?-N-N)](ClO(4))(2) (1-6) with either neutral aliphatic diamine (N-N = piperazine, pip) or aromatic diimine (N-N = 4,4'-bipyridine, 4,4'-bipy) linker are reported. The copper ligands L(-) (L(a-) = (E)-2-((2-aminoethylimino)methyl)phenolate, L(b-) = (E)-2-((2-aminopropylimino)methyl)-phenolate, L(c-) = (E)-2-((2-aminoethylimino)methyl)4-nitrophenolate, L(d-) = (E)-2-((2-aminoethylimino)methyl)4-methoxyphenolate) are NNO tridentate Schiff bases derived from the monocondensation of a substituted salicylaldehyde 5-G-salH (G = NO(2), H, OMe) with ethylenediamine, en, or 1,3-propylenediamine, tn. The crystal structures of compounds [(L(a))(2)Cu(2)(MeOH)(2)(?-4,4'-bipy)](ClO(4))(2) (1·2MeOH), [(L(b))(2)Cu(2)(MeOH)(2)(?-4,4'-bipy)](ClO(4))(2) (2·2MeOH), [(L(d))(2)Cu(2)(?-4,4'-bipy)](ClO(4))(2) (4), [(L(a))(2)Cu(2)(?-pip)](ClO(4))(2) (5) and [(L(b))(2)Cu(2)(?-pip)](ClO(4))(2) (6) have been determined, revealing the preferred (e-e)-chair conformation of the bridging piperazine in compounds 5 and 6. The presence of hydrogen-bond-mediated intermolecular interactions, that involve the methanol molecules, yields dimers of dinuclear units for 1·2MeOH, and infinite zig-zag chains for 2·2MeOH. The temperature dependences of the magnetic susceptibilities ?(M)(T) for all compounds were measured, indicating the presence of antiferromagnetic Cu-Cu exchange. For the compounds 2-4 with 4,4'-bipy, the coupling constants J are around -1 cm(-1), while in compound 1 no interaction could be detected. The compounds 5 and 6 with piperazine display higher Cu-Cu magnetic interactions through the ?-bonding backbone of the bridging molecule, with J around -8 cm(-1), and the coupling is favoured by the (e-e)-chair conformation of the diamine ring. The non-aromatic, but shorter, linker piperazine gives rise to stronger Cu-Cu antiferromagnetic couplings than the aromatic, but longer, 4,4'-bipyridine. In the latter case, the rotation along the C-C bond between the two pyridyl rings and the consequent non co-planarity of the two copper coordination planes play an important role in determining the magnetic communication. EPR studies reveal that the dinuclear species are not stable in solution, yielding the solvated [(L)Cu(MeOH)](+) and the mononuclear [(L)Cu(N-N)](+) species; it appears that the limited solubility of the dinuclear compounds is responsible for their isolation in the solid state. PMID:21340057

Rigamonti, Luca; Forni, Alessandra; Pievo, Roberta; Reedijk, Jan; Pasini, Alessandro

2011-04-01

7

Synthesis of some Schiff base metal complexes involving para substituted aromatic aldehydes and glycylglycine: Spectral, electrochemical, thermal and surface morphology studies  

NASA Astrophysics Data System (ADS)

Two Schiff base ligands, cumi-gg(L) and pcb-gg(L 1) were prepared via condensation of cuminaldehyde ( p-isopropylbenzaldehyde)/ p-chlorobenzaldehyde and glycylglycine. The ligands were characterized based on elemental analysis, mass, 1H and 13C NMR, IR and UV-Vis spectra. Co(II), Ni(II), Cu(II), Zn(II) and Ru(II) metal complexes are reported and characterized based on elemental analysis, mass, 1H and 13C NMR, molar conductance, IR, UV-Vis, magnetic moment, CV, ESR and thermal analyses, powder XRD and SEM. All the complexes were found to be non-electrolytic in nature. IR spectra show that the ligands are coordinated to the metal ions in a tridentate manner. The geometrical structures of these complexes are found to be octahedral. The thermal behavior of the synthesized complexes indicates the presence of lattice as well as coordinated water molecules in the complexes. The SEM image of [CoL 1(H 2O) 3] complex exhibit nano rod structure.

Arish, D.; Sivasankaran Nair, M.

2010-11-01

8

Phenoxyacetohydrazide Schiff Bases: ?-Glucuronidase Inhibitors.  

PubMed

Phenoxyacetohydrazide Schiff base analogs 1-28 have been synthesized and their in vitro ?-glucouoronidase inhibition potential studied. Compounds 1 (IC50 = 9.20 ± 0.32 µM), 5 (IC50 = 9.47 ± 0.16 µM), 7 (IC50 = 14.7 ± 0.19 µM), 8 (IC50 = 15.4 ± 1.56 µM), 11 (IC50 = 19.6 ± 0.62 µM), 12 (IC50 = 30.7 ± 1.49 µM), 15 (IC50 = 12.0 ± 0.16 µM), 21 (IC50 = 13.7 ± 0.40 µM) and 22 (IC50 = 22.0 ± 0.14 µM) showed promising ?-glucuronidase inhibition activity, better than the standard (D-saccharic acid-1,4-lactone, IC50 = 48.4 ± 1.25 µM). PMID:24968334

Jamil, Waqas; Perveen, Shagufta; Shah, Syed Adnan Ali; Taha, Muhammad; Ismail, Nor Hadiani; Perveen, Shahnaz; Ambreen, Nida; Khan, Khalid M; Choudhary, Muhammad I

2014-01-01

9

Syntheses, spectral characterization, and antimicrobial studies on the coordination compounds of metal ions with schiff base containing both aliphatic and aromatic hydrazide moieties.  

PubMed

An EtOH solution of 3-ketobutanehydrazide and salicylhydrazide on refluxing in equimolar ratio forms the corresponding Schiff base, LH3 (1). The latter reacts with Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Zr(OH)2(IV), MoO2(VI), and UO2(VI) ions in equimolar ratio and forms the corresponding coordination compounds, [M(LH)(MeOH)3] (2, M = Mn, Co, Ni), [Cu(LH)]2 (3), [M'(LH)(MeOH)] (4, M' = Zn, Cd), [Zr(OH)2(LH)(MeOH)2] (5), [MoO2(LH)(MeOH)] (6), and [UO2(LH)(MeOH)] (7). The coordination compounds have been characterized on the basis of elemental analyses, molar conductance, spectral (IR, reflectance, (1)H NMR, ESR) studies, and magnetic susceptibility measurements. They are nonelectrolytes in DMSO. The coordination compounds, except 3, are monomers in diphenyl. They are active against gram-positive bacteria (S. aureus, B. subtilis), gram-negative bacteria (E. coli, P. aeruginosa), and yeast (S. cerevisiae, C. albicans). 1 acts as a dibasic tridentate ONO donor ligand in 2-7 coordinating through its both enolic O and azomethine N atoms. The coordination compounds 2 and 3 are paramagnetic, while rest of the compounds are diamagnetic. A square-planar structure to 3, a tetrahedral structure to 4, an octahedral structure to 2, 6, and 7, and a pentagonal bipyramidal structure to 5 are proposed. PMID:24198736

Kumar, Dinesh; Chadda, Silky; Sharma, Jyoti; Surain, Parveen

2013-01-01

10

Polymeric schiff bases as low-voltage redox centers for sodium-ion batteries.  

PubMed

The redox entity comprising two Schiff base groups attached to a phenyl ring (?N?CH?Ar?HC?N?) is reported to be active for sodium-ion storage (Ar=aromatic group). Electroactive polymeric Schiff bases were produced by reaction between non-conjugated aliphatic or conjugated aromatic diamine block with terephthalaldehyde unit. Crystalline polymeric Schiff bases are able to electrochemically store more than one sodium atom per azomethine group at potentials between 0 and 1.5?V versus Na(+) /Na. The redox potential can be tuned through conjugation of the polymeric chain and by electron injection from donor substituents in the aromatic rings. Reversible capacities of up to 350?mA?h?g(-1) are achieved when the carbon mixture is optimized with Ketjen Black. Interestingly, the "reverse" configuration (?CH?N?Ar?N?HC?) is not electrochemically active, though isoelectronic. PMID:24757125

Castillo-Martínez, Elizabeth; Carretero-González, Javier; Armand, Michel

2014-05-19

11

Electrical Properties of Schiff Base Salts.  

National Technical Information Service (NTIS)

An electromagnetic evaluation was made on a series of Schiff Base Salts produced by Hoffmann-LaRoche Inc. The evaluation included standard and nonstandard tests in an attempt to determine time or physical condition dependent phenomena. The results were no...

W. S. Hammond

1995-01-01

12

Epoxy Schiff Base Resin Manufacturing Method.  

National Technical Information Service (NTIS)

A manufacturing method for epoxy Schiff base resin is described, characterized by the fact that at least one or more types of dicarboxylic acid having an azomethyne compound represented by the general expression: HOOC-R sub 1 -N=HC-R sub 2 -COOH, HOOC-R s...

T. Kimura

1986-01-01

13

Photophysics of Schiff bases: theoretical study of salicylidene methylamine.  

PubMed

The proton-transfer reaction in a model aromatic Schiff base, salicylidene methylamine (SMA), in the ground and in the lowest electronically-excited singlet states, is theoretically analyzed with the aid of second-order approximate coupled-cluster model CC2, time-dependent density functional theory (TD-DFT) using the Becke, three-parameter Lee-Yang-Parr (B3LYP) functional, and complete active space perturbation theory CASPT2 electronic structure methods. Computed vertical-absorption spectra for the stable ground-state isomers of SMA fully confirm the photochromism of SMA. The potential-energy profiles of the ground and the lowest excited singlet state are calculated and four photophysically relevant isomeric forms of SMA; ?, ?, ?, and ? are discussed. The calculations indicate two S(1)/S(0) conical intersections which provide non-adiabatic gates for a radiationless decay to the ground state. The photophysical scheme which emerges from the theoretical study is related to recent experimental results obtained for SMA and its derivatives in the low-temperature argon matrices (J. Grzegorzek, A. Filarowski, Z. Mielke, Phys. Chem. Chem. Phys. 2011, 13, 16596-16605). Our results suggest that aromatic Schiff bases are potential candidates for optically driven molecular switches. PMID:23150465

Jankowska, Joanna; Rode, Micha? F; Sadlej, Joanna; Sobolewski, Andrzej L

2012-12-21

14

A NEW EXPANDED SCHIFF-BASE CRYPTAND  

Microsoft Academic Search

A new expanded Schiff-base cryptand derived from the direct ‘2 + 3? cyclocondensation of tris(2-aminoethyl)amine (tren) and 2,6-bis[formylphenoxymethyl]-pyridine (bfpp) is reported with its dinuclear copper (II) perchlorate complex. Reaction of tren and bfpp in the same ratio and in the presence of metal templates gave metal complexes of ‘1 + 1’ and ‘2 + 2’ macrocycles bearing one and two

David E. Fenton; Blanca A. Nájera

2001-01-01

15

Schiff bases: a short survey on an evergreen chemistry tool.  

PubMed

The review reports a short biography of the Italian naturalized chemist Hugo Schiff and an outline on the synthesis and use of his most popular discovery: the imines, very well known and popular as Schiff Bases. Recent developments on their "metallo-imines" variants have been described. The applications of Schiff bases in organic synthesis as partner in Staudinger and hetero Diels-Alder reactions, as "privileged" ligands in the organometallic complexes and as biological active Schiff intermediates/targets have been reported as well. PMID:24108395

Qin, Wenling; Long, Sha; Panunzio, Mauro; Biondi, Stefano

2013-01-01

16

Factors determining tautomeric equilibria in Schiff bases  

NASA Astrophysics Data System (ADS)

Schiff bases derived from o-hydroxyaldehydes present keto and enol tautomeric forms; the relative equilibrium between these two tautomers depending on the particular aldehyde the Schiff bases is derived from. Thus benzaldehyde produces a stable enol tautomer, while a naphthaldehyde produces a mixture of keto and enol tautomers. The energy difference between these tautomers is very small (˜5 kJ/mol) and therefore close to current precision limits of ab initio and DFT based quantum calculations. NMR spectroscopy results, which allows for the determination of the stable structure when one tautomer is prevalent, can be very difficult to interpret when both tautomers are present. We calculate energy differences between the tautomers and demonstrate that the precision of current DFT calculations is not sufficient to predict the most stable structure. On the other hand, DFT calculations of the NMR chemical shifts (using the GIAO technique) can properly interpret the spectroscopy results allowing the characterization of the experimentally present tautomers and the estimation of the relative abundance of each when both are present.

Flores-Leonar, Martha; Esturau-Escofet, Nuria; Méndez-Stivalet, José M.; Marín-Becerra, Armando; Amador-Bedolla, Carlos

2011-12-01

17

Anion recognition by simple chromogenic and chromo-fluorogenic salicylidene Schiff base or reduced-Schiff base receptors.  

PubMed

This review contains extensive application of anion sensing ability of salicylidene type Schiff bases and their reduced forms having various substituents with respect to phenolic OH group. Some of these molecular systems behave as receptor for recognition or sensing of various anions in organic or aqueous-organic binary solvent mixture as well as in the solid supported test kits. Development of Schiff base or reduced Schiff base receptors for anion recognition event is commonly based on the theory of hydrogen bonding interaction or deprotonation of phenolic -OH group. The process of charge transfer (CT) or inhibition of excited proton transfer (ESIPT) or followed by photo-induced electron transfer (PET) lead to naked-eye color change, UV-vis spectral change, chemical shift in the NMR spectra and fluorescence spectral modifications. In this review we have tried to discuss about the anion sensing properties of Schiff base or reduced Schiff base receptors. PMID:24759755

Dalapati, Sasanka; Jana, Sankar; Guchhait, Nikhil

2014-08-14

18

Microwave-Induced Synthesis of Schiff Bases of Aminothiazolyl Bromocoumarins as Antibacterials  

PubMed Central

A fast and highly efficient method for the synthesis of some of the schiff bases of aminothiazolylbromocoumarin (4a-m) has been performed by microwave irradiation of 2?-amino-4?-(6-bromo-3-coumarinyl) thiazole (3) and substituted aromatic aldehydes (a-m). Microwave assisted reactions have resulted in better yields of the desired products than when prepared under conventional conditions. The resulting products were evaluated for their qualitative and quantitative antibacterial activity.

Venugopala, K. N.; Jayashree, B. S.

2008-01-01

19

Microwave-induced synthesis of schiff bases of aminothiazolyl bromocoumarins as antibacterials.  

PubMed

A fast and highly efficient method for the synthesis of some of the schiff bases of aminothiazolylbromocoumarin (4a-m) has been performed by microwave irradiation of 2'-amino-4'-(6-bromo-3-coumarinyl) thiazole (3) and substituted aromatic aldehydes (a-m). Microwave assisted reactions have resulted in better yields of the desired products than when prepared under conventional conditions. The resulting products were evaluated for their qualitative and quantitative antibacterial activity. PMID:20390087

Venugopala, K N; Jayashree, B S

2008-01-01

20

Facile synthesis of acridine derivatives by ZnCl2-promoted intramolecular cyclization of o-arylaminophenyl Schiff bases.  

PubMed

A concise and efficient method for the synthesis of a wide range of acridine derivatives and polycyclic aza-aromatic compounds from a ZnCl2-promoted cyclization reaction of readily available o-arylaminophenyl Schiff base compounds under convenient conditions was developed. Reaction conditions and scope of the new method were examined in detail. PMID:24350595

Su, Qing; Li, Pei; He, Mina; Wu, Qiaolin; Ye, Ling; Mu, Ying

2014-01-01

21

Study on preparation of modified lubricant containing nano-Schiff base and Schiff base copper complex in W\\/O microemulsion reactor  

Microsoft Academic Search

A successful preparation of Schiff base and Schiff base copper complex was carried out directly in polar base oil (vegetable\\u000a oil) using a water\\/oil microemulsion reactor. The prepared nanometer sized Schiff base and Schiff base copper complex dispersed\\u000a uniformly and spontaneously in the oil. The nanometer sized particles of the Cu(II) chelate of bissalicylaldehyde-ethylenediamine\\u000a and the bissalicylaldehyde-ethylenediamine in oil were

Xinlei Gao; Jian Li; Wanzhen Gao

2009-01-01

22

Synthesis, characterization and antibacterial properties of Schiff bases and Schiff base metal complexes derived from 2,3-diamino- pyridine  

Microsoft Academic Search

New copper(II), zinc(II) and nickel(II) Schiff base complexes derived from 2,3-diaminopyridine (DAPY) and selected aldehydes, namely salicylaldehyde (SalH), 4-hydroxybenzaldehyde (4-OHBenz) and 4-nitrobenzaldehyde (4-NO2Benz), and one mixed Schiff base, DAPY-{4-OHBenz}{SalH} were prepared and characterized by a combination of elemental analyses, i.r. and n.m.r. spectra, and magnetic susceptibility measurements. The Schiff bases and some of the metal complexes display antibacterial properties.

Tagenine Jeewoth; Minu G. Bhowon; Henri Li Kam Wah

1999-01-01

23

Enol-keto tautomerism of aromatic photochromic Schiff base N,N'-bis(salicylidene)-p-phenylenediamine: Ground state equilibrium and excited state deactivation studied by solvatochromic measurements on ultrafast time scale  

NASA Astrophysics Data System (ADS)

A photochromic symmetric Schiff base, N,N'-bis(salicylidene)-p-phenylenediamine, is proposed as a probe for the study of solvent dependent enol-keto tautomerism in the ground and excited states. The ground state equilibrium between the enol-keto tautomers is found to depend mainly not on polarity but on the proton donating ability of the solvent. Upon selective excitation of each of these tautomers, the same excited state of a keto tautomer is created: in enol, after the ultrafast excited state intramolecular proton transfer (ESIPT), reaction, and in keto tautomer, directly. Then some part (<30%) of excited molecules are transferred to the photochromic form in its ground state. The evidence of another ultrafast deactivation channel in the excited enol tautomer competing with ESIPT has been found. The solvent does not influence the ESIPT dynamics nor the efficiency of the creation of the photochrome.

Zió?ek, Marcin; Kubicki, Jacek; Maciejewski, Andrzej; Naskr?cki, Ryszard; Grabowska, Anna

2006-03-01

24

Mechanism of base-catalyzed Schiff base deprotonation in halorhodopsin  

SciTech Connect

It has been shown earlier that the deprotonation of the Schiff base of illuminated halorhodopsin proceeds with a much lower pK/sub a/ than that of the unilluminated pigment and the reversible protonation change is catalyzed by azide and cyanate. The authors have studied the kinetics of the proton-transfer events with flash spectroscopy and compared a variety of anionic bases with different pK/sub a/ with regard to the apparent binding constants and the catalytic activities. The results suggest a general base catalysis mechanism in which the anionic bases bind with apparently low affinity to halorhodopsin, although with some degree of size- and/or shape-dependent specificity. The locus of the catalysis is accessible from the cytoplasmic side of the membrane and is not at site I, where various anions bind and shift the pK/sub a/ of the deprotonation. Neither is it at site II, where a few specific anions (like chloride) bind to the all-trans pigment. It may be concluded that while the all-trans pigment loses its Schiff base proton very rapidly at its pK/sub a/, there is a kinetic barrier to this deprotonation in the 13-cis photointermediate that can be partially overcome by the reversible protonation of an extrinsic anionic base, which shuttles protons between the interior of the protein and the aqueous medium. The need for an extrinsic proton acceptor for efficient deprotonation of the Schiff base of halorhodopsin is one of the main differences between this pigment and the analogous retinal protein, bacteriorhodopsin.

Lanyi, J.K.

1986-10-21

25

Multistate/multifunctional switches based on photochromic Schiff base  

NASA Astrophysics Data System (ADS)

The salicylidene Schiff base derivative, namely, N-salicylidene-( S)-?-naphthylethylamine (SNEA) has been synthesized to study the characterization of multistate/multifunctional switches. Upon the stimulations of optical inputs (UV light and visible light) and chemical inputs (pH and Zn 2+), SNEA undergoes reversible photochromism, deprotonation and complexation reactions. In this case, four chemical species are involved. These interconversions of SNEA between four states have been systematically investigated by the absorption and the emission spectra. Spectroscopic studies indicate that the photochromic switch, pH switch and fluorescent switch can be realized using the single molecular entity of SNEA.

Zhao, Liyan; Hou, Qiufei; Sui, Dan; Wang, Yue; Jiang, Shimei

2007-07-01

26

Chiral copper-Schiff base catalyst for asymmetric henry reaction  

Microsoft Academic Search

Five copper-Schiff base complexes were synthesized conveniently from copper(II) acetate monohydrate, salicylaldehydes, and\\u000a amino alcohols. The complexes were shown to be effective as catalysts in the asymmetric Henry reaction affording nitro alkanols\\u000a in up to 98% yield with moderate and good enantiomeric excess (up to ee 38.6%).

Yong-guang Gao; Na Chen; Hua-jiang Wu; Xin-sheng Li

2007-01-01

27

Protein (tyrosine)-chromophore (protonated Schiff base) coupling in bacteriorhodopsin  

SciTech Connect

The kinetics of formation of both the tyrosinate ion (from its absorption at 296 nm) and the deprotonated Schiff base (M/sub 412/) (from its absorption at 404 nm) are studied simultaneously at different pH values (7-11) and temperatures (5-25/sup 0/C). Two formation rates are observed for M/sub 412/ in agreement with previous observations. The slow one is dominant under physiological conditions and is found to be slightly faster than that for the tyrosinate formation. This is in disagreement with the proposal that the tyrosinate formation is a prerequisite to the deprotonation of the Schiff base (M/sub 412/). The ratio of the amplitudes of the fast and slow components is found to be sensitive to pH and, at any pH, it can be used to calculate an amino acid pK/sub a/ value of 9.6. This is explained by proposing the existence of two sites for the protonated Schiff base within the protein. In one site, the Schiff base is near the neutral form of an amino acid residue with a pK/sub a/ value of 9.6 (giving rise to the slow component), while in the other, it is near its conjugate base. The formation of the tyrosinate ion as well as the formation of the slow and fast components of M/sub 412/ all have activation energies that are comparable to H-bond energies. A model is suggested to account for this and the comparable deprotonation rates of tyrosine and the slow component of the protonated Schiff base. It involves the reduction of their pK/sub a/ by their exposure to a positively charged species. 43 references, 2 figures, 2 tables.

Hanamoto, J.H.; Dupuis, P.; El-Sayed, M.A.

1984-11-01

28

Synthesis of Schiff bases of naphtha[1,2-d]thiazol-2-amine and metal complexes of 2-(2?-hydroxy)benzylideneaminonaphthothiazole as potential antimicrobial agents  

PubMed Central

Objective: A series of 2-benzylideneaminonaphthothiazoles were designed and synthesized incorporating the lipophilic naphthalene ring to render them more capable of penetrating various biomembranes. Methods: Schiff bases were synthesized by the reaction of naphtha[1,2-d]thiazol-2-amine with various substituted aromatic aldehydes. 2-(2?-Hydroxy)benzylideneaminonaphthothiazole was converted to its Co(II), Ni(II) and Cu(II) metal complexes upon treatment with metal salts in ethanol. All the compounds were evaluated for their antibacterial activities by paper disc diffusion method with Gram positive Staphylococcus aureus and Staphylococcus epidermidis and Gram negative Escherichia coli and Pseudomonas aeruginosa bacteria. The minimum inhibitory concentrations of all the Schiff bases and metal complexes were determined by agar streak dilution method. Results: All the compounds moderately inhibited the growth of Gram positive and Gram negative bacteria. In the present study among all Schiff bases 2-(2?-hydroxy)benzylideneaminonaphthothiazole showed maximum inhibitory activity and among metal complexes Cu(II) metal complex was found to be most potent. Conclusion: The results obtained validate the hypothesis that Schiff bases having substitution with halogens, hydroxyl group and nitro group at phenyl ring are required for the antibacterial activity while methoxy group at different positions in the aromatic ring has minimal role in the inhibitory activity. The results also indicated that the metal complexes are better antibacterial agents as compared to the Schiff bases.

Azam, Faizul; Singh, Satendra; Khokhra, Sukhbir Lal; Prakash, Om

2007-01-01

29

Construction of Novel Zn-Ni Trinuclear Schiff Base and a Ni2+ Chemosensor  

SciTech Connect

The novel Schiff base Zn-Ni trinuclear complex (Zn[Ni(sy- L2)]2(SCN)2, where sy-H2L2 = H2acacen = bis(acetylacetone)ethylenediamine), which is the first trinuclear compound based on symmetric acacen-base Schiff base ligand, was constructed through Ni2+-selective assembly of chemosensor Schiff base zinc compound Zn[(sy-H2L2)(SCN)]2?(CH3CN)2.

Li, Guo-Bi; Fang, Hua-Cai; Cai, Yue-Peng; Zhou, Zheng-Yuan; Thallapally, Praveen K.; Tian, Jian

2010-07-14

30

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

31

Synthesis and characterization of thermally stable Schiff base polymers and their copper(II), cobalt(II) and nickel(II) complexes  

Microsoft Academic Search

In this study, the Schiff base monomers [(M1; N,N?-p-phenylenebis(salicylideneimine)) and ethylenediamine (M2; N,N?-p-ethylenebis(salicylideneimine))] were synthesized by the condensation reaction between p-phenylenediamine and aromatic aldehydes. The Schiff base polymers (SBPs) having double azomethine groups were prepared by oxidative polycondensation (OP) reaction of monomers in aqueous alkaline medium with NaOCl [P1; poly-(N,N?-p-phenylenebis(salicylideneimine)) and P2; poly-(N,N?-p-ethylenebis(salicylideneimine))] as the oxidant at 90°C. Average molecular

M. Tunçel; A. Özbülbül

2008-01-01

32

Study of the schiff base mode in bovine rhodopsin and bathorhodopsin  

SciTech Connect

The authors have obtained the resonance Raman spectra of bovine rhodopsin, bathorhodopsin, and isorhodopsin for a series of isotopically labeled retinal chromophores. The specific substitutions are at retinal's protonated Schiff base moiety and include -HC=NH/sup +/-, -HC=ND/sup +/-. -H/sup 13/C=NH/sup +/-, and -H/sup 13/C=ND/sup +/-. Apart from the doubly labeled retinal, they find that the protonated Schiff base frequency is the same, within experimental error, for both rhodopsin and bathorhodopsin for all the substitutions measured here and elsewhere. They develop a force field that accurately fits the observed ethylenic (C=C) and protonated Schiff base stretching frequencies of rhodopsin and labeled derivatives. Using MINDO/3 quantum mechanical procedures, they investigate the response of this force field, and the ethylenic and Schiff base stretching frequencies, to the placement of charges close to retinal's Schiff base moiety. Specifically, they find that the Schiff base frequency should be measurably affected by a 3.0-4.5-A movement of a negatively charged counterion from the positively charged protonated Schiff base moiety. That there is no experimentally discernible difference in the Schiff base frequency between rhodopsin and bathorhodopsin suggests that models for the efficient conversion of light to chemical energy in the rhodopsin to bathorhodopsin photoconversion based solely on salt bridge separation of the protonated Schiff base and its counterion are probably incorrect. They discuss various alternative models and the role of electrostatics in the rhodopsin to bathorhodopsin primary process.

Deng, H.; Callender, R.H.

1987-11-17

33

Second harmonic generation from Langmuir-Blodgett films of retinal and retinal Schiff bases  

SciTech Connect

The second harmonic signal from monolayers of retinal and retinal Schiff bases is reported. The results have yielded information on the monolayer structure and demonstrate that retinal and retinal Schiff bases have large second-order molecular hyperpolarizabilities with values of 1.4 x 10/sup -28/, 1.2 x 10/sup -28/, and 2.3 x 10/sup -28/ esu for retinal, the unprotonated Schiff base, and the protonated Schiff base, respectively. These values compare well with the known variation in the alteration in the dipole moment of such chromophores upon excitation.

Huang, J.; Lewis, A.; Rasing, T.

1988-04-07

34

Synthesis and AntiBacterial\\/Catalytic Properties of Schiff Bases and Schiff Base Metal Complexes Derived from 2,3-Diaminopyridine  

Microsoft Academic Search

Two new Schiff bases (1a)-(2a) derived from 2,3-diaminopyridine (DAPY) with pyrrole-2-carboxaldehyde (Pyrr) and 2-hydroxy-1-naphthaldehyde (NaphH), and new copper(II), iron(III), nickel(II), ruthenium(II) and zinc(II) complexes (1b)-(1e), (2b)-(2f) and (3b)-(3d) derived from these two new Schiff bases, and the bis-condensed Schiff base of 2,3-diaminopyridine and salicylaldehyde (SalH) were synthesized. They were characterized by a combination of elemental analyses, magnetic susceptibility measurements, IR

T. Jeewoth; H. Li Kam Wah; Minu G. Bhowon; D. Ghoorohoo; K. Babooram

2000-01-01

35

Aminic nitrogen- bearing polydentate Schiff base compounds corrosion inhibitors iron acidic alkaline media: combined experimental Daft studies Aminic nitrogen- bearing polydentate Schiff base compounds corrosion inhibitors iron acidic alkaline media: combined experimental Daft studies LDV H Madkour  

EPA Pesticide Factsheets

Did you mean: Aminic nitrogen- bearing polydentate Schiff base compounds corrosion inhibitors iron acidic alkaline media: combined experimental Daft studies Aminic nitrogen- bearing polydentate Schiff base compounds corrosion inhibitors iron acidic alkaline media: combined experimental Daft studies LDV H Madkour ?

36

Copper(II) selective electrochemical sensor based on Schiff Base complexes  

Microsoft Academic Search

Plasticized membranes using Schiff Base complexes, derived from 2,3-diaminopyridine and o-vanilin have been prepared and explored as Cu2+-selective sensors. Effect of various plasticizers viz., dibutyl phthalate (DBP), dioctylphthalate (DOP), chloronaphthalene (CN), tri-n-butylphosphate (TBP) etc. and anion excluder, sodium tetraphenylborate (NaTPB) was studied in detail and improved performance was observed at several instances. Optimum performance was observed with Schiff Base (B)

Lok P. Singh; Jitendra M. Bhatnagar

2004-01-01

37

Synthesis, characterization, and analgesic activity of novel schiff base of isatin derivatives  

PubMed Central

In the present study, a series of novel Schiff bases of isatin [5a-5l] were synthesized by condensation of imesatin with different aromatic aldehydes. The imesatins were synthesized by the reaction of isatin with p-phenylenediamine. The chemical structures of the synthesized compounds were confirmed by means of Infrared (IR), Mass spectroscopy, and Elemental analysis. These compounds were screened for the analgesic activity by the tail-immersion method at a dose of 200 mg/kg body weight. Among the tested compounds 3-(4-(4-hydroxy-3-methoxylbenzylideneamino) phenylimino) indoline-2-one (5i) exhibited better analgesic activity when compared to standard pentazocine. From the above-mentioned results it may be concluded that compounds containing electron-donating groups exhibit better analgesic activity than the electron-withdrawing groups.

Chinnasamy, Rajaram Prakash; Sundararajan, Raja; Govindaraj, Saravanan

2010-01-01

38

Evidence for a bound water molecule next to the retinal Schiff base in bacteriorhodopsin and rhodopsin: a resonance Raman study of the Schiff base hydrogen/deuterium exchange.  

PubMed Central

The retinal chromophores of both rhodopsin and bacteriorhodopsin are bound to their apoproteins via a protonated Schiff base. We have employed continuous-flow resonance Raman experiments on both pigments to determine that the exchange of a deuteron on the Schiff base with a proton is very fast, with half-times of 6.9 +/- 0.9 and 1.3 +/- 0.3 ms for rhodopsin and bacteriorhodopsin, respectively. When these results are analyzed using standard hydrogen-deuteron exchange mechanisms, i.e., acid-, base-, or water-catalyzed schemes, it is found that none of these can explain the experimental results. Because the exchange rates are found to be independent of pH, the deuterium-hydrogen exchange can not be hydroxyl (or acid-)-catalyzed. Moreover, the deuterium-hydrogen exchange of the retinal Schiff base cannot be catalyzed by water acting as a base because in that case the estimated exchange rate is predicted to be orders of magnitude slower than that observed. The relatively slow calculated exchange rates are essentially due to the high pKa values of the Schiff base in both rhodopsin (pKa > 17) and bacteriorhodopsin (pKa approximately 13.5). We have also measured the deuterium-hydrogen exchange of a protonated Schiff base model compound in aqueous solution. Its exchange characteristics, in contrast to the Schiff bases of the pigments, is pH-dependent and consistent with the standard base-catalyzed schemes. Remarkably, the water-catalyzed exchange, which has a half-time of 16 +/- 2 ms and which dominates at pH 3.0 and below, is slower than the exchange rate of the Schiff base in rhodopsin and bacteriorhodopsin. Thus, there are two anomalous results, the inconsistency of the observed hydrogen exchange rates of retinal Schiff base in the two pigments with those predicted from the standard exchange schemes and the enhancement of the rate of hydrogen exchange in the two proteins over the model Schiff base in aqueous solution. We suggest that these results are explained by the presence of a structural water molecule (or molecules) at the retinal binding sites of the two pigments, quite close, probably-hydrogen bonded, to the Schiff base proton. In this case, the rate of exchange can be faster than that found for the model compound due to an "effective water concentration" near the Schiff base that is increased from that found in aqueous solution.

Deng, H.; Huang, L.; Callender, R.; Ebrey, T.

1994-01-01

39

Copper(II) Schiff-base complexes and apoglobin stability  

Microsoft Academic Search

N,N?-Propylene-bis-(N-salicylidene)copper(II) (Cu(Salprn)) explicitly stabilizes apomyoglobin. The optical spectrum of this copper(II) Schiff-base complex of apomyoglobin arises from the electronic excitations of ?*-O-Salprn?dx2-y2 and N-Salprn?dx2-y2. Shifts of these transitions with respect to those of the parent complex may be a consequence of hydrophobic solvatochromism or binding of an additional ligand. ESR parameters imply no change in the identity of the first

Joseph J. Stephanos; Leia M. Jackson; Anthony W. Addison

1999-01-01

40

The synthesis and antioxidant activity of the Schiff bases of chitosan and carboxymethyl chitosan  

Microsoft Academic Search

Five kinds of Schiff bases of chitosan and carboxymethyl chitosan (CMCTS) have been prepared according to a previous method and the antioxidant activity was studied using an established system, such as superoxide and hydroxyl radical scavenging. Obvious differences between the Schiff bases of chitosan and CMCTS were observed, which might be related to contents of the active hydroxyl and amino

Zhanyong Guo; Ronge Xing; Song Liu; Huahua Yu; Pibo Wang; Cuiping Li; Pengcheng Li

2005-01-01

41

Synthesis of a new series of chiral Schiff's bases and their copper complexes  

Microsoft Academic Search

A new series of chiral Schiff's bases containing 2-hydroxybenzilideneaniline moieties and their copper complexes were synthesized and studied by differential scanning calorimetry, polarized optical microscopy, X-ray diffraction and EPR measurement. The results show that most of the Schiff's bases and only two of the copper complexes exhibited chiral smectic liquid crystal phases.

Yanqing Tian; Fengyu Su; Peixiang Xing; Yingying Zhao; Xinyi Tang; Xiaoguang Zhao; Enle Zhou

1996-01-01

42

Synthesis, fluorescence study and biological evaluation of three Zn(II) complexes with Paeonol Schiff base  

Microsoft Academic Search

The synthesis of three Paeonol Schiff base ligand and their Zn(II) complexes are reported. The complexes were fully characterized by IR, 1H NMR, elemental analysis and molar conductivity. The experiment results show the three Zn(II) complexes can emit bright fluorescence at room temperature in DMF solution and solid state. The fluorescence quantum yields (?) of three Schiff base ligands and

Dong-Dong Qin; Zheng-Yin Yang; Gao-Fei Qi

2009-01-01

43

Controlling the pKa of the bacteriorhodopsin Schiff base by use of artificial retinal analogues  

SciTech Connect

Artificial bacteriorhodopsin pigments based on synthetic retinal analogues carrying an electron-withdrawing CF3 substituent group were prepared. The effects of CF3 on the spectra, photocycles, and Schiff base pKa values of the pigments were analyzed. A reduction of 5 units in the pKa of the Schiff base is observed when the CF3 substituent is located at the C-13 polyene position, in the vicinity of the protonated Schiff base nitrogen. The results lead to the unambiguous characterization of the (direct) titration of the Schiff base in bacteriorhodopsin and to the conclusion that the deprotonation rate of the Schiff base during the photocycle (i.e., the generation of the M412 intermediate) is determined by a structural change in the protein.

Sheves, M.; Albeck, A.; Friedman, N.; Ottolenghi, M.

1986-05-01

44

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

45

Two-photon, /sup 13/C and two-dimensional /sup 1/H NMR spectroscopic studies of retinyl Schiff bases, protonated Schiff bases, and Schiff base salts: evidence for a protonation induced. pi pi. * excited state level ordering reversal  

SciTech Connect

The ..pi pi..* excited singlet state manifolds of the visual chromophores, all-trans-retinylpyrrolidiniminium perchlorate (ATRSBS) and all-trans-N-retinylidene-n-butylimine:HCl (ATRPSB) are studied by using one-photon and two-photon laser spectroscopy. The goal is a better understanding of how protonation and counterion location affect level ordering in retinyl Schiff bases. Ambient temperature two-photon thermal lensing spectra indicate that ATRSBS has a lowest lying /sup 1/A/sub g/*/sup -/-like state as was observed previously for all-trans-retinal and the Schiff base of all-trans-retinal. In contrast, two-photon spectra of ATRPSB indicate that the protonated Schiff base has a lowest lying /sup 1/B/sub u/*/sup +/-like state. The origin of this level ordering reversal is analyzed by using molecular orbital theory as well as /sup 13/C and two-dimensional /sup 1/H NMR. They conclude that the relative level ordering of the low-lying covalent and ionic ..pi pi..* excited states of protonated Schiff bases and Schiff base salts is highly sensitive to counterion location (diffuseness). INDO-PSDCI molecular orbital theory is shown to be a reliable theoretical method of predicting the effect of counterion location on the one-photon and two-photon properties of retinyl protonated Schiff bases and Schiff base salts. This study provides further experimental support for the conclusions of a previous two-photon investigation of the rhodopsin binding site which demonstrated that the protein bound 11-cis-retinyl chromophore is protonated and occupies a neutral binding site.

Birge, R.R.; Murray, L.P.; Zidovetzki, R.; Knapp, H.M.

1987-04-01

46

Exceptionally small supramolecular hydrogelators based on aromatic-aromatic interactions  

PubMed Central

Summary We report herein the use of an aromatic–aromatic interaction to produce small molecule hydrogelators that self-assemble in water and form molecular nanofibers in the resulting hydrogels. Among these hydrogelators, a hydrogelator (6) made from a phenylalanine and a cinnamoyl group represents the lowest molecular weight (MW = 295.33 g/mol) peptide-based hydrogelator prepared to date. The supramolecular hydrogels were characterized by transmission electron micrograph (TEM) and fluorescence spectroscopy, and the results obtained by both techniques correlate well with their rheological properties. Notably, compound 6 can undergo cis/trans-isomerization upon UV irradiation.

Shi, Junfeng; Gao, Yuan; Yang, Zhimou

2011-01-01

47

Synthesis, characterization, and spectroscopic investigation of benzoxazole conjugated Schiff bases.  

PubMed

Two Schiff bases were synthesized by reaction of 2-(4'-aminophenyl)benzoxazole derivatives with 4-N,N-diethylaminobenzaldehyde. UV-visible (UV-vis) and steady-state fluorescence in solution were applied in order to characterize its photophysical behavior. The Schiff bases present absorption in the UV region with fluorescence emission in the blue-green region, with a large Stokes' shift. The UV-vis data indicates that each dye behaves as two different chromophores in solution in the ground state. The fluorescence emission spectra of the dye 5a show that an intramolecular proton transfer (ESIPT) mechanism takes place in the excited state, whereas a twisted internal charge transfer (TICT) state is observed for the dye 5b. Theoretical calculations were performed in order to study the conformation and polarity of the molecules at their ground and excited electronic states. Using density functional theory (DFT) methods at theoretical levels BLYP/Aug-SV(P) for geometry optimizations and B3LYP/6-311++G(2d,p) for single-point energy evaluations, the calculations indicate that the lowest energy conformations are in all cases nonplanar and that the dipole moments of the excited state relaxed structures are much larger than those of the ground state structures, which corroborates the experimental UV-vis absorption results. PMID:21988352

Santos, Fabiano S; Costa, Tania M H; Stefani, Valter; Gonçalves, Paulo F B; Descalzo, Rodrigo R; Benvenutti, Edilson V; Rodembusch, Fabiano S

2011-11-24

48

Titanium(IV) complexes of disulfide-linked Schiff bases.  

PubMed

With the goal of preparing Ti(IV) complexes bearing a sulfur-based redox function of possible use in electrocatalytic oxidations of alcohols at electrode surfaces, a series of seven 2,2'-dithiodianiline Schiff-base derivatives, including two new variations, were tested in reactions with Ti(OR)(4) (R = (i)Pr, (t)Bu). Instead of the expected dimetallic products of general formula [LTi(OR)(2)](2), mononuclear species LTi(OR)(2) were obtained, confirmed by crystallographic determinations to have an unprecedented, symmetrical, and macrocyclic arrangement with four-point binding to the metal center and with the disulfide moieties remaining uncoordinated. Cyclic voltammetry performed in CH(2)Cl(2) displayed oxidations at potentials useful for fuel cells (+1.1-1.5 V vs Ag/AgCl), but despite the uncoordinated disulfide moieties, the complexes were reticent to engage in reduction processes. PMID:22515278

Donzelli, Alberto; Metushi, Imir; Potvin, Pierre G

2012-05-01

49

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

50

The effect of some Schiff bases on the corrosion of aluminum in hydrochloric acid solution  

Microsoft Academic Search

The inhibition effect of Schiff bases benzylidene-(2-methoxy-phenyl)-amine (A), (2-methoxy-phenyl)-(4-methyl-benzylidene)-amine (B), (4-chloro-benzylidene)-(2-methoxy-phenyl)-amine (C) and (4-nitro-bezylidene)-(2-methoxy-phenyl)-amine (D) on the corrosion of aluminum in 1M HCl has been studied by polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. It has been found that all the studied Schiff bases are excellent inhibitors. Maximum inhibition was obtained for 0.01M Schiff base A. Results show

H. Ashassi-Sorkhabi; B. Shabani; B. Aligholipour; D. Seifzadeh

2006-01-01

51

Optical pH sensor based on spectral response of newly synthesized Schiff bases  

Microsoft Academic Search

In most of the common designs, pH optodes rely on weak acidic dyes whose dissociated and undissociated forms have different absorption or emission maximums. In this work the newly synthesized Schiff bases; N,N?-bis(4-diaminobenzyliden)-1,2-cyclohexandiamine [I], N,N?-bis(4-diaminobenzyliden)-1,2-ethanediamine [II] and 2,6-bis[(4-dimethylaminophenylimino)ethyl]pyridine [III], have been used for pH sensing in four different plasticized PVC matrices. The Schiff bases exhibited absorption and emission based optical

Cemal Hazneci; Kadriye Ertekin; Berrin Yenigul; Engin Cetinkaya

2004-01-01

52

Porous coordination polymers based on functionalized Schiff base linkers: enhanced CO2 uptake by pore surface modification.  

PubMed

We report the synthesis, structural characterization and adsorption properties of three new porous coordination polymers {[Cu(Meazpy)0.5(glut)](H2O)}n (2), {[Zn(azpy)0.5(terep)](H2O)}n (3), and {[Zn(Meazpy)0.5(terep)]}n (4) [glut = glutarate, terep = terephthalate, azpy = N,N'-bis-(pyridin-4-ylmethylene)hydrazine and Meazpy = N,N'-bis-(1-pyridin-4-ylethylidene)hydrazine] composed of mixed linkers systems. Structure determination reveals that all three compounds have three-dimensional (3D) coordination frameworks bridged by dicarboxylates and Schiff base linkers. In all cases 2D dicarboxylate layers are supported by paddle-wheel M2(CO2)4 SBUs extended in three dimensions by designed Schiff base linkers. Compound 1, which has been reported in a paper earlier by our group, is a robust porous three-dimensional (3D) framework whose pore surface was found to be decorated with the -CH=N- groups of a linear Schiff base (azpy) and it showed reversible single-crystal-to-single-crystal transformation and selective CO2 uptake. By using another linear Schiff base linker Meazpy, we have synthesized compound 2 which is isostructural with 1, having an additional methyl group pointing towards the pore. Like 1 it also shows a reversible single-crystal-to-single-crystal transformation upon dehydration and rehydration. The dehydrated framework of 2 exhibits 50% enhanced CO2 uptake compared to 1. This has been achieved by the pore surface modification effected upon changing the pillar backbone from a -CH=N- to -CMe=N- group. It also adsorbs water vapour at 298 K. In the case of the two isostructural 3D MOFs 3and 4, the use of a rigid carboxylate (terephthalate) linker arrested porosity by three-fold interpenetration. We showed that the use of aliphatic dicarboxylate (glutarate) results in a non-interpenetrated framework rather than the common interpenetrated framework with aromatic dicarboxylates in mixed ligand systems. PMID:24301962

Bhattacharya, Biswajit; Haldar, Ritesh; Dey, Rajdip; Maji, Tapas Kumar; Ghoshal, Debajyoti

2014-02-01

53

Polymer Supported Calix[4]arene Schiff Bases: A Novel Chelating Resin for Hg and Dichromate Anions  

Microsoft Academic Search

This article describes the synthesis and characterization of two new calix[4]arene Schiff bases and their polymeric resins. The extraction properties of these “proton switchable extractants” with alkali, transition, post transition metal cations and for dichromate anions are reported. The two new calix[4]arene based Schiff bases (5 and 6) have been synthesized from 5,17?diformyl?25,27?dipropoxy?26,28?dihydroxycalix[4]arene (4) by treatment with 3?amino?methylpyridine and 1,8?diaminooctane

Aysegül Karakücük; Erdal Kocabas; Abdulkadir Sirit; Shahabuddin Memon; Mustafa Yilmaz; D. Max Roundhill

2005-01-01

54

Catalytic, Asymmetric Cyclopropanation of Diphenylethene Mediated by Chiral Copper(Schiff Base) Complexes  

Microsoft Academic Search

Asymmetric cyclopropanation of diphenylethene with diazoacetates was catalyzed by new copper-(Schiff base) complexes. The\\u000a effects of the substituents in substituted salicylaldehyde on the ee's were studied, and a 94.5% ee was achieved.

Zhengning Li; Huilin Chen

2001-01-01

55

Efficient and enantioselective nitroaldol reaction catalyzed by copper Schiff-base complexes  

Microsoft Academic Search

Mild and efficient enantioselective nitroaldol reactions of nitromethane with various aldehydes were catalyzed by chiral copper Schiff-base complexes, which can be readily prepared from amino acid, yielding the corresponding adducts with high yields and good enantiometric excess (ee).

Changsheng Gan; Guoyin Lai; Zuhui Zhang; Zhiyong Wang; Ming-Ming Zhou

2006-01-01

56

Derivatives of phosphate Schiff base transition metal complexes: synthesis, studies and biological activity  

Microsoft Academic Search

We report the synthesis and structural characterization of series of tetra- and hexacoordinate metal chelate complexes of phosphate Schiff base ligands having the general composition LMXn·H2O and L2MXn (L=phosphate Schiff base ligand; M=Ag+, Mn2+, Cu2+, Zn2+, Cd2+, Hg2+, or Fe3+ and X=NO3?, Br? or Cl?). The structure of the prepared compounds was investigated using elemental analysis, IR, 1H and 31P

Z. H. Abd El-Wahab; M. R. El-Sarrag

2004-01-01

57

Cobalt (II), manganese (II) complexes with bidentate Schiff bases of benzhydrazide: Synthesis, characterization and electrochemical studies  

Microsoft Academic Search

The synthesis, characterization and cyclic voltammetry of some benzhydrazide Schiff bases and their metal complexes are reported. The structures of the novel complexes were elucidated by means of FTIR, FT 1H-NMR, 13C-NMR, elemental analyses, cyclic voltammetry studies and thermal gravimetric analyses. Tautomeric properties of the ligating Schiff bases were observed from the infrared and proton N MR data. The electrochemical

S. M. Rahuma; S. O. Sharifah Rohaiza; M. A. Hapipah; B. Wan Jefrey

58

A highly enantioselective chiral Schiff-base fluorescent sensor for mandelic acid  

Microsoft Academic Search

A chiral Schiff-base compound, 4-methyl-2,6-bis-[(2-hydroxy-1-phenylethylimino)methyl]phenol, is found to act as highly enantioselective fluorescent agent for ?-hydroxycarboxylic acid, e.g., mandelic acid. It is observed that, within a certain concentration range, one enantiomer of the chiral acid can increase the fluorescence intensity of the Schiff-base compound 122-fold while the other enantiomer enhances the intensity only 42-fold. Such highly enantioselective responses towards the

Koushik Dhara; Krishanu Sarkar; Partha Roy; Mahasweta Nandi; Asim Bhaumik; Pradyot Banerjee

2008-01-01

59

Schiff bases formed from retinal and phosphatidylethanolamine, phosphatidylserine, ethanolamine or serine  

PubMed Central

1. Conditions were established for the reaction of retinal with phosphatidylethanolamine, phosphatidylserine, ethanolamine and serine in chloroform, ethanol or ethanol–water solutions to form retinylidene compounds, or Schiff bases. 2. The Schiff bases were reduced to retinyl compounds with sodium borohydride. 3. Absorption maxima and molar extinction coefficients were determined for the various retinylidene and retinyl compounds and for the corresponding coloured products formed by their reaction with antimony trichloride.

Plack, P. A.; Pritchard, D. J.

1969-01-01

60

Complexes of a tridentate ONS Schiff base. Synthesis and biological properties  

Microsoft Academic Search

Several new complexes of a tridentate ONS Schiff base derived from the condensation of S-benzyldithiocarbazate with salicylaldehyde have been characterised by elemental analyses, molar conductivity measurements\\u000a and by i.r. and electronic spectra. The Schiff base (HONSH) behaves as a dinegatively charged ligand coordinating through\\u000a the thiolo sulphur, the azomethine nitrogen and the hydroxyl oxygen. It forms mono-ligand complexes: [M(ONS)X], [M=NiII,

M. Tofazzal H. Tarafder; Manaf A. Ali; D. Juan Wee; Kasbollah Azahari; Sidik Silong; Karen A. Crouse

2000-01-01

61

New antiferromagnetic copper(II) complexes with some dibasic tridentate ONS donor Schiff bases  

Microsoft Academic Search

Summary The syntheses of new copper(II) complexes of Schiff bases derived from salicylaldehyde, 5-chlorosalicylaldehyde, 5-bromosalicylaldehyde, 4-methoxysalicylaldehyde, 5-methoxysalicylaldehyde and 3-aminothiophenol are reported. The Schiff bases coordinate through O, N and S as tridentate dibasic ligands. The complexes, which are characterised by elemental analysis, i.r. and electronic spectra and magnetic susceptibility measurements are insoluble in common solvents and decompose above 250° without

Arun Syamal

1980-01-01

62

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

63

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

NASA Astrophysics Data System (ADS)

Schiff bases (SB1-SB3) were synthesized from the condensation of 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one with 2-aminopyridine (SB1), p-phenylenediamine (SB2) and o-phenylenediamine (SB3), while Schiff bases (SB4-SB6) were synthesized by condensation of 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one with 2-aminopyridine (SB4), p-phenylenediamine (SB5) and o-phenylenediamine (SB6). Schiff bases were characterized using elemental analysis, IR, UV-Vis, 1H NMR, 13C NMR and mass spectroscopy. These compounds were screened for antibacterial activities by micro-plate assay technique. Escherichia coli and Staphylococcus capitis were exposed to different concentrations of the Schiff bases. Results showed that the antibacterial effect of these Schiff bases on Gram-negative bacteria were higher than that on Gram-positive bacteria moreover, the Schiff bases containing substituent OCH3 on position five have higher antibacterial activity than that containing hydroxy group on the same position.

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

64

The effect of some Schiff bases on the corrosion of aluminum in hydrochloric acid solution  

NASA Astrophysics Data System (ADS)

The inhibition effect of Schiff bases benzylidene-(2-methoxy-phenyl)-amine (A), (2-methoxy-phenyl)-(4-methyl-benzylidene)-amine (B), (4-chloro-benzylidene)-(2-methoxy-phenyl)-amine (C) and (4-nitro-bezylidene)-(2-methoxy-phenyl)-amine (D) on the corrosion of aluminum in 1 M HCl has been studied by polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. It has been found that all the studied Schiff bases are excellent inhibitors. Maximum inhibition was obtained for 0.01 M Schiff base A. Results show that the inhibition efficiency increases with decreasing in temperature and increasing in concentration of Schiff base. Polarization curves reveal that the used inhibitors are mixed type inhibitors. The surface adsorption of the Schiff bases leads to a decrease of double layer capacitance as well as an increase of polarization resistance. The inhibitor performance depends strongly on the type of function groups substituted on benzene ring. The adsorption of used compounds on the aluminum surface obeys a Langmuir isotherm and has a physical mechanism. Thermodynamic parameters for both dissolution and adsorption processes were determined. The quantum chemical study of the corrosion inhibition efficiency of the Schiff bases on Al in molar HCl was carried out.

Ashassi-Sorkhabi, H.; Shabani, B.; Aligholipour, B.; Seifzadeh, D.

2006-04-01

65

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

PubMed

Schiff bases (SB(1)-SB(3)) were synthesized from the condensation of 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one with 2-aminopyridine (SB(1)), p-phenylenediamine (SB(2)) and o-phenylenediamine (SB(3)), while Schiff bases (SB(4)-SB(6)) were synthesized by condensation of 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one with 2-aminopyridine (SB(4)), p-phenylenediamine (SB(5)) and o-phenylenediamine (SB(6)). Schiff bases were characterized using elemental analysis, IR, UV-Vis, (1)H NMR, (13)C NMR and mass spectroscopy. These compounds were screened for antibacterial activities by micro-plate assay technique. Escherichia coli and Staphylococcus capitis were exposed to different concentrations of the Schiff bases. Results showed that the antibacterial effect of these Schiff bases on Gram-negative bacteria were higher than that on Gram-positive bacteria moreover, the Schiff bases containing substituent OCH(3) on position five have higher antibacterial activity than that containing hydroxy group on the same position. PMID:22591797

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

2012-09-01

66

New cellulose-lysine schiff-base-based sensor-adsorbent for mercury ions.  

PubMed

Mercury is a highly toxic environmental pollutant; thus, there is an urgent need to develop new materials for its simultaneous detection and removal from water. In the present study, new oxidized cellulose-based materials, including their Schiff bases, were synthesized and investigated as a sensor-adsorbent for simple, rapid, highly selective, and simultaneous detection and removal of mercury [Hg(II)] ions. Cellulose was extracted from the pine needles, etherified, oxidized, and modified to Schiff base by reaction with l-lysine. The well-characterized cellulose Schiff base materials were used as a sensor-adsorbent for Hg(II) from aqueous solution. Hg(II) sensing was analysed with naked-eye detection and fluorescence spectroscopy. Schiff base having a decyl chain, C10-O-cell-HC?N-Lys, was observed to be an efficient adsorbent with a very high maximum adsorption capacity of 258.75 mg g(-1). The data were analyzed on the basis of various kinetic and isotherm models, and pseudo-second-order kinetics and Langmuir isotherm were followed for Hg(II) adsorption. PMID:24654907

Kumari, Sapana; Chauhan, Ghanshyam S

2014-04-23

67

Synthesis and mesomorphic properties of symmetric tetradentate Schiff bases based on azo-containing salicylaldimines and their copper(II) complexes  

Microsoft Academic Search

Two new tetradentate Schiff bases, in which two identical aromatic bent core mesogenic units containing phenylazo are connected via a 1,2-phenylene spacer, N,N?-di-(5-(4-alkoxyphenyl)azo)-salicylidene-1,2-phenylene diimine (alkoxy?=?decyloxy, dodecyloxy), and their copper(II) complexes were synthesized and studied for their mesomorphic character. The ligands were prepared by the condensation of 5-((4-alkoxyphenyl)azo)salicylaldehydes with 1,2-phenylene diamine. The ligands and their copper complexes have been characterized by

Kamellia Nejati; Zolfaghar Rezvani; Eslam Alizadeh; Razie Sammimi

2011-01-01

68

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

PubMed

A library of Schiff bases was synthesized by condensation of aromatic amines incorporating sulfonamide, carboxylic acid or carboxymethyl functionalities as Zn(2+)-binding groups, with aromatic aldehydes incorporating tert-butyl, hydroxy and/or methoxy groups. The corresponding amines were thereafter obtained by reduction of the imines. These compounds were assayed for the inhibition of two cytosolic human carbonic anhydrase (hCA, EC 4.2.1.1) isoenzymes, hCA I and II. The Ki values of the Schiff bases were in the range of 7.0-21,400nM against hCA II and of 52-8600nM against hCA I, respectively. The corresponding amines showed Ki values in the range of 8.6nM-5.3?M against hCA II, and of 18.7-251nM against hCA I, respectively. Unlike the imines, the reduced Schiff bases are stable to hydrolysis and several low-nanomolar inhibitors were detected, most of them incorporating sulfonamide groups. Some carboxylates also showed interesting CA inhibitory properties. Such hydrosoluble derivatives may show pharmacologic applications. PMID:24746465

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

2014-05-15

69

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

70

Keto forms of salicylaldehyde Schiff bases: structural and theoretical aspects.  

PubMed

Twelve Schiff bases of methoxy-substituted salicylaldehyde have been examined by crystallographic and spectroscopic methods, as well as by DFT theoretical calculations in order to investigate the effect of the substituent's position on the keto-enol equilibrium in the crystalline state. Four out of the 10 structurally characterized compounds with methoxy substitution on the para and/or ortho positions with respect to the aldimine bridge and deriving from aliphatic amines or alkylarylamines are found as cis-keto tautomers and form dimers. In contrast, the five pure enol tautomers derive either from aliphatic or alkylarylamines and are meta substituted or from aniline or benzylamine and are para and/or ortho methoxy substituted. The DFT calculations support the crystallographic results and, moreover, they have shown that keto and enol tautomers are affected differently by the relative arrangement of the monomers. Overall, the DFT calculations point to a plausible hypothesis for the stabilization of the keto form in the crystalline state: In cases with a sufficiently low enol-keto energy difference of the isolated monomers, as when the methoxy group is at ortho and/or para positions with respect to the aldimino group, extra stabilization of the keto form is derived from molecular association, thus leading to its crystallization. PMID:17125330

Chatziefthimiou, Spyros D; Lazarou, Yannis G; Hadjoudis, Eugene; Dziembowska, Tereza; Mavridis, Irene M

2006-11-30

71

Synthesis, potentiometric and antimicrobial studies on metal complexes of isoxazole Schiff bases  

NASA Astrophysics Data System (ADS)

The metal complexes of Cu(II), Ni(II) and Co(II) with Schiff bases of 3-(2-hydroxy-3-ethoxybenzylideneamino)-5-methyl isoxazole [HEBMI] and 3-(2-hydroxy-5-nitrobenzylidene amino)-5-methyl isoxazole [HNBMI] which were obtained by the condensation of 3-amino-5-methyl isoxazole with substituted salicylaldehydes have been synthesized. Schiff bases and their complexes have been characterized on the basis of elemental analysis, magnetic moments, molar conductivity, thermal analysis and spectral (IR, UV, NMR and Mass) studies. The spectral data show that these ligands act in a monovalent bidentate fashion, co-ordinating through phenolic oxygen and azomethine nitrogen atoms. Chelates of Co(II), Ni(II) appear to be octahedral and Cu(II) appears to be distorted octahedral. To investigate the relationship between formation constants of binary complexes and antimicrobial activity, the dissociation constants of Schiff bases and stability constants of their binary metal complexes have been determined potentiometrically in aqueous solution at 30 ± 1 °C and at 0.1 M KNO 3 ionic strength and discussed. Antimicrobial activities of the Schiff bases and their complexes were screened. The structure-activity correlation in Schiff bases and their metal(II) complexes are discussed, based on the effect of their stability constants. It is observed that the activity enhances upon complexation and the order of activity is in accordance with stability order of metal ions.

Prashanthi, Y.; Kiranmai, K.; Subhashini, N. J. P.; Shivaraj

2008-06-01

72

Impact of proton transfer phenomena on the electronic structure of model Schiff bases: an AIM/NBO/ELF study.  

PubMed

Understanding of the electronic structure evolution due to a proton dynamics is a key issue in biochemistry and material science. This paper reports on density functional theory calculations of Schiff bases containing short, strong intramolecular hydrogen bonds where the bridged proton is located: (i) at the donor site, (ii) strongly delocalized, and (iii) at the acceptor site. The mobility of the bridged proton and its influence on the molecular structure and properties of the chosen Schiff base derivatives have been investigated on the basis of Atoms in Molecules, Natural Bond Orbitals, and Electron Localization Function theories. It has been observed that the extent of the bridged proton delocalization is strongly modified by the steric and inductive effects present in the studied compounds introduced by various substituents. It has been shown that: (i) potential energy profiles for the proton motion are extremely dependent on the substitution of the aromatic ring, (ii) the topology of the free electron pairs present at the donor?acceptor site, as well as their electron populations, are affected qualitatively by the bridged proton position, (iii) the distortion of the molecular structure due to the bridged proton dynamics includes the atomic charge fluctuations, which are in some cases non-monotonic, and (iv) topology of the ELF recognizes events of proton detachment from the donor and attachment to the acceptor. The quantitative and qualitative results shed light onto molecular consequences of the proton transfer phenomena. PMID:24160518

Panek, Jaros?aw J; Filarowski, Aleksander; Jezierska-Mazzarello, Aneta

2013-10-21

73

Photophysics of a Schiff base: theoretical exploration of the excited-state deactivation mechanisms of N-salicilydenemethylfurylamine (SMFA).  

PubMed

Excited state reaction coordinates and the consequent energy profiles of a new Schiff base, N-salicilydenemethylfurylamine (SMFA), have been investigated with the CC2 method, which is a simplified version of singles-and-doubles coupled cluster theory. The potential energy profiles of the ground and the lowest excited singlet state are calculated. In contrast to the ground state, the excited state potential energy profile shows a barrier-less dissociation pattern along the O-H stretching coordinate which verifies the proton transfer reaction at the S1 (??*) state. The calculations indicate two S1/S0 conical intersections (CIs) which provide non-adiabatic gates for radiation-less decay to the ground state. At the CIs, two barrier-free reaction coordinates direct the excited system to the ground state of enol-type minimum. According to calculation results, a trans-keto type structure obtained from photoexcitation of the enol, can be responsible for the photochromoic effect of SMFA. Furthermore, our results confirm the suggestion that aromatic Schiff bases are potential candidates for optically driven molecular switches. PMID:24358475

Moghadam, Ahmad J; Omidyan, Reza; Mirkhani, Valiollah

2014-02-14

74

Copper(II) ion selective electrode based on a newly synthesized Schiff-base chelate  

Microsoft Academic Search

A new Cu (II) ion-selective electrode has been fabricated in poly (vinyl chloride) matrix based on a recently synthesized\\u000a Schiff-base chelate. The addition of sodium tetraphenylborate (NaTPB) and various plasticizers viz. TBP, TEHP, DOS, and CN\\u000a have been found to substantially improve the performance of the electrode. The membrane of various compositions of the ionophore\\u000a (I) were investigated and it

Ajay Kumar Jain; Raj Kumar Singh; Shalabh Jain; Jitendra Raisoni

2008-01-01

75

Internal Proton Transfer in the External Pyridoxal 5?-Phosphate Schiff Base in Dopa Decarboxylase†  

PubMed Central

Combined quantum mechanical and molecular mechanical (QM/MM) simulations of dopa decarboxylase have been carried out to elucidate the factors that contribute to the tautomeric equilibrium of the intramolecular proton transfer in the external PLP–L-dopa Schiff base. The presence of a carboxylate anion on the ?-carbon of the Schiff base stabilizes the zwitterions and shifts the equilibrium in favor of the oxoenamine tautomer (protonated Schiff base). Moreover, protonation of the PLP pyridine nitrogen further drives the equilibrium toward the oxoenamine direction. On the other hand, solvent effects favor the hydroxyimine configuration, although the equilibrium favors the oxoenamine isomer with a methyl group as the substituent on the imino nitrogen. In dopa decarboxylase, the hydroxyimine form of the PLP(H+)–L-dopa Schiff base is predicted to be the major isomer with a relative free energy of ?1.3 kcal/mol over that of the oxoenamine isomer. Both Asp271 and Lys303 stabilize the hydroxyimine configuration through hydrogen-bonding interactions with the pyridine nitrogen of the PLP and the imino nitrogen of the Schiff base, respectively. Interestingly, Thr246 plays a double role in the intramolecular proton transfer process, in which it initially donates a hydrogen bond to the phenolate oxygen in the oxoenamine configuration and then switches to a hydrogen bond acceptor from the phenolic hydroxyl group in the hydroxyimine tautomer.

Lin, Yen-lin; Gao, Jiali

2010-01-01

76

Stereospecificity of sodium borohydride reduction of Schiff bases at the active site of aspartate aminotransferase.  

PubMed

Sodium boro[3H]hydride treatment of holoaspartate aminotransferase results in the reduction of the Schiff's base formed between pyridoxal phosphate and Lys 258. Treatment of the reduced enzyme with papain followed by acid hydrolysis liberates epsilon-N-[3H]pyridoxyl lysine which is degraded to [3H]pyridoxamine diHCl and stereochemically analyzed with apoaspartate aminotransferase. Sodium boro[3H]hydride treatment of active site carbamylated aspartate aminotransferase reconstituted with pyridoxyl phosphate and sodium aspartate results in the trapping of an enzyme x substrate complex through the reduction of the Schiff's base formed between pyridoxal phosphate and aspartate. Active site bound N-[3H]pyridoxyl aspartate is liberated by treatment with papain and degraded to [3H]pyridoxamine diHCl for stereochemical analysis. Borohydride reduction of the holoenzyme occurs from the re face of the pyridoxal phosphate Lys 258 Schiff's base. Similarly, reduction of active site carbamylated enzyme x substrate complex occurs from the re face of the pyridoxal phosphate-aspartate Schiff's base. These results indicate that when active site carbamylated enzyme binds substrate to pyridoxal phosphate it does so stereospecifically and without changing the face of the Schiff base that is available for reduction as compared to native enzyme. PMID:7410385

Zito, S W; Martinez-Carrion, M

1980-09-25

77

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

78

An extending evidence of molecular conformation on spectroscopic properties of symmetrical bis-Schiff bases  

NASA Astrophysics Data System (ADS)

The relationship between the molecular conformation and spectroscopic properties of symmetrical bis-Schiff bases, was explored experimentally. The synthesis, crystal structures, and spectroscopic behaviors of symmetrical bis-Schiff bases derived from 1,4-Phthalaldehyde, p-Ysbnd C6H4Ndbnd CHC6H4CHdbnd NC6H4sbnd p-Y (Y = OMe, Me, H, Cl, or F) were reported. The results show when the effect of distance between X or Y and the imine carbon was considered, a good correlation between the ?max or ?C(Cdbnd N) of symmetrical bis-Schiff bases and the substituent parameters was obtained. The correlation results indicate that for both symmetrical bis-Schiff bases derived from 1,4-Phenylenediamine and 1,4-Phthalaldehyde, the UV absorption spectrum is dependent on the substituent at the aniline ring and the dihedral angle ?, and the term sin(?) is suitable to modify the substituent effects on the ?max. However, experimental investigations indicate that the dihedral angle ? has a limited effect on the values of ?C(Cdbnd N). This study provides an extending evidence of molecular conformation effects on spectroscopic properties of symmetrical bis-Schiff bases.

Fang, Zhengjun; Cao, Chenzhong; Chen, Jianfang; Deng, Xingchen

2014-04-01

79

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)  

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 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.

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

2014-09-01

80

Pincer ligands based on ?-amino acids: IV. Schiff bases derived from pyridine-2,6-dicarbaldehyde. Synthesis and intramolecular dynamics  

Microsoft Academic Search

A number of pincer Schiff base and amine ligands were synthesized from pyridine-2,6-dicarbaldehyde and ?-amino acids, L-methionine\\u000a and L-serine. The Schiff base derived from L-serine was shown to exist as an equilibrium mixture with diastereoisomeric oxazolidines.\\u000a The ring-chain tautomerism was confirmed by the results of reduction of the azomethine bond. The reduction products, pincer\\u000a amines, exist in solution as mixtures

N. E. Borisova; T. G. Gulevich; M. D. Reshetova; V. A. Knizhnikov

2009-01-01

81

A new Schiff base fluorescent probe for imaging Cu2+ in living cells  

NASA Astrophysics Data System (ADS)

A novel probe based on ferrocenyl-1,3,4-thiadiazol-containing Schiff base was synthesized by the reaction of 5-ferrocenyl-1,3,4-thiadiazol-2-amine and 4-(diethylamino)salicylaldehyde, and characterized by IR, NMR, HRMS and X-ray analysis. UV-vis spectral and fluorescence property of the probe were investigated. The probe can be used to colorimetric sensitive and selective fluorescent recognition of Cu2+ in buffer solution. Moreover, the probe can detect Cu2+ by electrochemical method. Additionally, the Schiff base was successfully used as a selective and sensitive fluorescent probe for monitoring Cu2+ ions in living cells.

Ye, Hui; Ge, Fei; Zhou, Yi-Ming; Liu, Jin-Ting; Zhao, Bao-Xiang

2013-08-01

82

N,N'-dipyridoxyl Schiff bases: synthesis, experimental and theoretical characterization.  

PubMed

Three N,N'-dipyridoxyl Schiff bases (L1, L2 and L3) have been newly synthesized and characterized by IR, (1)H NMR, mass spectrometry and elemental analysis. Their optimized geometries together with the theoretical assignment of the vibrational frequencies and the (1)H NMR chemical shifts of them have been computed by using density functional theory (DFT) method. In the optimized structures of the Schiff bases, two pyridine rings are not in a same plane; however the substitutions are essentially in the same plane with the pyridine rings. Also, the benzene ring(s) in the bridge region is (are) not in the same plane with the pyridine rings and azomethine moieties. In all the species, engagement in intramolecular-hydrogen bonds causes to weakness of the phenolic O-H bonds. Consistency between the theoretical results and experimental evidence confirms suitability of the optimized geometries for the synthesized Schiff bases. PMID:21943715

Beyramabadi, S Ali; Morsali, Ali; Khoshkholgh, Malihe Javan; Esmaeili, Abbas Ali

2011-12-01

83

N,N'-dipyridoxyl Schiff bases: Synthesis, experimental and theoretical characterization  

NASA Astrophysics Data System (ADS)

Three N,N'-dipyridoxyl Schiff bases ( L1, L2 and L3) have been newly synthesized and characterized by IR, 1H NMR, mass spectrometry and elemental analysis. Their optimized geometries together with the theoretical assignment of the vibrational frequencies and the 1H NMR chemical shifts of them have been computed by using density functional theory (DFT) method. In the optimized structures of the Schiff bases, two pyridine rings are not in a same plane; however the substitutions are essentially in the same plane with the pyridine rings. Also, the benzene ring(s) in the bridge region is (are) not in the same plane with the pyridine rings and azomethine moieties. In all the species, engagement in intramolecular-hydrogen bonds causes to weakness of the phenolic O-H bonds. Consistency between the theoretical results and experimental evidence confirms suitability of the optimized geometries for the synthesized Schiff bases.

Beyramabadi, S. Ali; Morsali, Ali; Khoshkholgh, Malihe Javan; Esmaeili, Abbas Ali

2011-12-01

84

Nickel(II) and copper(II) complexes of unsymmetrical tetradentate reduced Schiff base ligands  

Microsoft Academic Search

Two new reduced Schiff base ligands, [HL1=4-{2-[(pyridin-2-ylmethyl)-amino]-ethylimino}-pentan-2-one and HL2=4-[2-(1-pyridin-2-yl-ethylamino)-ethylimino]-pentan-2-one] have been prepared by reduction of the corresponding tetradentate unsymmetrical Schiff bases derived from 1:1: 1 condensation of 1,2-ethanediamine, acetylacetone and pyridine-2-carboxaldehyde\\/2-acetyl pyridine. Four complexes, [Ni(L1)]ClO4 (1), [Cu(L1)]ClO4 (2), [Ni(L2)]ClO4 (3), and [Cu(L2)]ClO4 (4) with these two reduced Schiff base ligands have been synthesized and structurally characterized by X-ray crystallography. The

Apurba Biswas; Michael G. B. Drew; Ashutosh Ghosh

2010-01-01

85

An insight into synthetic Schiff bases revealing antiproliferative activities in vitro.  

PubMed

Schiff bases or azomethines are among the most important groups of biomolecules. These compounds have been found to reveal both remarkable biological activities and a variety of valuable practical applications. An interest in the exploration of novel series of synthetic Schiff bases has undoubtedly been growing due to their proven utility as attractive lead structures for the design of novel cytotoxic and cytostatic agents with a mechanism of action that sometimes differs from that of clinically authorized anticancer agents. Therefore, in the present paper we have focussed our attention on the collected synthetic simple Schiff bases of aldimine- and ketimine-types revealing anticancer activities in vitro, that have been described in the scientific literature during the last decade, and on structural variations whose affect the antiproliferative activity in sets of the designed molecules. PMID:23673213

Sztanke, Krzysztof; Maziarka, Agata; Osinka, Anna; Sztanke, Ma?gorzata

2013-07-01

86

Schiff base protonation changes in Siberian hamster ultraviolet cone pigment photointermediates.  

PubMed

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 taken for the purified pigment at time delays from 30 ns to 4.64 s 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, the 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

2012-03-27

87

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

88

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)

1980-01-01

89

Ground and Excited States of Retinal Schiff Base Chromophores by Multiconfigurational Perturbation Theory  

PubMed Central

We have studied the wavelength dependence of retinal Schiff base absorbencies on the protonation state of the chromophore at the multiconfigurational level of theory using second order perturbation theory (CASPT2) within an atomic natural orbital basis set on MP2 optimized geometries. Quantitative agreement between calculated and experimental absorption maxima was obtained for protonated and deprotonated Schiff bases of all-trans- and 11-cis-retinal and intermediate states covering a wavelength range from 610 to 353 nm. These data will be useful as reference points for the calibration of more approximate schemes.

Sekharan, Sivakumar; Weingart, Oliver; Buss, Volker

2006-01-01

90

Ab initio and DFT theoretical studies of pyridoxal-5?-phosphate methylamine Schiff base isomers  

NASA Astrophysics Data System (ADS)

Optimized geometries and harmonic frequencies of 15 different isomeric configurations for three tautomeric ( enol-, keto-, and zwitterionic) forms of pyridoxal-5'-phosphate methylamine Schiff base were obtained at the HF and B3LYP levels of theory with the 6-31G* basis set. Additionally, the B3LYP/6-31G* calculations of Raman activities and the B3LYP/6-31+G* calculations of optimized geometries and harmonic force fields were done for the most preferable isomers for investigated three forms of titled molecule. Theoretical vibrational frequencies were compared to FT Raman and infrared spectra of the solid pyridoxal-5'-phosphate methylamine Schiff base.

Kuramshina, G. M.; Takahashi, H.

2005-02-01

91

Immobilization of copper Schiff base complexes in zeolite matrix: Preparation, characterization and catalytic study  

Microsoft Academic Search

New zeolite-immobilized hybrid catalysts Cu(NO2-salen)–NaY have been prepared by encapsulating copper(II) Schiff base complexes [where NO2-salenH2 is N,N?-(ethylene)-bis-(5-nitro-salicylaldiimine)] in NaY zeolite matrix. The hybrid materials have been characterized by UV–vis, IR and EPR spectrometry and by X-ray powder diffraction analysis. The neat copper(II) Schiff base complex [Cu(NO2-salen)(EtOH)] (1) has also been synthesized and characterized. A brilliant color change (green–gray) has

Buddhadeb Dutta; Sreyashi Jana; Rajesh Bera; Pratap Kumar Saha; Subratanath Koner

2007-01-01

92

Zeolite-encapsulated copper (II) complexes with N 3O 2 Schiff bases: synthesis and characterization  

Microsoft Academic Search

Copper(II) complexes with N3O2 Schiff base ligands[B: bis-(acetylacetone)-3-amino-bis(propylenediimine) = H2(acac)2trien; C: bis-(acetylacetone)-3-methylamino-bis(propylenediimine) = H2(acac)2Metrien] were encapsulated in the supercages of zeolite Y in a two-step process: (i) adsorption of copper(II) acetylacetonate in the supercage of the zeolite; (ii) in-situ Schiff base condensation of the copper(II) acetylacetonate complex with corresponding triamine. The resulting materials were purified by Soxhlet extraction. Bulk and

I. Neves; C. Freire; A. N. Zakhárov; B. de Castro; J. L. Figueiredo

1996-01-01

93

Dinuclear Schiff-base copper(II) complexes with various bridging groups  

Microsoft Academic Search

Three new centrosymmetric dinuclear copper(II) complexes, [Cu2Cl2(L)2] (1), [Cu2(?1,3-NCS)2(L)2] (2), and [Cu2(?1,1-N3)2(L)2] (3), where L, L, and L are the deprotonated forms of the Schiff bases 1-[(2-propylaminoethylimino)methyl]naphthalen-2-ol (HL), 1-[(3-methylaminopropylimino)methyl]naphthalen-2-ol (HL), and 2-[(2-isopropylaminoethylimino)methyl]phenol (HL), respectively, have been prepared and characterized by elemental analysis, IR spectra, and single-crystal X-ray crystallography. Each Cu is coordinated by the three donors of the Schiff bases

Dong-Mei Xian; Zhong-Lu You; Mei Zhang; Peng Hou; Xiao-Hui Li

2011-01-01

94

Designing, structural elucidation and comparison of the cleavage ability of metal complexes containing tetradentate Schiff bases  

Microsoft Academic Search

New N2O2 donor type Schiff bases have been designed and synthesized by condensing acetylaceto-4-aminoantipyrine\\/acetoacetanilido-4-aminoantipyrine\\u000a with 2-amino benzoic acid in ethanol. Solid metal complexes of the Schiff bases with Cu(II), Ni(II), Co(II), Mn(II), Zn(II),\\u000a VO(IV), Hg(II) and Cd(II) metal ions were synthesized and characterized by elemental analyses, magnetic susceptibility, molar\\u000a conduction, FAB Mass, IR, UV-Vis., 1H NMR, and ESR spectral studies.

N. Raman; A. Sakthivel; J. Dhaveethu Raja; K. Rajasekaran

2008-01-01

95

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

NASA Astrophysics Data System (ADS)

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.

Asadi, Zahra; Shorkaei, Mohammad Ranjkesh

2013-03-01

96

A sandwich-type triple-decker lanthanide complex with mixed phthalocyanine and Schiff base ligands.  

PubMed

A new triple-decker dinuclear sandwich-type dysprosium complex based on both the phthalocyanine ligand and the tetradentate Schiff base ligand was synthesized, which is of interest for synthetic chemistry and also shows single-molecule magnetic behaviour. PMID:23818021

Gao, Feng; Li, Yu-Yang; Liu, Cai-Ming; Li, Yi-Zhi; Zuo, Jing-Lin

2013-08-21

97

Synthesis, Characterization, and Photochemical Studies of Some Copper Complexes of Schiff Bases Derived from 3?Hydrazino?6?methyl[1,2,4]triazin?5(4H)one  

Microsoft Academic Search

Cu(II) complexes of new bidentate and tridentate Schiff bases derived from the condensation of 3?hydrazino?6?methyl[1,2,4]triazin?5(4H)one and aromatic aldehyde derivatives were synthesized and characterized. The structure of the complexes proposed according to elemental analyses, molar conductance, IR UV?Visible absorption spectra is square?planar. The thermodecomposition kinetics of the complexes were investigated under non?isothermal condition. TG and DTG curves indicated that the complexes

Ahmed H. Osman; Magda S. Saleh; Sanaa M. Mahmoud

2004-01-01

98

Electron-rich salen-type Schiff base complexes of Cu(II) as catalysts for oxidation of cyclooctene and styrene with tert-butylhydroperoxide: A comparison with electron-deficient ones  

Microsoft Academic Search

Two square planar copper(II) complexes of tetradentate Schiff base ligands derived from aromatic aldehydes and 2,2?-dimethylpropandiamine (H2{salnptn(3-OMe)2}, H2{hnaphnptn}) have been prepared and used as catalysts for oxidation of cyclooctene and styrene with tert-butylhydroperoxide (TBHP). Oxidation of cyclooctene with TBHP gave cyclooctene oxide as the sole product, but in the case of styrene a mixture of styrene oxide and benzaldehyde has

Saeed Rayati; Saeed Zakavi; Marjan Koliaei; Andrzej Wojtczak; Anna Kozakiewicz

2010-01-01

99

Electrostatic interaction between anions bound to Site I and the retinal Schiff base of halorhodopsin  

SciTech Connect

The influence of different anions on the deprotonation of the retinal Schiff base of halorhodopsin in the dark was investigated. We find that a large number of anions cause a significant increase of the pK/sub a/ of the Schiff base, an effect attributed to binding to site I on the protein. The concentration dependencies of the spectroscopic shifts associated with the changes of the pK/sub a/ yielded dissociation constants (and thus binding energies) for the anions, which were related to the Stokes radii. The data fit the predictions of electrostatic interaction between the anions and the positive charge associated with site I, if the latter is located within a few angstroms from the surface of the protein. The specificity of site I toward various anions is quantitatively explained by the differences in the change of Born energy upon transfer of the anions from water to the binding site. The changes in the deprotonation energy of the Schiff base upon the binding of anions, ..delta delta..G/sub deprot/, could be calculated from the ..delta..pK/sub a/ at infinite anion concentration. Unexpectedly, the ..delta delta..G/sub deprot/ values were remarkably close to the energies of binding to site I. Thus, site I and the Schiff base are strongly electrostatically coupled, either because of close proximity or because of the possibility of allosteric energy transfer between them.

Schobert, B.; Lanyi, J.K.

1986-07-01

100

Theoretical characterization of proton-induced spectral shifts in Schiff base porphyrins  

SciTech Connect

The roles that substituents and protonation play in the electronic structure and spectrum of the Schiff base of magnesium 4-vinyl-8-formylporphine (MgPSB) have been investigated by ab initio self-consistent-field molecular orbital and configuration interaction calculations, using a floating spherical Gaussian orbital basis. The red shift of the visible band of the parent magnesium porphine (MgP) due to the presence of electron-withdrawing vinyl and Schiff base substituents is shown to arise from a small but significant destabilization of the highest occupied MpG ..pi..-orbital brought about by its conjugative interaction with the ..pi..-orbitals of the substituents. Changes in the ground-state electron density, however, result from larger perturbations of lower lying MgP orbitals. Protonation of the Schiff base leads to a dramatic differential stabilization of the high-lying ..pi..*-orbital of the Schiff base moiety, giving rise to new orbital interactions with low-lying MgP..pi..*-orbitals that significantly alter the ..pi..*-orbital structure of MgPSB. These changes, which affect only the excited states, are shown to be largely responsible for the additional proton-induced red shift (approx. 1000 cm/sup -1/) of the visible band the the unique doublet structure of the Soret band observed experimentally. 23 references, 5 figures, 1 table.

Petke, J.D.; Maggiora, G.M.

1984-05-30

101

Synthesis and characterization of linear cerium(IV) Schiff-base coordination polymers  

SciTech Connect

The first soluble linear Schiff-base rare earth coordination polymer, catena-poly[cerium-(4)-[mu]-N,N[prime],N[double prime],N[prime][double prime]-tetrasalicylidene (3,3[prime]-diaminobenzidinato)-O,N,N[prime],O[prime],O[double prime],N[double prime],N[prime][double prime],O[prime][double prime

Chen, H.; Cronin, J.A.; Archer, R.D. (Univ. of Massachusetts, Amherst, MA (United States). Dept. of Chemistry)

1994-04-11

102

New ionic dinuclear Ir(iii) Schiff base complexes with aggregation-induced phosphorescent emission (AIPE).  

PubMed

Two new ionic dinuclear Ir(iii) Schiff base complexes which are straightforward to synthesise have luminescence quantum yields as high as 37% in neat films. These are the first examples of dinuclear ionic Ir(iii) complexes that display aggregation-induced phosphorescent emission (AIPE). PMID:24852610

Li, Guangfu; Wu, Yong; Shan, Guogang; Che, Weilong; Zhu, Dongxia; Song, Baiqiao; Yan, Likai; Su, Zhongmin; Bryce, Martin R

2014-07-01

103

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

Microsoft Academic Search

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 ?-ketoacyl-acyl carrier protein synthase III (ecKAS III) were investigated in vitro and molecular docking simulation also surveyed. Top 10 PSB compounds which posses both good inhibitory

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

2009-01-01

104

Synthesis, Polymerization and Thermal Properties of a New Acetylene-Terminated Schiff Base.  

National Technical Information Service (NTIS)

A new acetylene-terminated Schiff base monomer, N, N1-(1,4-phenylenedimethylidyne)-bis-(4-ethynylaniline)(PPP), was synthesized and was characterized by nuclear magnetic resonance and infrared spectroscopy. This monomer was then polymerized to yield a new...

Y. Wei R. Hariharan J. K. Ray

1991-01-01

105

THE ISOTROPIC HYPERFINE INTERACTION IN SOME TETRADENTATE SCHIFF-BASE COMPLEXES OF COPPER (II)  

Microsoft Academic Search

The isotropic hyperfine constant is investigated for a series of tetradentate Schiff-base complexes of Copper II. In this series the immediate copper environment is essentially square planar and consists of two oxygen and two nitrogen atoms in cis positions. The constancy of ?, which is proportional to the hyperfine constants, indicates that it is quite independent of ligand substitution, depending

Harry C. Allen Jr; Michele I. Scullane

1978-01-01

106

Electrochemical and spectroelectrochemical properties of copper(II) Schiff-base complexes  

Microsoft Academic Search

The electrochemical behaviour of several copper(II) complexes with Schiff-base ligands containing pyrrole groups has been investigated in aprotic solvents by cyclic voltammetry and spectroelectrochemistry. Electrochemical oxidation of copper(II) complexes in acetonitrile produces conducting polymeric films at the electrode surface. The modified electrodes were electrochemically and spectrochemically characterized and their electrocatalytical properties have been examined.

J Losada; I del Peso; L Beyer

2001-01-01

107

SYNTHESIS OF THE NEW SCHIFF BASE POLYAZA MACROCYCLES AND THEIR COMPLEXES WITH Cu AND Ni  

Microsoft Academic Search

The new Schiff base macrocycles were synthesized from the condensation of diethylenetriamine or dipropylenetriamine with terephthalaldehyde. The relevant transition metal complexes were then formed with nickel and copper salts after the reduction of the macrocycles. CHN-analysis, IR, NMR, and mass spectroscopies were used for their structure characterization.

D. Habibi; V. Izadkhah

2004-01-01

108

A New Synthetic Route to Macrocyclic Nickel (II) Complexes with Uninegative, Schiff-Base Ligands.  

National Technical Information Service (NTIS)

Two series of nickel(II) complexes containing uninegative, macrocyclic Schiff-base ligands have been prepared via simple condensation reactions. Characterization of the new compounds Ni(AT)X and Ni(TAT)X, where AT is 11,13-dimethyl-1,4,7,10-tetraazacyclot...

S. C. Cummings R. E. Sievers

1969-01-01

109

On the Inhibition of Hydrogen Sulfide Corrosion of Steel with Schiff Bases  

Microsoft Academic Search

The synthesized Schiff bases effectively protect steel in hydrogen sulfide media. Different primary amines were used as the starting reagents to find out how the protection effect of azomethines depends on their nature. It was shown that the higher the electron-donating properties (in terms of normal Wepster constants sH) of substituents in benzaldehyde the better the inhibition of steel corrosion.

Yu. I. Kuznetsov; R. K. Vagapov

2001-01-01

110

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.

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

2012-01-01

111

Novel Lu(III) membrane sensor based on a new asymmetrically S–N Schiff's base  

Microsoft Academic Search

In this work we are happy to report the application of a new asymmetrically S–N Schiff's base, namely N-(thien-2-ylmethylene)pyridine-2,6-diamine (TPD), in the construction of a novel Lu(III) PVC-based membrane sensor. The linear dynamic range of the sensor lies between 1.0×10?2 and 1.0×10?6M, with a LDL, and a Nernstian slope of 8.0×10?7M and 20.5±0.4mVdecade?1, respectively. A membrane composition of 32% poly(vinyl

Mohammad Reza Ganjali; Atefeh Tamaddon; Parviz Norouzi; Mehdi Adib

2006-01-01

112

Syntheses, characterizations and structures of NO donor Schiff base ligands and nickel(II) and copper(II) complexes  

Microsoft Academic Search

New Schiff base derivatives (L1 and L2) were prepared by the condensation of 2-hydroxy-3-methoxybenzaldehyde (o-vanillin) and 3-hydroxy-4-methoxybenzaldehyde (iso-vanillin) with 5-methylfurfurylamine. Two new complexes [Ni(L1)2] and [Cu(L1)2] have been synthesized with bidentate NO donor Schiff base ligand (L1). The Ni(II) and Cu(II) atoms in each complex are four coordinated in a square planar geometry. Schiff bases (L1 and L2) and complexes

Cemal ?enol; Zeliha Hayvali; Hakan Dal; Tuncer Hökelek

2011-01-01

113

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; Solà, Miquel

2005-01-01

114

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

PubMed

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. PMID:24907971

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

2014-11-11

115

Synthesis and Reactivity of Unsymmetrical Schiff Base Ligand Towards Ni(II), Cu(II) and Pd(II)  

Microsoft Academic Search

The unsymmetrical Schiff base 1?-hydroxy-2?-acetonaphthoneacetylacetone-ethylendiimine (Hhan)(Hacac)en and its complexes with some transition metals have been synthesized and characterized by elemental analyses, conductometric measurements, infrared and electronic absorption, NMR and mass spectroscopy.

Davar M. Boghaei; S. J. S. Sabounchei; Saeed Rayati

2000-01-01

116

In situ hydrogel constructed by starch-based nanoparticles via a Schiff base reaction.  

PubMed

Polysaccharide-based hydrogels are remarkable materials for the biomedical fields because of its excellent biodegradation and biocompatibility. In this work, a novel polysaccharide-based hydrogel was fabricated by in situ crosslinking of starch-based nanoparticles and polyvinylamine. Starch was decorated with cholesterol group and aldehyde groups. TEM and DLS showed that the cholesterol modified oxidation starch (OCS) exhibited a core-shell nanoparticles with mean size of ?143nm in aqueous. The hydrogel was then synthesized via Schiff base reaction. Rheological measurements demonstrated the incorporation of cholesterol groups not only reduced the gel time but also improved the storage modulus of the hydrogel compared with the oxide starch crosslinked hydrogel. SEM showed the OCS based hydrogels possess a well-defined porous structure. Furthermore, doxorubicin (DOX) was used as model drug to investigate the control and release properties of OCS hydrogels. This OCS hydrogel would be a promising drug carrier for biomedical applications. PMID:24906732

Li, Yangling; Liu, Chang; Tan, Ying; Xu, Kun; Lu, Cuige; Wang, Pixin

2014-09-22

117

Synthesis, characterization and structure effects on selectivity properties of silica gel covalently bonded diethylenetriamine mono- and bis-salicyaldehyde and naphthaldehyde Schiff ,s bases towards some heavy metal ions  

Microsoft Academic Search

Four silica gel-immobilized new metal chelate Schiff,s bases were synthesized (I–IV). Silica gel chemically bonded diethylenetriamine mono-naphthaldehyde and mono-salicyaldehyde Schiff's bases (phases I and III) were produced via the interaction of silica gel-modified diethylenetriamine with naphthaldehyde and salicylaldehyde, respectively. However, phases II and IV arose through the interaction of bis-naphthaldehyde and bis-salicylaldehyde Schiff,s bases of diethylenetriamine with 3-chloropropyltrimethoxysilane modified silica

Ezzat M Soliman; Mohamed E Mahmoud; Salwa A Ahmed

2001-01-01

118

Synthesis, Characterization and Electrochemical Behaviour of Some Manganese and Copper Complexes with Tetradentate Schiff Base Ligands  

Microsoft Academic Search

A series of symmetrical tetradentate Schiff bases derived from substituted salicylaldehyde and ethylenediamine were prepared and characterized by elemental analysis, IR, UV-Visible and H NMR spectroscopy. The interaction of these bases with MnCl2 4H2O and CuCI2 2H2O have been studied, leading to the preparation of manganese(II) and copper(II) complexes. Microanalysis, molar conductance, IR, UV-Visible spectroscopy, magnetic measurements and ESR spectra

N. Tidjani-Rahmouni; S. Djebbar-Sid; N. Chenah; O. Benali-Baitich

1999-01-01

119

Synthesis, Spectroscopic and Polarographic Studies of Dibutyltin(IV) Complexes of Schiff Bases Derived from 2Aminophenol  

Microsoft Academic Search

A series of dibutyltin(IV) complexes of Schiff bases derived from 2-minophenol and benzaldehyde (HL), anisaldehyde (HL), 2-furfural (HL), acetophenone (HL), benzylmethyl ketone (HL), benzil (HL), salicylaldehyde (H2L), 2-hydroxy-l-naphthaldehyde (H2L) and 2-hydroxy-acetophenone (H2L) have been synthesized by the reaction of dibutyltin(IV) oxide with the preformed Schiff bases in 1:l or 1:2 molar ratios in benzene with azeotropical removal of water. The

Mala Nath; Nidhee Chaudhary

1998-01-01

120

Anion-controlled Formation of Silver(I) Complexes of A Hexaazamacrocyclic Schiff Base: Synthesis, Structures and Electrochemistry  

Microsoft Academic Search

Six silver(I) complexes of a macrocyclic Schiff Base (L) with different counter anions have been prepared and structurally characterized, where L is a hexaazamacrocyclic Schiff Base derived from the [2 + 2] condensation of terephthalaldehyde and 3-azapentane-1,5-diamine. [Ag2L(NO3)2] (1) crystallizes in the triclinic space group P1, with a = 7.705(7), b = 7.926(5), c = 12.06(1) Å, ? = 90.33(1),

Hai-Liang Zhu; Ye-Xiang Tong; La-Sheng Long; Ming-Liang Tong; Xiao-Ming Chen

1999-01-01

121

Investigations on the Liquid Crystalline Phase of Schiff's Base Complexes of Copper(II) and Their Corresponding Ligands  

Microsoft Academic Search

Some new liquid crystalline Schiff's base complexes with copper(II) have been prepared. Microscopic observations and D.S.C. measurements reveal broad nematic mesophases. X-ray investigations on magnetically oriented samples confirm the nematic mesophase and indicate a cybotactic one.Anisotropic magnetic susceptibility data of a mixture of Schiff's base complexes of copper(II) are presented. An orientation with the longitudinal axis parallel to the magnetic

Bettina Borchers; Wolfgang Haase

1991-01-01

122

Highly efficient chiral copper Schiff-base catalyst for asymmetric cyclopropanation of 2,5-dimethyl-2,4-hexadiene  

Microsoft Academic Search

A remarkable increase in catalytic activity is found for the asymmetric cyclopropanation of 2,5-dimethyl-2,4-hexadiene with diazoacetate by use of the chiral copper Schiff-base complexes, which are derived from substituted salicylaldehydes, chiral aminoalcohols, and copper acetate monohydrate. Furthermore, a combination of a chiral copper Schiff-base with a Lewis acid showed an increase in yield (up to 90%) and in enantioselectivity (up

Makoto Itagaki; Koji Hagiya; Masashi Kamitamari; Katsuhisa Masumoto; Katsuhiro Suenobu; Yohsuke Yamamoto

2004-01-01

123

Copper (II) Schiff base catalysed aerobic oxidative coupling of 2-naphthols: an efficient and simple synthesis of binaphthols  

Microsoft Academic Search

Copper (II) Schiff base complexes of 2-(1-phenylethyl imino) methylphenol (3), methyl-N-(2-hydroxyphenyl)-l-serine (4) and methyl-N-(2-hydroxyphenyl)-l-tyrosine (5) were found to be an efficient catalyst for the aerobic oxidative coupling of 2-naphthols to binaphthols. Among the various copper (II) Schiff base complexes, the complex 3 was found to be the most reactive for this transformation.

Vishal B. Sharma; Suman L. Jain; Bir Sain

2004-01-01

124

Exploring the distribution of copper–Schiff base complex covalently anchored onto the surface of mesoporous MCM 41 silica  

Microsoft Academic Search

A series of copper–Schiff base MCM 41 materials, synthesized by post-synthetic grafting, was studied by X-ray photoelectron spectroscopy (XPS) and nitrogen sorption (77K) to explore distribution of the copper–Schiff base complex immobilized on the porous Si-MCM 41. Additional information on the physico-chemical properties of the functionalized materials was obtained by powder X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), CHN microanalysis,

Udayshankar G.. Singh; Ruth T.. Williams; Keith R.. Hallam; Geoffrey C.. Allen

2005-01-01

125

Exploring the distribution of copper Schiff base complex covalently anchored onto the surface of mesoporous MCM 41 silica  

Microsoft Academic Search

A series of copper Schiff base MCM 41 materials, synthesized by post-synthetic grafting, was studied by X-ray photoelectron spectroscopy (XPS) and nitrogen sorption (77 K) to explore distribution of the copper Schiff base complex immobilized on the porous Si-MCM 41. Additional information on the physico-chemical properties of the functionalized materials was obtained by powder X-ray diffraction (XRD), atomic absorption spectroscopy

Udayshankar G. Singh; Ruth T. Williams; Keith R. Hallam; Geoffrey C. Allen

2005-01-01

126

Synthesis, Mesomorphism, and Spectroscopic Characterization of New Schiff Bases and Their Cu(II), Pd(II) Complexes  

Microsoft Academic Search

New Schiff bases have been prepared from 1,2-dialkyloxy-4-formyl-5-hydroxybenzene and 4,5-diamino-1,2-didodecyloxybenzene. Pd(II) and Cu(II) complexes are obtained with metal Schiff base ratio of 1:1. The new compounds have been characterized by elemental analyses; IR; and, H NMR, C NMR, and mass spectra. The mesomorphic properties of these complexes were investigated by polarizing microscopy and X-ray diffraction analysis. These complexes form columnar

?. Gürol; V. Ahsen

2005-01-01

127

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 multi—step 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

128

The Synthesis and Characterization of New Schiff Bases and Investigation 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 multi—step 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

129

Polymer complexes XXXVII novel models and structural of symmetrical poly-Schiff base on heterobinuclear complexes of dioxouranium(VI)  

Microsoft Academic Search

Some binary and ternary novel complexes of dioxouranium(VI) with 5-vinylsalicylaldehyde (VSH) have been prepared and characterized by various physico-chemical techniques. The amine exchange reactions of coordinated poly-Schiff bases in these complexes have been also carried out which give symmetrical tetradentate poly-Schiff base complexes. Metal exchange reaction of these dioxouranium(VI) complexes with copper(II) gives the corresponding Cu(II) complexes. Reaction of tetradentate

A. Z El-Sonbati; A. A El-Bindary; I. G. A Rashed

2002-01-01

130

Copper(II) and Zinc(II) Complexes of Schiff Bases Derived from Amino Acids and O-Vanillin  

Microsoft Academic Search

Some new Cu(II) and Zn(II) complexes of Schiff bases derived from o-vanillin and glycine, DL-alanine, DL-valine, DL-methionine, L-leucine, and L-phenylalanine have been synthesized and characterized by elemental analyses, molar electrical conductivity, electronic and infrared spectra, and thermogravimetric analyses. The results suggested that the Schiff bases are bivalent anions with tridentate ONO donors derived from the carboxylate oxygen, imino nitrogen, and

Guangbin Wang; James C. Chang

1994-01-01

131

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

PubMed

Deuterium isotope effects on 13C chemical shift of tetrabutylammonium salts of Schiff bases, derivatives of amino acids (glycine, L-alanine, L-phenylalanine, L-valine, L-leucine, L-isoleucine and L-methionine) and various ortho-hydroxyaldehydes in CDCl3 have been measured. The results have shown that the tetrabutylammonium salts of the Schiff bases amino acids, being derivatives of 2-hydroxynaphthaldehyde and 3,5-dibromosalicylaldehyde, exist in the NH-form, while in the derivatives of salicylaldehyde and 5-bromosalicylaldehyde a proton transfer takes place. The interactions between COO- and NH groups stabilize the proton-transferred form through a bifurcated intramolecular hydrogen bond. PMID:16741983

Rozwadowski, Z

2006-09-01

132

One-dimensional organic photoconductive nanoribbons built on Zn-Schiff base complex  

SciTech Connect

One-dimensional organic nanoribbons built on N-p-nitrophenylsalicylaldimine zinc complex were synthesized via a facile solvothermal route. The scanning electron microscope images revealed that the as-synthesized products were ribbon-like with width mainly of 300-600 nm, thickness of about 50 nm, and length of up to tens of micrometers. Fourier transform infrared spectrum was employed to characterize the structure. Ultraviolet-visible absorption and photoluminescence spectra showed that the products had good photoluminescent property and exhibited blue emission. The conductivity of a bundle of nanoribbons was also measured, which showed that the Schiff base zinc nanoribbons had good photoconductive property. This work might enrich the organic photoconductive materials and be applicable in light-controlled micro-devices or nano-devices in the future. - Graphical abstract: The Schiff base zinc nanoribbons nanowires exhibited good photoresponse under an incandescent lamp, which indicated their potential application as organic semiconductive or photoconductive nanodevices in the future.

Liu Li [Anhui Key Laboratory of Functional Molecular Solids, College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000 (China); Department of Biochemical Engineering, Anhui University of Technology and Science, Wuhu 241000 (China); Shao Mingwang, E-mail: mwshao@mail.ahnu.edu.c [Anhui Key Laboratory of Functional Molecular Solids, College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000 (China); Functional Nano and Soft Materials Laboratory (FUNSOM), Soochow University, Suzhou 215123 (China); Wang Xiuhua [Anhui Key Laboratory of Functional Molecular Solids, College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000 (China)

2010-03-15

133

[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

134

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

135

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

NASA Astrophysics Data System (ADS)

The synthesis and characterization of three hexa-coordinated ruthenium(II) Schiff base complexes of the type [RuCl(CO)(B)L] (B = PPh3/AsPh3/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)(PPh3)L] on HeLa were tested. The IC50 value for the ligand and the complex were 52.3 and 31.6 ?m respectively.

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

136

Cationic schiff base amphiphiles and their metal complexes: Surface and biocidal activities against bacteria and fungi.  

PubMed

A series of cationic surfactants containing schiff base groups was synthesized by condensation of four fatty amines namely: dodecyl, tetradecyl, hexadecyl and octadecyl amine and 4-diethyl aminobenzaldehyde (1-4), as well as their metal complexes with divalent transition metal ions including Co, Cu and Mn (5-16). The surface activities of the synthesized surfactants were influenced by their chemical structures and the type of the transition metals. The biological activity measurements of the parent cationic schiff bases showed high efficacy against Gram positive and Gram negative bacterial strains and fungi. While on complexation, the biocidal activity was increased remarkably. The biocidal activity of the tested compounds against sulfur reducing bacteria showed promising results in the field of biocide applications. PMID:20167455

Negm, N A; Zaki, M F; Salem, M A I

2010-05-01

137

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

138

Synthesis and characterization of copper(II) Schiff base complexes derived from salicylaldehyde and glycylglycylglycine  

Microsoft Academic Search

Two copper(II) tripeptide Schiff base complexes: [Mg(H2O)6][CuL]2·3.5H2O (1) and [Cd(H2O)4(CuL)2]·3.5H2O (2) (H3L=N-salicylideneglycylglycylglycine) have been synthesized and structurally characterized. Single crystal X-ray diffraction analyses showed that the copper atom exhibits square-planar geometry, with the chelating ONNO atoms of the deprotonated Schiff base ligand(L) in the basal plane. In 1, the anions [CuL]? and cations [Mg(H2O)6]2+ are stacked in well-separated columns along

Wen-Long Liu; Yang Zou; Chun-Lin Ni; Zhao-Ping Ni; Yi-Zhi Li; Yuan-Gen Yao; Qing-Jin Meng

2004-01-01

139

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

140

Deprotonation of hydrogen bonded Schiff bases by three strong nitrogen bases  

NASA Astrophysics Data System (ADS)

Three Schiff bases obtained from substituted salicylaldehydes and 2-hydroxy-1-naphthaldehyde and aliphatic amines were investigated in terms of possible withdrawal of tautomeric proton from intramolecular hydrogen bridge. Three strong nitrogen bases: 1,8-bis(dimethylamino)naphtalene (DMAN), 1,1,3,3-tetramethylguanidine (TMG) and 1,8-bis(tetramethylguanidino)naphthalene (TMGN) were used as deprotonating agents in acetonitrile solution at room temperature. In the specified conditions it was found that only in the case of 5-nitrosalicylaldehyde and isopropyl amine derivative this process could be performed using TMG and TMGN as a base. The other derivatives, where bridged proton is shifted to oxygen or nitrogen atom, do not undergo such reaction. The deprotonation process was monitored by nitrogen and proton NMR measurements.

Schilf, Wojciech; Cmoch, Piotr; Szady-Che?mieniecka, Anna; Grech, Eugeniusz

2009-03-01

141

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

PubMed

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

Reiss, Aurora; Chifiriuc, Mariana Carmen; Amzoiu, Emilia; Spînu, Cezar Ionu?

2014-01-01

142

Spin crossover complexes of iron(III) with an N 4 tetradentate Schiff base ligand  

Microsoft Academic Search

Iron(III) complexes of the Schiff base formed from the condensation of 2-aminobenzaldehyde and ethylenediamine, H2amben, were prepared by the reaction of H2amben with iron(III) halides in acetone. Fe(amben)Cl and Fe(amben)Br·H2O exhibit a spin crossover between the 2T and 6A states as shown by magnetic susceptibility measurements, variable temperature Mössbauer spectra, and electron spin resonance at 77 K. Structural investigation of

Greg Brewer; Jerry Jasinski; William Mahany; Leopold May; Sergey Prytkov

1995-01-01

143

Synthesis, characterization, antifungal, antibacterial and DNA cleavage studies of some heterocyclic Schiff base metal complexes  

Microsoft Academic Search

Co(II), Ni(II), Cu(II) and Zn(II) complexes of the Schiff base derived from indole-3-carboxaldehyde and m-aminobenzoic acid were synthesized and characterized by elemental analysis, molar conductance, IR, UV–Vis, magnetic moment, powder XRD and SEM. The IR results demonstrate the bidentate binding mode of the ligand involving azomethine nitrogen and carboxylato oxygen atoms. The electronic spectral and magnetic moment results indicate that

Madhavan Sivasankaran Nair; Dasan Arish; Raphael Selwin Joseyphus

144

Synthesis and two-photon optical characterization of D–?–D type Schiff bases  

Microsoft Academic Search

The title compounds, several Schiff bases with D–?–D type have been successfully synthesized from reaction of 4-(N-dialkylamino) benzaldehyde and hydrazine or p-phenylenediamine in ethanol. These compounds were characterized by IR, 1H NMR, elemental analysis and electronspray mass spectrometry. One-photon fluorescence and two-photon fluorescence properties have been investigated. The two-photon absorption (TPA) cross section (?) of these compounds was obtained by

Lei Tian; Zhangjun Hu; Pengfei Shi; Hongping Zhou; Jieying Wu; Yupeng Tian; Yufang Zhou; Xutang Tao; Minghua Jiang

2007-01-01

145

Chemistry of rhenium and technetium. II. Schiff base complexes with polyfunctional amino acids  

SciTech Connect

Amino acid Schiff base technetium(V) complexes of salicylaldehyde with l-cysteine, l-serine, l-histodine, l-threonine, l-glutamic acid and l-tryptophan have been preapred by direct reaction and by constituent combination. The amino acid part of the ligands coordinates to the technetium through the carboxylate group, while the other available functional group of the amino acids plays a more minor role as blocking group or in intramolecular bonding. 3 tables.

Du Preez, J.G.H.; Gerber, T.I.A.; Fourie, P.J.; Van Wyk, A.J.

1984-01-01

146

Carbon steel corrosion inhibition in hydrochloric acid solution using a reduced Schiff base of ethylenediamine  

Microsoft Academic Search

The behavior of the Schiff base N,N?-bis(salicylidene)-1,2-ethylenediamine (Salen), its reduced form (N,N?-bis(2-hydroxybenzyl)-1,2-ethylenediamine) and a mixture of its preceding molecules, ethylenediamine and salicylaldehyde, as carbon steel corrosion inhibitors in 1molL?1 HCl solution was studied by corrosion potential measurements, potentiodynamic polarization curves, electrochemical impedance spectroscopy and spectrophotometry measurements. The experimental results showed that the reduced Salen presented the highest efficiency among the

Adriana Barbosa da Silva; Eliane D’Elia; José Antonio da Cunha Ponciano Gomes

2010-01-01

147

Complexation Properties of Schiff Bases Containing the N-Phenylaza-15-crown-5 Moiety  

Microsoft Academic Search

The complexation of a series of new Schiff bases containing theN-phenylaza-15-crown-5 (Ph-A15C5) moiety with alkali and alkaline-earth metal ions (incl. Be2+ and Mg2+, is studied by means of UV-Vis spectroscopy. The corresponding stability constant values are determined and discussed from two aspects: the position of the Ph-A15C5 moiety in the ligand molecule and the nature of the metal ion.

Liudmil Antonov; Maria Vladimirova; Elena Stanoeva; Walter M. F. Fabian; Loreto Ballester; Mariana Mitewa

2001-01-01

148

Asymmetric Cyclopropanation Catalyzed by a Series of Copper(Schiff-Base) Complexes with Two Chiral Centers  

Microsoft Academic Search

A series of copper-(Schiff-base) complexes with two chiral centers derived from 1,2-diphenyl-2-amino-ethanol were synthesized and applied to catalyze the asymmetric cyclopropanation of ethenes with diazoacetates. A mechanism that can explain the observed results was proposed. Some of these complexes were also efficient catalysts for asymmetric cyclopropanation of 1,1-diphenylethene with ethyl diazoacetate, affording high e.e. of up to 98.6%. An e.e.

Changsheng Jiang; Zhang Ming; Qitao Tan; Dai Qian; Tianpa You

2002-01-01

149

Carbenoid insertions into the silicon?hydrogen bond catalyzed by chiral copper (I) schiff base complexes  

Microsoft Academic Search

An asymmetric insertion reaction of ?-diazoesters derived from methyl arylacetates into the silicon-hydrogen bond of silanes was achieved using a copper (I) catalyst associated with a chiral, C2 symmetric Schiff base. Addition of the diazoesters 1 (1 equiv) to the Cu·Lig complex (R,R)-3 (0.1 equiv) in the presence of the silane reagent (1.5 equiv) at ?40° C yielded the corresponding

Les A. Dakin; Scott E. Schaus; Eric N. Jacobsen; James S. Panek

1998-01-01

150

Epoxidation of styrene with iodosylbenzene in the presence of copper(II) Schiff-base complexes  

Microsoft Academic Search

Copper(II) complexes with salen Schiff-base ligands derived from ethylenediamine or (S,S)-1,2-diphenylethylenediamine and salicylaldehyde or 5-methoxy, 5-bromo and 5-nitrosalicylaldehyde have been tested as catalysts for the epoxidation of styrene with iodosylbenzene, in dichoromethane as a solvent. The reactions were followed by gas chromatographic analysis and mass spectrometry. Catalytic activities were found to be dependent upon both the Lewis acidity of the

Santiago Zolezzi; Evgenia Spodine; Antonio Decinti

2003-01-01

151

Electrochemical behaviour of the complexes of copper(II) with a Schiff base compartmental ligand  

Microsoft Academic Search

The ethylenediamine Schiff base derivative ofo-acetoacetylphenol, H4aapen, is a ligand able to form both mononuclear and dinuclear complexes with copper(II) ion. Mononuclear positional isomers can be obtained, having the copper in the O2O2 site and in the N2O2 site. The electrochemistry of these copper(II) complexes in dimethylsulfoxide shows that the two positional isomers are reduced at different potentials through an

Piero Zanello; Pietro Alessandro Vigato; Gian Antonio Mazzocchin

1982-01-01

152

Thermal and spectral studies on complexes derived from tetradentate Schiff bases  

Microsoft Academic Search

Several new complexes of Schiff bases ligands H4La and H4Lb with transition metal ions such as Cr(III), Fe(III), Co(II) and Zn(II) are synthesized. Elemental analysis, infrared, UV–Vis\\u000a and thermal analysis, as well as conductivity and magnetic susceptibility measurements are used to elucidate the structure\\u000a of the newly prepared metal complexes. A square planar geometry is suggested for Zn(II) complexes, while

H. M. Abdel-Fattah; A. L. El-Ansary; N. S. Abdel-Kader

2009-01-01

153

Design, structural elucidation, DNA interaction and antimicrobial activities of metal complexes containing tetraazamacrocyclic Schiff bases  

Microsoft Academic Search

Tetraazamacrocyclic Schiff bases, designed and synthesized from 3-hydroxy-4-nitrobenzylideneacetoacetanilide\\/3-hydroxy-4-nitrobenzylidene-o-acetoacetotoluidide and 1,2-diaminobenzene, are tetradentate ligands and form solid cationic complexes with Cu, Ni, Co, Zn, Mn, and VO salts in ethanol. Microanalytical data, magnetic moment, electronic, IR, Mass, C NMR, H NMR, and electron spin resonance (ESR) techniques were used to characterize the synthesized compounds. Electronic absorption and IR spectra suggest that

N. Raman; A. Sakthivel; K. Rajasekaran

2009-01-01

154

Hydrogenation of schiff bases with group 6 metal carbonyls and sodium methoxide as catalyst precursors  

Microsoft Academic Search

Summary Schiff bases are hydrogenated to secondary amines by H2 in the presence of [M(CO)6](M=Cr, Mo or W) and NaOMe in methanol solution at 60–160 °C andca. 100 bar H2 pressure. The reaction is significantly slower in the absence of NaOMe. In a stoichiometric reaction, [HCr(CO)5]- hydrogenatesN- benzylidene-aniline at 75 °C toN-benzylaniline forming [Cr2(CO)10]2-.

József Palágyi; Zsuzsa Nagy-Magos; László Markó

1985-01-01

155

Synthesis, characterization, and sorption properties of silica gel-immobilized Schiff base derivative  

Microsoft Academic Search

Silica gel was derivatized with benzophenone 4-aminobenzoylhydrazone (BAH), a Schiff base derivative, after silanization of silica by 3-chloropropyltrimethoxysilane (CPTS) by using a reported method. Characterization of the surface modification was confirmed through infrared spectroscopy, thermogravimetry, and elemental analysis. The immobilized surface was used for Cu(II), Ni(II), Zn(II), and Co(II) sorption from aqueous solutions. The influence of the amount of sorbent,

?. Hilal Gübbük; Ramazan Güp; Mustafa Ersöz

2008-01-01

156

Spectroscopic studies and biological activity of some transition metal complexes of unusual Schiff base  

NASA Astrophysics Data System (ADS)

Unusual Schiff base ligand, 4-ethanimidoyl-6-[(1E)-N-(2-hydroxy-4-methylphenyl)ethanimidoyl]benzene-1,3-diol, L, was synthesized via catalytic process involving the interaction of some metal ions with a macrocyclic Schiff base (MSB). The transition metal derivatives [ML(H2O)4](NO3)3, M = Cr(III) and Fe(III), [NiL(H2O)4](NO3)2, [ML(H2O)2](NO3)2, M = Zn(II) and Cd(II), [Cl2Pd(?-Cl)2PdL], [PtL(Cl)2] and [PtL(Cl)4] were also synthesized from the corresponding metal species with L. The Schiff bases and complexes were characterized by elemental analysis, mass spectrometry, IR and 1H NMR spectroscopy. The crystal structure of L was determined by X-ray analysis. The spectroscopic studies revealed a variety of structure arrangements for the complexes. The biological activities of L and metal complexes against the Escherchia coli as Gram-negative bacteria and Staphylococcus aureus as Gram-positive bacteria, and the two fungus Aspergillus flavus and Candida albicans were screened. The cytotoxicity of [PtL(Cl)2] complex, a cis-platin analogous, was checked as an antitumor agent on two breast cancer cell lines (MCF7 and T47D) and human liver carcinoma cell line (HepG2).

Abu Al-Nasr, Ahmad K.; Ramadan, Ramadan M.

2013-03-01

157

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

NASA Astrophysics Data System (ADS)

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, 1H 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 51V 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.

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

2012-06-01

158

Oxo-molybdenum and oxo-tungsten complexes of Schiff bases relevant to molybdoenzymes.  

PubMed

A series of octahedral dioxomolybdenum(VI) complexes of the type [MoO(2)L(2)] {L = 4-Ar-pent-2-en-ol; L(i-Pr2Ph) with Ar = 2,6-diisopropylphenyl (1); L(Me2Ph) with Ar = 2,6-dimethylphenyl (2), L(MePh) with Ar = 2-methylphenyl (3) and with Ar = phenyl (4)} and dioxotungsten(VI) compounds [WO(2)L(2)] {L(i-Pr2Ph) (5); L(Me2Ph) (6) and L(MePh) (7)} with Schiff bases have been synthesized as models for oxotransferases. Spectroscopic characterization in solution shows with the sterically encumbered ligands L(i-Pr2)Ph and L(Me2)Ph isomerically pure products whereas the ligand with only one substituent in ortho position at the aromatic ring L(MePh) revealed a dynamic mixture of three isomers as confirmed by variable temperature NMR spectroscopy. Single crystal X-ray diffraction analyses of compounds 1, 2, and 4 and showed them to be in the N,N-trans conformation consistent with the larger steric demand at nitrogen. Oxygen atom transfer (OAT) properties towards trimethylphosphine were investigated leading to the isolation of two mononuclear molybdenum(IV) compounds [MoO(PMe(3))(L(Me2Ph))(2)] (8) and [MoO(PMe(3))(L(MePh))(2)] (9) as confirmed by spectroscopic and crystallographic means. The kinetics of OAT between complex [MoO(2)(L(Me2Ph))(2)] (2) and PMe(3) was investigated by UV/Vis spectroscopy under pseudo-first-order conditions revealing single-step reactions with Eyring values of DeltaH(double dagger) = +60.79 kJ mol(-1) and DeltaS(double dagger) = -112 J mol(-1) K(-1) and a first-order dependence of phosphine consistent with a slow nucleophilic attack of the phosphine showing the octahedral geometries of this system to be unfavorable for OAT. Compound 1 showed no OAT reactivity towards PMe(3) emphasizing the influence of sterical properties. Furthermore, the reactivity of the reduced compounds [MoO(PMe(3))(L(Me2Ph))(2)] (8) and [MoO(PMe(3))(L(MePh))(2)] (9) towards molecular oxygen was investigated leading, in the case of 8, to the substitution of PMe(3) by O(2) under formation of the peroxo compound [MoO(O(2))(L(Me2Ph))(2)] (10). In contrast, the analogous reaction employing 9 led to oxidation forming the dioxo compound [MoO(2)(L(MePh))(2)] (3). PMID:20449078

Lyashenko, Ganna; Saischek, Gerald; Judmaier, Martina E; Volpe, Manuel; Baumgartner, Judith; Belaj, Ferdinand; Jancik, Vojtech; Herbst-Irmer, Regine; Mösch-Zanetti, Nadia C

2009-08-01

159

A novel Mn(2+) PVC membrane electrode based on a recently synthesized Schiff base.  

PubMed

A new PVC membrane electrode for manganese(II) ion based on a recently synthesized Schiff base of 5-[(4-nitrophenylazo)-N-hexylamine]salicylaldimine is reported. The electrode exhibits a Nernstian response for Mn(2+) ions over a wide concentration range (4.0x10(-7) to 1.8x10(-2)molL(-1)) with a slope of 30.1 (+/-1.0). The limit of detection is 1.0x10(-7)molL(-1). The electrode has a fast response time ( approximately 10s), a satisfactory reproducibility and relatively long life time. The proposed sensor revealed good selectivities over a wide variety of other cations include hard and soft metals. This electrode could be used in a pH range of 4.5-7.5. It was used as an indicator electrode in potentiometric titration of manganese(II) ions with EDTA solution. PMID:19071730

Mashhadizadeh, Mohammad Hossein; Taheri, Ehsan Pour; Sheikhshoaie, Iran

2007-05-15

160

Synthesis and Biological Activity of the Schiff Base N,N?-bis(Salicylidene)thiourea and Its Complexes of Copper (II), Nickel (II) and Zinc (II)  

Microsoft Academic Search

The Schiff base N,N?-bis(salicylidene)thiourea and its complexes of copper(II), nickel(II) and zinc(II) have been synthesized and characterized by elemental analyses, molar conductivity measurements, thermal analyses, infrared and electronic spectral data. The Schiff base ligand has been further identified by H NMR and mass spectra. The results suggest that the Schiff base behaves as a quadridentate ligand attached to the metal

Zhu Xinde; Wang Chenggang; Lu Zhiping; Le Zhifeng; Wu Zishen

1996-01-01

161

Synthesis, Characterization and Anticancer Activity of L-Alanine Schiff Base Complexes of Copper(II), Zinc(II), Nickel(II) and Cobalt(II)  

Microsoft Academic Search

A new series of copper(II), zinc(II), nickel(II) and cobalt(II) complexes with the Schiff base derived from 4-hydroxysalicylaldehyde and L-alanine has been synthesized. These compounds have been characterized by elemental analyses, thermoanalyses, conductivity measurements, infrared and electronic spectra. The Schiff base ligand and its zinc(II) complex have been further identified by H NMR. The results suggest that the Schiff base acts

Wu Zishen; Gui Ziqi; Yen Zhenhuan

1990-01-01

162

Factors affecting the C=N stretching in protonated retinal Schiff base: a model study for bacteriorhodopsin and visual pigments  

SciTech Connect

Factors affecting the C=N stretching frequency of protonated retinal Schiff base (RSBH/sup +/) were studied with a series of synthetic chromophores and measured under different conditions. Interaction of RSBH/sup +/ with nonconjugated positive charges in the vicinity of the ring moiety or a planar polyene conformation (in contrast to the twisted retinal conformation in solution) shifted the absorption maxima but did not affect the C=N stretching frequency. The latter, however, was affected by environmental perturbations in the vicinity of the Schiff base linkage. Diminished ion pairing achieved either by substituting a more bulky counteranion or by designing models with a homoconjugation effect lowered the C=N stretch energy. Decreasing solvation of the positively charged nitrogen leads to a similar trend. These effects in the vicinity of the Schiff base linkage also perturb the deuterium isotope effect observed upon deuteriation of the Schiff base. The results are interpreted by considering the mixing of the C=N stretching and C=N-H bending vibration. The C=N mode is shifted due to electrostatic interaction with nonconjugated positive charges in the vicinity of the Schiff base linkage, an interaction that does not influence the isotope effect. Weak hydrogen bonding between the Schiff base linkage in bacteriorhodopsin (bR) and its counteranion or, alternatively, poor solvation of the positively charged Schiff base nitrogen can account for the C=N stretching frequency of 1640 cm/sup -1/ and the deuterium isotope effect of 17 cm/sup -1/ observed in this pigment. Conversion of bR to the photochemically induced intermediate K/sub 610/ involves environmental perturbation in the vicinity of the C=N linkage, lowering the C=N stretch energy.

Baasov, T.; Friedman, N.; Sheves, M.

1987-06-02

163

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

PubMed

A series of novel Schiff bases containing pyrazole group were synthesized using 1-aryl-3-methyl-4-benzoyl-5-pyrazolone and phenylenediamine as the starting materials. All as-synthesized Schiff bases were characterized by means of NMR, FT-IR, and MS; and the molecular geometries of two Schiff bases as typical examples were determined by means of single crystal X-ray diffraction. In the meantime, the ultraviolet-visible light absorption spectra and fluorescent spectra of various as-synthesized products were also measured. Moreover, the B3LYP/6-1G(d,p) method was used for the optimization of the ground state geometry of the Schiff bases; and the spectroscopic properties of the products were computed and compared with corresponding experimental data based on cc-pVTZ basis set of TD-B3LYP method. It has been found that all as-synthesized Schiff bases show a remarkable absorption peak in a wavelength range of 270-370 nm; and their maximum emission peaks are around 344 nm and 332 nm, respectively. PMID:22617219

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

2012-09-01

164

Carbonyl compound dependent hydrolysis of mono-condensed Schiff bases: A trinuclear Schiff base complex and a mononuclear mixed-ligand ternary complex of copper(II)  

Microsoft Academic Search

Two Schiff bases, HL1 and HL2 have been prepared by the condensation of N-methyl-1,3-propanediamine (mpn) with salicylaldehyde and 1-benzoylacetone (Hbn) respectively. HL1 on reaction with Cu(ClO4)2·6H2O in methanol produced a trinuclear CuII complex, [(CuL1)3(?3-OH)](ClO4)2·H2O·0.5CH2Cl2 (1) but HL2 underwent hydrolysis under similar reaction conditions to result in a ternary CuII complex, [Cu(bn)(mpn)ClO4]. Both complexes have been characterised by single-crystal X-ray analyses,

Subrata Naiya; Biswarup Sarkar; You Song; Sandra Ianelli; Michael G. B. Drew; Ashutosh Ghosh

2010-01-01

165

Synthesis, spectral, antimicrobial and antitumor assessment of Schiff base derived from 2-aminobenzothiazole and its transition metal complexes  

NASA Astrophysics Data System (ADS)

N-(thiophen-2-ylmethylene)benzo[ d]thiazol-2-amine Schiff base (L) derived from 2-aminobenzothiazole and 2-thiophenecarboxaldehyde was synthesized and characterized using elemental analysis, IR, mass spectra, 1H NMR and UV-vis spectra. Its complexes with Cu(II), Fe(III), Ni(II) and Zn(II) were prepared and isolated as solid products and characterized by elemental and thermal analyses, spectral techniques as well as magnetic susceptibility. The IR spectra showed that the Schiff base under investigation behaves as bidentate ligand. The UV-vis spectra and magnetic moment data suggested octahedral geometry around Cu(II) and Fe(III) and tetrahedral geometry around Ni(II) and Zn(II). In view of the biological activity of the Schiff base and its complexes, it has been observed that the antimicrobial activity of the Schiff base increased on complexation with the metal ion. In vitro antitumor activity assayed against five human tumor cell lines furnished the significant toxicities of the Schiff base and its complexes.

Etaiw, Safaa Eldin H.; Abd El-Aziz, Dina M.; Abd El-Zaher, Eman H.; Ali, Elham A.

2011-09-01

166

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

167

Synthesis, interaction with DNA and antiproliferative activities of two novel Cu(II) complexes with Schiff base of benzimidazole.  

PubMed

Two novel copper(II) complexes with Schiff base of benzimidazole [Cu(L)Cl]2·CH3OH have been synthesized. HL(1) (N-(benzimidazol-2-ymethyl)-5-chlorosalicylideneimine, C15H11ClN3O) and HL(2) (N-(benzimidazol-2-ymethyl)-salicylideneimine, C15H12N3O) are ligands of complex (1) and complex (2), respectively. The complexes were characterized by elemental analysis, IR, UV-Vis, TGA and X-ray diffraction. Within the complexes, Cu(II) ions were four coordinated by two nitrogen atom of azomethine and imine, one phenolic oxygen atom from HL and one chloride atom. A distorted quadrilateral structure was formed. Complex (1) crystallized in the triclinic crystal system. Results showed that ?-? stacking effect occurred due to the existence of aromatic ring from Schiff base and hydrogen bonding between methanol and adjacent atoms. The DNA binding properties of the complexes were investigated by electronic absorption spectra, fluorescence spectra and viscosity measurements. Results indicated that complexes bound to DNA via partial intercalation mode. The DNA binding constants Kb/(L mol(-1)) were 1.81×10(4) (1), 1.37×10(4) (2), 6.27×10(3) (HL(1)) and 3.14×10(3) (HL(2)) at 298 K. The title complexes could quench the emission intensities of EB-DNA system significantly. The results of agarose gel electrophoresis indicated complex (1) could cleave supercoiled DNA through the oxidative mechanism. The inhibition ratios revealed that complex (1) and HL(1) had strong antiproliferative activities against human breast cancer cells (MCF-7) lines and human colorectal cancer cells (COLO205) lines in vitro. The antiproliferative activities of complex (1) against MCF-7 lines (IC50=16.9±1.5 ?mol L(-1)) and against COLO205 lines (IC50=16.5±3.4 ?mol L(-1)) is much stronger than that of HL(1), which had the potential to develop anti-cancer drug. PMID:24220672

Song, Wen-Ji; Cheng, Jian-Ping; Jiang, Dong-Hua; Guo, Li; Cai, Meng-Fei; Yang, Hu-Bin; Lin, Qiu-Yue

2014-03-01

168

Electrochemistry of oxo-technetium(V) complexes containing Schiff base and 8-quinolinol ligands  

SciTech Connect

The electrochemistry of six-coordinate, monooxo technetium(V) complexes containing Schiff base ligands has been studied in acetonitrile and N,N'-dimethylformamide solutions. The complexes have the general formula TcOCl(L/sub B/)/sub 2/ or TcO(L/sub T/)(L/sub B/), where L/sub B/ represents a bidentate-N,O Schiff base ligand or a bidentate-N,O 8-quinolinol ligand and L/sub T/ represents a tridentate-O,N,O Schiff base ligand. Cyclic voltammetry at a platinum-disk electrode, controlled-potential coulometry, and thin-layer spectroelectrochemistry were used to probe both the oxidation and the reduction of these complexes. The results of these studies, and previously reported results on the analogous Re(V) complexes, can be understood within a single general reaction scheme. The salient features of this scheme are (i) one-electron reduction of Tc(V) to Tc(IV), (ii) subsequent loss of a ligand situated cis to the Tc/identical to/O linkage, and (iii) subsequent isomerization of this unstable Tc(IV) product to more stable complex in which the site trans to the Tc/identical to/O linkage is vacant. The Tc(IV) complexes can also be reduced to analogous Tc(III) species, which appear to undergo the same ligand loss and isomerization reactions. The technetium complexes are 400-500 mV easier to reduce than are their rhenium analogues. The 8-quinolinol ligands, and especially the 5-nitro derivative, both thermodynamically and kinetically stabilize the Tc(IV) and Tc(III) oxidation states. These electrogenerated species are unusual in that they constitute the bulk of the known examples of monomeric Tc(IV) and Tc(III) complexes containing only N- and O-donating ligands. 34 refs., 9 figs., 1 tab.

Refosco, F.; Mazzi, U.; Deutsch, E.; Kirchhoff, J.R.; Heineman, W.R.; Seeber, R.

1988-11-16

169

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).

2012-01-01

170

Regiodivergent Kinetic Resolution of Terminal and Internal rac-Aziridines with Malonates under Dinuclear Schiff Base Catalysis.  

PubMed

Regiodivergent parallel kinetic resolution of aziridines with malonates was achieved under dinuclear Schiff base catalysis. The regiodivergent reaction proceeded under catalyst-control irrespective of the substituents on the aziridines, and 2.5-10 mol % of a Y(OTf)3/La(OiPr)3/a dinucleating Schiff base = 1:1:1 mixture gave versatile ?-amino acid derivatives in 96 ? >99.5% ee. Not only terminal but also internal racemic aziridines reacted smoothly under suitably combined Lewis acid/Brønsted base catalysis. PMID:24912964

Xu, Yingjie; Kaneko, Keiichi; Kanai, Motomu; Shibasaki, Masakatsu; Matsunaga, Shigeki

2014-06-25

171

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

172

Highly Fluorescent BF2 Complexes of Hydrazine-Schiff Base Linked Bispyrrole.  

PubMed

A series of BF2 complexes of hydrazine-Schiff base linked bispyrrole have been prepared from a simple two-step reaction from commercially available substances and are highly fluorescent in solution, film, and solid states with larger Stokes shift and excellent photostabilities comparable or even super to those of their BODIPY analogues. These resultant fluorescent dyes are highly susceptible to the postfunctionalization, as demonstrated in this work via the Knoevenagel condensation to introducing functionalities or tether groups to the chromophore. PMID:24850322

Yu, Changjiang; Jiao, Lijuan; Zhang, Ping; Feng, Zeya; Cheng, Chi; Wei, Yun; Mu, Xiaolong; Hao, Erhong

2014-06-01

173

Preparation of macrocyclic Schiff-base ligand and antibacterial activities of transition metal complexes thereof  

Microsoft Academic Search

A macrocyclic Schiff-base (H2L) ligand is prepared via condensation of 2,6-pyridine dicarboxaldehyde with triethylene tetramine. The ligand is characterized using elemental analysis, by mass spectrometry, infrared (IR) spectroscopy, and proton nuclear magnetic resonance spectroscopy. The corresponding 1:1 metal complexes with Cr(III), Fe(III), Co(II), Ni(II), Cu(II), Cd(II), UO2(II), and Th(IV) are additionally characterized by determining their magnetic moment, molar conductance, thermal

Gehad G. Mohamed; Mohamed M. Omar; Mohsen S. Abou El-Ela; Ahmed M. M. Hindy

2011-01-01

174

Tridentate (NNO) Schiff-base copper(II) complex: synthesis, crystal structure, and magnetic study  

Microsoft Academic Search

A new azido adduct of a tridentate Schiff-base copper(II) complex has been synthesized and characterized structurally and magnetically. X-ray single crystal structure analysis reveals that the asymmetric unit of [Cu2(L)2(µ1,1-N3)2][Cu(L)(N3)] (1) [HL = 1-(N-ortho-hydroxyacetophenimine)-2,2-diethyl-aminoethane] has two independent moieties. One of these forms a dimer, containing end-on azido bridges, with its center of inversion related equivalents. The complex crystallizes in monoclinic

Chandan Adhikary; Rupam Sen; Gabriele Bocelli; Andrea Cantoni; Massimo Solzi; Siddhartha Chaudhuri; Subratanath Koner

2009-01-01

175

Synthesis, Crystal Structures and Antibacterial Activities of Two Schiff Base Copper(II) Complexes  

Microsoft Academic Search

Two new mononuclear Schiff base copper(II) complexes, [CuBr2L] (1) and [CuBr(NCS)L] (2), where L=N,N?dimethyl?N??(1?pyridinylmethylidene)propane?1,3?diamine, have been obtained from a similar synthetic procedure. The complexes were characterized by elemental analyses and single crystal X?ray diffraction. In 1, the copper(II) ion is five?coordinated in a distorted square?pyramidal configuration, with three N atoms of L and one terminal Br atom defining the basal

2006-01-01

176

Copper (II) complexes of two new oxamidate bis-tetradentate Schiff-base ligands  

Microsoft Academic Search

Two novel symmetrical bis-tetradentate Schiff base ligands, H2L1 and H4L2, have been prepared from the condensation of N,N?-bis (3-aminopropyl) oxamide with pyridine-2-carbaldehyde and pyrrol-2-carbaldehyde, respectively. The ligands react with copper (II) nitrate in basic medium to yield the dinuclear complexes [Cu2L1] (NO3) 2 and [Cu2L2] . [Cu2L1] (NO3) 2 reacts with sodium azide to yield the neutral dinuclear complex [Cu2L1

Jose M. Dominguez-Vera; Natividad Galvez; Jose M. Moreno; Enrique Colacio

1998-01-01

177

New acyclic Schiff-base copper(II) complexes and their electrochemical, catalytic, and antimicrobial studies  

Microsoft Academic Search

A new series of acyclic mononuclear copper(II) complexes have been prepared by Schiff-base condensation derived from 5-methylsalicylaldehyde, diethylenetriamine, tris(2-aminoethyl) amine, triethylenetetramine, N,N-bis(3-aminopropyl)ethylene diamine, N,N-bis(aminopropyl) piperazine, and copper perchlorate. All the complexes were characterized by elemental and spectral analyses. Electronic spectra of the complexes show a d–d transition in the range 500–800?nm, electrochemical studies of the complexes show irreversible one-electron-reduction process

A. Vijayaraj; R. Prabu; R. Suresh; C. Sivaraj; N. Raaman; V. Narayanan

2011-01-01

178

Synthesis and Characterization of Some Indium(III) Complexes of Schiff Bases  

Microsoft Academic Search

Several new indium(III) complexes of Schiff bases having the general formula InCIL [H2L = R(NCH-o-C6H3ROH), R = (CH2)3, CH2C(CH3)2CH2; R = H, 5-OCH3 6-OCH3] were prepared. These complexes were characterized by elemental analysis, conductivity measurement, UV-Vis, IR, NMR and mass spectral data. A square pyramidal structure with an apical chlorine atom was suggested for these complexes.

Cheng-Hsien Lin

1993-01-01

179

Some Metal(II) Complexes of Potentially Terdentate Heterocyclic Schiff Bases  

Microsoft Academic Search

Complexes of copper(II), cobalt(II) and oxovanadium(IV) with Schiff bases obtained by condensing salicylaldehyde, substituted salicylaldehydes and 2-hydroxy-l-naphthaldehyde with 2-aminopyridine (ampy), 5-methyI-2-aminopyridine (CH3ampy) and 4-aminopyridine (4-ampy) have been synthesized and characterized. Two types of complexes [MLCI(H2O)n and ML2] were obtained, depending on whether the metal chloride or metal acetate was used for the synthesis. There is evidence that the three donor

Gabriel A. Kolawole; Adegboye O. Adeyemo

1990-01-01

180

Synthesis of salicylaldehyde Schiff base modified Cu nanocrystals by thermal treatment in liquid paraffin  

NASA Astrophysics Data System (ADS)

Cuboid copper nanocrystals were synthesized by thermal treatment in liquid paraffin without any inert gas protection with salicylaldehyde Schiff base copper (II) (Cu (II)-Salen) complex as precursor. Liquid paraffin was used as solvent and reductant. The obtained copper nanocrystals are morphology-controlled and stable when exposed to air for one year. The nanocrystals were characterized by X-ray diffraction measurements (XRD), UV-visible spectroscopy (UV-vis), transmission electron microscope (TEM), and Fourier transform infrared spectroscopy (FT-IR). The results showed that the stable cuboid copper nanocrystals are synthesized by using Salen as capping agents.

Wen, Yueli; Huang, Wei; Wang, Bin; Fan, Jinchuan; Gao, Zhihua; Yin, Lihua

2011-11-01

181

Synthesis, DNA binding, and antimicrobial studies of novel metal complexes containing a pyrazolone derivative Schiff base  

Microsoft Academic Search

A novel series of Co(II), Ni(II), Cu(II), Zn(II), and VO(IV) complexes has been synthesized from the Schiff base derived from\\u000a 4-[(3,4-dimethoxybenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one and 1,2-diaminobenzene. Structural features\\u000a were determined by analytical and spectral techniques. Binding of synthesized complexes with calf thymus DNA (CT DNA) was\\u000a studied by spectroscopic methods and viscosity measurements. Experimental results indicate that the complexes are able to\\u000a form

Natarajan Raman; Ramaraj Jeyamurugan; Mariyyappan Subbulakshmi; Raja Boominathan; Chithu Ramakrishnan Yuvarajan

2010-01-01

182

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.

Singh, Har Lal; Varshney, A. K.

2006-01-01

183

An electrochemical procedure coupled with a Schiff base method; application to electroorganic synthesis of new nitrogen-containing heterocycles  

NASA Astrophysics Data System (ADS)

The synthesis of Nitrogen-containing heterocycles has been achieved using chemical and electrochemical methods, respectively. The direct chemical synthesis of nucleophiles proceeds through the Schiff base chemical reaction. This procedure offers an alternate reaction between dicarbonyl compounds and diamines leads to the formation of products. The results indicate that the Schiff base chemical method for synthesis of the product has successfully performed in excellent overall yield. In the electrochemical step, a series of Nitrogen-containing compounds were electrosynthesized. Various parameters such as the applied potential, pH of the electrolytic solution, cell configuration and also purification techniques, were carried out to optimize the yields of corresponding products. New Nitrogen-containing heterocycle derivatives were synthesized using an electrochemical procedure coupled with a Schiff base as a facile, efficient and practical method. The products have been characterized after purification by IR, 1H NMR, 13C NMR and ESI-MS2.

Dowlati, Bahram; Othman, Mohamed Rozali

2013-11-01

184

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

185

Effect of Schiff base ligand on the size and the optical properties of TiO2 nanoparticles  

NASA Astrophysics Data System (ADS)

The effect of a Schiff-base ligand (N,N'-ethylenebis(acetylacetone iminato)dianion = acacen) on size and optical properties of TiO2 nanoparticles in a two-step sol-gel method was investigated. Different amounts of Schiff-base ligand were applied and the as-prepared products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectrum, Electron Dispersive X-ray spectroscopy (EDX) and ultraviolet-visible (UV-Vis) spectroscopy. Molecular orbital structure of acacen was calculated by density functional theory (DFT) in order to determine the exact orbital energies and electron transfer pathways. The results demonstrated that applying the appropriate amount of Schiff-base ligand could be effective in particle size control.

Masjedi, Maryam; Mir, Noshin; Noori, Elham; Gholami, Tahereh; Salavati-Niasari, Masoud

2013-10-01

186

Synthesis, spectroscopic characterization and antibacterial studies of lanthanide(III) Schiff base complexes containing N, O donor atoms  

NASA Astrophysics Data System (ADS)

A series of six Ln(III) Schiff base complexes, Pr(III), Sm(III), Gd(III), Tb(III), Er(III) and Yb(III), were synthesized using sodium salt of Schiff base, 2-[(5-bromo-2-hydroxy-benzylidene)-amino]-3-hydroxy-propionic acid, derived from L-serine and 5-bromosalicylaldehyde. These complexes having general formula [Ln(L)(NO3)2(H2O)]·NO3 were characterized by elemental analysis, conductivity measurements, UV-Vis, FT-IR, mass spectrometry and fluorescence studies. Elemental analysis and conductivity measurements suggest the complexes have a 1:1 stoichiometry. From the spectral studies it has been concluded that Ln(III) complexes display eight coordination. The Schiff base and its Ln(III) metal complexes have also been screened for their antibacterial activities by Agar diffusion method.

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

2014-01-01

187

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

PubMed

The condensation reaction of 3,5-diamino-1,2,4-triazole with methoxy-, chloro-, bromo-, iodo- and nitro-substituted 2-hydroxybenzaldehydes formed triazole Schiff bases (L(1))-(L(6)). The synthesized ligands have been characterized through physical, spectral and analytical data. Furthermore, the reaction of synthesized Schiff bases with the oxovanadium(IV) sulphate in (1:2) (metal:ligand) molar ratio afforded the oxovanadium(IV) complexes (1)-(6). All the complexes were non-electrolytic and showed a square-pyramidal geometry. The synthesized compounds have been screened for in-vitro antibacterial, antifungal and brine shrimp bioassay. The bioactivity data showed the complexes to be more active than the original Schiff bases. PMID:23116556

Sumrra, Sajjad H; Chohan, Zahid H

2013-12-01

188

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

189

Suppression of the back proton-transfer from Asp85 to the retinal Schiff base in bacteriorhodopsin: A theoretical analysis of structural elements.  

SciTech Connect

The transfer of a proton from the retinal Schiff base to the nearby Asp85 protein group is an essential step in the directional proton-pumping by bacteriorhodopsin. To avoid the wasteful back reprotonation of the Schiff base from Asp85, the protein must ensure that, following Schiff base deprotonation, the energy barrier for back proton-transfer from Asp85 to the Schiff base is larger than that for proton-transfer from the Schiff base to Asp85. Here, three structural elements that may contribute to suppressing the back proton-transfer from Asp85 to the Schiff base are investigated: (1) retinal twisting; (2) hydrogen-bonding distances in the active site; and (3) the number and location of internal water molecules. The impact of the pattern of bond twisting on the retinal deprotonation energy is dissected by performing an extensive set of quantum-mechanical calculations. Structural rearrangements in the active site, such as changes of the Thr89:Asp85 distance and relocation of water molecules hydrogen-bonding to the Asp85 acceptor group, may participate in the mechanism which ensures that following the transfer of the Schiff base proton to Asp85 the protein proceeds with the subsequent photocycle steps, and not with back proton transfer from Asp85 to the Schiff base.

Bondar, A.N. [University of California, Irvine; Suhai, Sandor [German Cancer Research Center, Heidelberg; Fischer, S. [University of Heidelberg; Smith, Jeremy C [ORNL; Elstner, Marcus [Technical University of Braunschweig

2007-03-01

190

Suppression of the back proton-transfer from Asp85 to the retinal Schiff base in bacteriorhodopsin: A theoretical analysis of structural elements  

SciTech Connect

The transfer of a proton from the retinal Schiff base to the nearby Asp85 protein group is an essential step in the directional proton-pumping by bacteriorhodopsin. To avoid the wasteful back reprotonation of the Schiff base from Asp85, the protein must ensure that, following Schiff base deprotonation, the energy barrier for back proton-transfer from Asp85 to the Schiff base is larger than that for proton-transfer from the Schiff base to Asp85. Here, three structural elements that may contribute to suppressing the back proton-transfer from Asp85 to the Schiff base are investigated: (i) retinal twisting; (ii) hydrogen-bonding distances in the active site; and (iii) the number and location of internal water molecules. The impact of the pattern of bond twisting on the retinal deprotonation energy is dissected by performing an extensive set of quantum-mechanical calculations. Structural rearrangements in the active site, such as changes of the Thr89:Asp85 distance and relocation of water molecules hydrogen-bonding to the Asp85 acceptor group, may participate in the mechanism which ensures that following the transfer of the Schiff base proton to Asp85 the protein proceeds with the subsequent photocycle steps, and not with back proton transfer from Asp85 to the Schiff base.

Bondar, A.N. [University of California, Irvine; Suhai, Sandor [German Cancer Research Center, Heidelberg; Fischer, S. [University of Heidelberg; Smith, Jeremy C [ORNL; Elstner, Marcus [Technical University of Braunschweig

2007-03-01

191

Suppression of the back proton-transfer from Asp85 to the retinal Schiff base in bacteriorhodopsin: A theoretical analysis of structural elements  

SciTech Connect

The transfer of a proton from the retinal Schiff base to the nearby Asp85 protein group is an essential step in the directional proton-pumping by bacteriorhodopsin. To avoid the wasteful back reprotonation of the Schiff base from Asp85, the protein must ensure that, following Schiff base deprotonation, the energy barrier for back proton-transfer from Asp85 to the Schiff base is larger than that for proton-transfer from the Schiff base to Asp85. Here, three structural elements that may contribute to suppressing the back proton-transfer from Asp85 to the Schiff base are investigated: (1) retinal twisting; (2) hydrogen-bonding distances in the active site; and (3) the number and location of internal water molecules. The impact of the pattern of bond twisting on the retinal deprotonation energy is dissected by performing an extensive set of quantum-mechanical calculations. Structural rearrangements in the active site, such as changes of the Thr89:Asp85 distance and relocation of water molecules hydrogen-bonding to the Asp85 acceptor group, may participate in the mechanism which ensures that following the transfer of the Schiff base proton to Asp85 the protein proceeds with the subsequent photocycle steps, and not with back proton transfer from Asp85 to the Schiff base.

Bondar, A.N. [University of California, Irvine; Suhai, Sandor [German Cancer Research Center, Heidelberg; Fischer, S. [University of Heidelberg; Smith, Jeremy C [ORNL; Elstner, Marcus [Technical University of Braunschweig

2006-10-01

192

Convergence of Schiff base costimulatory signaling and TCR signaling at the level of mitogen-activated protein kinase ERK2.  

PubMed

Schiff base formation on specialized T cell surface amines provides a costimulatory signal to T cells through a mechanism that activates Na+ and K+ transport, substantially enhancing TCR-dependent IL-2 production. Schiff base-forming molecules that mimic the natural carbonyl donor potently enhance immune responses and provide the first mechanism-based, orally active immunopotentiatory agents. In the present study, costimulation by the Schiff base-forming molecule tucaresol was investigated at the level of mitogen-activated protein kinase (MAPK) in T cell lines. Both TCR-directed stimulation by anti-CD3 and Schiff base stimulation by tucaresol produced a distinct mobility shift in MAPK, characterized by direct immunoblotting of cell lysate proteins subjected to SDS-PAGE, that corresponded with increased phosphorylation. Combined TCR-CD3 and tucaresol stimulation substantially enhanced and prolonged the MAPK response, providing a biochemical basis for the costimulatory nature of the pathway utilized by Schiff base signaling. The MAPK affected was identified by immunoprecipitation as ERK2. Both the direct effects and the TCR signal-enhancing effects of tucaresol on MAPK activation were also demonstrated in a functional MAPK assay measuring substrate phosphorylation. Borohydride reduction of tucaresol's Schiff base-forming carbonyl group abolished both enhancement of MAPK phosphorylation and IL-2 production, as did a selective inhibitor of the MAPKK, MEK1. Tucaresol had no effect on TCR-mediated rises in intracellular free Ca2+ or inositol 1,4,5-triphosphate generation, while tucaresol signaling occurred normally in the lck-deficient J.CaM1.6 T cell line, consistent with convergence of tucaresol- and TCR-induced signals downstream of early TCR-mediated events. PMID:9278316

Chen, H; Hall, S; Heffernan, B; Thompson, N T; Rogers, M V; Rhodes, J

1997-09-01

193

Metal-Based Biologically Active Compounds: Synthesis, Spectral, and Antimicrobial Studies of Cobalt, Nickel, Copper, and Zinc Complexes of Triazole-Derived Schiff Bases  

PubMed Central

A series of cobalt, nickel, copper, and zinc complexes of bidentate Schiff bases derived from the condensation reaction of 4-amino-5-mercapto-3-methyl/ethyl-1,2,4-triazole with 2,4-dichlorobenzaldehyde were synthesized and tested as antimicrobial agents. The synthesized Schiff bases and their metal complexes were characterized with the aid of elemental analyses, magnetic moment measurements, spectroscopic and thermogravimetric techniques. The presence of coordinated water in metal complexes was supported by infrared and thermal gravimetric studies. A square planar geometry was suggested for Cu(II) and octahedral geometry proposed for Co(II), Ni(II), and Zn(II) complexes. The Schiff bases and their metal complexes have been screened for antibacterial (Pseudomonas aeruginosa, Bacillus subtilis) and antifungal activities (Aspergillus niger, A. flavus). The metal complexes exhibited significantly enhanced antibacterial and antifungal activity as compared to their simple Schiff bases.

Singh, Kiran; Kumar, Yogender; Puri, Parvesh; Sharma, Chetan; Aneja, Kamal Rai

2011-01-01

194

Structural and biological behaviors of some nonionic Schiff-base amphiphiles and their Cu(II) and Fe(III) metal complexes.  

PubMed

Novel series of nonionic Schiff bases was synthesized and characterized using microelemental analysis, FTIR and (1)H NMR spectra. These Schiff bases and their complexes with Cu and Fe have been evaluated for their antibacterial activity against bacterial species such as Staphylococcus aureus, Pseudomonas aureus, Candida albi, Bacillus subtilis and Escherichia coli and their fungicidal activity against Aspcrgillus niger and Aspcrgillus flavus. The results of the biocidal activities showed high potent action of the synthesized Schiff bases towards both bacteria and fungi. Furthermore, complexation of these Schiff bases by Cu(II) and Fe(III) show the metal complexes to be more antibacterial and antifungal than the Schiff bases. The results were correlated to the surface activity and the transition metal type. The mode of action of these complexes was discussed. PMID:18325743

Negm, Nabel A; Zaki, Mohamed F

2008-07-15

195

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

196

Interaction of water-soluble amino acid Schiff base complexes with bovine serum albumin: fluorescence and circular dichroism studies.  

PubMed

Fluorescence spectroscopy in combination with circular dichroism (CD) spectroscopy were used to investigate the interaction of water-soluble amino acid Schiff base complexes, [Zn(L1,2)(phen)] where phen is 1,10-phenanthroline and H2L1,2 is amino acid Schiff base ligands, with bovine serum albumin (BSA) under the physiological conditions in phosphate buffer solution adjusted to pH 7.0. The quenching mechanism of fluorescence was suggested as static quenching according to the Stern-Volmer equation. Quenching constants were determined using the Stern-Volmer equation to provide a measure of the binding affinity between amino acid Schiff base complexes and BSA. The thermodynamic parameters DeltaG, DeltaH and DeltaS at different temperatures (298, 310 and 318K) were calculated. The results indicate that the hydrophobic and hydrogen bonding interactions play a major role in [Zn(L1)(phen)]-BSA association, whereas hydrophobic and electrostatic interactions participate a main role in [Zn(L2)(phen)]-BSA binding process. Binding studies concerning the number of binding sites and apparent binding constant Kb were performed by fluorescence quenching method. The distance R between the donor (BSA) and acceptor (amino acid Schiff base complexes) has been obtained utilizing fluorescence resonant energy transfer (FRET). Furthermore, CD spectra were used to investigate the structural changes of the BSA molecule with the addition of amino acid Schiff base complexes. The results indicate that the interaction of amino acid Schiff base complexes with BSA leads to changes in the secondary structure of the protein. Fractional contents of the secondary structure of BSA (f(alpha), f(beta), f(turn) and f(random)) were calculated with and without amino acid Schiff base complexes utilizing circular dichroism spectroscopy. Our results clarified that amino acid Schiff base complexes could bind to BSA and be effectively transported and eliminated in the body, which could be a useful guideline for further drug design. PMID:18701343

Gharagozlou, Mehrnaz; Boghaei, Davar M

2008-12-15

197

Studies on the complexing behavior of a potentially tetradentate Schiff-base ligand with some transition metal ions  

Microsoft Academic Search

The Schiff base furfural-histidine with Co(II), Ni(II), Cu(II), and Zn(II) in solution gives M(AB), M(AB)B, or M(AB)2. The Schiff base is tetradentate in M(AB)2 and M(AB)B and tridentate in M(AB)2; [M(AB)2] · 2H2O (M = Co, Ni and Zn) and [Cu(AB)]NO3 were synthesized and characterized by elemental analysis, molecular weight determination, conductance, IR, UV–Vis, and CV. The electronic spectral measurements

M. Sivasankaran Nair; C. Ravi Samuel Raj

2009-01-01

198

Preparation and characterization of a copper(II) compound with a new glycine Schiff base containing an ester function  

Microsoft Academic Search

Summary A new Schiff base was obtained from glycine and ethyl-a-ketocyclopentylcarboxylate. This forms a potassium salt K(Rgly)·H2O, where Rgly=C10H14O4N. From this salt a new copper(II) complex was prepared, Cu(Rgly')·2H2O, where Rgly'=C10H13O4N (deprotonated Schiff base). The compounds were characterized by i.r. spectroscopy, differential thermal analysis (d.t.a.) and thermogravimetric analysis (t.g.). The activation energy corresponding to the dehydration process for compounds was

Miguel A. Bafiares; Amador Angoso; Juan L. Manzano; Emilio Rodriguez; Práxedes Dévora

1989-01-01

199

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

200

Complexes of divalent transition metal chlorides with the tetradentate Schiff base ligand 1,2-bis(2?-pyridylmethyleneimino)-benzene  

Microsoft Academic Search

Transition metal(II) chloro complexes of the new Schiff base ligand 1,2-bis(2'-pyridylmethyleneimino)benzene (L), derived from 2-pyridinecarboxaldehyde and 1,2-phenylenediamine, were prepared. Compounds of [MnLCl2]-H2O, [CoLCl2]·2H2O, [NiLCl2] and [Zn3L2Cl4]Cl2 were prepared. Details are given of the formation of the complex [Cu(L·EtOH)Cl2], in which one molecule of EtOH adds across only one of the Schiff base {ie531-01} groups to give the coordinated ligand L·EtOH.

Spyridoula Kasselouri; Achilleas Garoufis; George Kalkanis; Spyros P. Perlepes; Nick Hadjiliadis

1993-01-01

201

Self-assembling dicopper(II) complexes of di-2-pyridyl ketone Schiff base ligands derived from S-alkyldithiocarbazates  

Microsoft Academic Search

Condensation of di-2-pyridyl ketone with S-methyldithiocarbazate or S-benzyldithiocarbazate yields potentially bridging ligands of the form Py2CNNHC(S)SR; Hdpksme (R=Me; the di-2-pyridyl ketone Schiff base of S-methyldithiocarbazate) and Hdpksbz (R=Bz; the di-2-pyridyl ketone Schiff base of S-benzyldithiocarbazate). Complexation of these ligands with Cu(II) in a 1:1M ratio leads to the formation of dinuclear complexes of the general formula [Cu(NNNS)X]2 (X=Cl?, NO3?, H2O).

Mohammad Akbar Ali; Aminul H. Mirza; Ray J. Butcher; Paul V. Bernhardt; Mohammad Rezaul Karim

2011-01-01

202

Synthesis, Characterization, and BSA Binding Studies of Some New Benzamides Related to Schiff Base  

PubMed Central

Condensation of amine 1 with aldehyde 2 gives Schiff base, N-(4-((benzofuran-2-ylmethylene) amino)phenyl)acetamide 3. Schiff base on N-acylation with different substituted acid chlorides in the presence of triethylamine gives the corresponding benzamides, N-acetyl-N-(4-((benzofuran-2-ylmethylene)amino)phenyl)substitutedbenzamide (NABP) 5a–j. The structures of newly synthesized compounds were characterized by elemental analysis, 1H NMR, 13C NMR FT-IR, and mass spectral studies. Compounds 3 and 5a–j have been screened for their antimicrobial activity using the disc diffusion and minimum inhibitory concentration (MIC) method against the selected bacterial and fungal strain. Compounds 5a, 5e, 5g, and 5h were found to be more active against all tested strains. The antioxidant properties were evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radical scavenging methods. Compounds 5i and 5j showed predominant antioxidant activities among the synthesized analogues. The interaction between NABP and bovine serum albumin (BSA) was investigated using fluorescence and ultraviolet spectroscopic techniques at 298?K under imitated physiological conditions. The results revealed that NABP caused the fluorescence quenching of BSA through a static quenching procedure. The binding constants and the number of binding sites were calculated. The binding distance between the donor (BSA) and acceptor (NABP) was determined based on Forster's theory.

Prashanth, M. K.; Madaiah, M.; Revanasiddappa, H. D.; Amruthesh, K. N.

2013-01-01

203

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

204

Fast O2 Binding at Dicopper Complexes Containing Schiff-Base Dinucleating Ligands  

PubMed Central

A new family of dicopper(I) complexes [CuI2RL](X)2, (R = H, 1X, R = tBu, 2X and R = NO2, 3X, X = CF3SO3, ClO4, SbF6 or BArF, BArF = [B{3,5-(CF3)2-C6H3}4]?), where RL is a Schiff-base ligand containing two tridentate binding sites linked by a xylyl spacer have been prepared, characterized, and their reaction with O2 studied. The complexes were designed with the aim of reproducing structural aspects of the active site of type 3 dicopper proteins; they contain two three-coordinate copper sites and a rather flexible podand ligand backbone. The solid state structures of 1ClO4, 2CF3SO3, 2ClO4 and 3BArF·CH3CN have been established by single crystal X-ray diffraction analysis. 1ClO4 adopts a polymeric structure in solution while 2CF3SO3, 2ClO4 and 3BArF·CH3CN are monomeric. The complexes have been studied in solution by means of 1H and 19F NMR spectroscopy, which put forward the presence of dynamic processes in solution. 1-3BArF and 1-3CF3SO3 in acetone react rapidly with O2 to generate metaestable [CuIII2(?-O)2(RL)]2+ 1-3(O2) and [CuIII2(?-O)2(CF3SO3)(RL)]+ 1-3(O2)(CF3SO3) species, respectively that have been characterized by UV-vis spectroscopy and resonance Raman analysis. Instead, reaction of 1-3BArF with O2 in CH2Cl2 results in intermolecular O2 binding. DFT methods have been used to study the chemical identities and structural parameters of the O2 adducts, and the relative stability of the CuIII2(?-O)2 form with respect to the CuII2(?-?2: ?2-peroxo) isomer. The reaction of 1X, X = CF3SO3 and BArF with O2 in acetone has been studied by stopped-flow exhibiting an unexpected very fast reaction rate (k = 3.82(4) × 103 M?1s?1, ?H‡ = 4.9 ± 0.5 kJ·mol?1, ?S‡ = ?148 ± 5 J·K?1·mol?1), nearly three orders of magnitude faster than in the parent [CuI2(m-XYLMeAN)]2+. Thermal decomposition of 1-3(O2) does not result in aromatic hydroxylation. The mechanism and kinetics of O2 binding to 1X (X = CF3SO3 and BArF) is discussed and compared with those associated to selected examples of reported models of O2-processing copper proteins. A synergistic role of the copper ions in O2 binding and activation is clearly established from this analysis.

Company, Anna; Gomez, Laura; Mas-Balleste, Ruben; Korendovych, Ivan V.; Ribas, Xavi; Poater, Albert; Parella, Teodor; Fontrodona, Xavier; Benet-Buchholz, Jordi; Sola, Miquel; Que, Lawrence; Rybak-Akimova, Elena; Costas, Miquel

2008-01-01

205

Fast O2 binding at dicopper complexes containing Schiff-base dinucleating ligands.  

PubMed

A new family of dicopper(I) complexes [CuI2RL](X)2 (R=H, 1X, R=tBu, 2X and R=NO2, 3X, X=CF3SO3, ClO4, SbF6, or BArF, BArF=[B{3,5-(CF3)2C6H3}4]-), where RL is a Schiff-base ligand containing two tridentate binding sites linked by a xylyl spacer, has been prepared and characterized, and its reaction with O2 has been studied. The complexes were designed with the aim of reproducing structural aspects of the active site of type 3 dicopper proteins; they contain two three-coordinate copper sites and a rather flexible podand ligand backbone. The solid-state structures of 1ClO4, 2CF3SO3, 2ClO4, and 3BArF.CH3CN have been established by single-crystal X-ray diffraction analysis. 1ClO4 adopts a polymeric structure in the solid state while 2CF3SO3, 2ClO4, and 3BArF.CH3CN are monomeric. The complexes have been studied in solution by means of 1H and 19F NMR spectroscopy, which put forward the presence of dynamic processes. 1-3BArF and 1-3CF3SO3 in acetone react rapidly with O2 to generate metaestable [CuIII2(mu-O)2(RL)]2+ 1-3(O2) and [CuIII2(mu-O)2(CF3SO3)(RL)]+ 1-3(O2)(CF3SO3) species, respectively, that have been characterized by UV-vis spectroscopy and resonance Raman analysis. Instead, reaction of 1-3BArF with O2 in CH2Cl2 results in intermolecular O2 binding. DFT methods have been used to study the chemical identities and structural parameters of the O2 adducts, and the relative stability of the CuIII2(mu-O)2 form with respect to the CuII2(mu-eta2:eta2-O2) isomer. The reaction of 1X, X = CF3SO3 and BArF, with O2 in acetone has been studied by stopped-flow UV-vis exhibiting an unexpected very fast reaction rate (k=3.82(4)x10(3) M-1 s-1, DeltaH=4.9+/-0.5 kJ.mol-1, DeltaS=-148+/-5 J.K-1.mol-1), nearly 3 orders of magnitude faster than in the parent [CuI2(m-XYLMeAN)]2+. Thermal decomposition of 1-3(O2) does not result in aromatic hydroxylation. The mechanism and kinetics of O2 binding to 1X (X=CF3SO3 and BArF) are discussed and compared with those associated with selected examples of reported models of O2-processing copper proteins. A synergistic role of the copper ions in O2 binding and activation is clearly established from this analysis. PMID:17500512

Company, Anna; Gómez, Laura; Mas-Ballesté, Rubén; Korendovych, Ivan V; Ribas, Xavi; Poater, Albert; Parella, Teodor; Fontrodona, Xavier; Benet-Buchholz, Jordi; Solà, Miquel; Que, Lawrence; Rybak-Akimova, Elena V; Costas, Miquel

2007-06-11

206

Nonlinear optical analyses of organic N-(9-Anthrylmethylidene) methylamine Schiff base.  

PubMed

The organic NLO Schiff base of N-(9-Anthrylmethylidene) methylamine was synthesized by condensation process. The material was characterized through Powder XRD, FT-IR, and Raman techniques. The various planes of reflection are identified from the Powder XRD pattern. The formation of Schiff base is confirmed through FT-IR and Raman analysis. The intra molecular charge transfer interaction and the existence of the first-order molecular hyperpolarizability (?) are identified from the red shift of the UV-Vis analysis. The structure of the molecule was optimized by density functional theory (DFT) using B3LYP method with 6-31G basis set. The NBO analysis is used to interpret the delocalization. The dipole moment and first hyperpolarizability values were also computed by HF/6-31G. These values indicate that the compound is a good candidate with nonlinear optical properties. This is the first time report on the existence of a second harmonic generation (SHG), ?(2), efficiency that has been identified by Powder Kurtz-Perry method. PMID:23542516

Vijayalakshmi, S; Kalyanaraman, S; Krishnakumar, V

2013-05-15

207

Nonlinear optical analyses of organic N-(9-Anthrylmethylidene) methylamine Schiff base  

NASA Astrophysics Data System (ADS)

The organic NLO Schiff base of N-(9-Anthrylmethylidene) methylamine was synthesized by condensation process. The material was characterized through Powder XRD, FT-IR, and Raman techniques. The various planes of reflection are identified from the Powder XRD pattern. The formation of Schiff base is confirmed through FT-IR and Raman analysis. The intra molecular charge transfer interaction and the existence of the first-order molecular hyperpolarizability (?) are identified from the red shift of the UV-Vis analysis. The structure of the molecule was optimized by density functional theory (DFT) using B3LYP method with 6-31G basis set. The NBO analysis is used to interpret the delocalization. The dipole moment and first hyperpolarizability values were also computed by HF/6-31G. These values indicate that the compound is a good candidate with nonlinear optical properties. This is the first time report on the existence of a second harmonic generation (SHG), ?2, efficiency that has been identified by Powder Kurtz-Perry method.

Vijayalakshmi, S.; Kalyanaraman, S.; Krishnakumar, V.

2013-05-01

208

Theoretical study of structure and electronic absorption spectra of some Schiff bases and their zinc complexes.  

PubMed

Tetradentate Schiff bases (H(2)L(i)), derivatives of salicylic aldehyde (H(2)L(1), H(2)L(2)) or o-vanillin (H(2)L(3), H(2)L(4)) with ethylenediamine or o-phenylenediamine as a bridge, and their zinc complexes were studied experimentally and theoretically in view of their possible application as emitters in organic light emitting diodes (OLEDs). The composition of thin films of the complexes was analyzed using a combination of different experimental and molecular modeling techniques taking into account changes in the Gibbs free energy of dehydration and dimerization reactions. The absorption spectra of the initial Schiff bases were investigated in methanol solutions, while the absorption spectra of their zinc complexes were investigated in thin films. Experimental results of elemental analysis, IR spectroscopy, laser desorption/ionization mass spectrometry (LDI MS), and X-ray diffraction as well as theoretical analysis of electronic absorption spectra by the quantum-chemical TD DFT method demonstrate that thin films of the zinc complexes contain binuclear anhydrous molecules. This conclusion should be taken into account when considering both transport and luminescence properties of these complexes in OLED heterostructures. A comparison of the results of CIS, TD DFT/PBE, and TD DFT/PBE0 calculations reveals the crucial importance of the inclusion of the exact exchange in the E(XC) functional for the further correct description of potential energy surfaces of excited states for the systems studied. PMID:19891422

Vladimirova, Kseniya G; Freidzon, Alexandra Ya; Kotova, Oxana V; Vaschenko, Andrei A; Lepnev, Leonid S; Bagatur'yants, Alexander A; Vitukhnovskiy, Alexei G; Stepanov, Nickolai F; Alfimov, Michael V

2009-12-01

209

Antibacterial and Antifungal Studies on Some Schiff Base Complexes of Zinc(II)  

PubMed Central

Two Schiff base ligands L1 and L2 were obtained by the condensation of glycylglycine respectively with imidazole-2-carboxaldehyde and indole-3-carboxaldehyde and their complexes with Zn(II) were prepared and characterized by microanalytical, conductivity measurement, IR, UV-Vis., XRD and SEM. The molar conductance measurement indicates that the Zn(II) complexes are 1 : 1 electrolytes. The IR data demonstrate the tetradentate binding of L1 and tridentate binding of L2. The XRD data show that Zn(II) complexes with L1 and L2 have the crystallite sizes of 53 and 61 nm respectively. The surface morphology of the complexes was studied using SEM. The in vitro biological screening effects of the investigated compounds were tested against the bacterial species Staphylococcus aureus, Escherichia coli, Klebsiella pneumaniae, Proteus vulgaris and Pseudomonas aeruginosa and fungal species Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans by the disc diffusion method. A comparative study of inhibition values of the Schiff base ligands and their complexes indicates that the complexes exhibit higher antimicrobial activity than the free ligands. Zinc ions are proven to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium.

Joseyphus, R. Selwin

2008-01-01

210

Antibacterial and Antifungal Studies on Some Schiff Base Complexes of Zinc(II).  

PubMed

Two Schiff base ligands L1and L2 were obtained by the condensation of glycylglycine respectively with imidazole-2-carboxaldehyde and indole-3-carboxaldehyde and their complexes with Zn(II) were prepared and characterized by microanalytical, conductivity measurement, IR, UV-Vis., XRD and SEM. The molar conductance measurement indicates that the Zn(II) complexes are 1: 1electrolytes. The IR data demonstrate the tetradentate binding of L1and tridentate binding of L2. The XRD data show that Zn(II) complexes with L1and L2 have the crystallite sizes of 53 and 61nm respectively. The surface morphology of the complexes was studied using SEM. The in vitro biological screening effects of the investigated compounds were tested against the bacterial species Staphylococcus aureus, Escherichia coli, Klebsiella pneumaniae, Proteus vulgaris and Pseudomonas aeruginosa and fungal species Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans by the disc diffusion method. A comparative study of inhibition values of the Schiff base ligands and their complexes indicates that the complexes exhibit higher antimicrobial activity than the free ligands. Zinc ions are proven to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium. PMID:23990740

Joseyphus, R Selwin; Nair, M Sivasankaran

2008-06-01

211

Ruthenium(II)-Schiff base complexes derived from substituted salicylaldimines and triphenylphosphine  

SciTech Connect

Synthesis and characterization of a series of octahedral ruthenium(II) Schiff base complexes obtained from the interaction of RuCl{sub 2}(PPh{sub 3}){sub 3} with N,N{prime}-ethylene-bis-(5-R-salicylideneimine) are presented. Redox properties and the stability towards oxidation of [Ru(II)(5R-sal{sub 2}en)(PPh{sub 3}){sub 2}] complexes, (R = H-(1), Cl-(2), Br-(3), CH{sub 3}O-(4), NO{sub 2}-(5)) were related to the electron-withdrawing or releasing ability of the substituent in the phenyl ring of the Schiff base. Results show that electron-withdrawing substituents stabilize Ru(II) complexes, while electron-donating groups favour oxidation to Ru(III). Changes in E{sub 1/2} for the complexes, due to remote substituent effects, could be related to changes in basicity of the phenolic oxygen. This variation has more influence on E{sub 1/2} than changes in basicity of the phosphorus in the phosphine ligand. 32 refs., 7 figs., 3 tabs.

Armando, M.B.; Lena, R.R.; Rafael, M.E.; Federico, D.R.P.J.

1993-12-31

212

Spectrophotometric investigation of interaction between iodine and pentadentate Schiff base ligands  

NASA Astrophysics Data System (ADS)

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 KAD 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 ECT 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 ID of each Schiff base was estimated from the corresponding complex band energy, using an empirical equation. An inverse relationship between ID and KAD values was found. Blue and red shift observed for the 445 nm band of iodine were also discussed on the basis of theoretical considerations.

Khouba, Z.; Benabdallah, T.; Maschke, U.

213

Bistable Retinal Schiff Base Photodynamics of Histidine Kinase Rhodopsin HKR1 from Chlamydomonas reinhardtii.  

PubMed

The photodynamics of the recombinant rhodopsin fragment of the histidine kinase rhodopsin HKR1 from Chlamydomonas reinhardtii was studied by absorption and fluorescence spectroscopy. The retinal cofactor of HKR1 exists in two Schiff base forms RetA and RetB. RetA is the deprotonated 13-cis-retinal Schiff base (RSB) absorbing in the UVA spectral region. RetB is the protonated all-trans RSB absorbing in the blue spectral region. Blue light exposure converts RetB fully to RetA. UVA light exposure converts RetA to RetB and RetB to RetA giving a mixture determined by their absorption cross sections and their conversion efficiencies. The quantum efficiencies of conversion of RetA to RetB and RetB to RetA were determined to be 0.096 ± 0.005 and 0.405 ± 0.01 respectively. In the dark thermal equilibration between RetA and RetB with dominant RetA content occurred with a time constant of about 3 days at room temperature. The fluorescence emission behavior of RetA and RetB was studied, and fluorescence quantum yields of ?F (RetA) = 0.00117 and ?F (RetB) = 9.4 × 10(-5) were determined. Reaction coordinate schemes of the photodynamics are developed. PMID:24460585

Penzkofer, Alfons; Luck, Meike; Mathes, Tilo; Hegemann, Peter

2014-07-01

214

[Di-n-butytin tridentate acylhydrazone Schiff base complexes: synthesis and studies by infrared spectroscopy].  

PubMed

Four tridentate acylhydrazone schiff base ligands H2L [H2L1:C6H5C(O)NHN = CHC6H4OH-2, H2L2:C6H5C(O)NHN = CHC6H3(OH)(2)-2,4, H2L3:NC5H4C(O)NHN = CHC6H4OH-2, H2L4:NC5H4C(O)NHN = CHC6H3(OH)(2)-2,4] were synthesized and use to form four novel di-n-Butytin complexes of the type (n-Bu)2SnL with di-n-Butytin oxide [(n-Bu)2SnO]. All these ligands and complexes were characterized by elemental analysis and infrared spectroscopy. Their principal infrared spectral absorption peaks were assigned and discussed for the region of 4,000-400 cm-1. A comparison of the infrared spectra of the ligands with those of the corresponding complexes reveals that the disappearance of the bands assigned to carbonyl unambiguously confirms that the ligands coordinate with tin in the enol form. The coordination manner for tridentate acylhydrazone schiff base ligands with tin atom in the complexes was determined. The results indicated that the Sn atom in these complexes is five-coordinated. PMID:12939967

Wang, Shao-ling; Lu, Wen-guan; Liu, Hong-wen; Chen, Xiao-kang

2003-02-01

215

A study of in vitro antibacterial activity of lanthanides complexes with a tetradentate Schiff base ligand  

PubMed Central

Objective To establish the antibacterial activity of lanthanides complexes with a tetradentate Schiff base ligand L. Methods (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. The antimicrobial activity of the resultant Ln (III) complexes was investigated using agar well diffusion and micro-broth dilution techniques; the latter was used to establish the minimum inhibitory concentrations for each compound investigated. Results Most of Ln (III) complexes were found to exhibit antibacterial activities against a number of pathogenic bacteria with MICs ranging between 1.95-250.00 µg/mL. Staphylococcus aureus was the most susceptible bacterial species to [LaL(NO3)2(H2O)](NO3) complex while Shigella dysenteriae and Escherichia coli required a relatively higher MIC (250 µg/mL). The complexes La (III) and Pr (III) were effective inhibitors against Staphylococcus aureus, whereas Sm (III) complex was effective against Serratia marcescens. On the other hand, Gd (III), La (III) and Nd (III) were found to be more potent inhibitors against Pseudomonas aeruginosa than two of commonly used antibiotics. The remaining Ln (III) complexes showed no remarkable activity as compared to the two standard drugs used. Conclusions Tetradentate Schiff base ligand L and its complexes could be a potential antibacterial compounds after further investigation.

Al Momani, Waleed Mahmoud; Taha, Ziyad Ahmed; Ajlouni, Abdulaziz Mahmoud; Shaqra, Qasem Mohammad Abu; Al Zouby, Muaz

2013-01-01

216

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

NASA Astrophysics Data System (ADS)

A new series of three biologically active triazole derived Schiff base ligands L1-L3 have been synthesized in equimolar reaction of 3-amino-1H-1,2,4-triazole with pyrrol-2-carboxaldehyde, 4-bromo-thiophene-2-carboxaldehyde, and 5-iodo-2-hydroxy benzaldehyde. The prepared Schiff bases were used for further complex formation reaction with different metal elements like Co(II), Ni(II), Cu(II) and Zn(II) as chlorides by using a molar ratio of ligand:metal as 2:1. The structure and bonding nature of all the compounds were identified by their physical, spectral and analytical data. All the metal(II) complexes possessed an octahedral geometry except the Cu(II) complexes which showed a distorted octahedral geometry. All the synthesized compounds, were studied for their in vitro antibacterial, and antifungal activities, against four Gram-negative (Escherichia coli, Shigella sonnei, Pseudomonas aeruginosa and Salmonella typhi) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and against six fungal strains (Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glabrata) by using agar-well diffusion method. It has been shown that all the synthesized compounds showed moderate to significant antibacterial activity against one or more bacterial strains. In vitro Brine Shrimp bioassay was also carried out to investigate the cytotoxic properties of these compounds. The data also revealed that the metal complexes showed better activity than the ligands due to chelation/coordination.

Hanif, Muhammad; Chohan, Zahid H.

2013-03-01

217

Simulation of cis- trans photoinduced transitions IB bis-Schiff base molecules  

NASA Astrophysics Data System (ADS)

Quantum chemical and molecular dynamics simulations of photoinduced UV-absorption and circular dichroism of a new synthesized symmetrical-base derived from condensation of two mole 5-(4-diethylamino-phenyl)-penta-2,4-dienal with a chiral diamine were performed. Photoinduced changes from trans- to cis-isomers in chromophore and transitions between the trans-trans and cis-cis isomers corresponding to right- and left-enantiomers through the metastable cis-trans conformation may explain the observed spectral measurements. The crucial role in the observed transitions is played by C?C bonds close to the benzyl planes of the bis-based molecules (bis-Schiff base, BSB). At the same time rotation of the benzoate rings (about 110°) seems to be important. The performed simulations show that among the calculational technique Adamo-Barone DFT method gave better agreement with experiment.

Lemercier, G.; Alexandre, M.; Andraud, C.; Kityk, I. V.

2004-03-01

218

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

219

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

Talancón, Daniel; Bosque, Ramon; López, Concepción

2010-05-21

220

Synthesis, Polymerization, and Thermal Properties of a New Acetylene-Terminated Schiff Base. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

A new acetylene-terminated Schiff base monomer, N,N'-(1,4-phenylene dimethylidyne) -bis-(4-ethynylaniline) (PPP), was synthesized and was characterized by nuclear magnetic resonance and infrared spectroscopy. This monomer was then polymerized to yield a n...

Y. Wei R. Hariharan J. K. Ray

1991-01-01

221

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

PubMed

Two series of mono- and binuclear complexes cyclic or acyclic thio-ferocine Schiff base ligands, derived from the condensation of 2-aminobenzenthiol (L) with monoacetyl ferrocene in the molar ratio 1:1 or in the molar ratio 1:2 for diacetyl ferocine have been prepared. The condensation reactions yield the corresponding Schiff Base ligands, HLa-Maf and H2Lb-Daf. The chelation of the ligands to metal ions occurs through the sulfur of the thiol group as well as the nitrogen atoms of the azomethine group of the ligands. HLa-Maf acts as monobasic bidentate or dibasic tetradentate, while H2Lb-Daf behaves as twice negatively cargend tetradentate ligand. The structures of these ligands were elucidated by elemental analysis, infrared, ultraviolet-visible spectra, as well as (1)H 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, (1)H 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

222

Highly efficient and enantioselective cyclopropanation of styrene with diazoacetates using a new copper-(Schiff-base) catalyst  

Microsoft Academic Search

A new copper-(Schiff-base) complex, derived from (S)-2-amino-1,1-di(3,5-di-t-butylphenyl)propanol, 2-hydroxy-5-nitrobenzaldehyde and copper acetate monohydrate, was used as an efficient catalyst for the cyclopropanation of styrene with diazoacetates, affording ees of up to 98%.

Zhengning Li; Zhuo Zheng; Huilin Chen

2000-01-01

223

Characteristic spectral studies and in vitro antifungal activity of some Schiff bases and their organotin (IV) complexes  

Microsoft Academic Search

The synthesis andin vitro antifungal activity of some Schiff bases and their Sn (IV) complexes has been tested against plant pathogenic fungi and it\\u000a is found that they possess excellent fungicidal activity. On the basis of1H-,13C-,119Sn NMR-,119Sn Mössbauer, IR and Elemental analysis the tetrahedral geometry is proposed for the synthesized compounds.

Wajid Rehman; Musa Kaleem Baloch; Bakhtiar Muhammad; Amin Badshah; Khalid M. Khan

2004-01-01

224

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

225

Chromium(III) selective membrane sensors based on Schiff bases as chelating ionophores.  

PubMed

The two chromium chelates of Schiff bases, N-(acetoacetanilide)-1,2-diaminoethane (L(1)) and N,N'-bis(acetoacetanilide)-triethylenetetraammine (L(2)), have been synthesized and explored as neutral ionophores for preparing poly(vinylchloride) (PVC) based membrane sensors selective to Cr(III). The addition of lipophilic anion excluder (NaTPB) and various plasticizers viz. o-Nitrophenyloctyl ether (o-NPOE), dioctylpthalate (DOP), dibutylphthalate (DBP), tris(2-ethylhexyl)phosphate (TEHP), and benzyl acetate (BA) have found to improve the performance of the sensors. The best performance was obtained for the membrane sensor having a composition of L(1):PVC:DBP:NaTPB in the ratio 5:150:250:3 (w/w). The sensor exhibits Nernstian response in the concentration range 8.9 x 10(-8) to 1.0 x 10(-1) M Cr(3+) with limit of detection 5.6 x 10(-8) M. The proposed sensor manifest advantages of relatively fast response (10s) and good selectivity over some alkali, alkaline earth, transition and heavy metal ions. The selectivity behavior of the proposed electrode revealed a considerable improvement as compared to the best previously PVC-membrane electrode for chromium(III) ion. The potentiometric response of the proposed sensor was independent of pH of the test solution in the range of 2.0-7.0. The sensor has found to work satisfactorily in partially non-aqueous media up to 20% (v/v) content of methanol, ethanol and acetonitrile and could be used for a period of 3 months. The proposed electrode was used as an indicator electrode in potentiometric titration of chromium ion with EDTA and in direct determination in different water and food samples. PMID:17386662

Singh, A K; Gupta, V K; Gupta, Barkha

2007-02-28

226

The complex extracellular domain regulates the deprotonation and reprotonation of the retinal Schiff base during the bacteriorhodopsin photocycle  

SciTech Connect

During the L {r_arrow} M reaction of the bacteriorhodopsin photocycle the proton of the retinal Schiff base is transferred to the anionic D85. This step, together with the subsequent reprotonation of the Schiff base form D96 in the M {r_arrow} N reaction, results in the translocation of a proton across the membrane. The first of these critical proton transfers occurs in an extended hydrogen-bonded complex containing two negatively charged residues (D85 and D212), two positively charged groups (the Schiff base and R82), and coordinated water. We simplified this region by replacing D212 and R82 with neutral residues, leaving only the proton donor and acceptor as charged groups. The D212N/R82Q mutant shows essentially normal proton transport, but in the photocycle neither of this protein nor of the D212N/R82Q/D96N triple mutant does a deprotonated Schiff base (the M intermediate) accumulate. Instead, the photocycle contains only the K, L, and N intermediates. Infrared difference spectra of D212N/R82Q and D212N/R82Q/D96N demonstrate that although D96 becomes deprotonated in N, D85 remains unprotonated. On the other hand, M is produced at pH>8, where according to independent evidence the L {leftrightarrow} M equilibrium should shift toward M. Likewise, M is restored in the photocycle when the retinal is replaced with the 14-fluoro analogue that lowers the pK{sub a} of the protonated Schiff base, and now D85 becomes protonated as in the wild type. We conclude from these results that the proton transfers to and from the Schiff base, and now D85 becomes protonated as in the wild type. We conclude form these results that the proton transfers to and from the Schiff base probably both occur after photoexcitation of D212N/R82Q, but the L {leftrightarrow} M and M {leftrightarrow} N equilibria are shifted away from M, and, untypically, D85 does not retain the proton it had gained. 72 refs., 11 figs., 1 tab.

Brown, L.S.; Varo, G.; Lanyi, J.K. [Univ. of California, Irvine, CA (United States)] [and others

1995-10-03

227

Triiodide-selective polymeric membrane electrodes based on Schiff base complexes of Cu (II) and Fe (III)  

Microsoft Academic Search

Poly(vinyl chloride) (PVC) membrane electrodes based on two complexes of Schiff base 2,2?[4,4?-diphenylmethane bis (nitromethylidyne)] bisphenol, L, with copper (II) and iron (III) ions were prepared, characterized and used for determination of triiodide ions. The electrodes based on CuL and FeL complexes show an anionic response slope of ?60mV per decade in a linear activity range 6.0×10?1 to 8.0×10?6moll?1 and

Susan Sadeghi; Abolfazl Gafarzadeh; Mohammed Ali Naseri; Hashem Sharghi

2004-01-01

228

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

229

A sensitive schiff-base fluorescent chemosensor for the selective detection of zn(2+).  

PubMed

A Schiff-base fluorescent probe - N, N(/)-bis(salicylidene) trans 1, 2 - diaminocyclohexane (H 2 L) was synthesized and evaluated as a chemoselective Zn(2+) sensor. Upon treatment with Zn(2+), the complexation of H 2 L with Zn(2+) resulted in a bathochromic shift with a pronounced enhancement in the fluorescence 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+). 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. PMID:24740551

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

2014-07-01

230

"Test kit" for detection of biologically important anions: a salicylidene-hydrazine based Schiff base.  

PubMed

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 H(2)PO(4)(-), Cl(-), Br(-), I(-), NO(3)(-), NO(2)(-), HSO(4)(-), HSO(3)(-), and ClO(4)(-) in aqueous-acetonitrile solvent. The colorimetric test results and UV-vis spectral analysis are in well agreement with (1)H NMR titration results in d(6)-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. PMID:23220673

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

2013-02-01

231

``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

232

Schiff base oxovanadium(IV) complexes of phenanthroline bases showing DNA photocleavage activity at near-IR light and photocytotoxicity  

Microsoft Academic Search

Oxovanadium(IV) complexes [VO(L)(B)](ClO4) (1–3) of N-2-pyridylmethylidine-2-hydroxyphenylamine (HL) Schiff base and phenanthroline bases (B), viz. 1,10-phenanthroline (phen in 1), dipyrido[3,2-d:2?,3?-f]quinoxaline (dpq in 2) or dipyrido[3,2-a:2?,3?-c]phenazine (dppz in 3), were prepared, characterized and their DNA binding property, photo-induced DNA cleavage activity and photocytotoxicity in HeLa cells studied. The crystal structure of 1 shows the presence of a VO2+ moiety in VO2N4 coordination

Puja Prasad; Pijus K. Sasmal; Imran Khan; Paturu Kondaiah; Akhil R. Chakravarty

2011-01-01

233

PVC-based Cu (II)-Schiff base complex membrane coated graphite electrode for the determination of the triiodide ion  

Microsoft Academic Search

A triiodide-selective electrode based on copper (II)-Schiff base complex as a membrane carrier is proposed. The electrode\\u000a was prepared by incorporating the carrier into a plasticized polyvinylchloride (PVC) membrane and was directly coated on the\\u000a surface of a graphite electrode. The obtained electrode showed a near Nernstian slope of 57.0 ± 0.4 mV\\/decade to I\\u000a 3\\u000a ?\\u000a ions over an

S. Sadeghi; A. Gafarzadeh; H. Naeimi

2006-01-01

234

Antibacterial activity of Pd(II) complexes with salicylaldehyde-amino acids Schiff bases ligands.  

PubMed

Palladium(II) complexes with Schiff bases ligands derived from salicylaldehyde and amino acids (Ala, Gly, Met, Ser, Val) have been synthesized and characterized by Fourier transform (FT)-IR, UV-Vis and (1)H-NMR spectroscopy. The electrospray mass spectrometry (ES-MS) spectrometry confirms the formation of palladium(II) complexes in 1/2 (M/L) molar ratio. All the Pd(II) complexes 1, [Pd(SalAla)2]Cl2; 2, [Pd(SalGly)2]Cl2; 3, [Pd(SalMet)2]Cl2; 4, [Pd(SalSer)2]Cl2; 5, [Pd(SalVal)2]Cl2; have shown antibacterial activity against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli. PMID:24390488

Rîmbu, Cristina; Danac, Ramona; Pui, Aurel

2014-01-01

235

Synthesis, Structural, and Biological Studies of Some Schiff Bases and Their Metal Complexes  

PubMed Central

New bidentate or tridentate Schiff bases and their VO(II) and Co(II) complexes formed by the condensation of methyl isobutyl ketone with nicotinamide (mna)/2-amino-4-chlorophenol (map) and 2-hydroxy acetophenone with nicotinamide (han)/isoniazide (hai). Physicochemical characterization has been carried out to determine the structure of the complexes. The FAB mass and thermal data show degradation pattern of the complexes. XRD analysis reveals that all the studied complexes crystallize as tetragonal crystal system. Some of the complexes have been screened for their antimicrobial activity by the well diffusion technique using DMSO as solvent on different species of pathogenic bacteria/fungi, that is, E. coli, S. aureus, S. fecalis, A. niger, T. polysporum, and their antimicrobial potency have been discussed. It has been found that all the complexes are antimicrobially active and show higher activity than the free ligand. Metal chelation affects significantly the antimicrobial/bioactive behavior of the organic ligands.

Mishra, A. P.; Soni, Monika

2008-01-01

236

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

237

Some QSAR Studies for a Group of Sulfonamide Schiff Base as Carbonic Anhydrase CA II Inhibitors  

PubMed Central

In the present study, quantitative structure–activity-relationship (QSAR) study on a group of sulfonamide Schiff-base inhibitors of Carbonic Anhydrase (CA) enzyme has been carried out using Codessa Pro methodology and software. Linear regression QSAR models of the biological activity (Ki) of 38 inhibitors of carbonic anhydrase CA-II isozyme were established with 12 different molecular descriptors which were selected from more than hundreds of geometrical, topological, quantum-mechanical, and electronic types of descriptors and calculated using Codessa Pro software. Among the models presented in this study, statistically the most significant one is a five-parameter equation with correlation coefficient, R2 values of ca. 0.840, and the cross-validated correlation coefficient, R2 values of ca. 0.777. The obtained models allowed us to reveal some physicochemical and structural factors, which are strongly correlated with the biological activity of the compounds.

Eroglu, Erol

2008-01-01

238

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

239

Dihydroxycoumarin Schiff base synthesis and structure determination from powder diffraction data  

NASA Astrophysics Data System (ADS)

The titled compound with systematic name 4-hydroxy-3-((E)-1-(2-((E)-1-(4-hydroxy-2-oxo-2H-chromen-3-yl)ethylideneamino)ethylimino) ethyl)-2H-chromene-2-one is a new tetradentate (ONNO) Schiff-base which was synthesized by condensation of ethylenediamine and 3-acethyl 4-hydroxycoumarin. Its crystal structure was ab initio determined from laboratory X-ray powder diffraction data by using the direct space approach. The structure is monoclinic with space group P21/n and unit cell parameters a = 10.4153(4) Å, b = 12.8319(4) Å, c = 7.48229(15) Å, ? = 98.892(3) Å, V = 987.97(5) Å3. The asymmetric part of the structure contains one half of the centrosymmetric molecule. The obtained product was also characterized by infrared, UV-VIS and 1H NMR spectroscopy.

Rohlí?ek, Jan; Ketata, Imen; Ayed, Taïcir Ben; Hassen, Rached Ben

2013-11-01

240

Complexes of technetium(V) with potentially tridentate schiff bases derived from s-methyldithiocarbazate  

SciTech Connect

The syntheses and characterization of several new neutral oxotechnetium(V) complexes with potentially dianionic tridentate Schiff bases, derived from S-methyldithiocarbazate, are described. For a 1:1 metal ion to ligand ratio the five-coordinate complexes TcOLCl were isolated in all cases. Only in one case could a six-coordinate TcOL/sub 2/Cl, with the ligand acting as a bidentate chelate, be isolated from a 1:2 metal ion to ligand ratio. Magnetic susceptibility measurements of the complex TcO(HAF)Cl surprisingly indicate paramagnetism with a d/sup 2/ electronic configuration, while all the other compounds were found to be diamagnetic. The relative strength of the Tc=O bond is mainly determined by the electronic influence of the cis-ligands. The complexes have been characterized by elemental analyses, infrared and electronic spectra, and conductance measurements.

DuPreez, J.G.H.; Gerber, T.I.A.; Knoesen, O.

1987-01-01

241

Preparation and characterization of new tetradentate Schiff base metal complexes and biological activity evaluation  

NASA Astrophysics Data System (ADS)

A new Schiff base (N,N'-ethylene (bis 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazine-1-yl)-quinoline-3-carboxylic acid) and its Zn(II), Zr(IV), Ce(IV) and U(VI) complexes were synthesized and characterized by elemental analysis, molar conductance, IR, UV-Vis, 1H NMR spectra, magnetic moment, thermal analysis as well as mass spectra. The IR results demonstrate that the tetradentate binding mode of the ligand involving azomethine nitrogen and carboxylato oxygen atoms. The calculated bond length and the bond stretching force constant, F(Udbnd O), values for UO2 bond are 1.744 Å and 654.49 N m-1. The antimicrobial activity of the synthesized ligand and its complexes were screened and the results showed that the metal complexes were found to be more active than free ligand.

Sadeek, S. A.; El-Attar, M. S.; Abd El-Hamid, S. M.

2013-11-01

242

The role of a dielectric medium in a smectogenic Schiff base compound: A computational analysis  

SciTech Connect

A computational analysis of ordering in a smectogenic Schiff base compound, N-(4-n-heptyloxybenzylidine)-4-hexylaniline, has been carried out with the help of quantum mechanics and computer simulation. The complete neglect differential overlap (CNDO/2) method has been employed to compute the net atomic-charge and atomic dipole moment at each atomic center. The modified Rayleigh-Schroedinger perturbation theory with the multicentered-multipole expansion method has been employed to evaluate long-range intermolecular interactions, while a '6-exp' potential function has been assumed for short-range interactions. The interaction-energy values obtained through these computations were used to calculate the probability of each configuration in a dielectric medium at the phase-transition temperature (353 K). An attempt has been made to develop a new model of a smectogen in a dielectric medium. The present investigation provides theoretical support to the experimental observations.

Ojha, D. P. [Andhra Loyola College, Liquid Crystal Research Laboratory, Post-Graduate Department of Physics (India)], E-mail: durga_ojha@hotmail.com

2006-12-15

243

Structure-directed functional properties of symmetrical and unsymmetrical Br-substituted Schiff-bases  

NASA Astrophysics Data System (ADS)

This study deals with the investigation of two low molecular weight Schiff base compounds with bromine end groups, differing only by the presence or absence of one methyl group, with the aim of better understanding the solution and the solid state optical, electrochemical and thermic properties generated by the small structural features. The compounds were structurally characterized by 1H NMR, 13C NMR and FTIR spectroscopies, single-crystal X-ray diffraction and gas chromatography analysis. Their thermal behavior was evidenced by polarized light microscopy and differential scanning calorimetry. The single crystal structure of the compounds reveals the versatility of bromine substituents which can adopt an attractive or repulsive electron effect, driven by the structural environment. A comparison of the structures shows that the introduction of a methyl unit as a bulky group hinders completely the ?-? stacking interaction within the structural rows, inducing larger intermolecular distances resulting in quite different functional physical and chemical properties.

Marin, Luminita; Harabagiu, Valeria; van der Lee, Arie; Arvinte, Adina; Barboiu, Mihail

2013-10-01

244

Phenol-quinone tautomerism in (arylazo)naphthols and the analogous Schiff bases: benchmark calculations.  

PubMed

Tautomerization energies of a series of isomeric [(4-R-phenyl)azo]naphthols and the analogous Schiff bases (R = N(CH3)2, OCH3, H, CN, NO2) are calculated by LPNO-CEPA/1-CBS using the def2-TZVPP and def2-QZVPP basis sets for extrapolation. The performance of various density functionals (B3LYP, M06-2X, PW6B95, B2PLYP, mPW2PLYP, PWPB95) as well as MP2 and SCS-MP2 is evaluated against these results. M06-2X and SCS-MP2 yield results close to the LPNO-CEPA/1-CBS values. Solvent effects (CCl4, CHCl3, CH3CN, and CH3OH) are treated by a variety of bulk solvation models (SM8, IEFPCM, COSMO, PBF, and SMD) as well as explicit solvation (Monte Carlo free energy perturbation using the OPLSAA force field). PMID:24417622

Ali, S Tahir; Antonov, Liudmil; Fabian, Walter M F

2014-01-30

245

Efficient Water Oxidation Catalyzed by Mononuclear Ruthenium(II) Complexes Incorporating Schiff Base Ligands.  

PubMed

Four new charge-neutral ruthenium(II) complexes containing dianionic Schiff base and isoquinoline or 4-picoline ligands were synthesized and characterized by NMR and ESI-MS spectroscopies, elemental analysis, and X-ray diffraction. The complexes exhibited excellent chemical water oxidation activity and high stability under acidic conditions (pH?1.0) using (NH4 )2 Ce(NO3 )6 as a sacrificial electron acceptor. The high catalytic activities of these complexes for water oxidation were sustained for more than 10?h at low concentrations. High turnover numbers of up to 3200 were achieved. A water nucleophilic attack mechanism was proposed. A Ru(V) ?O intermediate was detected during the catalytic cycle by high-resolution mass spectrometry. PMID:24888489

Li, Ting-Ting; Chen, Yong; Li, Fu-Min; Zhao, Wei-Liang; Wang, Chuan-Jun; Lv, Xiao-Jun; Xu, Quan-Qing; Fu, Wen-Fu

2014-06-23

246

The effect of donor groups and geometry on the redox potential of copper Schiff base complexes  

Microsoft Academic Search

We report a study which correlates the metrical parameters of the unsubstituted tetradentate copper Schiff base complexes containing N2O2, N2N2 and N2S2 donors with their respective redox potentials. To achieve this aim we were required to structurally characterise many of the seminal species including, [CuAmbpr-H2], [CuH4Amben][ClO4]2, [CuH4Ambpr][ClO4]2, [CuH4Ambbu][ClO4]2, CuH4Salpr and [Cu(SSalen)2][ClO4]2 which were absent from the crystallographic catalogue. The oxidative

Michelle K. Taylor; John Reglinski; Leonard E. A. Berlouis; Alan R. Kennedy

2006-01-01

247

Double-stranded monohelical complexes from an unsymmetrical chiral Schiff-base ligand.  

PubMed

A new Schiff-base ligand is prepared by a two-step reaction of 3-formylsalicylic acid and (1R, 2R)-diaminocyclohexane in alcoholic solvents. The 1:1 condensation product exists as a zwitterion in the solid state and forms pleated hydrogen-bonded sheets. Metalation of the ligand with divalent iron, nickel, cobalt, and zinc resulted in the formation of double-stranded monohelices with exclusively M-helicity. Each complex has two tridentate ligands, with the carboxylic acid groups remaining uncoordinated. In the crystal lattice, these complexes form extended M-helical strands through intermolecular hydrogen bonding interactions. Metalation of the ligand with copper salts resulted in a distinctly different type of complex, in which the ligand has transformed into a symmetric tetradentate salen ligand with uncoordinated carboxylic acid groups. PMID:18166045

Lalehzari, Azadeh; Desper, John; Levy, Christopher J

2008-02-01

248

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

249

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

Microsoft Academic Search

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)Å, b=10.794(5)Å, c=11.350(5)Å, ?=70.262(6)°, ?=70.816(6)°, ?=78.360(6)°, V=955.4(7)Å3, Z=2, Dc=1.571 Mg·m?3, and the final R1=0.0393, wR2=0.0994 for the observed reflections 2620(I>2?(I)). The molecular geometry is

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

2005-01-01

250

Derivatives of phosphate Schiff base transition metal complexes: synthesis, studies and biological activity.  

PubMed

We report the synthesis and structural characterization of series of tetra- and hexacoordinate metal chelate complexes of phosphate Schiff base ligands having the general composition LMX(n).H(2)O and L(2)MX(n) (L=phosphate Schiff base ligand; M=Ag(+), Mn(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), or Fe(3+) and X=NO(3)(-), Br(-) or Cl(-)). The structure of the prepared compounds was investigated using elemental analysis, IR, 1H and 31P NMR, UV-vis, mass spectra, solid reflectance, magnetic susceptibility and conductance measurements as well as conductometric titration. In all the complexes studied, the ligands act as a chelate ligand with coordination involving the phosphate-O-atom and the azomethine-N-atom. IR, solid reflectance spectra and magnetic moment measurement are used to infer the structure and to illustrate the coordination capacity of ligand. IR spectra show the presence of coordinated nitrate and water molecule, the magnetic moments of all complexes show normal magnetic behavior and the electronic spectra of the metal complexes indicate a tetra- and octahedral structure for Mn(2+), octahedral structure of Fe(3+) and both square-planar and distorted octahedral structure for Cu(2+) complexes. Antimicrobial activity of the ligands and their complexes were tested using the disc diffusion method and the chosen strains include Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Microsporum canis, Trichophyton mentagrophyte and Trichophyton rubrum. Some known antibiotics are included for the sake of comparison and the chosen antibiotic are Amikacin, Doxycllin, Augmantin, Sulperazon, Unasyn, Septrin, Cefobid, Ampicillin, Nitrofurantion, Traivid and Erythromycin. PMID:14670488

Abd El-Wahab, Z H; El-Sarrag, M R

2004-01-01

251

Photocytotoxicity and near-IR light DNA cleavage activity of oxovanadium(IV) Schiff base complexes having phenanthroline bases  

Microsoft Academic Search

Oxovanadium(IV) complexes [VO(L)(B)] (1–3), where H2L is a Schiff base ligand 2-(2-hydroxybenzylideneamino)phenol and B is 1,10-phenanthroline (phen for 1), dipyrido[3,2-d:2?,3?-f]quinoxaline (dpq for 2) or dipyrido[3,2-a:2?,3?-c]phenazine (dppz for 3), have been prepared, characterized and their DNA binding property and photo-induced DNA cleavage activity studied. Complex 3 which is structurally characterized by X-ray crystallography shows the presence of an oxovanadium(IV) moiety in

Puja Prasad; Pijus K. Sasmal; Ritankar Majumdar; Rajan R. Dighe; Akhil R. Chakravarty

2010-01-01

252

Hydrogen bond and ?…? interaction based 3D supramolecular architecture of chiral cobalt(III) azido tridentate chelating Schiff base  

Microsoft Academic Search

Cobalt(II) perchlorate reacts with tridentate chelating Schiff base, N-((phenyl)formylidene)-N?-(2-aminoethyl)ethane-1,2-diamine (pfad) and azide in methanol–acetonitrile solution in 1:1:3 molar ratio to afford a chiral cobalt(III) complex [Co(pfad)(X)3] (1). The meridional arrangements of three N atoms of the tridentate chelator and three N3- in cobalt(III) center that construct a 3D supramolecular network through N–H…N hydrogen bonding and weak ?…? interaction. Single band

Sk. Hafijur Rahaman; Habibar Chowdhury; Heather L. Milton; Alexandra M. Z. Slawin; J. Derek Woollins; Barindra Kumar Ghosh

2005-01-01

253

The Effect of Substituents on Characteristics of Functional Material: Consequences of Fusing Schiff Bases and Some of Its Proton Substitutes on Isobenzofuran  

Microsoft Academic Search

Research on functional materials is one of the hot technology-related topics. Isobenzofurans and Schiff bases are important building blocks for functional materials. In this study, fundamental aspects of hybrid structures were studied based on B3LYP calculations. The results confirm that fused ortho-amino Schiff bases can have significant impact on the electronic structure of isobenzofuran. The derivatives are unique structures, the

TAREQ IRSHAIDAT

2010-01-01

254

Chemistry of technetium. Elaboration of the mechanism of action of skeletal imaging agents and development of technetium Schiff base complexes  

SciTech Connect

Tc-99m skeletal imaging agents contain diphosphonate ligands coordinated to a technetium center. To investigate the chemistry of coordinated diphosphonates, complexes of the type ((en)/sub 2/Co(O/sub 2/P(OH)C(R)(R')P(OH)O/sub 2/)/sup n+/ have been synthesized and characterized. The affinities of these species for calcium ion in solution have been determined and found to be dependent on the substituents, R and R', of the diphosphonate moiety. The single crystal X-ray structural determination of ((en)/sub 2/Co(O/sub 2/P(OH)CH/sub 2/P(OH)O/sub 2/)ClO/sub 4/ x 2H/sub 2/O illustrates the configuration of a coordinated diphosphonate in the solid state and allows for the implication of possible binding modes of this species to the calcium ion in solution. A series of Tc(V) complexes containing tetradentate Schiff base ligands (derived from diamines and either acetylacetonates or salicylaldehyde) has been synthesized and characterized. An investigation of the reactivity of the Tc(V)-Schiff base complexes with phosphines led to the development of a series of Tc(III)-Schiff base complexes containing two coordinated phosphine ligands, i.e., tr-(Tc(Schiff base)(PRR')/sub 2/)PF/sub 6/. These complexes show intriguing redox behavior in that they exhibit both reversible Tc(III)/Tc(II) and Tc(III)/Tc(IV) couples. The substituents on the Schiff base and phosphine ligands have significant effects on the redox potentials of the technetium(III) center and on the MTLCT bands observed for these complexes. Those substituents which make the Schiff base and phosphine ligands better sigma donors make the Tc(III) more difficult to reduce to Tc(II) and easier to oxidize to Tc(IV). The relatonship between the energy of the MTLCT band and the E/sup 0/ values for these complexes is linear with slopes to unity, suggesting that the ligands contribute equally to these properties.

Jurisson, S.S.

1982-01-01

255

Synthesis, spectroscopic characterization and antimicrobial activity of mono-, bi- and tri-nuclear metal complexes of a new Schiff base ligand  

Microsoft Academic Search

Condensation of o-acetoacetylphenol and 1,2-diaminopropane in 1:1 molar ratio under condition of high dilution yielded the mono-condensed dibasic Schiff base ligand with a N2O2 donors. The mono-condensed ligand has been used for further condensation with 2-hydroxy-5-nitrobenzaldehyde to obtain the new asymmetrical dicompartmental Schiff base ligand, H3L, with N2O3 donors. The structure of the ligand was elucidated by analytical and spectroscopic

Magdy Shebl; Saied M. E. Khalil; Saleh A. Ahmed; Hesham A. A. Medien

2010-01-01

256

Synthesis and Catalytic Activity of Polymer Supported Schiff Base Complexes of Copper(II) and Iron(III) Ions in Comparison to Unsupported Complexes  

Microsoft Academic Search

The polymer supported metal complexes of N,N??bis(acetyl acetone)o?phenylene?diamine (ACPDA) Schiff base were synthesized by suspension copolymerization of styrene and allyl chloride in the presence of divinyl benzene (DVB) as cross?linker and azobisisobutyronitrile (AIBN) as initiator at 70±0.1°C and then ACPDA Schiff base and metal ions were loaded on the resulting polymer beads. The cross?linked density in polymer beads was varied

K. C. Gupta; H. K. Abdulkadir

2007-01-01

257

Novel homo- and hetero-nuclear copper(II) complexes of tetradentate Schiff bases: Synthesis, characterization, solvent-extraction and catalase-like activity studies  

Microsoft Academic Search

Twelve homo- and hetero-nuclear copper(II) complexes of tetradentate Schiff base ligands containing N4 donor sets have been prepared by employing several steps. The characterization and nature of bonding of the complexes have been deduced from elemental analysis, FT-IR, molar conductivity, magnetic moment measurements and thermal analysis. The three Schiff base ligands were further identified using 1H and 13C NMR spectra.

Bülent Dede; Fatma Karipcin; Mustafa Cengiz

2009-01-01

258

Synthesis and spectroscopic studies of binuclear metal complexes of a tetradentate N 2O 2 Schiff base ligand derived from 4,6-diacetylresorcinol and benzylamine  

Microsoft Academic Search

A tetradentate N2O2 donor Schiff base ligand, H2L, was synthesized by the condensation of 4,6-diacetylresorcinol with benzylamine. The structure of the ligand was elucidated by elemental analyses, IR, 1H NMR, electronic and mass spectra. Reaction of the Schiff base ligand with nickel(II), cobalt(II), iron(III), cerium(III), vanadyl(IV) and uranyl(VI) ions in 1:2 molar ratio afforded binuclear metal complexes. Also, reaction of

Magdy Shebl

2008-01-01

259

Investigation of the active site at the deuterated Schiff-base complex formed between the coenzyme vitamin B 6 and the primary amine  

Microsoft Academic Search

The Schiff-base complex ion formed between the vitamin B6 molecule and the primary amine was investigated by electrospray ionization MS\\/MS in the gas phase. The two observed fragments at the MS\\/MS spectrum were different from the normal alkene loss (Onium reaction or McLafferty rearrangement) fragments of immonium ions. The R–CH–ND loss fragment from the 3H\\/D-deuterated Schiff-base complex ion was observed

Min-Hee Lee; Bo-Ra Kim; Ho-Tae Kim

2007-01-01

260

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

PubMed

The present work stems from our interest in the synthesis, characterization, and antibacterial evaluation of organosilicon(IV) complexes of a class of amino-acid-based Schiff base which have been prepared by the interaction of ethoxytrimethylsilane with the Schiff bases (N OH) in 1?:?1 molar ratio. These complexes have been characterized by elemental analysis, molar conductance, and spectroscopic studies including electronic IR and NMR ((1)H, (13)C, and (29)Si) spectroscopy. The analytical and spectral data suggest trigonal bipyramidal geometry around the silicon atom in the resulting complexes. The ligands and their organosilicon complexes have also been evaluated for in vitro antimicrobial activity against bacteria (Bacillus cereus, Nocardia spp., E. aerogenes, Escherichia coli, Klebsiella spp., and Staphylococcus spp.). The complexes were found to be more potent as compared to the ligands. PMID:23983671

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

2013-01-01

261

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.

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

2013-01-01

262

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

PubMed

A new series of oxovanadium(IV) complexes have been designed and synthesized with a new class of triazole Schiff bases derived from the reaction of 3,5-diamino-1,2,4-triazole with 2-hydroxy-1-naphthaldehyde, pyrrole-2-carboxaldehyde, pyridine-2-carboxaldehyde and acetyl pyridine-2-carboxaldehyde, respectively. Physical (magnetic susceptibility, molar conductance), spectral (IR, (1)H NMR, (13)C NMR, mass and electronic) and analytical data have established the structures of these synthesized Schiff bases and their oxovanadium(IV) complexes. The Schiff bases, predominantly act as bidentate and coordinate with the vanadium(IV) metal to give a stoichiometric ratio of 1:2 [M:L], forming a general formulae, [M(L-H)(2)] and [M(L)(2)]SO(4) where L = (L(1))-(L(4)) and M = VO(IV) of these complexes in a square-pyramidal geometry. In order to evaluate the biological activity of Schiff bases and to assess the role of vanadium(IV) metal on biological activity, the triazole Schiff bases and their oxovanadium(IV) complexes have been studied for in vitro antibacterial activity against four Gram-negative (Escherichia coli, Shigella flexenari, Pseudomonas aeruginosa, Salmonella typhi) and two Gram-positive (Staphylococcus aureus, Bacillus subtilis) bacterial strains, in vitro antifungal activity against Trichophyton longifucus, Candida albican, Aspergillus flavus, Microscopum canis, Fusarium solani and Candida glaberata. The simple Schiff bases showed weaker to significant activity against one or more bacterial and fungal strains. In most of the cases higher activity was exhibited upon coordination with vanadium(IV) metal. Brine shrimp bioassay was also carried out for in vitro cytotoxic properties against Artemia salina. PMID:20338672

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

2010-07-01

263

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

264

Design of molecular switching and signaling based on proton transfer in 2-hydroxy Schiff bases: a computational study.  

PubMed

The present work aims to exploit the possibility of using the tautomerism in 2-hydroxy Schiff bases for molecular switching. The enol imine (E)? enaminone (K) tautomerization in a series of 2-hydroxy Schiff bases have been investigated theoretically at the DFT/B3LYP/6-311G** level of theory. The intramolecular proton transfer processes have been explored, transition structures have been located and characterized. The kinetics and thermodynamics of the proton transfer process, and its time scale have been computed and discussed in the framework of the suitability as molecular switches. Substituent effects have been computed and its effect on the enthalpy changes (?H*) and activation energies (?G*) have been analyzed and discussed. Nonspecific solvent effects have also been taken into account by using the polarized continuum model (IPCM) of two different solvent. The tautomerization energies are decreased and hence the endothermic nature of the enol imine ? enaminone tautomerization. The potential energy barriers, on the other hand, are increased due to the relative destabilization of the transition states. The NBO charge populations show that there is a high positive charge on the hydrogen atom during the process in all cases, which confirms that the proton transfer proceeds through a three-center interaction. The proton transfer processes, in all cases studied are kinetically allowed. The low potential energy barrier suggests that interconversion between the two tautomeric forms is spontaneous and the two forms may coexist. PMID:22961622

Abood Hameed, Salem; Alrouby, Saaban K; Hilal, Rifaat

2013-02-01

265

New asymmetric heptaaza Schiff base macrocyclic complex of Mn(II): Crystal structure, biological and DFT studies.  

PubMed

A new asymmetric heptaaza Schiff base macrocyclic bis(pendant donor) manganese(II) complex, [MnL(1)](ClO(4))(2).CH(3)CN (1), has been prepared and characterized by X-ray diffraction and spectroscopic methods. The antimicrobial activity of 1 and a series of its familiar symmetric heptaaza [15]pydieneN(5), [16]pydieneN(5), and [17]pydieneN(5)-based bis-(2-aminoethyl) pendant armed Schiff base macrocyclic complexes of Mn(II) were tested against Escherichia coli, Staphylococcus aureus and Candida albicans. The results showed that the symmetric heptaaza [16]pydieneN(5), and [17]pydieneN(5)-based Schiff base macrocyclic complexes of Mn(II) had remarkable inhibition zone on the culture of S. aureus and E. coli as compared with standard drugs. The optimized geometry of the prepared complex has been obtained from density functional method, DFT, using B3LYP/6-31G* basis set. PMID:20637685

Khanmohammadi, Hamid; Amani, Saeid; Abnosi, Mohammad H; Khavasi, Hamid R

2010-10-01

266

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

267

Synthesis, crystal structure and magnetic properties of nickel(II) and cobalt(III) complexes of a pentadentate Schiff base  

NASA Astrophysics Data System (ADS)

Two new Schiff base complexes, [Ni2(HL)2(?1,3-N3)]ClO4·H2O (1) and [Co(L)(N3)] (2) where L = 2,2'-{(methylimino)bis[propane-3,1-diylnitrilomethylylidene]}diphenolate ion, have been synthesized by the reaction of equimolar amounts of nickel(II) or cobalt(II) perchlorate with the pentadentate Schiff base ligand (H2L) in presence of azide ion. The complexes have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1 is an end-to-end azido-bridged binuclear complex in which each nickel(II) adopts irregular octahedral geometry. In contrast, 2 is a mononuclear octahedral cobalt(III) complex containing the azide ion in one of its apical positions. Low temperature magnetic measurements on 1 indicate noticeable intradimer ferromagnetic interactions.

Layek, Manas; Ghosh, Mahendra; Sain, Saugata; Fleck, Michel; Muthiah, Packianathan Thomas; Jenniefer, Samson Jegan; Ribas, Joan; Bandyopadhyay, Debasis

2013-03-01

268

Characterisation of the PT-form of o-hydroxy acylaromatic Schiff bases by NMR spectroscopy and DFT calculations  

NASA Astrophysics Data System (ADS)

A series of o-hydroxy Schiff bases showing tautomerism to a varying degree are investigated together with compounds totally at the proton transfer form (enamines). Deuterium isotope effects on 13C chemical shifts are measured at different temperatures. Structural features determining the equilibrium constants are discussed. DFT calculations are done in order to obtain structures. Schiff bases derived from dehydracetic acid (3-acetyl-6-methyl-pyran-2,4-dione) as well as from 1,3,5-triacetyl-2,4,6-trihydroxybenzene are found to be fully at the PT-form. These forms are characterised and the use of these compounds as reference for the PT-form in general is discussed.

Hansen, Poul Erik; Filarowski, Alexander

2004-11-01

269

Dielectric effects due to the environment on the structure and proton affinity of retinal Schiff base models  

NASA Astrophysics Data System (ADS)

We performed DFT calculations, using the DMOL implementation of the COSMO solvent model, to investigate the effect of different dielectric responses of the environment on the structure and electronic configuration of two unsubstituted Schiff base models of retinal, including three and four conjugated double bonds, as well as a monomethylated model. The results show that the application of different dielectric constants in the calculations significantly influences the proton affinity of the molecule. Applying a continuum model as a model for the protein environment, we may conclude that the protein can efficiently adjust the pK a of the chromophore by modifying local screening effects in the vicinity of the retinal Schiff base and, in this way, control the proton transfer.

Tajkhorshid, Emadeddin; Suhai, Sándor

1999-01-01

270

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

271

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

PubMed

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) free radical scavenging and reducing power activity of superoxide anion radical generated non-enzymatic systems. Electrochemical and thermal properties of the compounds were investigated. PMID:21752697

Ceyhan, Gökhan; Çelik, Cumali; Uru?, Serhan; Demirta?, ?brahim; Elmasta?, Mahfuz; Tümer, Mehmet

2011-10-15

272

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

PubMed

The Bürgi-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-à-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

273

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

Microsoft Academic Search

The new complexes, cis-[WO2(Hsap)2], [Ru(PPh3)2(Hsap)2], [Pd(Hsap)Cl(H2O)], [Pd(PPh3)2(Hsap)]Cl, [Ag(Hsap)(H2O)2], [Ni(Hsap)(AcO)(H2O)2], [Ni(Hsap)2] and [Cu(Hsap)Cl(H2O)] are reported, where H2sap 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 H2sap behaves as a bidentate chelate with the deprotonated 2-hydroxy and azomethine nitrogen centers with the

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

2010-01-01

274

Synthesis and Crystal Structures of Ternary Copper(II) Complex Containing Salicylaldehyde Schiff Base and 4,4?Bipyridine  

Microsoft Academic Search

\\u000a Abstract  A new ternary mixed-ligand complex [Cu2(sal-glu)2(bipy)(H2O)2] · (H2O) (bipy = 4,4?-bipyridine and sal-glu = salicylaldehyde l-glutamic Schiff base) has been synthesized and characterized by X-ray diffraction. It crystallizes in the triclinic system,\\u000a space group P-1 with a = 9.6199(13) Å, b = 9.9111(13) Å, c = 9.9167(13) Å. The amino acid Schiff base coordinates to the Cu(II) ion in a tridentate mode including phenol-hydroxyl oxygen,\\u000a carboxyl oxygen and amide nitrogen atom, while the bipy coordinates

Xun Feng; Cheng-Zhi Xie; Li-Ya Wang; Yu-Fang Wang; Lu-Fang Ma

2008-01-01

275

Synthesis, spectroscopic characterization and antibacterial activity of new cobalt(II) complexes of unsymmetrical tetradentate (OSN2) Schiff base ligands.  

PubMed

Cobalt ion complexes with the Schiff bases, (4-X-2-{[2-(2-pyridine-2-yl-ethylsulfanyl)ethylimino]methyl}phenol (X=methoxy (OMe), phenylazo (N(2)Ph), bromo (Br), nitro (NO(2))),were synthesized and investigated by several techniques using elemental analysis (C, H, N), FTIR, electronic spectra and molar conductivity. The thermal stability of free ligands and related cobalt complexes were studied by using differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA). Cyclic voltammetry indicates that the investigated cobalt complexes, under the experimental conditions, have irreversible redox behavior. The synthesized compounds have antibacterial activity against the four Gram-positive bacteria: Streptococcus pyogenes, Streptococcus agalactiae, Staphylococcus aureus and Bacillus anthracis and also against the two Gram-negative bacteria: Klebsiella pneumoniae and Pseudomonas aeruginosa. The activity data show that the parent Schiff bases are more potent antibacterials than the cobalt complexes. PMID:19608303

Saghatforoush, Lotf Ali; Chalabian, Firoozeh; Aminkhani, Ali; Karimnezhad, Ghasem; Ershad, Sohrab

2009-11-01

276

DFT studies on Schiff base formation of vitamin B6 analogues. Reaction between a pyridoxamine-analogue and carbonyl compounds.  

PubMed

A comprehensive theoretical study based on density functional theory calculations (B3LYP and M06-2X functionals) of the formation of Schiff bases of pyridoxamine analogues with two different aldehydes was conducted. The reaction mechanism was found to involve two steps, namely: (1) formation of a carbinolamine and (2) dehydration of the carbinolamine to give the final imine. Also, consistent with available experimental evidence, the carbinolamine dehydration was the rate-determining step of the process determined by means of M06-2X functional. Using an appropriate solvation method and reactant conformation ensures that all proton transfers involved will be intramolecular, which substantially reduces energy barriers and facilitates reaction in all cases. The formation of a Schiff base between pyridoxal 5-phosphate (PLP) and an amine or amino acid requires the contribution of an external water molecule in order to facilitate proton transfers. On the other hand, the formation of a Schiff base between pyridoxamine 5-phosphate (PMP) and a carbonyl compound requires no external aid since the spatial arrangement of the functional groups in PMP ensures that all proton transfers will be intramolecular. PMID:20235562

Ortega-Castro, J; Adrover, M; Frau, J; Salvà, A; Donoso, J; Muñoz, F

2010-04-01

277

High-sensitivity neutron diffraction of membranes: Location of the Schiff base end of the chromophore of bacteriorhodopsin  

SciTech Connect

Three important events in the functional cycle of bacteriorhodopsin occur at the chromophore: the primary absorption of light, the isomerization from the all-trans to the 13-cis form, and the deprotonation and reprotonation of its Schiff base. The protonated Schiff base linkage of the chromophore with lysine-216 plays an essential role in the color regulation of the pigment and is most likely directly involved in the charge translocation of this light-driven proton pump. Although much is known about the structure of the protein, the position of this key functional group has not yet been determined. The authors have synthesized a retinal in which the five protons closest to the Schiff base are replaced by deuterons. The labeled retinal was spontaneously incorporated into bacteriorhodopsin by using a mutant of Halobacterium halobium that is deficient in the synthesis of retinal. The position of the labeled Schiff base end of the chromophore was determined in the two-dimensional projected density of dark-adapted bacteriorhodopsin by neutron diffraction. The result fits very well with their previous work using retinals that were selectively deuterated in the middle of the polyene chain or in the cyclohexene ring. A coherent structure emerges with the three labeled positions on one line, separated by distances that are in good agreement with the tilt angle of the polyene chain (about 20{degree}). The results show that it is possible to locate a small group containing as few as five deuterons in a membrane protein of molecular weight 27,000.

Heyn, M.P.; Westerhausen, J.; Wallat, I.; Seiff, F. (Freie Universitaet Berlin (West Germany))

1988-04-01

278

Graphene coupled Schiff-base porous polymers: towards nitrogen-enriched porous carbon nanosheets with ultrahigh electrochemical capacity.  

PubMed

Schiff-base type porous polymer sheets with ultrahigh nitrogen content have been successfully synthesized by utilizing aminated graphene oxide as a 2D structure-directing template via dynamic covalent chemistry. Nitrogen-enriched porous carbon nanosheets were thus prepared by thermal pyrolysis of the 2D porous polymers, showing exceptionally high capacitance up to 424 F g(-1) at 0.1 A g(-1) in 6 m KOH, superior to that of porous carbons without graphene involved. PMID:24519968

Zhuang, Xiaodong; Zhang, Fan; Wu, Dongqing; Feng, Xinliang

2014-05-21

279

NMR studies of novel Schiff bases derived from L-alpha-amino methyl esters and 3-hydroxypyridin-4-carboxaldehyde.  

PubMed

Schiff bases of 3-hydroxypyridin-4-carboxaldehyde and L-alpha-amino esters as well as those derived from the structurally related amines lacking the ester function have been synthesised. In two cases a tetrahydro-1H-imidazo[4,5-c]pyridine was formed as a by-product. (1)H, (13)C, (15)N-NMR spectral data and density functional theory (DFT) calculations established the structure of all compounds. PMID:18618628

Perona, Almudena; Sanz, Dionisia; Claramunt, Rosa M; Elguero, José

2008-10-01

280

Synthesis, characterization and antimicrobial activity of transition metal complexes with the Schiff base derived from imidazole-2-carboxaldehyde and glycylglycine  

Microsoft Academic Search

The Co(II), Ni(II) and Cu(II) complexes of the Schiff base derived from imidazole-2-carboxaldehyde and glycylglycine were synthesized and characterized by elemental analysis, PMR, molar conductance, IR, electronic, magnetic measurements, ESR, redox properties, thermal studies, XRD and SEM. Conductance measurements indicate that the complexes are 1 : 1 electrolytes. IR data show that the ligand is tetradentate with imidazole nitrogen, azomethine

R. Selwin Joseyphus; M. Sivasankaran Nair

2009-01-01

281

A semiempirical study of the optimized ground and excited state potential energy surfaces of retinal and its protonated Schiff base  

NASA Technical Reports Server (NTRS)

The electronic ground and first excited states of retinal and its Schiff base are optimized for the first time using the semiempirical AM1 Hamiltonian. The barrier for rotation about the C(11)-C(12) double bond is characterized by variation of both the twist angle delta(C(10)-C(11)-C(12)-C(13)) and the bond length d(C(11)-C(12)). The potential energy surface is obtained by varying these two parameters. The calculated ground state rotational barrier is equal to 15.6 kcal/mol for retinal and 20.5 kcal/mol for its Schiff base. The all-trans conformation is more stable by 3.7 kcal/mol than the 11-cis geometry. For the first excited state, S(1,) the 90 degrees twisted geometry represents a saddle point for retinal with the rotational barrier of 14.6 kcal/mol. In contrast, this conformation is an energy minimum for the Schiff base. It can be easily reached at room temperature from the planar minima since it is separated from them by a barrier of only 0.6 kcal/mol. The 90 degrees minimum conformation is more stable than the all-trans by 8.6 kcal/mol. We are thus able to present a reaction path on the S(1) surface of the retinal Schiff base with an almost barrier-less geometrical relaxation into a twisted minimum geometry, as observed experimentally. The character of the ground and first excited singlet states underscores the need for the inclusion of double excitations in the calculations.

Parusel, A. B.; Pohorille, A.

2001-01-01

282

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

SciTech Connect

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.

Otto, H.; Marti, T.; Holz, M.; Mogi, T.; Lindau, M.; Khorana, H.G.; Heyn, M.P. (Freie Universitaet Berlin (Germany, F.R.))

1989-12-01

283

Exploring the distribution of copper-Schiff base complex covalently anchored onto the surface of mesoporous MCM 41 silica  

SciTech Connect

A series of copper-Schiff base MCM 41 materials, synthesized by post-synthetic grafting, was studied by X-ray photoelectron spectroscopy (XPS) and nitrogen sorption (77 K) to explore distribution of the copper-Schiff base complex immobilized on the porous Si-MCM 41. Additional information on the physico-chemical properties of the functionalized materials was obtained by powder X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), CHN microanalysis, FTIR spectroscopy, {sup 29}Si and {sup 13}C CP MAS NMR spectroscopy. The effect of copper-Schiff base complex loading and reaction times on the surface properties of Si-MCM 41 (surface area and pore parameters) in addition to its distribution within the Si-MCM 41 was explored by nitrogen sorption and XPS coupled with argon etching. Argon etching of a surface to a depth of 45 A confirmed that the copper-Schiff base complex was distributed both on the external surface (pore end) and within the pores of Si-MCM 41. The amount of complex located in the pores at this depth was about one-third of the amount detected on the external surface of MCM 41. Nitrogen sorption isotherms measured at 77 K confirmed the reduction in total pore volume and surface area was the result of pore narrowing of Si-MCM 41 following grafting of complex in the 8 h samples. A significant decrease in surface area and pore volume for the 20 h sample (longer reaction time), with the highest copper loading (0.65 mmol g{sup -1}), confirmed pore blocking in this material. The uneven distribution of the copper complex between the external and internal surface of Si-MCM 41 was attributed to the bulky nature of the complex, which restricted access to the pores.

Singh, Udayshankar G. [Department of Chemistry, Open University, Milton Keynes MK7 6AA (United Kingdom)]. E-mail: usingh@engr.ucsb.edu; Williams, Ruth T. [Department of Chemistry, Open University, Milton Keynes MK7 6AA (United Kingdom)]. E-mail: r.t.williams@open.ac.uk; Hallam, Keith R. [Interface Analysis Centre, University of Bristol, Bristol BS2 8BS (United Kingdom)]. E-mail: k.r.hallam@bristol.ac.uk; Allen, Geoffrey C. [Interface Analysis Centre, University of Bristol, Bristol BS2 8BS (United Kingdom)]. E-mail: g.c.allen@bristol.ac.uk

2005-11-15

284

Synergistic effect of 1-dodecanethiol upon inhibition of Schiff bases on carbon steel corrosion in sulphuric acid media  

Microsoft Academic Search

Purpose – In this paper, the main aim is to study the synergistic effects of alkanethiols upon inhibition of Schiff bases, N,N?-ethylen-bis and N,N?-ortho-phenylen-bis in 0.5 M sulphuric acid solutions. Design\\/methodology\\/approach – Measurements were carried out in a three-electrode cell assembly connected to the corrosion measurement system using software for Tafel polarization. Impedance measurements were carried out at open circuit

Maryam Ehteshamzadeh; Taghi Shahrabi; Mirghasem Hosseini

2006-01-01

285

Synthesis and characterization of molybdenum complexes with bidentate Schiff base ligands within nanoreactors of MCM-41 as epoxidation catalysts  

Microsoft Academic Search

The mesoporous molecular sieve MCM-41 was covalently grafted with 3-aminopropyl trimethoxysilane to give aminopropyl modified MCM-41 (AmpMCM-41). Reaction of this material with furfural, pyrrolcarbaldehyde, 2-acetylpyrrol, 2-aminoacetophenone, salicylaldehyde and acetylacetone afforded the corresponding supported Schiff base ligands. Subsequent reaction with bis(acetylacetonato)dioxomolybdenum(VI) leads to various molybdenum complexes supported on MCM-41 through propyl chain spacer. Characterization of these materials was carried out with

M. Masteri-Farahani; F. Farzaneh; M. Ghandi

2006-01-01

286

Syntheses, characterization, redox behavior and Lewis acidity of chiral nickel(II) and copper(II) Schiff base complexes  

Microsoft Academic Search

Chiral nickel(II) and copper(II) Schiff base complexes with [N2O2] coordination derived from (1R.2R)- and (1S.2S)-1,2-diamino- cyclohexane were prepared and characterized by 1H, 13C NMR, IR and mass spectroscopy and polarimetric measurement in the case of the ligands. Cyclovoltammetric and spectrophotometric measurements revealed that the redox behavior and the Lewis acidity are influenced strongly by the substituents of the ligand. Substituents

Ernst-G. Jäger; Kerstin Schuhmann; Herlmar Görls

1997-01-01

287

Synthesis, characterization, and antimicrobial activities of nickel(II) and copper(II) Schiff-base complexes  

Microsoft Academic Search

Ni(II) and Cu(II) metal complexes of simple unsymmetrical Schiff-base ligands derived from salicylaldehyde\\/5-methylsalicylaldehyde and ethylenediamine or diaminomaleonitrile (DMN) were synthesized. The ligands and their complexes were characterized by elemental analysis, H NMR, FT IR, and mass spectroscopy. The electronic spectra of the complexes show d–d transitions in the region at 450–600 nm. Electrochemical studies of the complexes reveal that all

M. Rajasekar; S. Sreedaran; R. Prabu; V. Narayanan; R. Jegadeesh; N. Raaman; A. Kalilur Rahiman

2010-01-01

288

Huge Antiferromagnetic Exchange Interactions in Newly Reported Copper(ii) Complex of the Antiprine Schiff Base of 3-FORMYLSALICYLIC Acid  

NASA Astrophysics Data System (ADS)

This study reports the magnetic properties of newly reported copper(II) complex of the antiprine Schiff base of 3-formylsalicylic acid. Although the separation of Cu centers and the bridge angle is not known, from the magnetic analysis it is suggested that there are strong antiferromagnetic interactions between the metal centers in dimeric units. It is also suggested that the system becomes demagnetized below a certain temperature.

Bayri, Ali

289

Exclusive fluoride ion recognition and fluorescence "turn-on" response with a label-free DMN Schiff base.  

PubMed

A label-free DMN Schiff base (4) has been explored as a highly selective and sensitive fluoride ion receptor. Fluoride-induced deprotonation results in a charge transfer (CT) transition red shifted with a fluorescence 'turn-on'. Anion selectivity can be tuned by the electron push-pull property of substituents at the phenyl para-position. Selectivity for F(-) is attributed to the suitable acidity of -NH2. PMID:23875184

Kaloo, Masood Ayoub; Sankar, Jeyaraman

2013-09-01

290

Synthesis, characterization and crystal structures of dinuclear macrocyclic Schiff base copper(I) complexes bearing different bridges  

Microsoft Academic Search

Utilizing a new 20-membered macrocyclic Schiff base ligand with two coordination sites formed from the [2+2] condensation of 1,3-diaminopropane and benzene-1,3-dicarboxaldehyde in the presence of CuX (X=Cl?, Br?, I?) salts, air-stable dicopper(I) complexes were synthesized in acetonitrile, intramolecularly linked via two halide groups, and characterized by different physico-chemical techniques. The single crystal X-ray diffraction technique indicates these complexes consist of

Ali Akbar Khandar; Ray J. Butcher; Marjan Abedi; Seyed Abolfazl Hosseini-Yazdi; Mehmet Akkurt; M. Nawaz Tahir

2010-01-01

291

Excited state proton transfer reaction of two new intramolecularly hydrogen bonded Schiff bases at room temperature and 77K  

Microsoft Academic Search

Two new orthohydroxy Schiff bases, 7-phenylsalicylidene benzylamine (PSBA) and 7-ethylsalicylideneaniline (ESA) have been synthesized. The excited state intramolecular proton transfer (ESIPT) and the structure of PSBA and ESA in its crystalline form and in the solvents n-hexane, n-heptane and 1,4-dioxane have been investigated by means of absorption, emission and nanosecond spectroscopy at room temperature and 77K. One ground state species

A. Koll; A Filarowski; D Fitzmaurice; E Waghorne; A Mandal; S Mukherjee

2002-01-01

292

Synthesis and solid state structures of two new copper(II) complexes of Schiff bases derived from furfuryl and tetrahydrofurfurylamine  

Microsoft Academic Search

Two Schiff base copper(II) complexes, bis(N-furfurylsalicylaldiminato)copper(II) (I) and bis(N-tetrahydrofurfurylsalicylaldiminato)copper(II) (II), were synthesized and their solid state structures were determined by X-ray crystallography. Complex I has a square planar geometry. In contrast, complex II displays a distorted square planar geometry. Thus, the geometry around copper in the solid state structures of I and II is determined by a combination of steric

W. Chen; P. Miao; Y. G. Li; H. L. Zhu; Q. F. Zeng

2010-01-01

293

Spectral characterization, cyclic voltammetry, morphology, biological activities and DNA cleaving studies of amino acid Schiff base metal(II) complexes  

Microsoft Academic Search

Metal complexes are synthesized with Schiff bases derived from o-phthalaldehyde (opa) and amino acids viz., glycine (gly) l-alanine (ala), l-phenylalanine (pal). Metal ions coordinate in a tetradentate or hexadentate manner with these N2O2 donor ligands, which are characterized by elemental analysis, molar conductance, magnetic moments, IR, electronic, 1H NMR and EPR spectral studies. The elemental analysis suggests the stoichiometry to

M. A. Neelakantan; F. Rusalraj; J. Dharmaraja; S. Johnsonraja; T. Jeyakumar; M. Sankaranarayana Pillai

2008-01-01

294

Metal Complexes of Non-Symmetric Tetradentate Schiff Bases Derived from N-(1-hydroxy-2-acetonaphthone)-1-amino-2-phenyleneimine  

Microsoft Academic Search

Novel non-symmetrical tetradentate Schiff base complexes with N2O2 and N3O donor sites have been obtained using the half-unit N-(l-hydroxy-2-acetonaphthone)-l-amino-2-phenyleneimine (HL). Two reaction pathways have been used (i) preparation of the free ligand which is then reacted with the desired metal salt, and (ii) template synthesis without isolation of the free ligand. The prepared nickel and copper complexes have been characterized

Davar M. Boghaei; Maryam Lashanizadegan

2000-01-01

295

A Facile and Convenient Synthesis of some Novel Hydrazones, Schiff's Base and Pyrazoles Incorporating Thieno[2,3-b]thiophenes  

PubMed Central

A facile and convenient synthesis of some novel hydrazones, schiff’s base and pyrazoles from thieno[2,3-b]thiophene derivatives 1 have been achieved in high yields assisted by microwave and classical methods. The structures of all the title compounds have been elucidated by elemental analysis, IR, MS, 1H-NMR and 13C-NMR. Generally, these findings represent a new class of sulfur and nitrogen moieties that should also be of interest as new materials.

Mabkhot, Yahia Nasser; Barakat, Assem; Al-Majid, Abdullah Mohammed; Al-Othman, Zeid Abdullah; Alamary, Abdullah Saleh

2011-01-01

296

A one-dimensional azido-bridged manganese(III) complex with bidentate Schiff base: Crystal structure and magnetic properties  

SciTech Connect

The synthesis, structural characterization, and magnetic behavior of a novel one-dimensional azido-bridged manganese(III) complex of formula [Mn(L){sub 2}N{sub 3}] (1) is reported, where HL is the bidentate Schiff base obtained from the condensation of salicylaldehyde with 4-methoxy aniline. Complex 1 crystallizes in the monoclinic system, space group P2{sub 1}/n, with a=11.743(4) A, b=24.986(9) A, c=13.081(5) A, {beta}=95.387(7){sup o} and Z=2. The complex is of one-dimensional chain structure with single end-to-end azido bridges and the manganese(III) ion has an elongated octahedral geometry. Magnetic studies show that the weak antiferromagnetic interaction is mediated by the single end-to-end azido bridge with the exchange parameter J=-5.84 cm{sup -1}. - Graphical abstract: A novel azido-bridged manganese(III) complex with bidentate Schiff base ligands has been prepared and characterized structurally and magnetically. The complex is of one-dimensional chain structure with single end-to-end azido bridges in axial positions. Two bidentate Schiff base ligands coordinate in the equatorial mode. The magnetic measurements show that the complex exhibits weak antiferromagnetic interaction.

Li Wei; Li Zongwei [Department of Chemistry, Nankai University, 94 Weijing Road, Tianjin 300071 (China); Li Licun [Department of Chemistry, Nankai University, 94 Weijing Road, Tianjin 300071 (China); State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (China)], E-mail: llicun@nankai.edu.cn; Liao Daizheng; Jiang Zonghui [Department of Chemistry, Nankai University, 94 Weijing Road, Tianjin 300071 (China)

2007-10-15

297

Spectral properties of protonated Schiff base porphyrins and chlorins. INDO-CI calculations and resonance raman studies  

SciTech Connect

INDO-CI calculations successfully reproduce the striking changes in optical spectra that occur upon protonation of mono- and disubstituted porphyrin, chlorin, and bacteriochlorin Schiff base complexes. They ascribe the changes to Schiff base C=N ..pi..* orbitals which drop in energy upon protonation and mix with and perturb the ..pi..* orbitals of the macrocycle, a result consistent with resonance Raman data. The perturbation is predicted to affect not only transition energies and intensities but also dipole moment directions. The symmetry of the porphyrin and the substitution site of the chlorin are shown to play an important role, especially in governing whether the lowest energy transition will red shift or blue shift. Blue shifts are calculated for protonation of ketimine and enamine isomers of pyrochlorophyll a (PChl). Comparison with reported optical spectra suggests that PChl a Schiff base may undergo isomerization upon protonation. Resonance Raman data on CHO, CHNR, CHNHR/sup +/, and pyrrolidine adducts of chlorin demonstrate the isolation of the peripheral C=O and C=N groups from the macrocycle ..pi.. system intramolecular hydrogen bonding, and selective enhancement of v/sub C=N/ for those species with a split Soret band. V/sub C=N/ is observed with 488.0-nm excitation into the lower-energy Soret and absent for 406.7-nm excitation into the higher-energy Soret, a result predicted by the calculations. 44 references, 10 figures, 2 tables.

Hanson, L.K.; Chang, C.K.; Ward, B.; Callahan, P.M.; Babcock, G.T.; Head, J.D.

1984-07-11

298

New tetradentate Schiff bases of 2,2-dimethyl-1,3-diaminopropane and acetylacetone derivatives and their vanadyl complexes.  

PubMed

A series of new VO(IV) complexes with two new tetradentate Schiff base of 4,4'-(2,2-dimethylpropane-1,3-diyl)-bis(azan-1-yl-1-yldene)dipent-2-en-2-ol) [H(2)L(1)] and 3,3'-(2,2-dimethylpropane-1,3-diyl)azan-1-yl-1-ylidene)-bis(1-phenylbut-1-en-1-ol) [H(2)L(2)] (which have been derived from 2,2-dimethyl-1,3-diaminopropan, and diketones of acetylacetone and benzoylacetone) were synthesized and characterized by (1)H NMR, (13)C NMR, FT-IR, mass and UV-Vis spectrophotometry. The electrochemical properties of the vanadyl complexes were investigated by means of cyclic voltammetry. The oxidation potentials are increased by increasing the electron-withdrawing properties of functional groups of the Schiff base ligands according to the trend of MeSchiff base characteristics. The thermal decomposition of the studied reactions was first order. The kinetic parameters for the decomposition steps in vanadyl complexes thermograms have been calculated. PMID:22885931

Mohammadi, Khosro; Rastegari, Mina

2012-11-01

299

New tetradentate Schiff bases of 2,2-dimethyl-1,3-diaminopropane and acetylacetone derivatives and their vanadyl complexes  

NASA Astrophysics Data System (ADS)

A series of new VO(IV) complexes with two new tetradentate Schiff base of 4,4'-(2,2-dimethylpropane-1,3-diyl)-bis(azan-1-yl-1-yldene)dipent-2-en-2-ol) [H2L1] and 3,3'-(2,2-dimethylpropane-1,3-diyl)azan-1-yl-1-ylidene)-bis(1-phenylbut-1-en-1-ol) [H2L2] (which have been derived from 2,2-dimethyl-1,3-diaminopropan, and diketones of acetylacetone and benzoylacetone) were synthesized and characterized by 1H NMR, 13C NMR, FT-IR, mass and UV-Vis spectrophotometry. The electrochemical properties of the vanadyl complexes were investigated by means of cyclic voltammetry. The oxidation potentials are increased by increasing the electron-withdrawing properties of functional groups of the Schiff base ligands according to the trend of Me < Ph. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the VO(IV) complexes were carried out in the range of 20-700 °C. The complexes were decomposed in two stages. Also, decomposition of the synthesized complexes is related to the Schiff base characteristics. The thermal decomposition of the studied reactions was first order. The kinetic parameters for the decomposition steps in vanadyl complexes thermograms have been calculated.

Mohammadi, Khosro; Rastegari, Mina

2012-11-01

300

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

PubMed

Some novel trinuclear, oxo-centered, carboxylate-bridged, mixed-valence iron complexes of the general formula [Fe(3)O(OOCR)(3)(SB)(3)L(3)] (where R=C(13)H(27), C(15)H(31) or C(17)H(35,) HSB=Schiff bases and L=Ethanol) have been synthesized by the stepwise substitutions of acetate ions from ?(3)-oxo-hexa(acetato)tri(aqua)iron(II)diiron(III), first with straight chain carboxylic acids and then with Schiff bases. The complexes were characterized by elemental analyses, molecular weight determinations and spectral (electronic, infrared, FAB mass, Mössbauer and powder XRD) studies. Molar conductance measurements indicated the complexes to be non-electrolytes in nitrobenzene. Bridging nature of carboxylate and Schiff base anions in the complexes was established by their infrared spectra. Mössbauer spectroscopic studies indicated two quadrupole-split doublets due to Fe(II) and Fe(III) ions at 80, 200 and 295K, confirming the complexes are mixed-valence species. This was also supported by the observed electronic spectra of the complexes. Magnetic susceptibility measurements displayed octahedral geometry around iron in mixed-valence state and a net antiferromagnetic exchange coupling via ?-oxo atom. Trinuclear nature of the complexes was confirmed by their molecular weight determination and FAB mass spectra. A plausible structure for these complexes has been established on the basis of spectral and magnetic moment data. PMID:22939284

Singh, Atresh Kumar; Singh, Alok Kumar

2012-10-01

301

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; Özdemir, Sadin; Okumu?, Veysi; Öztomsuk, Abdussamet; Cornejo, Mauricio

2014-09-15

302

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.

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

2014-01-01

303

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

PubMed

Novel mixed ligand bivalent copper complexes [Cu. L. A. ClO 4 ] and [Cu. L. A] where "L" is Schiff bases, namely 2-((3,4-dimethylisoxazol-5-ylimino)methyl)-4-bromophenol (DMIIMBP)/2-((3,4-dimethylisoxazol-5-ylimino)methyl)-4-chlorophenol (DMIIMCP), and "A" is heterocyclic compound, such as 1,10-phenanthroline (phen)/2,2(1)-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

304

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

NASA Astrophysics Data System (ADS)

Some novel trinuclear, oxo-centered, carboxylate-bridged, mixed-valence iron complexes of the general formula [Fe3O(OOCR)3(SB)3L3] (where R = C13H27, C15H31 or C17H35, HSB = Schiff bases and L = Ethanol) have been synthesized by the stepwise substitutions of acetate ions from ?3-oxo-hexa(acetato)tri(aqua)iron(II)diiron(III), first with straight chain carboxylic acids and then with Schiff bases. The complexes were characterized by elemental analyses, molecular weight determinations and spectral (electronic, infrared, FAB mass, Mössbauer and powder XRD) studies. Molar conductance measurements indicated the complexes to be non-electrolytes in nitrobenzene. Bridging nature of carboxylate and Schiff base anions in the complexes was established by their infrared spectra. Mössbauer spectroscopic studies indicated two quadrupole-split doublets due to Fe(II) and Fe(III) ions at 80, 200 and 295 K, confirming the complexes are mixed-valence species. This was also supported by the observed electronic spectra of the complexes. Magnetic susceptibility measurements displayed octahedral geometry around iron in mixed-valence state and a net antiferromagnetic exchange coupling via ?-oxo atom. Trinuclear nature of the complexes was confirmed by their molecular weight determination and FAB mass spectra. A plausible structure for these complexes has been established on the basis of spectral and magnetic moment data.

Singh, Atresh Kumar; Singh, Alok Kumar

2012-10-01

305

Nonadiabatic ab initio dynamics of two models of Schiff base retinal.  

PubMed

On-the-fly classical dynamics calculations combined with ab initio quantum chemical computations are carried out for two models of protonated Schiff base retinal in vacuo. The models are the 6pi system of 2-cis-penta-2,4-dieneimminium cation and the 12pi system in which two methyl groups are removed from the Schiff base of retinal. The CASSCF(6,6) level with the 6-31G basis set was employed for the quantum chemical part and the velocity Verlet algorism is utilized for time evolution of trajectories. The probabilities of nonadiabatic transition between the excited and ground state are estimated by the Zhu-Nakamura formulas. The 9-cis form product in addition to the all-trans one is generated in the present gas phase calculation for the 12pi model, despite the 9-cis generation being suppressed in protein. We have found that energy relaxation on the ground state occurs in two steps in the 12pi model. In the first step a metastable intermediate state is formed at approximately 100 fs after photoexcitation at the energy around 20-40 kcal/mol down from the excited potential energy surface, then it further relaxes to the energy around 60-80 kcal/mol from the excited surface, leading to the final state (second step). This relaxation pattern can be seen in all the three pathways to the all-trans, 9-cis, and (reverted) 11-cis form. Fourier transformation analysis reveals that the effective vibrational frequencies of the intermediate state are 1600-2000 cm(-1), which can be attributed to the conjugate CC bond frequencies in the electronic ground state. The two-step relaxation may be due to dynamical barriers. The two-step relaxation is not revealed in the smaller 6pi model. The crank-shaft motion of the C11C12 and C9C10 bonds is found in the isomerization, which indicates the motion is intrinsic in retinal, not due to the surrounding protein. The branching ratio is about 1:1:2 for the all-trans, 9-cis, and 11-cis form generation. The ratio is different from earlier works where Tully's fewest switching scheme was employed. The bond length and the dihedral angle at the transitions are also analyzed to investigate the transition mechanism. PMID:19298071

Ishida, Toshimasa; Nanbu, Shinkoh; Nakamura, Hiroki

2009-04-23

306

Tuning coordination modes of pyridine/thioether Schiff base (NNS) ligands to mononuclear manganese carbonyls.  

PubMed

We have investigated the coordination modes of NNS Schiff base, thioether ligands to manganese(i) carbonyls. The ligands contain ortho substituted pyridines (H, CH3, OCH3, fluorophenyl) and varying substituents (H, CH3) at the Schiff base linkage. In general, reaction of [Mn(CO)5Br] with a tridentate NNS ligand in CH2Cl2 affords species in which the thioether-S may be bound or unbound to the manganese center, depending on the steric and electronic substitution in the ligand framework; as a result, the complexes exhibit two or three carbonyl ligands, respectively. Aldehyde-derived ligand frames (R1NHNS) generally afford complexes of type [(RNNS)Mn(CO)3Br] (, , ; R = H, OCH3, CH3) that exhibit incomplete ligation of the chelate (S not bound) in X-ray structures. In contrast, use of the iminomethyl ligand (NMeNS) affords a complex of formula [(NMeNS)Mn(CO)2Br] (), in which the mixed N/thioether-S stabilizes the {Mn(CO)2}(+) fragment. In solid state IR spectra, complexes of type [(RNNS)Mn(CO)3Br] ( through ) afford three ?(CO) in the range ?2060-1865 cm(-1); the dicarbonyl complex [(NMeNS)Mn(CO)2Br] () exhibits two carbonyl stretches in the range ?1920-1845 cm(-1). Prolonged storage of the tricarbonyl [(MeNNS)Mn(CO)3Br] () in presence of trace dioxygen affords the dibromide species [(MeNNS)Mn(Br)2] (), in which the thioether S reliably binds to the Mn(ii) center. Complexes exhibit simple, diamagnetic (1)H NMR spectra in CD2Cl2. The S-ligated complex exhibits spectra consistent with a mixture of an S-bound (6-coordinate) and S-unbound (5-coordinate) species as represented by [(NMeNS)Mn(CO)2Br] ? [(NMeNS)Mn(CO)2Br]. Lastly, we obtained crystal structures of the S-bound and S-unbound conformers derived from the same ligand - the fluorophenyl derived FPhNNS, namely [(FPhNNS)Mn(CO)3Br] () and [(FPhNNS)Mn(CO)2Br] (). This report represents several examples of a thioether-stabilized {Mn(CO)2}(+) fragment, a deviation from the usual 'piano stool' Mn(i) tricarbonyl motif. We highlight that coordination of these NNS ligands to Mn(i) carbonyls occurs on a soft conformational landscape, and that ligand substituents can be rationally employed to favor the desired coordination mode. PMID:24818845

Lumsden, Simone E A; Durgaprasad, Gummadi; Thomas Muthiah, Keren A; Rose, Michael J

2014-06-24

307

Design and synthesis of binucleating macrocyclic clefts derived from Schiff-base calixpyrroles.  

PubMed

The syntheses, characterisation and complexation reactions of a series of binucleating Schiff-base calixpyrrole macrocycles are described. The acid-templated [2+2] condensations between meso-disubstituted diformyldipyrromethanes and o-phenylenediamines generate the Schiff-base pyrrolic macrocycles H(4)L(1) to H(4)L(6) upon basic workup. The single-crystal X-ray structures of both H(4)L(3).2 EtOH and H(4)L(6).H2O confirm that [2+2] cyclisation has occurred, with either EtOH or H2O hydrogen-bonded within the macrocyclic cleft. A series of complexation reactions generate the dipalladium [Pd2(L)] (L=L(1) to L(5)), dinickel [Ni2(L(1))] and dicopper [Cu2(L)] (L=L(1) to L(3)) complexes. All of these complexes have been structurally characterised in the solid state and are found to adopt wedged structures that are enforced by the rigidity of the aryl backbone to give a cleft reminiscent of the structures of Pacman porphyrins. The binuclear nickel complexes [Ni2(mu-OMe)2Cl2(HOMe)2(H(4)L(1))] and [Ni2(mu-OH)2Cl2(HOMe)(H(4)L(5))] have also been prepared, although in these cases the solid-state structures show that the macrocyclic ligand remains protonated at the pyrrolic nitrogen atoms, and the Ni(II) cations are therefore co-ordinated by the imine nitrogen atoms only to give an open conformation for the complex. The dicopper complex [Cu2(L(3))] was crystallised in the presence of pyridine to form the adduct [Cu2(py)(L(3))], in which, in the solid state, the pyridine ligand is bound within the binuclear molecular cleft. Reaction between H(4)L(1) and [Mn(thf){N(SiMe(3))2}2] results in clean formation of the dimanganese complex [Mn2(L(1))], which, upon crystallisation, formed the mixed-valent complex [Mn2(mu-OH)(L(1))] in which the hydroxo ligand bridges the metal centres within the molecular cleft. PMID:17245783

Givaja, Gonzalo; Volpe, Manuel; Leeland, James W; Edwards, Michael A; Young, Thomas K; Darby, S Barnie; Reid, Stuart D; Blake, Alexander J; Wilson, Claire; Wolowska, Joanna; McInnes, Eric J L; Schröder, Martin; Love, Jason B

2007-01-01

308

Synthesis and antioxidant activities of 2-oxo-quinoline-3-carbaldehyde Schiff-base derivatives.  

PubMed

A series of 2-oxo-quinoline-3-carbaldehyde Schiff-base derivatives 4a(1)-4n(2) were designed and synthesized based on the 2-oxo-quinoline structure core as novel antioxidants. In vitro antioxidant activities of these compounds were evaluated and compared with commercial antioxidants ascorbic acid, BHT and BHA, employing DPPH() assay, ABTS(+) assay, O(2)(-) assay and OH() assay. The results showed that IC(50) of most compounds were lower than standard value 10mg/mL, indicating good antioxidant activities of these compounds. In addition, in vitro antioxidant activities screening revealed that 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities of compounds 4b(2), 4e(1), 4e(2) and 4g(2), 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) cation (ABTS(+)) radical scavenging activities of compounds 4a(1), 4e(1), 4e(2), 4f(1), 4f(2), 4g(1), 4g(2), 4h(1), 4h(2), 4k(1), 4k(2), 4n(1) and 4n(2), superoxide anion radical scavenging activities of 4b(1), 4e(1), 4f(2), 4j(1), 4k(1), 4k(2), 4m(1), 4m(2), and 4n(2), and hydroxyl radical scavenging activity of almost all the compounds except 4f(1), 4f(2), 4j(2), 4l(1) and 4l(2) were better than that of the commercial antioxidant butylated hydroxytoluene (BHT). PMID:23206864

Zhang, Ye; Fang, Yilin; Liang, Hong; Wang, Hengshan; Hu, Kun; Liu, Xianxian; Yi, Xianghui; Peng, Yan

2013-01-01

309

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

310

Tunable emissive lanthanidomesogen derived from a room-temperature liquid-crystalline Schiff-base ligand.  

PubMed

A novel photoluminescent room-temperature liquid-crystalline salicylaldimine Schiff base with a short alkoxy substituent and a series of lanthanide(III) complexes of the type [Ln(LH)3(NO3)3] (Ln = La, Pr, Sm, Gd, Tb, Dy; LH = (E)-5-(hexyloxy)-2-[{2-(2-hydroxyethylamino)ethylimino]methyl}phenol) have been synthesized and characterized by FTIR, (1)H and (13)C?NMR, UV/Vis, and FAB-MS analyses. The ligand coordinates to the metal ions in its zwitterionic form. The thermal behavior of the compounds was investigated by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The ligand exhibits an enantiotropic hexagonal columnar (Col(h)) mesophase at room temperature and the complexes show an enantiotropic lamellar columnar (Col(L)) phase at around 120?°C with high thermal stability. Based on XRD results, different space-filling models have been proposed for the ligand and complexes to account for the columnar mesomorphism. The ligand exhibits intense blue emission both in solution and in the condensed state. The most intense emissions were observed for the samarium and terbium complexes, with the samarium complex glowing with a bright-orange light (ca. 560-644?nm) and the terbium complex emitting green light (ca. 490-622?nm) upon UV irradiation. DFT calculations performed by using the DMol3 program at the BLYP/DNP level of theory revealed a nine-coordinate structure for the lanthanide complexes. PMID:23939837

Pramanik, Harun A R; Das, Gobinda; Bhattacharjee, Chira R; Paul, Pradip C; Mondal, Paritosh; Prasad, S Krishna; Rao, D S Shankar

2013-09-23

311

Synthesis and antioxidant activities of novel 4-Schiff base-7-benzyloxy-coumarin derivatives.  

PubMed

4-Schiff base-7-benzyloxy-coumarins 5a(1)-5h(2) and its derivative 6 were designed and synthesized based on the 7-benzyloxy-coumarin structure as novel antioxidants. The in vitro antioxidant activities screening revealed that 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities of compounds 5b(1), 5d(1), 5f(1), 5f(2), 5g(1) and 5g(2), and 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) cation (ABTS(+)) radical scavenging activities of compounds 5a(1), 5b(1), 5c(1), 5c(2), 5d(1), 5e(1), 5e(2), 5f(2), 5g(1), 5g(2) and 5h(1) were better than that of the commercial antioxidant butylated hydroxytoluene (BHT), while the superoxide anion radical scavenging activities of 5a(2) and 5g(2) were stronger than that of the commercial antioxidant butylated hydroxyanisole (BHA), and the hydroxyl radical scavenging activity of 5e(1) was much better than that of the common antioxidant ascorbic acid. PMID:21978674

Zhang, Ye; Zou, Biqun; Chen, Zhenfeng; Pan, Yingming; Wang, Hengshan; Liang, Hong; Yi, Xianghui

2011-11-15

312

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.

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

313

Electronic-structure and quantum dynamical study of the photochromism of the aromatic Schiff base salicylideneaniline  

SciTech Connect

The ultrafast proton transfer dynamics of salicylideneaniline has been theoretically analyzed in the ground and first singlet excited electronic states using density functional theory (DFT) and time-dependent DFT calculations, which predict a ({pi},{pi}*) barrierless excited state intramolecular proton transfer (ESIPT). In addition to this, the photochemistry of salicylideneaniline is experimentally known to present fast depopulation processes of the photoexcited species before and after the proton transfer reaction. Such processes are explained by means of conical intersections between the ground and first singlet ({pi},{pi}*) excited electronic states. The electronic energies obtained by the time-dependent density functional theory formalism have been fitted to a monodimensional potential energy surface in order to perform quantum dynamics study of the processes. Our results show that the proton transfer and deactivation of the photoexcited species before the ESIPT processes are completed within 49.6 and 37.7 fs, respectively, which is in remarkable good agreement with experiments.

Ortiz-Sanchez, Juan Manuel; Gelabert, Ricard; Moreno, Miquel; Lluch, Jose M. [Departament de Quimica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)

2008-12-07

314

Electronic-structure and quantum dynamical study of the photochromism of the aromatic Schiff base salicylideneaniline  

NASA Astrophysics Data System (ADS)

The ultrafast proton transfer dynamics of salicylideneaniline has been theoretically analyzed in the ground and first singlet excited electronic states using density functional theory (DFT) and time-dependent DFT calculations, which predict a (?,?*) barrierless excited state intramolecular proton transfer (ESIPT). In addition to this, the photochemistry of salicylideneaniline is experimentally known to present fast depopulation processes of the photoexcited species before and after the proton transfer reaction. Such processes are explained by means of conical intersections between the ground and first singlet (?,?*) excited electronic states. The electronic energies obtained by the time-dependent density functional theory formalism have been fitted to a monodimensional potential energy surface in order to perform quantum dynamics study of the processes. Our results show that the proton transfer and deactivation of the photoexcited species before the ESIPT processes are completed within 49.6 and 37.7 fs, respectively, which is in remarkable good agreement with experiments.

Ortiz-Sánchez, Juan Manuel; Gelabert, Ricard; Moreno, Miquel; Lluch, José M.

2008-12-01

315

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

National Technical Information Service (NTIS)

Langmuir-Blodgett (LB) film formation has been investigated for polymers in which nonlinear optical (NLO) moieties are attached in the side chain of polymethacrylate (PMA) backbone. Polymer monolayer was successfully transferred onto hydrophilic glass sub...

D. M. Galotti L. Samuelson P. Miller T. Takahashi Y. M. Chen

1991-01-01

316

Excited-state properties and environmental effects for protonated schiff bases: a theoretical study.  

PubMed

Complete active space self-consistent field (CASSCF), multireference configuration interaction (MRCI), density functional theory (DFT), time dependent DFT (TDDFT) and the singles and doubles coupled-cluster (CC2) methodologies have been used to study the ground state and excited states of protonated and neutral Schiff bases (PSB and SB) as models for the retinal chromophore. Systems with two to four conjugated double bonds are investigated. Geometry relaxation effects are studied in the excited pipi* state using the aforementioned methods. Taking the MRCI results as reference we find that CASSCF results are quite reliable even though overshooting of geometry changes is observed. TDDFT does not reproduce bond alternation well in the pipi* state. CC2 takes an intermediate position. Environmental effects due to solvent or protein surroundings have been studied in the excited states of the PSBs and SBs using a water molecule and solvated formate as model cases. Particular emphasis is given to the proton transfer process from the PSB to its solvent partner in the excited state. It is found that its feasibility is significantly enhanced in the excited state as compared to the ground state, which means that a proton transfer could be initiated already at an early step in the photodynamics of PSBs. PMID:16941558

Aquino, Adélia J A; Barbatti, Mario; Lischka, Hans

2006-10-13

317

Selective anion binding by a cofacial binuclear zinc complex of a Schiff-base pyrrole macrocycle.  

PubMed

The synthesis of the new cofacial binuclear zinc complex [Zn(2)(L)] of a Schiff-base pyrrole macrocycle is reported. It was discovered that the binuclear microenvironment between the two metals of [Zn(2)(L)] is suited for the encapsulation of anions, leading to the formation of [K(THF)(6)][Zn(2)(?-Cl)(L)]·2THF and [Bu(n)(4)N][Zn(2)(?-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 preorganization to stabilize the host. In the absence of added anion, aggregation of [Zn(2)(L)] was inferred and investigated by successive dilutions and by the addition of coordinating solvents to [Zn(2)(L)] solutions using NMR spectroscopy as well as isothermal microcalorimetry (ITC). On anion addition, evidence for deaggregation of [Zn(2)(L)], combined with the formation of the 1:1 host-guest complex, was observed by NMR spectroscopy and ITC titrations. Furthermore, [Zn(2)(L)] binds to Cl(-) selectively in THF as deduced from the ITC analyses, while other halides induce only deaggregation. These conclusions were reinforced by density functional theory (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 L; Sessler, Jonathan L; Love, Jason B

2011-04-01

318

DNA binding and nuclease activity of an oxovanadium valinato-Schiff base complex.  

PubMed

A new oxovanadium complex [VO(sal-l-val)(phen)] (sal-l-val=Schiff base derived from salicylaldehyde and l-valine; phen=1,10-phenanthroline) has been designed and synthesized with the aim of developing potential DNA nuclease. The interaction of DNA with this structurally characterized oxovanadium complex has been studied by various physicochemical tools like UV-vis, fluorescence, viscosity and circular dichroism (CD). The intrinsic binding constant of the complex with DNA is determined by electronic absorption studies and calculated to be (4.74±0.02)×10(5)M(-1). The spectroscopic studies and the viscosity measurements indicate that the complex binds calf thymus DNA (CT-DNA) by intercalative mode. The ability of the complex to induce DNA cleavage was studied by gel electrophoresis techniques. The complex has been found to promote cleavage of pUC19 plasmid DNA from the super coiled (SC) form I to nicked coiled (NC) relaxed form II with good efficiency. PMID:24560950

Saha, Urmila; Mukherjea, Kalyan K

2014-05-01

319

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

320

Cobalt-Schiff base complex catalyzed oxidation of para-substituted phenolics. Preparation of benzoquinones  

SciTech Connect

Para-substituted phenolics, serving as models for lignin (a renewable source of carbon), are oxidized to the corresponding benzoquinone with oxygen in the presence of catalytic amounts of Co-Schiff base complexes. The reaction products observed depend on the structure of the catalyst. The 5-coordinate catalysts (pyridine)[bis(salicylidene)ethylenediamine]cobalt[(pyr)Co(salen)]and[bis(salicylideneamino)ethylamine]cobalt [Co(n-Me salpr)] convert syringyl alcohol (3,5-dimethoxy-4-hydroxybenzyl alcohol) to 2,6-dimethoxybenzoquinone in high yield. In contrast, syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde) is unreactive toward these catalysts. However, the 4-coordinate Co(salen) converts syringaldehyde to 2,6-dimethoxybenzoiquinone in 72% isolated yield. Phenols bearing a single methoxy group on the ring are unreactive toward any catalyst in MeOH. However, vanillyl alcohol (3-methoxy-4-hydroxybenzyl alcohol) is converted to 2-methoxybenzo-quinone with Co(N-Me salpr) and oxygen in 43% yield in CH{sub 2}Cl{sub 2} and 58% yield in CH{sub 2}Cl{sub 2} in the presence of 1% CuCl{sub 2}. The success of the oxidations appears to be related to the ease of removal of the phenolic hydrogen by the Co/O{sub 2} complex. Competitive deactivation of the catalyst occurs with substrates of lower reactivity. 84 tabs.

Bozell, J.J.; Hames, B.R. [National Renewable Energy Lab., Golden, CO (United States); Dimmel, D.R. [Institute of Paper Science and Technology, Atlanta, GA (United States)

1995-04-21

321

Photoisomerization for a model protonated Schiff base in solution: Sloped/peaked conical intersection perspective  

SciTech Connect

The topographical character of conical intersections (CIs)-either sloped or peaked-has played a fundamental and important role in the discussion of the efficiency of CIs as photochemical 'funnels.' Here this perspective is employed in connection with a recent study of a model protonated Schiff base (PSB) cis to trans photoisomerization in solution [Malhado et al., J. Phys. Chem. A 115, 3720 (2011)]. In that study, the calculated reduced photochemical quantum yield for the successful production of trans product versus cis reactant in acetonitrile solvent compared to water was interpreted in terms of a dynamical solvent effect related to the dominance, for the acetonitrile case, of S{sub 1} to S{sub 0} nonadiabatic transitions prior to the reaching the seam of CIs. The solvent influence on the quantum yield is here re-examined in the sloped/peaked CI topographical perspective via conversion of the model's two PSB internal coordinates and a nonequilibrium solvent coordinate into an effective branching space description, which is then used to re-analyze the generalized Langevin equation/surface hopping results. The present study supports the original interpretation and enriches it in terms of topographical detail.

Malhado, Joao Pedro [Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05314-970 Sao Paulo, SP (Brazil); Hynes, James T. [Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215 (United States); Chemistry Department, Ecole Normale Superieure, UMR ENS-CNRS-UPMC 8640, 24 rue Lhomond, 75005 Paris (France)

2012-12-14

322

Excited-state dynamics of protonated retinal Schiff base in solution  

SciTech Connect

The dynamics of all-trans and 13-cis retinal protonated Schiff base (RPSB) were studied in different solvents by means of picosecond transient spectroscopy. The decay time of the excited state absorption was found to be wavelength dependent due to the contribution of the faster decay of stimulated emission. The stimulated emission has a lifetime of a 2.5-4 ps while the excited state absorption decay is biexponential with lifetimes of 2.5-4 and 10-12 ps. The fluorescence quantum yield is strongly temperature dependent but viscosity has a small effect on both excited-state lifetime and fluorescence quantum yield. This leads to the conclusion that there is a {approx}600 cm{sup -1} barrier in the excited-state which results from intramolecular electronic factors and not from the solvent viscosity. The comparison of these results with those for the retinal in rhodopsin and bacteriorhodopsin is discussed in terms of the protein catalysis for the retinal photoisomerization. 31 refs., 8 figs., 2 tabs.

Logunov, S.L.; Li, S.; El-Sayed, M.A. [Georgia Inst. of Technology, Atlanta, GA (United States)] [Georgia Inst. of Technology, Atlanta, GA (United States)

1996-11-21

323

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

324

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, Gökhan; Köse, Muhammet; McKee, Vickie; Uru?, Serhan; Gölcü, Ay?egül; Tümer, Mehmet

325

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

326

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.

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

2011-01-01

327

Luminescence and structural properties of lanthanide complexes of Schiff bases derived from pyridoxal and amino acids.  

PubMed

Lanthanide complexes of Schiff bases (SBs) with 1:1 and 1:2 (M:Lig) stoichiometric ratios were prepared by condensation of pyridoxal (PL) and aspartic acid (Asp) or l-histidine (His), respectively, in the presence of the appropriate metal chloride as a templating agent. These complexes were studied by optical spectroscopy and single crystal X-ray diffraction techniques. Crystallographic studies of 1:1 ([Eu(PL-Asp)(H(2)O)(4)](H(2)O)) and 1:2 ([Eu(PL-His)(2)(H(2)O)(2)]Cl(H(2)O)(4)) complexes show that Eu(III) is eight-coordinate in both structures, in a distorted square antiprism environment formed by the phenolic oxygen of PL, the nitrogen atom of carbon-nitrogen double bond, oxygen atoms of the carboxylate groups of His or Asp, and oxygen atoms of the water molecules. The main species formed in aqueous solutions containing these SBs have been determined by analysis of the luminescence spectra, lifetimes of Eu(III) excited states and vibronic interaction as well as structural features of the Eu(III) coordination sphere. Possible tetradentate coordination function of SBs in aqueous solutions with relatively high concentrations as well as the potential application of the lanthanide SB complexes as new luminescence materials are discussed. PMID:17828370

Puntus, Lada; Zhuravlev, Konstantin; Lyssenko, Konstantin; Antipin, Mikhail; Pekareva, Irina

2007-09-28

328

Novel nanohybrids of cobalt(III) Schiff base complexes and clay: Synthesis and structural determinations  

NASA Astrophysics Data System (ADS)

The [Co(Me2Salen)(PBu3)(OH2)]BF4 and [Co(Me2Salen)(PPh3)(Solv)]BF4, complexes were synthesized and characterized by FT-IR, UV-Vis, 1H NMR spectroscopy and elemental analysis techniques. The coordination geometry of [Co(Me2Salen)(PPh3)(H2O)]BF4 was determined by X-ray crystallography. It has been found that the complex is containing [Co(Me2Salen)(PPh3)(H2O)]BF4 and [Co(Me2Salen)(PPh3)(EtOH)]BF4 hexacoordinate species in the solid state. Cobalt atom exhibits a distorted octahedral geometry and the Me2Salen ligand has the N2O2 coordinated environment in the equatorial plane. The [Co(Me2Salen)(PPh3)(H2O)]BF4 complex shows a dimeric structure via hydrogen bonding between the phenolate oxygen and hydrogens of coordinated H2O molecule. These complexes were incorporated into Montmorillonite-K10 nanoclay. The modified clays were identified by FT-IR, XRD, EDX, TGA/DTA, SEM and TEM techniques. According to the XRD results of the new nanohybrid materials, the Schiff base complexes are intercalated in the interlayer spaces of the clay. SEM and TEM micrographs show that the resulting hybrid nanomaterials have layer structures. Also, TGA/DTG results show that the intercalation reaction was taken place successfully.

Kianfar, Ali Hossein; Mahmood, Wan Ahmad Kamil; Dinari, Mohammad; Azarian, Mohammad Hossein; Khafri, Fatemeh Zare

2014-06-01

329

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

330

Preparation and biodistribution of copper-67 complexes with tetradentate Schiff-base ligands.  

PubMed

Uncharged, lipophilic, low molecular weight copper complexes labeled with generator-produced copper-62 are of interest as potential radiopharmaceutials for imaging the brain with positron emission tomography (PET). We report here the synthesis and biodistribution of a series of [67Cu]copper(II) complexes with tetradentate N2O2(2-)Schiff-base ligands. The compounds studied varied in lipophilicity from log P = 1.7 to log P = 3.6, where P is the octanol/water partition coefficient. In rat biodistribution studies the tracers were generally found to penetrate the blood-brain barrier following intravenous injection, but some far better than others. For closely related compounds brain uptake at 1 min postinjection increased with increasing lipophilicity, although log P was clearly not the sole determinant of high brain uptake. Substantial variations were also observed in the rate at which these various compounds are cleared from brain, with a few exhibiting the prolonged cerebral retention of tracer that would be desired for imaging with 62Cu and PET. PMID:8046620

John, E K; Bott, A J; Green, M A

1994-04-01

331

Proton transfer reaction of a new orthohydroxy Schiff base at room temperature and 77 K  

NASA Astrophysics Data System (ADS)

One new orthohydroxy Schiff base, 2-( N-benzyl-?-iminoethyl)naphthol (BEIN) has been synthesized. The proton transfer reaction of BEIN has been investigated by means of absorption, steady state and time resolved fluorescence spectroscopy in different solvents at room temperature and 77 K. The behavior of BEIN in ethanol and water, has been studied in neutral, acidic and basic conditions. Excited state intramolecular proton transfer (ESIPT) is evidenced by a large Stokes shifted (˜11,000 cm -1) fluorescence in solid crystalline media at room temperature. We present the observation of phosphorescence both in non-polar and protic solvents at 77 K. The observed decay dynamics of the phosphorescence and delayed fluorescence indicates that the triplet state can be attributed to the cis-keto form. The molecular structures are determined by B3LYP/6-31G ?? calculation. From theoretical study it is suggested that the strengthening of hydrogen bond result from the steric repulsion of the phenyl ring. The presence of benzene ring increases the proton transfer barrier in case of BEIN compared to previously studied 7-ethylsalicylidenebenzylamine (ESBA).

Mandal, A.; Fitzmaurice, D.; Waghorne, E.; Koll, A.; Filarowski, A.; Quinn, S.; Mukherjee, S.

2004-03-01

332

Novel Organotin(IV) Schiff Base Complexes with Histidine Derivatives: Synthesis, Characterization, and Biological Activity  

PubMed Central

Five novel tin Schiff base complexes with histidine analogues (derived from the condensation reaction between L-histidine and 3,5-di-tert-butyl-2-hydroxybenzaldehyde) have been synthesized and characterized. Characterization has been completed by IR and high-resolution mass spectroscopy, 1D and 2D solution NMR (1H, 13C??and 119Sn), as well as solid state 119Sn NMR. The spectroscopic evidence shows two types of structures: a trigonal bipyramidal stereochemistry with the tin atom coordinated to five donating atoms (two oxygen atoms, one nitrogen atom, and two carbon atoms belonging to the alkyl moieties), where one molecule of ligand is coordinated in a three dentate fashion. The second structure is spectroscopically described as a tetrahedral tin complex with four donating atoms (one oxygen atom coordinated to the metal and three carbon atoms belonging to the alkyl or aryl substituents), with one molecule of ligand attached. The antimicrobial activity of the tin compounds has been tested against the growth of bacteria in vitro to assess their bactericidal properties. While pentacoordinated compounds 1, 2, and 3 are described as moderate effective to noneffective drugs against both Gram-positive and Gram-negative bacteria, tetracoordinated tin(IV) compounds 4 and 5 are considered as moderate effective and most effective compounds, respectively, against the methicillin-resistant Staphylococcus aureus strains (Gram-positive).

Garza-Ortiz, Ariadna; Camacho-Camacho, Carlos; Sainz-Espunes, Teresita; Rojas-Oviedo, Irma; Gutierrez-Lucas, Luis Raul; Gutierrez Carrillo, Atilano; Vera Ramirez, Marco A.

2013-01-01

333

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 (420-680 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. PMID:24784270

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

2014-04-28

334

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

PubMed

Three Schiff base ligands (H(2)L(1)-H(2)L(3)) with N(2)O(2) 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 ((1)H, (13)C NMR) and 2D (COSY, HETCOR, HMBC and TOSCY) NMR techniques were used to characterize the structures of the ligands and establish the (1)H and (13)C resonance assignments of the three ligands. Ligands H(2)L(1) and H(2)L(3) 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. PMID:22571942

Ceyhan, Gökhan; Köse, Muhammet; McKee, Vickie; Uru?, Serhan; Gölcü, Ay?egül; Tümer, Mehmet

2012-09-01

335

QM study and conformational analysis of an isatin Schiff base as a potential cytotoxic agent.  

PubMed

Isatin is an important compound from the biological aspect of view. It is an endogenous substance and moreover; various pharmacological activities have been reported for isatin and its derivatives. In-vitro cytotoxic effects of the prepared isatin Schiff bases toward HeLa, LS180 and Raji human cancer cell lines has been reported in our previous work. 3-(2-(4-nitrophenyl)hydrazono) indolin-2-one was found to be the most potent one among the studied compounds (IC(30)?=12.2 and 21.8 ?M in HeLa and LS-180 cell lines, respectively). Obtained biological data could be well interpreted using docking binding energies toward vascular endothelial growth factor receptor (VEGFR-2); a key anticancer target being biologically investigated against various isatin derivatives. In the present work, quantum mechanical (QM) method including functional B3LYP in association with split valence basis set using polarization functions (Def2-SVP) was used to estimate individual ligand-residue interaction energies for the docked 3-(2-(4-nitrophenyl)hydrazono) indolin-2-one into VEGFR-2 active site. Results were further interpreted via calculated polarization effects induced by individual amino acids of the receptor active site. A fairly good correlation could be found between polarization effects and estimated binding energies (R(2)?=0.7227). Conformational analysis revealed that 3-(2-(4-nitrophenyl) hydrazono) indolin-2-one might not necessarily interact with the VEGFR-2 active site in its minimum energy conformation. PMID:23053004

Miri, Ramin; Razzaghi-asl, Nima; Mohammadi, Mohammad K

2013-02-01

336

Schiff Base Switch II Precedes the Retinal Thermal Isomerization in the Photocycle of Bacteriorhodopsin  

PubMed Central

In bacteriorhodopsin, the order of molecular events that control the cytoplasmic or extracellular accessibility of the Schiff bases (SB) are not well understood. We use molecular dynamics simulations to study a process involved in the second accessibility switch of SB that occurs after its reprotonation in the N intermediate of the photocycle. We find that once protonated, the SB C15?=?NZ bond switches from a cytoplasmic facing (13-cis, 15-anti) configuration to an extracellular facing (13-cis, 15-syn) configuration on the pico to nanosecond timescale. Significantly, rotation about the retinal’s C13?=?C14 double bond is not observed. The dynamics of the isomeric state transitions of the protonated SB are strongly influenced by the surrounding charges and dielectric effects of other buried ions, particularly D96 and D212. Our simulations indicate that the thermal isomerization of retinal from 13-cis back to all-trans likely occurs independently from and after the SB C15?=?NZ rotation in the N-to-O transition.

Wang, Ting; Facciotti, Marc T.; Duan, Yong

2013-01-01

337

Corrosion inhibition of mild steel by some schiff base compounds in hydrochloric acid  

NASA Astrophysics Data System (ADS)

The corrosion inhibition of mild steel in 1 M HCl by benzylidene-pyridine-2-yl-amine (A), (4-benzylidene)-pyridine-2-yl-amine (B) and (4-chloro-benzylidene)-pyridine-2-yl-amine (C) has been studied at 25 °C using electrochemical and weight loss measurements. Polarization curves reveal that the used compounds are mixed type inhibitors. Results show that inhibition efficiency increases when the inhibitor concentration increases. The inhibition efficiency changes with the type of functional groups substituted on benzene ring. The experimentally obtained adsorption isotherms follow the Langmuir equation. The effect of temperature on the corrosion behavior in the presence of 10 -2 M of inhibitors was studied in the temperature range of 25-43 °C. The associated activation energy of corrosion and other thermodynamic parameters have been determined. It has been found that all those schiff base compounds are excellent inhibitors. Obvious correlation was found between corrosion inhibition efficiency and quantum chemical parameters, using the linear and non-linear QSAR models. The obtained theoretical results have been compared with the experimental results.

Ashassi-Sorkhabi, H.; Shaabani, B.; Seifzadeh, D.

2005-01-01

338

Epoxidation of cyclohexene with K10-montmorillonite and Schiff-base macrocyclic copper complexes  

Microsoft Academic Search

Copper(II) complexes of 12- and 13-membered diaza dioxa Schiff-base macrocyclic ligand, 1,4-diaza-7,10-dioxacyclododeca-1,3-diene, H2[12]1,3-dieneN2O2; 2,3-dimethyl-1,4-diaza-7,10-dioxacyclododeca-1,3-diene, (CH3)2[12]1,3-dieneN2O2; 2,3-diphenyl-1,4-diaza-7,10-dioxacyclododeca-1,3-diene, (C6H5)2[12]1,3-dieneN2O2; 2,4-dimethyl-1,5-diaza-8,11-dioxacyclotrideca-1,4-diene, (CH3)2[13]1,4-dieneN2O2; 2,4-diphenyl-1,5-diaza-8,11-dioxacyclotrideca-1,4-diene, (C6H5)2[13]1,4-dieneN2O2 were entrapped into an montmorillonite-K10 (denoted as K10) by simultaneous\\/pillaring encapsulation method. In this method the simultaneous encapsulation also occurred but the complex, also dissolved in methanol, was added to the clay dispersion. All materials were characterized by FTIR,

Masoud Salavati-Niasari; Elham Zamani; Mehdi Bazarganipour

2007-01-01

339

The synthesis and characterization of mono and dinuclear group 13 complexes derived from a Schiff base.  

PubMed

The coordination preferences of the tetradentate Schiff base, N,N'-ethylenebis(acetylacetoimine), H(2)L, with a variety of group 13 precursors, led to the formation of a series of mono and binuclear products. The reaction of H(2)L with AlMe(3) and Me(2)GaCl afforded the binuclear complexes, [L{Al(Me)(2)}(2)] 1 and [H(2)L{GaCl(Me)(2)}(2)], 3, the latter an adduct of the neutral ligand. Treatment of 1 with iodine generated the cationic Al(III) complex, [LAl(thf)(2)]I, 2, while the addition of n-BuLi to H(2)L, followed by reaction with GaCl(3) and InCl(3) led to an ionic complex [{LGaCl}(2)(?Li)]GaCl(4), 4, an In(III) dimer, [LInCl](2), 5 and monomeric [LInCl(thf)], 6. In contrast, the reaction of [In{N(SiMe(3))(2)}(3)] with H(2)L yielded a homoleptic, air stable, indium complex, [L(3)In(2)], 7. All products were definitively characterized by X-ray crystallography and their structures confirmed by pertinent spectroscopic techniques. PMID:22653153

Aprile, Antonino; Wilson, David D J; Richards, Anne F

2012-07-28

340

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

341

Photoisomerization for a model protonated Schiff base in solution: Sloped/peaked conical intersection perspective  

NASA Astrophysics Data System (ADS)

The topographical character of conical intersections (CIs)--either sloped or peaked--has played a fundamental and important role in the discussion of the efficiency of CIs as photochemical ``funnels.'' Here this perspective is employed in connection with a recent study of a model protonated Schiff base (PSB) cis to trans photoisomerization in solution [Malhado et al., J. Phys. Chem. A 115, 3720 (2011)]. In that study, the calculated reduced photochemical quantum yield for the successful production of trans product versus cis reactant in acetonitrile solvent compared to water was interpreted in terms of a dynamical solvent effect related to the dominance, for the acetonitrile case, of S1 to S0 nonadiabatic transitions prior to the reaching the seam of CIs. The solvent influence on the quantum yield is here re-examined in the sloped/peaked CI topographical perspective via conversion of the model's two PSB internal coordinates and a nonequilibrium solvent coordinate into an effective branching space description, which is then used to re-analyze the generalized Langevin equation/surface hopping results. The present study supports the original interpretation and enriches it in terms of topographical detail.

Malhado, Joa~o. Pedro; Hynes, James T.

2012-12-01

342

Photoisomerization for a model protonated Schiff base in solution: sloped/peaked conical intersection perspective.  

PubMed

The topographical character of conical intersections (CIs)--either sloped or peaked--has played a fundamental and important role in the discussion of the efficiency of CIs as photochemical "funnels." Here this perspective is employed in connection with a recent study of a model protonated Schiff base (PSB) cis to trans photoisomerization in solution [Malhado et al., J. Phys. Chem. A 115, 3720 (2011)]. In that study, the calculated reduced photochemical quantum yield for the successful production of trans product versus cis reactant in acetonitrile solvent compared to water was interpreted in terms of a dynamical solvent effect related to the dominance, for the acetonitrile case, of S(1) to S(0) nonadiabatic transitions prior to the reaching the seam of CIs. The solvent influence on the quantum yield is here re-examined in the sloped/peaked CI topographical perspective via conversion of the model's two PSB internal coordinates and a nonequilibrium solvent coordinate into an effective branching space description, which is then used to re-analyze the generalized Langevin equation/surface hopping results. The present study supports the original interpretation and enriches it in terms of topographical detail. PMID:23249080

Malhado, João Pedro; Hynes, James T

2012-12-14

343

Novel nanohybrids of cobalt(III) Schiff base complexes and clay: Synthesis and structural determinations.  

PubMed

The [Co(Me2Salen)(PBu3)(OH2)]BF4 and [Co(Me2Salen)(PPh3)(Solv)]BF4, complexes were synthesized and characterized by FT-IR, UV-Vis, (1)H NMR spectroscopy and elemental analysis techniques. The coordination geometry of [Co(Me2Salen)(PPh3)(H2O)]BF4 was determined by X-ray crystallography. It has been found that the complex is containing [Co(Me2Salen)(PPh3)(H2O)]BF4 and [Co(Me2Salen)(PPh3)(EtOH)]BF4 hexacoordinate species in the solid state. Cobalt atom exhibits a distorted octahedral geometry and the Me2Salen ligand has the N2O2 coordinated environment in the equatorial plane. The [Co(Me2Salen)(PPh3)(H2O)]BF4 complex shows a dimeric structure via hydrogen bonding between the phenolate oxygen and hydrogens of coordinated H2O molecule. These complexes were incorporated into Montmorillonite-K10 nanoclay. The modified clays were identified by FT-IR, XRD, EDX, TGA/DTA, SEM and TEM techniques. According to the XRD results of the new nanohybrid materials, the Schiff base complexes are intercalated in the interlayer spaces of the clay. SEM and TEM micrographs show that the resulting hybrid nanomaterials have layer structures. Also, TGA/DTG results show that the intercalation reaction was taken place successfully. PMID:24637279

Kianfar, Ali Hossein; Mahmood, Wan Ahmad Kamil; Dinari, Mohammad; Azarian, Mohammad Hossein; Khafri, Fatemeh Zare

2014-06-01

344

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

NASA Astrophysics Data System (ADS)

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

Shibata, Mikihiro; Kandori, Hideki

2007-12-01

345

Complexes of trivalent metal ions with potentially heptadentate N{sub 4}O{sub 3} Schiff base and amine phenol ligands of varying rigidity  

SciTech Connect

The synthesis and characterization of several potentially heptadentate N{sub 4}O{sub 3} Schiff bases and amine phenols, as well as a series of their mononuclear and dinuclear complexes with indium and the lanthanides are reported. Schiff bases containing imidazolidine rings were the products of the known condensation reaction of triethylenetetramine with 3 equiv of 5-substituted salicylaldehydes to form H{sub 3}api (5-H-substituent), H{sub 3}Clapi (5-Cl-substituent), or H{sub 3}Brapi (5-Br-substituent); KBH{sub 4} reduction of these Schiff bases gave the appropriate isomeric N{sub 4}O{sub 3} amine phenols H{sub 3}(1,2,4-btt) and H{sub 3}(1,1,4-btt), as well as an acetone adduct, H{sub 3}(1,2,4-ahi). The Schiff bases reacted with 1 equiv of a lanthanide (Ln{sup 3+}) nitrate to produce mononuclear nine-coordinated [Ln(H{sub 3}Xapi)-(NO{sub 3}){sub 3}] complex wherein the ligand adopts a tridentate capping coordination mode, whereas the amine phenols formed mononuclear seven-coordinate complexes with the lanthanides and indium; homodinuclear complexes [LnL]{sub 2} were also obtained with the Schiff bases. The X-ray structures of the Schiff bases H{sub 3}api and H{sub 3}Clapi, the mononuclear amine phenol complexes Yb(1,2,4-btt){center_dot}0.5CH{sub 3}OH and In(1,1,4-btt), and the homodinuclear Schiff base complex [La(Brapi)]{sub 2}{center_dot}2CHCl{sub 3} have been determined.

Yang, L.W.; Liu, S.; Wong, E.; Rettig, S.J.; Orvig, C. [Univ. of British Columbia, Vancouver (Canada)

1995-04-12

346

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

PubMed

Water-soluble cobalt(II) tetradentate Schiff base complexes have been shown to form charge transfer (CT) complexes with a series of nucleoside monophosphates including adenosine-5'-monophosphate (AMP) and cytidine-5'-monophosphate (CMP). The investigated water-soluble cobalt(II) Schiff base complexes are (i) disodium[{bis(5-sulfo-salicylaldehyde)-o-phenylenediiminato}cobalt(II)], Na2[Co(SO3-salophen)] (1); (ii) disodium[{bis(5-sulfo-salicylaldehyde)-4,5-dimethyl-o-phenylenediiminato}cobalt(II)], Na2[Co(SO3-sal-4,5-dmophen)] (2) and (iii) disodium[{bis(4-methoxy-5-sulfo-salicylaldehyde)-4,5-dimethyl-o-phenylenediiminato}cobalt(II)], Na(2)[Co(SO3-4-meosal-4,5-dmophen)] (3). The formation constant and thermodynamic parameters for charge transfer complex formation of water-soluble cobalt(II) Schiff base complexes with nucleoside monophosphates were determined spectrophotometrically in aqueous solution at constant ionic strength (I = 0.2 mol dm(-3) KNO3) under physiological condition (pH 7.0) and at various temperatures between 288 and 308 K. The stoichiometry has been found to be 1:1 (water-soluble cobalt(II) Schiff base complex: nucleoside monophosphate) in each case. Our spectroscopic and thermodynamic results show that the interaction of water-soluble cobalt(II) Schiff base complexes with the investigated nucleoside monophosphates occurs mainly through the phosphate group. The trend of the interaction according to the cobalt(II) Schiff base complexes due to electronic and steric factors is as follows: Na2[Co(SO3-salophen)] > Na2[Co(SO3-sal-4,5-dmophen)] > Na2[Co(SO3-4-meosal-4,5-dmophen)]. Also the trend of the interaction of a given cobalt(II) Schiff base complex according to the nucleoside monophosphate is as follows: CMP > AMP. PMID:15950536

Boghaei, Davar M; Gharagozlou, Mehrnaz

2006-01-01

347

Syntheses and characterization of a chelating resin containing ONNO donor quadridentate Schiff base and its coordination complexes with copper(II), nickel(II), cobalt(II), iron(III), zinc(II), cadmium(II), molybdenum(VI) and uranium(VI) 1 ONNO indicates donor sites of the quadridentate Schiff base. 1 , 2 Presented at the National Seminar on Reactive and Functional Polymers held at Gujarat University, Ahmedabad, Gujarat, India in March, 1996. 2  

Microsoft Academic Search

A new mixed Schiff base N,N?-ethylenemono(3-carboxysalicylideneimine)mono(salicylideneimine) has been synthesized by the condensation of equimolar quantities of ethylenediamine, salicylaldehyde and 3-formylsalicylic acid. A polymer supported Schiff base (PS–CH2–LH2) has been synthesized by the reaction of chloromethylated polystyrene (containing 3.9 mmol of chlorine per g of resin and 2% cross-linked with divinylbenzene) and the Schiff base N,N?-ethylenemono(3-carboxysalicylideneimine)mono(salicylideneimine). The polymer-anchored Schiff base reacts

A. Syamal; M. M. Singh; D. Kumar

1999-01-01

348

Tautomeric effect of hydrazone Schiff bases in tetranuclear Cu(II) complexes: magnetism and catalytic activity towards mild hydrocarboxylation of alkanes.  

PubMed

Three new tetranuclear copper(II) complexes [Cu(HL(1))]4·4EtOH (1·4EtOH), [Cu(HL(2))]4 (2) and [Cu(H2L(3))]4(NO3)4·2H2O (3·2H2O) have been synthesized using three different hydrazone Schiff base ligands derived from the condensation of the aromatic acid hydrazides 2-hydroxybenzo-, 2-aminobenzo- or benzo-hydrazide, with 2,3-dihydroxybenzaldehyde. Complexes 1 and 3 have been characterized by single crystal X-ray diffraction analysis. The coordinating behaviour of the ligand depends on the nature of the ortho substituent present in the hydrazide moiety. The ligands bearing a strong electron donating group (by resonance) in the ortho position undergo complexation via enolization and deprotonation, whereas the absence of such an effect leads to complexation via the keto form, and two different types of tetranuclear Cu(II) clusters, viz. open-cubane and cubane, are obtained. Variable temperature magnetic susceptibility measurements of complexes 1 and 3 have been carried out to examine the nature of magnetic interaction between the Cu(II) centres. All the three complexes (1-3) act as good catalyst precursors towards mild hydrocarboxylation of linear and cyclic alkanes into carboxylic acids in water-acetonitrile medium. PMID:24068161

Sutradhar, Manas; Kirillova, Marina V; Guedes da Silva, M Fátima C; Liu, Cai-Ming; Pombeiro, Armando J L

2013-12-21

349

Synthesis and anti-microbial screening of novel schiff bases of 3-amino-2-methyl quinazolin 4-(3H)-one  

PubMed Central

In the present study, novel Schiff bases were synthesized by condensation of 3-amino-2-methyl quinazolin-4-(3H)-ones with different aromatic aldehydes. The 3-amino-2-methyl quinazolin-4-(3H)-one was synthesized from anthranilic acid via the 2-methyl benzoxazin-4-one. The chemical structures of the synthesized compounds were confirmed by means of Infrared (IR), 1H-NMR, 13C-NMR, Mass spectral, and Elemental analysis. These compounds were screened for anti-bacterial (Staphylococcus aureus ATCC 9144, Staphylococcus epidermidis ATCC 155, Micrococcus luteus ATCC 4698, Bacillus cereus ATCC 11778, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 2853, and Klebsiella pneumoniae ATCC 11298)) and anti-fungal (Aspergillus niger ATCC 9029 and Aspergillus fumigatus ATCC 46645) activities, using the paper disk diffusion technique. The minimum inhibitory concentrations (MIC) of the compounds were also determined by the agar streak dilution method. Most of the synthesized compounds exhibited significant anti-bacterial and anti-fungal activities. Among the synthesized compounds, 3-(4-hydroxy benzylideneamino)-2-methyl quinazolin-4(3H)-one 4g and 4c was found to exhibit the highest anti-bacterial activity and 3-(4-hydroxy-3-methoxy benzylideneamino)-2-methyl quinazolin-4(3H)-one 4k exhibited the highest anti-fungal activity.

Saravanan, Govindaraj; Pannerselvam, Perumal; Prakash, Chinnasamy Rajaram

2010-01-01

350

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

351

A colorimetric and turn-on fluorescent chemosensor for Al(III) based on a chromone Schiff-base.  

PubMed

A simple Schiff-base receptor 7-methoxychromone-3-carbaldehyde-(pyridylformyl) hydrazone (MCNH) was prepared. It exhibits an "off-on-type" mode with high sensitivity in the presence of Al(3+). This compound could be used as Al(3+) probe in ethanol and it features visible light excitation (433 nm) and emission (503 nm) profiles. Upon binding of Al(3+), a significant fluorescence enhancement with a turn-on ratio over 800-fold was triggered. However, other metal ions had no such significant effect on the fluorescence. MCNH can also be used as a colorimetric chemosensor for Al(3+), which is easily observed from colorless to yellow-green by the naked-eye. The detection limit of MCNH for Al(3+) was as low as 1.9×10(-7) M. PMID:24140792

Fan, Long; Li, Tian-rong; Wang, Bao-dui; Yang, Zheng-yin; Liu, Chun-jiao

2014-01-24

352

A Role for Internal Water Molecules in Proton Affinity Changes in the Schiff Base and Asp85 for One-way Proton Transfer in Bacteriorhodopsin†  

PubMed Central

Light-induced proton pumping in bacteriorhodospin is carried out through five proton transfer steps. We propose that the proton transfer to Asp85 from the Schiff base in the L-to-M transition is accompanied by the relocation of a water cluster on the cytoplasmic side of the Schiff base from a site close to the Schiff base in L to the Phe219-Thr46 region in M. The water cluster present in L, formed at 170 K, is more rigid than that at room temperature. This may be responsible for blocking the conversion of L to M at 170 K. In the photocycle at room temperature, this water cluster returns to the site close to the Schiff base in N, with a rigid structure similar to that of L at 170 K. The increase in the proton affinity of Asp85, which is a prerequisite for the one-way proton transfer in the M-to-N transition, is suggested to be facilitated by a structural change which disrupts interactions between Asp212 and the Schiff base, and between Asp212 and Arg82. We propose that this liberation of Asp212 is accompanied by a rearrangement of the structure of water molecules between Asp85 and Asp212, stabilizing the protonated Asp85 in M.

Morgan, Joel E.; Gennis, Robert B.; Maeda, Akio

2014-01-01

353

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 ML·2H 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

354

Synthesis and electrochemical studies of heterobinuclear complexes containing copper and molybdenum nitrosyl groups linked by Schiff base ligands  

Microsoft Academic Search

The reaction of [MoCl(NO)Tp\\u000a * = tris(3,5-dimethylpyrazolylborate] with copper Schiff base complexes derived by condensation of one mole each of 2,5-dihydroxybenzaldehyde\\u000a and salicylaldehyde with ?,? diamines [NH2(CH2)\\u000a n\\u000a NH2, n = 2–4] yields heterobinuclear complexes with two potential redox centres. I.r., electronic and e.s.r. spectroscopic properties\\u000a of these complexes are described. Cyclic voltammetric data of the base complexes in DMSO

Samwel T. Lutta

2000-01-01

355

Metal complexes of a novel Schiff base derived from sulphametrole and varelaldehyde. Synthesis, spectral, thermal characterization and biological activity  

Microsoft Academic Search

Metal complexes of a novel Schiff base (HL=3-(4?-ethylazomethinobenzene sulphonamide)-4-methoxy-1,2,5-thiadiazole) derived from condensation of sulphametrole and varelaldehyde are reported and characterized based on elemental analyses, IR, solid reflectance, magnetic moment, molar conductance, and thermal analysis (TG). From the elemental analyses data, 1:1 metal complexes are formed having the general formulae [MCl3(HL)(H2O)]·3H2O (M=Cr(III), Fe(III)) and [MCl2(HL)(H2O)2]·yH2O (where M=Mn(II), Fe(II), Co(II), Ni(II), Cu(II)

Gehad G. Mohamed; M. A. Zayed; S. M. Abdallah

2010-01-01

356

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

Microsoft Academic Search

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 (CuN3O2) in which the ONO donor Schiff base is bonded to the Cu(II) in the basal plane. The N,N donor heterocyclic base

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

2011-01-01

357

Oxorhenium(V) complexes containing tridentate Schiff-base and monothiol coligands  

PubMed Central

The reaction of [n-(C4H9)4N][ReOBr4(OPPh3)] with the tridentate Schiff-base [HOC6H4C(H)NC6H4SH] allows for the isolation of [ReOBr{?3-(OC6H4C(H)NC6H4S)}] (1). The reaction of [n-(C4H9)4N][ReOBr4(OPPh3)] with [HOC6H4C(H)NC6H4SH] and the appropriate benzenethiol (C6H4X-4-SH) where X=H, Br, Cl, F, and OCH3 in methanol–acetonitrile treated with triethylamine has led to the isolation of a series of rhenium complexes of the type [ReO{?3-(OC6H4C(H)NC6H4S)} (?1-C6H4X-4-S)] (X=H (2), Br (3), Cl (4), F (5), and OCH3 (6)). Likewise, under similar reaction conditions, the use of benzylmercaptan ligands of the type (C6H4X-4-CH2SH) where X=H, Cl, F, and OCH3 has led to the isolation of a series of rhenium complexes of the type [ReO{?3-(OC6H4C(H)NC6H4S)} (?1-C6H4X-4-CH2S)] (X=H (7), Cl (8), F (9), and OCH3 (10)). The incorporation of the appropriate amine functionality into the substituent R of the monodentate ligand allows for the isolation of a cationic oxorhenium(V) species, namely, [ReO{?3-(OC6H4C(H)NC6H4S)} (?1-C5H4NH-2-S)][Br] (11).

Femia, Frank J.; Chen, Xiaoyuan; Babich, John W.; Zubieta, Jon

2010-01-01

358

Stereoconversion of amino acids and peptides in uryl-pendant binol schiff bases.  

PubMed

(S)-2-Hydroxy-2'-(3-phenyluryl-benzyl)-1,1'-binaphthyl-3-carboxaldehyde (1) forms Schiff bases with a wide range of nonderivatized amino acids, including unnatural ones. Multiple hydrogen bonds, including resonance-assisted ones, fix the whole orientation of the imine and provoke structural rigidity around the imine C==N bond. Due to the structural difference and the increase in acidity of the alpha proton of the amino acid, the imine formed with an L-amino acid (1-l-aa) is converted into the imine of the D-amino acid (1-D-aa), with a D/L ratio of more than 10 for most amino acids at equilibrium. N-terminal amino acids in dipeptides are also predominantly epimerized to the D form upon imine formation with 1. Density functional theory calculations show that 1-D-Ala is more stable than 1-L-Ala by 1.64 kcal mol(-1), a value that is in qualitative agreement with the experimental result. Deuterium exchange of the alpha proton of alanine in the imine form was studied by (1)H NMR spectroscopy and the results support a stepwise mechanism in the L-into-D conversion rather than a concerted one; that is, deprotonation and protonation take place in a sequential manner. The deprotonation rate of L-Ala is approximately 16 times faster than that of D-Ala. The protonation step, however, appears to favor L-amino acid production, which prevents a much higher predominance of the D form in the imine. Receptor 1 and the predominantly D-form amino acid can be recovered from the imine by simple extraction under acidic conditions. Hence, 1 is a useful auxiliary to produce D-amino acids of industrial interest by the conversion of naturally occurring L-amino acids or relatively easily obtainable racemic amino acids. PMID:18816560

Park, Hyunjung; Nandhakumar, Raju; Hong, Jooyeon; Ham, Sihyun; Chin, Jik; Kim, Kwan Mook

2008-01-01

359

Structure and spectroscopic characteristics of Schiff bases of salicylaldehyde with 2,3-diaminopyridine  

NASA Astrophysics Data System (ADS)

The Schiff bases 2-amino-3-salicylideneaminopyridine ( 1) and 2,3-bis(salicylideneamino)pyridine (bimorphous, 2a and 2b) were prepared and characterized by X-ray crystallography and by IR and NMR spectrometry. ( 1) C 12H 11N 3O, Mr = 213.240, monoclinic, space group P2 1/ c, a = 12.00(2), b = 6.594(3), c = 14.06(2) Å, ? = 104.90(8)°, V = 1075(2) Å 3, Z = 4, Dx = 1.317 g cm -3, ?(Mo K?) = 0.71073 Å, ? = 0.82 cm -1, F(000) = 448, T = 295 K, R = 0.047, Rw = 0.028 for 886 reflections with I -?( I). ( 2a) C 19H 15N 3O 2, Mr = 317.348 monoclinic, space group P2 1, a = 6.202(3), b = 17.622(7), c = 14.724(8) Å, ? = 91.85(3)°, V = 1608(1) Å 3, Z = 4 (two crystallographically independent molecules A and B), Dx = 1.311 g cm -3, ?(Mo K?) = 0.71073 Å, ? = 0.816 cm -1, F(000) = 664, T = 295 K, R = 0.058, Rw = 0.034 for 972 reflections with I > 3?( I). The angle between the benzene and the pyridine ring is 51.5(2)° in 1, whereas in 2a the corresponding angles are 51.1(4)° in molecule A and 51.8(4)° in molecule B. Molecules of 1 are connected in pairs by two centrosymmetric hydrogen bonds N?H⋯N Py of 3.024(5)Å. Intermolecular bonding of 1 does not take place in CHCl 3 solution. No evidence was found in the IR and NMR spectra for tautomeric interconversion of 1 and 2 into the ketoamine or for cyclization of 2 into the cyclic diamine.

Cimerman, Zvjezdana; Galeši?, Nikola; Bosner, Branka

1992-11-01

360

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

361

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

362

Is the Photoinduced Isomerization in Retinal Protonated Schiff Bases a Single- or Double-Torsional Process?  

NASA Astrophysics Data System (ADS)

Nonadiabatic photodynamical simulations are presented for the all-trans and 5-cis isomers of the hepta-3,5,7-trieniminium cation (PSB4) with the goal of characterizing the types of torsional modes occurring in the cis-trans isomerization processes in retinal protonated Schiff base (RPSB), the rhodopsin and bacteriorhodopsin chropomhore. Steric hindrance of these processes due to environmental effects have been modeled by imposing different sets of mechanical restrictions on PSB4 and studying its response in the photodynamics. Both the mechanism toward the conical intersection and the initial phase of the hot ground state dynamics has been studied in detail. A total of 600 trajectories have been computed using a complete active space self-consistent field wave function. Careful comparison with higher level methods has been made in order to verify the accuracy of the results. The most important mechanism driving restricted PSB4 isomerization in the excited state is characterized by two concerted twist motions (bipedal and closely related to it nonrigid bipedal) from which only one torsion tends to be continued during the relaxation into the ground state. The one-bond-flip is found to be important for the trans isomer as well. The main isomerization trend is a torsion around C5C6 (equivalent to C11C12 in RPSB) in the case of the cis isomer and around C3C4 (C13C14 in RPSB) in the case of the trans isomer. The simulations show an initial 70 fs relaxation into twisted regions and give an average internal conversion time of 130-140 fs, timings that are fully compatible with the general picture described by femtosecond transient absorption spectroscopic studies.

Szymczak, Jaroslaw J.; Barbatti, Mario; Lischka, Hans

2009-08-01

363

Synthesis, characterization, and biological-pharmacological evaluation of new phosphazenes bearing dioxybiphenyl and schiff base groups.  

PubMed

A new spirocyclophosphazene, 2,2-bis(2-formylphenoxy)-4,4,6,6-bis[spiro(2',2?-dioxy-1'-1?-biphenylyl)]cyclotriphosphazene (3), was obtained from the reaction of 2,2-dichloro-4,4,6,6-bis[spiro(2',2?-dioxy-1'-1?-biphenylyl)]cyclotriphosphazene (2) with 2-hydroxybenzaldehyde. New phosphazene derivatives bearing Schiff base and dioxybiphenyl groups have been synthesized by the reactions of 3 with different amines. The structures of the compounds were defined by elemental analysis, IR, (1) H, (13) C, and (31) P NMR spectroscopy. All the synthesized compounds were screened for their antibacterial activity against both types of Gram-negative and Gram-positive bacteria. The most potent antibacterial compound of this series was compound 12 which has the low MIC value of 3.75-0.9375?µg/mL. Both minimal inhibitory concentrations (MIC) and inhibition zones were determined in order to monitor the efficacy of the synthesized compounds. New compounds were also screened for anticonvulsant, CNS depressant, and sedative-hypnotic activity. After i.p. injection to mice at doses of 30, 100, and 300?mg/kg body weight phosphazenes were examined in the maximal electroshock-induced seizure (MES) and subcutaneous pentylenetetrazole (scPTZ) induced seizure models in mice. The neurotoxicity was assessed using the rotorod method. Compounds 4, 5, and 11 were found to be active in both MES screen and scPTZ screen at 0.5?h. All except 12 showed more than 44% decrease in locomotor activity after 1?h of compound administration via actophotometer screen. CNS-depressant activity screened with the help of the forced swim method resulted in some potent compounds. Except for 7 and 12 other tested compounds were found to exhibit potent CNS depressants activity as indicated by increased immobility time. PMID:22415712

Cil, Erol; Tanyildizi, Mehmet Ali; Ozen, Furkan; Boybay, Mustafa; Arslan, Mustafa; Gorgulu, Ahmet Orhan

2012-06-01

364

Theoretical spectroscopic study of seven zinc(II) complex with macrocyclic Schiff-base ligand.  

PubMed

Seven zinc complexes, which are [ZnL(1)](2+), [ZnL(2)](2+), [ZnL(3)](2+), [ZnL(4)](2+), [ZnL(5)](2+), [ZnL(6)](2+) and [ZnL(7)](2+), are studied as theoretically. Structural parameters, vibration frequencies, electronic absorption spectra and (1)H and (13)C NMR spectra are obtained for Zn(II) complexes of macrocyclic penta and heptaaza Schiff-base ligand. Vibration spectra of Zn(II) complexes are studied by using Density Functional Theory (DFT) calculations at the B3LYP/LANL2DZ. The UV-VIS and NMR spectra of the zinc complexes are obtained by using Time Dependent-Density Functional Theory (TD-DFT) method and Giao method, respectively. The agreements are found between experimental data of [ZnL(5)](2+), [ZnL(6)](2+) and [ZnL(7)](2+) complex ions and their calculated results. The geometries of complexes are found as distorted pentagonal planar for [ZnL(1)](2+), [ZnL(2)](2+) and [ZnL(3)](2+) complex ions, distorted tetrahedral for [ZnL(4)](2+) complex ion and distorted pentagonal bipyramidal for [ZnL(5)](2+), [ZnL(6)](2+) and [ZnL(7)](2+) complex ions. Ranking of biological activity is determined by using quantum chemical parameters and this ranking is found as: [ZnL(7)](2+)>[ZnL(6)](2+)>[ZnL(5)](2+)>[ZnL(3)](2+)>[ZnL(2)](2+)>[ZnL(1)](2+). PMID:24967540

Sayin, Koray; Kariper, Sultan Erkan; Sayin, Tuba Alagöz; Karaka?, Duran

2014-12-10

365

Dynamical friction effects on the photoisomerization of a model protonated Schiff base in solution.  

PubMed

Photoisomerization involving a conical intersection (CI) for a model protonated Schiff base (PSB) in modeled water and acetonitrile solvents is examined with the inclusion of energy- and momentum-transfer effects described via a generalized Langevin equation (GLE) frictional approach and surface-hopping dynamics. Short-time GLE frictional effects on the model's three coordinates, the intramolecular bond length alternation and torsional PSB coordinates and a solvent coordinate, eliminate several unphysical features associated with a no-friction inertial description and have the general feature of accelerating nonadiabatic transitions to the ground electronic state. The inertial prediction of equal probability formation of ground-state trans and cis isomer products subsequent to the Franck-Condon excitation of the ground cis isomer is replaced by the GLE prediction of a preferential higher proportion of ground-state trans isomer, that is, a successful cis to trans photoreaction. This preference is solvent-dependent and is enhanced in water solvent with its higher friction intensity and short time scales. For the fast water solvent motion, the nonadiabatic transitions to the S(0) ground state are centered around the CI seam (which is due to the solvent coordinate's role as a tuning coordinate), facilitating direct transitions to the ground-state trans isomer. In contrast, for the slower acetonitrile solvent motion, the decay occurs, on average, away from the CI seam in regions with a finite free-energy gap between the excited and ground states, resulting in reduced trans isomer production. Some directions for the extension of the model description are also discussed. PMID:20932049

Malhado, João Pedro; Spezia, Riccardo; Hynes, James T

2011-04-28

366

Morphology-controlled hydrothermal synthesis of MnCO{sub 3} hierarchical superstructures with Schiff base as stabilizer  

SciTech Connect

Graphical abstract: MnCO3 microcrystals with hierarchical superstructures were synthesized by using the CO2 in atmosphere as carbonate ions source and Schiff base as shape guiding-agent in water/ethanol system under hydrothermal condition. Highlights: {yields} The most interesting in this work is the use of the greenhouse gases CO{sub 2} in atmosphere as carbonate ions source to precipitate with Mn{sup 2+} for producing MnCO{sub 3} crystals. {yields} This work is the first report related to the small organic molecule Schiff base as shape guiding-agent to produce different MnCO{sub 3} hierarchical superstructures. {yields} We are controllable synthesis of the MnCO{sub 3} hierarchical superstructures such as chrysanthemum, straw-bundle, dumbbell and sphere-like microcrystals. {yields} The as-prepared MnCO{sub 3} could be used precursor to fabricate the Mn{sub 2}O{sub 3} hierarchical superstructures after thermal decomposition at high temperature. -- Abstract: MnCO{sub 3} with hierarchical superstructures such as chrysanthemum, straw-bundle, dumbbell and sphere-like were synthesized in water/ethanol system under environment-friendly hydrothermal condition. In the synthesis process, the CO{sub 2} in atmosphere was used as the source of carbonate ions and Schiff base was used as shape guiding-agent. The different superstructures of MnCO{sub 3} could be obtained by controlling the hydrothermal temperature, the molar ratio of manganous ions to the Schiff base, or the volume ratio of water to ethanol. A tentative growth mechanism for the generation of MnCO{sub 3} superstructures was proposed based on the rod-dumbbell-sphere model. Furthermore, the MnCO{sub 3} as precursor could be further successfully transferred to Mn{sub 2}O{sub 3} microstructure after heating in the atmosphere at 500 {sup o}C, and the morphology of the Mn{sub 2}O{sub 3} was directly determined by that of the MnCO{sub 3} precursor.

Hu, He; Xu, Jie-yan; Yang, Hong; Liang, Jie [Department of Chemistry, Shanghai Normal University, No. 100, Guilin Road, Shanghai 200234 (China)] [Department of Chemistry, Shanghai Normal University, No. 100, Guilin Road, Shanghai 200234 (China); Yang, Shiping, E-mail: shipingy@shnu.edu.cn [Department of Chemistry, Shanghai Normal University, No. 100, Guilin Road, Shanghai 200234 (China)] [Department of Chemistry, Shanghai Normal University, No. 100, Guilin Road, Shanghai 200234 (China); Wu, Huixia [Department of Chemistry, Shanghai Normal University, No. 100, Guilin Road, Shanghai 200234 (China)] [Department of Chemistry, Shanghai Normal University, No. 100, Guilin Road, Shanghai 200234 (China)

2011-11-15

367

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

368

Bacteriorhodopsin's M sub 412 intermediate contains a 13-cis,14-s-trans,15-anti-retinal Schiff base chromophore  

SciTech Connect

The structure of the retinal chromophore about the C{double bond}N and C{sub 14}-C{sub 15} bonds in bacteriorhodopsin's M{sub 412} intermediate has been determined by analyzing resonance Raman spectra of {sup 2}H and {sup 13}C isotopic derivatives. Normal mode calculations on 13-cis-retinal Schiff bases demonstrate that the C{sub 15}-D rock and N-C{sub Lys} stretch are strongly coupled for C{double bond}N-syn chromophores and weakly coupled for C{double bond}N-anti chromophores. When the Schiff base geometry is anti, the C{sub 25}-D rock appears as a localized resonance Raman active mode at {approx} 980 cm{sup {minus}1}, which is moderately sensitive to {sup 13}C substitution at positions 14 and 15 ({approx} 7 cm{sup {minus}1}) and insensitive to {sup 13}C substitution at the {epsilon} position of lysine. When the Schiff base geometry is syn, in-phase and out-of-phase combinations of the C{sub 15}-D rock and N-C{sub Lys} stretch are predicted at {approx} 1060 and {approx} 910 cm{sup {minus}1}, respectively. The in-phase mode is more sensitive to {sup 13}C substitution at positions 14 and 15 and at the {epsilon} position of lysine. Calculations and comparison with experimental data on dark-adapted bacteriorhodopsin indicate that the in-phase mode at {approx} 1060 cm{sup {minus}1} carries the majority of the resonance Raman intensity. The authors conclude that M{sub 412} contains a 13-cis,14-s-trans,15-anti chromophore. This result supports the recently proposed C-T model for the mechanism of the proton pump in bacteriorhodopsin.

Ames, J.B.; Fodor, S.P.A.; Gebhard, R.; Raap, J.; van den Berg, E.M.M.; Lugtenburg, J.; Mathies, R.A. (Univ. of California, Berkeley (USA))

1989-05-02

369

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

370

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; Aceña, José Luis; Soloshonok, Vadim A

2014-02-28

371

Synthesis, crystal structures and electronic properties of Schiff base nickel (II) complexes: Towards solvatochromism induced by a photochromic solute  

Microsoft Academic Search

Two new mononuclear nickel (II) complexes incorporating Schiff base ligands, bis(N-R-1-phenylethyl- or N-2-propyl-3,5-dichlorosalicydenaminato)nickel (II), have been synthesized and characterized. The former chiral brown paramagnetic complex adopts a compressed tetrahedral [NiN2O2] coordination geometry of ?(R,R) absolute configuration with the coordination bond angles of N–Ni–N=116.3(2)° and O–Ni–O=141.4(2)°. On the other hand, the latter green diamagnetic complex adopts a square planar trans-[NiN2O2] coordination

Takashiro Akitsu; Yasuaki Einaga

2005-01-01

372

DFT Studies on second-order nonlinear optical properties of mono (salicylaldiminato) Nickel(II) polyenyl Schiff base metal complexes  

NASA Astrophysics Data System (ADS)

Density function theory (DFT) B3LYP/6-31g(d)-finite field (FF) method was employed to investigate the second-order nonlinear optical (NLO) properties of Nickel(II) polyenyl Schiff base complexes and its polyenyl ligands. It is found that the complexes display higher second-order NLO responses than their ligands. An enhancement of second-order NLO properties of complexes because the Ni 2+ ion increased the electron densities distribution of coordinated atoms and adjacent carbon atoms in frontier molecular orbitals, and reduced the gaps between occupied and unoccupied orbitals. Thus the metal complexes display better second-order NLO responses.

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

2007-07-01

373

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?ütcü, Hatice; Agar, Guleray; Sar?, Nur?en

2014-06-01

374

Thermodecomposition Kinetics of Dy(III) Complex with Schiff Base Derived from Furfural and DL???Alanine  

Microsoft Academic Search

A new Schiff base complex of the composition [Dy(C8H8NO3)(NO3)(H2O)]NO3·H2O (C8H8NO3 = furfurylidenealanine) has been synthesized and characterized by elemental analyses, IR, UV and molar conductance. The thermodecomposition kinetics of the complex were investigated under non?isothermal condition. TG and DTG curves indicate that the complex decomposes in four steps. The kinetics of steps (1) and (3) were calculated by a combination of Achar

Yuhua Fan; Caifeng Bi; Jinying Li

2003-01-01

375

Biological and spectral studies of transition metal complexes with a quinquedentate Schiff base, 2,6-diacetylpyridine bis(thiocarbohydrazone)  

Microsoft Academic Search

Manganese(II), cobalt(II), and copper(II) complexes with a quinquedentate Schiff base, 2,6-diacetylpyridine bis(thiocarbohydrazone), have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibility, and IR, H NMR, C NMR, mass (for ligand), UV and Electron Paramagnetic Resonance spectroscopies. The complexes are [M(L)X]X, where M=Mn(II), Co(II), and Cu(II), L = 2,6-diacetylpyridine bis(thiocarbohydrazone), and X= and Oac. The ligand with five

Sulekh Chandra; Amit Kumar Sharma

2009-01-01

376

Phenyl-substituted copper di-Schiff base, a potent Cu 2Zn 2 superoxide dismutase mimic surviving competitive biochelation  

Microsoft Academic Search

[N,N?-bis(2-pyridyl-phenyl)methylene-1,4-butanediamine]-(N,N?,N?,N?)-copper(II), Cu(II)PuPhePy, a copper(II) di-Schiff base in both its chloride and perchlorate form, has been prepared and crystallized with a yield of 50 ± 10%. IR spectra confirmed the successful preparation. The electronic absorption ?690 was 136 M?1 cm?1. The EPR parameters g? = 2.048 and g? = 2.217 were in close agreement with the respective values of intact Cu2Zn2

Jörg Müller; Klaus Felix; Cäcilie Maichle; Edmund Lengfelder; Joachim Strähle; Ulrich Weser

1995-01-01

377

Synthesis, characterization, and thermal decomposition of fluorinated salicylaldehyde Schiff base derivatives (salen) and their complexes with copper(II)  

Microsoft Academic Search

Trifluoromethoxy functionalized copper(II) Schiff base complexes N,N?-bis(5-trifluoromethoxysalicylaldehyde)cyclohexanediiminatodiaquacopper(II) and N,N?-bis(5-trifluoromethoxysalicylaldehyde)phenylenediiminatocopper(II) were synthesized and characterized. Thermal decompositions\\u000a of the synthesized complexes were studied by thermogravimetry in order to evaluate their thermal stability and thermal decomposition\\u000a pathways. Three similar decomposition steps occurred for the two copper complexes. Mass losses and evolved gasses were characterized\\u000a by TG\\/DTA-MS. Kinetic parameters were calculated and the results

Göktürk Avsar; Hüseyin Altinel; Mustafa Kemal Yilmaz; Bilgehan Guzel

2010-01-01

378

Synthesis and characterization of tetradentate bis-Schiff base complexes of di- and tri-valent transition metals  

Microsoft Academic Search

The bis-Schiff bases of N2O2 dibasic ligands, H2La and H2Lb are synthesized by the condensation of ethylenediamine (a) and trimethylenediamine (b) with 6-formyl-7-hydroxy-5-methoxy-2-methylbenzo-pyran-4-one. The ligands are characterized using elemental analysis, IR, UV–Vis, H-NMR and mass spectroscopy. The ionization constant pKa values are determined spectrophotometrically. The H-NMR spectra of the ligands show the presence of phenolic coordinating groups. New complexes of

Aida L. El-Ansary; Hussein M. Abdel-Fattah; Nora S. Abdel-Kader

2008-01-01

379

Synthesis, characterization and crystal structures of di-three-coordinated copper(I) macrocyclic Schiff base complexes  

Microsoft Academic Search

The air-stable di-copper(I) complexes Cu2L(SCN)2 (1) and Cu2L(SCN)1.86I0.14 (2) of the N4 macrocyclic Schiff base ligand L have been synthesized and characterized by IR, elemental analysis, UV–Vis and crystal structure determination. X-ray analysis of the complexes shows an approximate distorted trigonal planar geometry around each copper(I) ion that is constructed from one N-bonded thiocyanate (or iodide in 2) group and

Ali Akbar Khandar; Ray J. Butcher; Marjan Abedi; Seyed Abolfazl Hosseini-Yazdi; Mehmet Akkurt; M. Nawaz Tahir

2011-01-01

380

A new Co(II) complex with N,O-donor Schiff base: Synthesis, structure and characterization  

Microsoft Academic Search

A new Co(II) complex with tridentate Schiff base ligand with a N,N,O donor set has been synthesized and characterized by single\\u000a X-ray technique and spectroscopic techniques. The thermochemical properties have been studied. X-ray structure analysis of\\u000a the title compound Co(II)L2 [HL = 2-methyl-6-(2?-hydroxybenzylideneamino) pyridine] shows that the polyhedron around Co(II) is a distorted tetrahedron,\\u000a and the self-assembly via intermolecular ?-?

L. Xu; Yu. V. Mironov; X. Qi; S.-J. Kim

2006-01-01

381

Dissociation constants of some Schiff bases and stability constants of their copper, cobalt, nickel and zinc complexes  

Microsoft Academic Search

The stoichiometry and stability constant of metal complexes with 4-(3-methoxy-salicylideneamino)-5-hydroxynaphthalene-2,7-disulfonic\\u000a acid monosodium salt (H2L) and 4-(3-methoxysalicylideneamino)-5-hydroxy-6-(2,5-dichlorophenylazo)-2,7-naphthalene disulfonic acid monosodium salt\\u000a (H2L1) were studied by potentiometric titration. The stability constants of H2L and H2L1 Schiff bases have been investigated by potentiometric titration and u.v.–vis spectroscopy in aqueous media. The dissociation\\u000a constants of the ligand and the stability constants of the metal

Mehmet Tunçel; Hayati Sar?

2007-01-01

382

Synthesis, crystal structure, and fluorescence properties of a two-dimensional copper(II) complex with Schiff base  

Microsoft Academic Search

A new Schiff base ligand C19H13NO5(H2L) was synthesized using 2-aminoterephthalic acid and 2-hydroxy-1-naphthaldehyde. A complex of this ligand [Cu(C19H11NO5)(C2H6O)]\\u000a n\\u000a was synthesized and characterized by IR, UV, fluorescence spectroscopy and X-ray diffraction single-crystal analysis. The\\u000a crystal crystallizes in the monoclinic system, space group Pbca with a = 8.7745(18), b = 18.613(4), c = 24.644(5) Å, V = 4024.9(14) Å3, Z

Y. H. Fan; Y. F. Wang; C. F. Bi; Q. Wang; X. Zhang; X. Y. Liu

2010-01-01

383

Synthesis and spectral characterization of homo-and hetero-dinuclear complexes with a new septadentate Schiff base ligand  

Microsoft Academic Search

Reaction between 3-formylsalicylic acid and bis-(2-aminophenyl)-disulphide yields a septadentate Schiff base with N2SO4 donor frame of which the inner compartment is N2SO2 and the outer is O2O2 type. It forms several complexes with inner copper centre and outer nontransition\\/transition metal ions. The complexes have\\u000a been characterised by elemental analyses, spectral (IR, absorption, diffused reflectance), thermal and magnetic data. Dinuclear\\u000a copper

J K Nag; D Das; S Pal; C Sinha

2001-01-01

384

Synthesis, crystal structures, and urease inhibition studies of two new Schiff-base copper complexes derived from n-butylamine  

Microsoft Academic Search

Two Schiff-base copper(II) complexes, bis(N-n-butyl-5-chlorosalicylaldiminato) copper(II) (1) and bis(N-n-butyl-4-methoxysalicylaldiminato) copper(II) (2), were synthesized and their solid-state structures were determined by X-ray crystallography. Complex 1 displays a distorted square-planar geometry, while 2 possesses square-planar geometry. Copper(II) complexes 1 and 2 showed strong inhibitory activity against jack bean urease (IC50?=?2.7, 3.5?µmol?L), compared with acetohydroxamic acid (IC50?=?63.00?µmol?L). A molecular modeling study was carried

Yuguang Li; Zuowen Li; Yang Liu; Xiongwei Dong; Yongming Cui

2011-01-01

385

Synthesis, crystal structures, and urease inhibition studies of two new Schiff-base copper complexes derived from n-butylamine  

Microsoft Academic Search

Two Schiff-base copper(II) complexes, bis(N-n-butyl-5-chlorosalicylaldiminato) copper(II) (1) and bis(N-n-butyl-4-methoxysalicylaldiminato) copper(II) (2), were synthesized and their solid-state structures were determined by X-ray crystallography. Complex 1 displays a distorted square-planar geometry, while 2 possesses square-planar geometry. Copper(II) complexes 1 and 2 showed strong inhibitory activity against jack bean urease (IC50?=?2.7, 3.5?µmol?L), compared with acetohydroxamic acid (IC50?=?63.00?µmol?L). A molecular modeling study was carried

Yuguang Li; Zuowen Li; Yang Liu; Xiongwei Dong; Yongming Cui

2012-01-01

386

Copper(II) complexes with chiral reduced Schiff bases: Helical self-assembly via intermolecular C–H?O interactions  

Microsoft Academic Search

Copper(II) complexes having the general formula [Cu(Ln)2] with the N,O-donor reduced Schiff bases N-(2-hydroxy-5-X-benzyl)-(R)-?-methylbenzylamine and N-(2-hydroxy-5-X-benzyl)-(S)-?-methylbenzylamine (X=Cl and Br) (HLn) are described. These chiral complexes crystallize in the noncentrosymmetric P212121 (X=Cl) and P21 (X=Br) space groups. In each case, self-assembly via intermolecular C–H?O interaction leads to a supramolecular helical superstructure.

Vamsee Krishna Muppidi; Sunirban Das; Pallepogu Raghavaiah; Samudranil Pal

2007-01-01

387

Effect of ligand substitution on DNA binding ability of two new square planar copper(II)–Schiff base complexes  

Microsoft Academic Search

Two terdentate NNO donor Schiff base ligands CH3C(OH)CHC(CH3)NCH2C5H4N [HL1] and C6H5C(OH)CHC(CH3)NCH2C5H4N [HL2] were used to synthesize two mononuclear square planar copper(II) complexes, [CuL1(CF3COO)] (1) and [CuL2(CF3COO)] (2). The complexes were characterized by elemental analyses, FT-IR, UV–vis spectral methods and their structures were established by single crystal X-ray diffraction study. The biochemical activity of the complexes towards DNA binding were performed

Dipali Sadhukhan; Aurkie Ray; Saurabh Das; Corrado Rizzoli; Georgina M. Rosair; Samiran Mitra

2010-01-01

388

Metal chelates of ligands containing the ONS donor grouping, part I. Metal chelates of Schiff bases derived from fluorinated ? -diketones and thiosemicarbazide  

Microsoft Academic Search

Summary The Schiff bases RC(OFl)=CFlC(CF3)=NNlJC(S)NH2 (R = 2-thienyl, Ph,p-BrC6H4,p-MeC6H4,p-MeOC6H4,m-McOC6H4, ß-naphthy], Pri) have been prepared by condensation of fluorinated ß-diketones with thiosemicarbazide. By the loss of one or two protons from their tautomeric iminothiol form RC(OH)=CHC(CF3)=NN=C(SH)NH2 the Schiff bases act as (i) doubly negatively charged ONS tridentate or (ii) singly negatively charged NS bidentate ligands, respectively. The Schiff bases give dimeric

Stanley E. Livingstone; Justin E. Oluka

1977-01-01

389

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

390

Synthesis and Characterization of a New Schiff Base and its Metal Complexes Derived from the Mannich Base, N-(1-piperidinobenzyl)acetamide  

Microsoft Academic Search

New neutral Schiff base complexes of Cu(II), Co(II), Ni(II), and Zn(II) derived from 4-aminoantipyrine and N-(1-piperidinobenzyl)acetamide (Mannich base) have been synthesized. The structural features of the complexes have been characterized by microanalytical data, IR, UV-Vis, H NMR, ESR, CV, TGA and powder XRD techniques. Electronic absorption spectra of the complexes indicate an octahedral geometry around the metal ion. The neutral

N. Raman; S. Ravichandran

2005-01-01

391

Novel Asymmetric Tetradentate Schiff Base Ligands Derived from 6-Metwia-Formyl4Hydroxy2-(1H)-Quinolone and Their Metal Complexes  

Microsoft Academic Search

Novel asymmetric, tetradentate, dibasic Schiff base ligands were synthesized by the condensation of the half-unit Schiff base ligand 3-[o-aminophenyliminomethyl]-4-hydroxy-6-methyl-2-(1H)-quinolone with acetylacetone and salicylaldehyde. Cu(II), Ni(II), UO2 (VI) and Fe(III) complexes of both ligands were prepared using different salts in the case of Cu(II) and Ni(II) cations The structures of the ligands and the complexes were elucidated by chemical analyses, IR,

Adel A. A. Emara

1999-01-01

392

Investigation of the solid-state conductivity and the potentiometric stability constant relationships of new amino acid-Schiff bases and their complexes  

Microsoft Academic Search

CuII, NiII and CoII complexes of new tridentate amino acid-Schiff bases derived from furfural and DL-alanine, DL-valine and DL-phenylalanine were prepared and characterized by analytical, spectroscopic, (i.r., u.v.–vis., 1H-n.m.r and 13C-n.m.r) techniques, molar conductivity, magnetic and thermal measurements. Protonation constants of the Schiff bases and stability constants of the complexes have been determined potentiometrically in water. Solid-state conductivities of the

Nur?en Sarì; Perihan Gürkan

2003-01-01

393

The Interaction of Nickel(II) and Copper(II) Schiff Base Complexes with Diorganotin(IV) Dichlorides in Acetonitrile: A Thermodynamic Study  

Microsoft Academic Search

Adduct formation of nickel(II) and copper(II) Schiff base complexes, (NiL) and (CuL), as donors with diorganotin(IV) dichlorides as acceptors has been investigated spectrophotometrically, in acetonitrile. L is ?,??-Me2-salen, N,N -ethylenebis(?-methylsalicylideneiminate) (1), ?,??-Me2-salpn, N,N -1,2-propylenebis(?-methylsalicylideneiminate) (2), ?,??-Ph2-salen, N,N -ethylenebis(?-phenylsalicylideneiminate) (3), and ?,??-Ph2-salpn, N,N -1,2-propylenebis(?-phenylsalicylidene- iminate) (4). The trend of adduct formation of the nickel(II) and copper(II) Schiff base complexes with a

Zahra Asadi; Mozaffar Asadi; Fatemeh Mosalanezhad

2011-01-01

394

Magnetic and catalytic properties of a new copper(II)–Schiff base 2D coordination polymer formed by connected helical chains  

Microsoft Academic Search

A dicyanamide bridged 2D polynuclear complex of copper(II) having molecular formula [Cu2(L)(?1,5-dca)2]n (1) has been synthesized using the Schiff base ligand N,N?-bis(salicylidene)-1,3-diaminopentane, (H2L) and sodium dicyanamide (dca). The complex presents a 2D hexagonal structure formed by 1,5-dca singly bridged helical chains connected through double 1,5-dca bridges. The chelating characteristics of the H2L Schiff base ligand results in the formation of

Dipali Sadhukhan; Aurkie Ray; Ray J. Butcher; Carlos J. Gómez García; Bülent Dede; Samiran Mitra

2011-01-01

395

Synthesis and Characterization of Copper(II), Nickel(II) and Cobalt(II) Complexes with Azo?Linked Schiff Base Ligands  

Microsoft Academic Search

Diazo compounds were prepared by coupling of benzenediazonium chloride ions with 4?amino?5?hydroxy?2,7?naphthalenedisulfonic acid mono sodium salt under alkaline conditions, and new Schiff bases H2L and H2L were then obtained by the condensation of 4?amino?5?hydroxy?6?(2,5?dicholorophenylazo)?2,7?naphthalene disulfonic acid disodium salt and 4?amino?5?hydroxy?6?(2?nitrophenylazo)?2,7?naphthalenedisulfonic acid disodium salt with o?vanillin. New Cu(II), Ni(II) and Co(II) complexes of the Schiff base ligands were also prepared and

Mehmet Tunçel; Selahattin Serin

2005-01-01

396

Synthesis and characterization of Ni(II), Cu(II) and Zn(II) complexes with new macrocyclic Schiff base ligands containing piperazine moiety  

Microsoft Academic Search

Two new macrocyclic Schiff base ligands L1 and L2 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 [NiL1](ClO4)2, [CuL1](ClO4)2 and [ZnL1](ClO4)2 were prepared from the reaction of a mixture

Hassan Keypour; Parisa Arzhangi; Nasibeh Rahpeyma; Majid Rezaeivala; Yalcin Elerman; Orhan Büyükgüngör; Laura Valencia; Hamid Reza Khavasi

2010-01-01

397

Synthesis and Structural Characterization of Two New Schiff Bases incorporating a Piperazine Skeleton, and their Reactions with Copper(II) Perchlorate  

Microsoft Academic Search

The synthesis of Schiff bases N,N??bis(4?dodecyloxy?benzylidene?N?propyl)?piperazine (2) and N,N??bis?[4?(4??octyloxy?benzoic)?ester?benzylidene?N?propyl]?piperazine (6) in a multistep process is reported. The intermediates as well as the products were characterized by elemental analysis, melting point and IR, H and C?NMR spectroscopy. The complex formation of these Schiff bases with copper(II) perchlorate resulted in disruption of the imino bond and yielded N,N??bis(3?aminopropyl)piperazineperchloratocopper(II) perchlorate, Cu(L)(ClO4)2, where L

Liliana Cseh; Ramona Tudose; Otilia Costisor; Ingo Pantenburg; Gerd Meyer; Wolfgang Linert

2008-01-01

398

Synthesis and Characterisation of Binuclear Cu(II), Ni(II) and Co(II) Chelates with Tetradentate Schiff Base Ligands Derived from 1,5Diaminonaphthalene  

Microsoft Academic Search

A new series of copper(II), nickel(II) and cobalt(II) chelates containing the binucleating tetradentate Schiff base ligands N,N?-bis(salicylidene)-1,5-diaminonaphthalene (H2L), N,N?-bis(3-methoxysalicylidene)-1,5-diaminonaphthalene (H2L?) and N,N?-bis(4-hydroxysalicylidene)-1,5-diaminonaphthalene (H2L) have been synthesized. These compounds have been characterized by elemental analyses, conductivity measurements, magnetic susceptibility, thermoanalyses (TG-DTA), infrared and electronic spectral data. The results suggest that the Schiff bases function as tetradentate ligands coordinating through the ONNO

Hüseyin Köksal; Mehmet Tümer; Selahattin Serin

1996-01-01

399

Synthesis and characterization of polystyrene-anchored monobasic bidentate Schiff base and its complexes with bi-, tri-, tetra- and hexavalent metal ions  

Microsoft Academic Search

A new monobasic bidentate ON donor Schiff base PS–LH2 (where PS–LH2 = polystyrene-anchored Schiff base obtained by condensation of chloromethylated polystyrene (containing 1.17 mmol of chlorine per gram of resin cross-linked with 2% divinylbenzene), 2-hydroxy-1-naphaldehyde and 4-aminosalicylic acid has been synthesized. PS–LH2 reacts with metal complexes to form polystyrene-anchored complexes: PS–LHM(CH3Coo) · DMF (where M = Cu, Zn, Cd, UO2),

D. Kumar; A. Syamal; L. K. Sharma

2008-01-01

400

The preparation, characterization, crystal structure and biological activities of some copper(II) complexes of the 2-benzoylpyridine Schiff bases of S-methyl- and S-benzyldithiocarbazate  

Microsoft Academic Search

The complexes [Cu(NNS)X] (HNNS represents the 2-benzoylpyridine Schiff bases of S-methyl- or S-benzyldithiocarbazate; X?Cl, Br, NO3) have been prepared and characterized by a variety of physico-chemical techniques. Magnetic and spectral evidence support a square-planar structure for the [Cu(Bp?SR)X] (Bp?SR=the benzoylpyridine Schiff bases; R?CH3, CH2C6H5; X?Cl, Br) and [Cu(Bp?SMe)NO3] complexes and a five-coordinate distorted square-pyramidal structure for the [Cu(Bp?SBz)NO3] complex. The

M. E. Hossain; M. N. Alam; J. Begum; M. Akbar Ali; M. Nazimuddin; F. E. Smith; R. C. Hynes

1996-01-01

401

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

PubMed

Metal Schiff-base complexes show biological activity but they are usually insoluble in water so four new water-soluble metal Schiff base complexes of Na2[M(5-SO3-1,2-salben]; (5-SO3-1,2-salben denoted N,N'-bis(5-sulphosalicyliden)-1,2-diaminobenzylamine and M=Mg, Mn, Cu, Zn) were synthesized and characterized. The formation constants of the metal complexes were determined by UV-Vis absorption spectroscopy. The interaction of these complexes with bovine serum albumin (BSA) was studied by fluorescence spectroscopy. Type of quenching, binding constants, number of binding sites and binding stoichiometries were determined by fluorescence quenching method. The results showed that the mentioned complexes strongly bound to BSA. Thermodynamic parameters indicated that hydrophobic association was the major binding force and that the interaction was entropy driven and enthalpically disfavoured. The displacement experiment showed that these complexes could bind to the subdomain IIA (site I) of albumin. Furthermore the synchronous fluorescence spectra showed that the microenvironment of the tryptophan residues was not apparently changed. Based on the Förster theory of non-radiation energy transfer, the distance between the donor (Trp residues) and the acceptor metal complexes was obtained. The growth inhibitory effect of complexes toward the K562 cancer cell line was measured. PMID:24996211

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

2014-12-10

402

Synthesis, structural, thermal studies and biological activity of a tridentate Schiff base ligand and their transition metal complexes.  

PubMed

Schiff base (L) ligand is prepared via condensation of pyridine-2,6-dicarboxaldehyde with -2-aminopyridine. The ligand and its metal complexes are characterized based on elemental analysis, mass, IR, solid reflectance, magnetic moment, molar conductance, and thermal analyses (TG, DTG and DTA). The molar conductance reveals that all the metal chelates are non-electrolytes. IR spectra shows that L ligand behaves as neutral tridentate ligand and bind to the metal ions via the two azomethine N and pyridine N. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Fe(III), Co(II), Ni(II), Cu(II), and Th(IV)) and tetrahedral (Mn(II), Cd(II), Zn(II), and UO2(II)). The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters, such as, E*, ?H*, ?S* and ?G* are calculated from the DTG curves using Coats-Redfern method. The synthesized ligand, in comparison to their metal complexes also was screened for its antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus pyogones and Fungi (Candida). The activity data shows that the metal complexes to be more potent/antibacterial than the parent Schiff base ligand against one or more bacterial species. PMID:21130026

Abd El-halim, Hanan F; Omar, M M; Mohamed, Gehad G

2011-01-01

403

Synthesis, structure, and single-molecule magnetic properties of rare-earth sandwich complexes with mixed phthalocyanine and Schiff base ligands.  

PubMed

Double- and quadruple-decker complexes of rare-earth metals with mixed phthalocyanine and Schiff base ligands have been synthesized and structurally and magnetically characterized. These complexes (see picture: Dy?pink, Ca?green, N?blue, C?black) extend the scope of sandwich-type tetrapyrrole-based rare-earth molecular materials. PMID:23281042

Wang, Hailong; Cao, Wei; Liu, Tao; Duan, Chunying; Jiang, Jianzhuang

2013-02-11

404

Complexes of a porphyrin-like N4-donor Schiff-base macrocycle.  

PubMed

A metal-free 16-membered N4-donor [1 + 1] Schiff-base macrocycle was isolated as HL(Pr)·2acid, by 1?:?1 condensation of diphenylamine-2,2'-dicarboxaldehyde (1), dipropylene triamine and an excess of either acetic or formic acid, or as HL(Pr)·(tosylic acid) when just one equivalent of tosylic acid was employed. Interestingly, the acid-free synthesis employed for the 14-membered analogue HL(Et) failed to generate pure HL(Pr) macrocycle, but nevertheless the crude product obtained was able to be used in subsequent complexation reactions to form five mononuclear complexes: Zn(II)L(Pr)(BF4)·H2O·0.5IPA (where IPA is isopropylalcohol), [Cu(II)L(Pr)](BF4), [Ni(II)L(Pr)](BF4), [Co(II)L(Pr)](BF4)·0.5H2O, [Fe(III)L(Pr)(NCS)2]·1.5H2O. Crystal structure determinations show that, like the HL(Et) analogues, [Ni(II)L(Pr)](BF4) features a square planar N4 coordinated Ni(II) centre and [Fe(III)L(Pr)(NCS)2]·0.15MeOH·0.2H2O features an octahedral N6 coordinated Fe(III) centre (two NCS anions bound axially). In both cases the N4-donor macrocycle is bound equatorially to the metal ion. Cyclic voltammograms of the BF4 complexes were carried out in MeCN vs. 0.01 mol L(-1) AgNO3/Ag and revealed multiple redox processes. The Zn(II) complex exhibits multiple ligand-centered redox processes. Interestingly, [Ni(II)L(Pr)](BF4) has two reversible redox processes, at E(m) = +0.38 (?E = 0.06 V) and -1.7 V (?E = 0.06 V), whereas the previously reported analogue [Ni(II)L(Et)](BF4) had a process at E(pc) = +0.59 V with only a weak return wave. Likewise, [Cu(II)L(Pr)](BF4) has a reversible process, at E(m) = -1.17 V (?E = 0.06 V) plus a process at E(pc) = +0.45 V, whereas previously reported [Cu(II)L(Et)](BF4) only featured irreversible processes, with the oxidation occurring at E(pc) = +0.50 V. PMID:23400271

Wilson, Rajni K; Brooker, Sally

2013-06-14

405

Targeted inhibition of Snail family zinc finger transcription factors by oligonucleotide-Co(III) Schiff base conjugate  

PubMed Central

A transition metal complex targeted for the inhibition of a subset of zinc finger transcription factors has been synthesized and tested in Xenopus laevis. A Co(III) Schiff base complex modified with a 17-bp DNA sequence is designed to selectively inhibit Snail family transcription factors. The oligonucleotide-conjugated Co(III) complex prevents Slug, Snail, and Sip1 from binding their DNA targets whereas other transcription factors are still able to interact with their target DNA. The attachment of the oligonucleotide to the Co(III) complex increases specificity 150-fold over the unconjugated complex. Studies demonstrate that neither the oligo, or the Co(III) Schiff base complex alone, are sufficient for inactivation of Slug at concentrations that the conjugated complex mediates inhibition. Slug, Snail, and Sip1 have been implicated in the regulation of epithelial-to-mesenchymal transition in development and cancer. A complex targeted to inactivate their transcriptional activity could prove valuable as an experimental tool and a cancer therapeutic.

Harney, Allison S.; Lee, Jiyoun; Manus, Lisa M.; Wang, Peijiao; Ballweg, David M.; LaBonne, Carole; Meade, Thomas J.

2009-01-01

406

Ligating behaviour of Schiff base ligands derived from heterocyclic ?-diketone and ethanol or propanol amine with oxovanadium (IV) metal ion  

NASA Astrophysics Data System (ADS)

Synthesis and evaluation of six new oxovanadium (IV) complexes, formed by the interaction of vanadyl sulphate pentahydrate and the Schiff base, viz.; (HL 1)-(HL 3) and (HL 4)-(HL 6) such as 5-hydroxy-3-methyl-1(2-chloro)phenyl-1H-pyrazolone-4-carbaldehyde (I), 5-hydroxy-3-methyl-1(3-chloro)phenyl-1H-pyrazolone-4-carbaldehyde (II) and 5-hydroxy-3-methyl-1(3-sulphoamido)phenyl-1H-pyrazolone-4-carbaldehyde (III) with ethanol amine and propanol amine, respectively, in aqueous ethanol medium. The ligands and their Schiff base ligands have been characterized by elemental analyses, IR and 1H NMR. The resulting complexes have been characterized by elemental analyses, IR, 1H NMR, mass, electronic, electron spin resonance spectra, magnetic susceptibility measurement, molar conductance and thermal studies. The IR spectral data suggest that the ligand behaves as a dibasic bidentate with ON donor sequence towards metal ion. The molar conductivity data show them to be non-electrolytes. From the electronic, magnetic and ESR spectral data suggest that all the oxovanadium (IV) complexes have distorted octahedral geometry.

Thaker, B. T.; Barvalia, R. S.

2009-12-01

407

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

408

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) Å, b = 22.340(5) Å, c = 13.528(5) Å, ? = 92.882(5)°, V = 1325.7(16) Å3, 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.

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

2014-06-01

409

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

410

Synthesis, physicochemical studies, embryos toxicity and DNA interaction of some new Iron(II) Schiff base amino acid complexes  

NASA Astrophysics Data System (ADS)

New Fe(II) Schiff base amino acid complexes derived from the condensation of o-hydroxynaphthaldehyde with L-alanine, L-phenylalanine, L-aspartic acid, L-histidine and L-arginine were synthesized and characterized by elemental analysis, IR, electronic spectra, and conductance measurements. The stoichiometry and the stability constants of the complexes were determined spectrophotometrically. The investigated Schiff bases exhibited tridentate coordination mode with the general formulae [Fe(HL)2]·nH2O for all amino acids except L-histidine. But in case of L-histidine, the ligand acts as tetradentate ([FeL(H2O)2]·2H2O), where HL = mono anion and L = dianion of the ligand. The structure of the prepared complexes is suggested to be octahedral. The prepared complexes were tested for their toxicity on chick embryos and found to be safe until a concentration of 100 ?g/egg with full embryos formation. The interaction between CT-DNA and the investigated complexes were followed by spectrophotometry and viscosity measurements. It was found that, the prepared complexes bind to DNA via classical intercalative mode and showed a different DNA cleavage activity with the sequence: nhi > nari > nali > nasi > nphali. The thermodynamic Profile of the binding of nphali complex and CT-DNA was constructed by analyzing the experimental data of absorption titration and UV melting studies with the McGhee equation, van't Hoff's equation, and the Gibbs-Helmholtz equation.

Abdel-Rahman, Laila H.; El-Khatib, Rafat M.; Nassr, Lobna A. E.; Abu-Dief, Ahmed M.

2013-05-01

411

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

412

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

413

A new nano-structured Ni(II) Schiff base complex: synthesis, characterization, optical band gaps, and biological activity  

NASA Astrophysics Data System (ADS)

New Ni(II) Schiff base complexes [{Ni(L)(H2O)Cl} where HL = 2-((pyridin-3-ylmethylene)amino)phenol] have been synthesized using the reflux and sonochemical methods. The nickel oxide NiO nanopowder was obtained from the metal complexes after calcination at 650 °C for 2 h. The Schiff base complexes and NiO powders were characterized in detail. The HL and its metal complexes were depicted high activity towards microorganism and breast carcinoma cells. The inhibitory activity against breast carcinoma (MCF-7) were detected with IC50 = 5.5, 12.5 and 9.6 for HL, complex (1) and complex (2), respectively. The optical band gap energy was 3.6, 3.0 and 2.37 eV for Ni complexes (1), (2) and NiO, respectively. The microstructure of the formed NiO powders appeared as cubic-like structure. Furthermore, magnetic properties of NiO sample were identified and paramagnetic property was found at a room temperature. The saturation magnetization and coercive force for the NiO sample were 0.47 emu/g and 42.68 Oe, respectively.

Rashad, M. M.; Hassan, A. M.; Nassar, A. M.; Ibrahim, N. M.; Mourtada, A.

2014-05-01

414

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.

415

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

416

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.

Abdulghani, Ahlam Jameel; Khaleel, Asmaa Mohammed Noori

2013-01-01

417

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

PubMed

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 CN 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 OH?O and intramoleculer NH?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)Å, b=22.340(5)Å, c=13.528(5)Å, ?=92.882(5)°, V=1325.7(16)Å(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. PMID:24657931

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

2014-06-01

418

A new carbazole-based Schiff-base as fluorescent chemosensor for selective detection of Fe3+ and Cu2+  

NASA Astrophysics Data System (ADS)

A new carbazole-based Schiff-base (1) as a multi-functional fluorescent chemosensor was designed, synthesized and characterized, which can selectively recognized Fe3+ and Cu2+ ions over a number of other metal ions. Compound 1 could detect Fe3+ and Cu2+ by UV-Vis method and fluorescence method. The stoichiometry ratio of 1-Fe3+ and 1-Cu2+ are 2:1 and 1:1, respectively, by the method of Job's plot. Moreover, the detection limits were calculated to be 4.23 × 10-6 mol/L for Fe3+ ion and 5.67 × 10-6 mol/L for Cu2+ ion. In the presence of Fe3+/Cu2+ ions, the fluorescence enhancement was attributed to the inhibited Cdbnd N isomerization and the obstructed excited state intramolecular proton transfer (ESIPT) of compound 1. At the same time, the interactions of compounds 1 with other ions were also investigated and unobvious UV-Vis absorption and fluorescence spectral changes were observed. Thus a new kind of chemosensor for Fe3+/Cu2+with high sensitivity and selectivity was introduced.

Yang, Lianlian; Zhu, Weiju; Fang, Min; Zhang, Qing; Li, Cun

2013-05-01

419

New acyclic 1,2,4-triazole-based Schiff base hydrazone: synthesis, characterization, spectrophotometric and computational studies.  

PubMed

A new 1,2,4-triazole-based Schiff base hydrazone with N, O, S donor set of atoms, H(4)L, has been prepared by condensation reaction of N,N'-bis(3-formyl-5-methylsalicylidene)ethane-1,2-diamine, H(2)L, with 4-amino-3-(4-pyridyl)-5-mercapto-1,2,4-triazole. The structure of H(4)L was characterized by using FT-IR, UV-Vis and (1)H NMR spectroscopic methods as well as elemental analysis data. The formation constants of copper(II), cadmium(II), mercury(II) and silver(I) complexes of H(4)L in DMSO were calculated using a hard model chemometrics method applying the spectrophotometric data. The protonation constants of H(4)L were also measured in DMSO-water (1:10) mixture. Furthermore, (1)H chemical shifts of H(4)L were studied by the gauge independent atomic orbital (GIAO) and continuous set of gauge transformations (CSGTs) methods at the level of density functional theory using B3LYP/6-311++G(*) basis sets in gas phase. The computed chemical shifts are in reasonably good agreement with the experimental data. PMID:23321219

Khanmohammadi, Hamid; Erfantalab, Malihe; Azimi, Golamhassan

2013-03-15

420

Synthesis, spectroscopic characterization and DNA nuclease activity of Cu(II) complexes derived from pyrazolone based NSO-donor Schiff base ligands  

Microsoft Academic Search

Two neutral mononuclear Cu(II) complexes have been prepared in EtOH using Schiff bases derived from 4-toluoyl pyrazolone and thiosemicarbazide. Both the ligands have been characterized on the basis of elemental analysis, IR, 1H NMR, 13C NMR and mass spectral data. The molecular geometry of one of these ligands has been determined by single crystal X-ray study. It reveals that these

Komal M. Vyas; Rushikesh G. Joshi; R. N. Jadeja; C. Ratna Prabha; Vivek K. Gupta

2011-01-01

421

X-ray and DFT-calculated structures of a vanadyl Schiff base complex: (methanol-?O)[2-methoxy-6-({2-[(2-oxido-3-methoxybenzylidene)amino]benzyl}iminomethyl)phenolato-?4O1,N,N,O1']oxidovanadium(IV) monohydrate.  

PubMed

The central V(V) atom in the title mononuclear oxovanadium complex, [VO(C(23)H(20)N(2)O(4))(CH(3)OH)]·H(2)O, has a distorted octahedral coordination. Two N atoms and two O atoms of the Schiff base define the base of the bipyramid and two O atoms are in the apical positions, one from vanadyl and the second from methanol. Density functional theory (DFT) calculations were performed for the title complex and its ligand to compare their geometry in the solid and gas phases. Additional analyses were made of the changes in the geometry of the ligand during complex formation. The HOMA (harmonic oscillator model of aromaticity) descriptor of ?-electron delocalization was calculated to estimate the aromaticity of the benzene rings in the title complex and its ligand. PMID:22669188

Kurzak, Krzysztof; Ejsmont, Krzysztof; Koprek, Katarzyna

2012-06-01

422

Synthesis, structure, magnetic properties and DFT calculations of two hydroxo-bridged complexes based on Mn(III)(Schiff-Bases).  

PubMed

Two hydroxo-bridged complexes, {[Mn(III)(3-CH(3)O)salen](2)[Cr(III)(salen)(OH)(2)]}ClO(4)·6H(2)O (1) and {[Mn(III)(5-CH(3))salen](2)(OH)}ClO(4)·3H(2)O (2) [salen = N,N'-ethylenebis(salicylideneiminato) dianion], have been synthesized by the hydrolysis of the corresponding Mn(III)(Schiff-Bases) derivatives and [Cr(salen)(H(2)O)(2)]Cl precursors. X-Ray structure characterization reveals the discrete linear arched trinuclear structure of 1 and the 1D chain arrangement of 2. Magnetic experimental data and density functional theory (DFT) calculations both indicate the dominant antiferromagnetic interaction mediated by the hydroxo-bridges in both 1 and 2. Frequency-dependent AC susceptibilities reveal slow relaxation of 1 in low temperature. It is worth noting that the structure and magnetic properties of 1 is comparable to a reported cyano-bridged SMM, K[(5-Brsalen)(2)(H(2)O)(2)Mn(2)Cr(CN)(6)]·2H(2)O. PMID:21541410

Zhou, Hong-Bo; Wang, Hui-Sheng; Chen, Ying; Xu, Yong-Lu; Song, Xiao-Jiao; Song, You; Zhang, Yi-Quan; You, Xiao-Zeng

2011-06-14

423

Spectroscopic, colorimetric and theoretical investigation of salicylidene hydrazine based reduced Schiff base and its application towards biologically important anions.  

PubMed

A reduced Schiff base anionic receptor 1 [N,N'-bis-(2-hydroxy-5-nitro-benzyl)hydrazine] has been synthesized, characterized and reported as a selective chromogenic receptor for fluoride, acetate and phosphate anions over the other tested anions such as chloride, bromide, iodide and hydrogensulphite. Colorimetric naked-eye detection and UV-vis absorption spectroscopic techniques were used to distinguish the recognition behaviours towards various anions. The receptor-anion complexation mainly occurs via hydrogen bonding interactions which facile to generate the charge transfer band in the UV-vis spectra and cause large bathochromic shift as well as naked-eye colour change. Complexation stoichiometry, binding constant and free energy change due to complex formation were determined from Benesi-Hildebrand plot. The binding constant and the free energy change values are well interactive for spontaneous complexation. The experimental results have been correlated with the theoretical calculations using B3LYP hybrid functional and 6-311++G(d,p) basis set for both the receptor and complex by Density Functional Theory (DFT) method. PMID:22446759

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

2012-06-15