Bidentate Schiff Base Ligand Research Articles

Synthesis, characterization, in vitro antimicrobial and cytotoxic studies of Co(II), Ni(II), Cu(II), and Zn(II) complexes obtained from Schiff base ligands of 1, 2, 3, 4‐tetrahydro‐naphthalen‐1‐ylamine

The transition metal complexes of Co(II), Ni(II), Cu(II) and Zn(II) with bidentate Schiff base ligands (HL1−5) were obtained from condensation of 1, 2, 3, 4‐tetrahydro‐naphthalen‐1‐ylamine with methanolic solution of 3‐hydroxy‐salicylaldehyde, 4‐hydroxy‐salicylaldehyde, 5‐bromo‐salicylaldehyde, 3,5‐dibromo‐salicylaldehyde, and 2‐hydroxy‐1‐napthaldehyde. The synthesized compounds were structurally elucidated by spectral and physical methods. The spectral characterization emphasized bidentate nature (NO) of Schiff base ligands which gets chelated with metal via nitrogen atom of imine group and deprotonated oxygen of salicylaldehyde/2‐hydroxy‐1‐napthaldehyde group to form octahedral geometry around metal atom. Thermal results supported that the complexes are stable upto 200°C leaving metal oxide as an end products. The reported compounds (1–25) in this series were screened against the bacterial strains, that is, two Gram positive: Bacillus subtilis and Staphylococcus aureus, two Gram negative: Pseudomonas aeruginosa and Escherichia coli, and two fungal strains: Candida albicans and Aspergillus niger and their results that indicated moderate to good activity with compounds 20 and 21 having good antimicrobial activity (minimum inhibitory concentration [MIC] value 0.0269–0.0067 μmol/ml) as compared with control drugs ciprofloxacine and fluconazole. Furthermore, cytotoxic studies of synthesized compounds were carried out against three human cancer cell lines: HCT‐116 (colon), A549 (alveolar), and MCF‐7 (breast) using standard drug paclitaxel. The results demonstrated that compounds 1 (IC50 values = 12.93, 15.13, 17.24), 3 (11.9, 9.29, 12.64), 9 (17.06, 20.06, 22.87), 14 (16.21, 18.47, 20.00), and 25 (17.54, 17.21, 20.23) for three cancer cell lines were found to be most potent candidates among the synthesized compounds.

Synthesis and structural studies of Pd(II) complexes of bidentate Schiff bases and their catalytic activities as pre-catalysts in the Mizoroki-Heck reaction

Pd(II) complexes 5a-u were synthesized from the bidentate Schiff base ligands 4a-u and Pd(OAc)2 in acetonitrile under an argon atmosphere and their catalytic activities were evaluated in the Mizoroki-Heck reaction. The bidentate Schiff base ligands 4a-u were synthesized by the condensation of 3,5-di-tert-butylsalicylaldehyde, 3-tert-butylsalicylaldehyde, 5-tert-butylsalicylaldehyde or salicylaldehyde with aniline or its derivatives. The Pd(II) Schiff base complexes were characterized by 1H NMR, 19F NMR, 13C NMR and FT-IR spectroscopy, HRMS and CHNS analysis. The molecular structures of complexes 5d and 5u were confirmed by the single crystal XRD method. The trans-[Pd(II)(N,O)2] complexes were obtained after the complexation of the ligands derived from condensation of 3,5-di-tert-butylsalicylaldehyde and aniline, 2-methylaniline, 2-fluoroaniline, 2-bromoaniline, 2-hydroxyaniline, 4-tert-butylaniline or 2,3,4,5,6-pentafluoroaniline, 5-tert-butylsalicylaldehyde and aniline or 4-methoxyaniline, and salicylaldehyde and aniline, 2-methoxyaniline or 4-methoxyaniline. A mixture of cis- and trans-(N,O)2Pd(II) complexes were obtained with the ligands derived from 3,5-di-tert-butylsalicylaldehyde and 4-methylaniline, 4-fluoroaniline, 4-bromoaniline, 4-chloroaniline, 2-methoxyaniline, 4-methoxyaniline or 4-hydroxyaniline, and 3-tert-butylsalicylaldehyde and aniline or 4-methoxyaniline. The interconversions of the cis–trans isomers of the Pd(II) complexes show that the thermal stability of the cis-Pd(II) and trans-Pd(II) complexes is dependent on the structure of the ligands in acetonitrile. The complex 5a (5 mol%) acts as an efficient pre-catalyst for the Mizoroki-Heck reaction of aryl halide (iodide and bromide) with alkenes (styrene and acrylate) using NaHCO3 as a base in DMF at 140 °C, where the corresponding trans-alkenes were afforded in 21–99% yields.

Synthesis, spectral studies and antimicrobial evaluation of transition metal complexes of bidentate Schiff base ligands derived from 4-amino quinoline

Coordination compounds of Co(II) , Ni(II), Cu(II) and Zn(II) of the type [M(L1-2)2(H2O)2] were obtained from Schiff base ligands [HL1-2] by the condensation reaction of 5-bromosalicyldehyde/5-chlorosalicyldehyde with 4-amino quinoline using methanol as a solvent in (1:1) molar ratio. The metal complexes were synthesized by reacting the aqueous methanolic solution of metal acetates M(CH3COO)2xH2O with the hot methanolic solution of their respective Schiff base ligands in (1:2) molar ratio. Various physicochemical techniques i.e. elemental analysis, molar conductance measurements, magnetic moment studies and different spectral studies (1H NMR, 13C NMR, UV–Vis, FT-IR, ESR) and mass spectrometry were used for characterization of compounds. The spectral data confirmed the bidentate nature (NO) of Schiff base ligands coordinating through nitrogen atom of azomethine group and oxygen atom of hydroxyl group resulting in the formation of octahedral geometry of all metal complexes. The Schiff base ligands and their transition metal complexes were screened against two gram-positive bacterial species i.e. (S. aureus, B. subtilis), two-gram negative bacterial species i.e. (E. coli, P. aeruginosa) and two fungal species (A. niger and C. albicans) using serial dilution method with ciprofloxacin and fluconazole as reference drug. The results obtained from antimicrobial studies showed that metal complexes are more active than their respective Schiff base ligands. Complex 5 and 6 are potent antimicrobial agent.

New bidentate Schiff base ligands derived from histidine and their metal complexes: synthesis, structural analysis, antibacterial and antioxidant evaluation

New bidentate Schiff base ligands derived from histidine and their metal complexes: synthesis, structural analysis, antibacterial and antioxidant evaluation

Synthesis and characterization of some novel complexes of Pd(II) and Pt(II) with bidentate Schiff base ligand

A novel series of Pd(II) and Pt(II) complexes with Schiff base ligand 2-(pyridine-2′-carbaldehydeimino) pyrazine have been synthesized and characterized by micro elemental analysis, molar conductivity, magnetic susceptibility, FTIR, NMR and electronic absorption spectra. General molecular formula of the complexes has been found to be [M(L)(B)2] where M= Pd(II) and Pt(II) cations L=Schiff base and B= bases such as water, ammonia, pyridine and ɑ-picoline. All the bases contain nitrogen and oxygen as their donor sites. The molar conductance values of metal complexes suggest their electrolytic nature. On the basis of elemental analysis, molar conductance, magnetic moment measurements and spectral data complexes were proposed to be square planar.

N-((1H-Pyrrol-2-yl)methylene)-6-methoxypyridin-3-amine and Its Co(II) and Cu(II) Complexes as Antimicrobial Agents: Chemical Preparation, In Vitro Antimicrobial Evaluation, In Silico Analysis and Computational and Theoretical Chemistry Investigations.

Researchers are interested in Schiff bases and their metal complexes because they offer a wide range of applications. The chemistry of Schiff bases of heterocompounds has got a lot of attention because of the metal’s ability to coordinate with Schiff base ligands. In the current study, a new bidentate Schiff base ligand, N-((1H-pyrrol-2-yl)methylene)-6-methoxypyridin-3-amine (MPM) has been synthesized by condensing 6-methoxypyridine-3-amine with pyrrole-2-carbaldehyde. Further, MPM is used to prepare Cu(II) and Co(II) metal complexes. Analytical and spectroscopic techniques are used for the structural elucidation of the synthesized compounds. Both MPM and its metal complexes were screened against Escherichia coli, Bacillus subtilis, Staphylococcus aureus and Klebsiella pneumoniae species for antimicrobial studies. Furthermore, these compounds were subjected to in silico studies against bacterial proteins to comprehend their best non-bonded interactions. The results confirmed that the Schiff base ligand show considerably higher binding affinity with good hydrogen bonding and hydrophobic interactions against various tested microbial species. These results were complemented with a report of the Conceptual DFT global reactivity descriptors of the studied compounds together with their biological scores and their ADMET computed parameters.

Aziridination of olefins mediated by a [CuI(L1)2]+ complex via nitrene transfer reaction

Copper-catalyzed aziridination of alkenes is dominated in the literature compared to any other metal catalysts. This catalytic reaction is believed to be mediated by the elusive Cu-nitrene intermediate. However, analytical characterization of this intermediate is extremely scarce in the literature. In this article, we intend to shed the light on the electronic structure of the Cu-nitrene intermediate. The reaction of Cu(I) salt in the presence of the redox-active bidentate Schiff base ligand (C21H20N2; L1) led us to isolate a monomeric copper(I) complex with the molecular formula of [Cu(L1)2]ClO4. 2C6H6 (1), which was structurally characterized. 1 behaves as an excellent catalyst that promotes the nitrene group transfer to the variety of alkenes in the presence of (N-(p-tolylsulfonyl)imino)phenyliodinane (PhINTs). The intermediate generated from 1 by the addition of PhINTs shows an m/z peak at 832.3079 g/mol which corresponds to an M+ ion peak of the intermediate with the molecular formula of [(L1)2CuII-NTs]+ (where Ts = Tosyl). Further, based on the detailed experimental studies (in-situ UV–Vis measurement and X-band EPR measurements) we propose that the active catalyst that possesses the copper ion in its +2 oxidation state under our experimental condition, whose electronic structure can be best described as [(L1)2CuII-NTs]+ nitrene radicals. The optimized structure of the Cu-nitrene intermediate suggests that the triplet state was found to be the ground state. Besides, we propose a mechanism for this catalytic reaction.

Synthesis, Spectral Characterization, Crystal Structure and Antibacterial Activity of dichloro-{2-[(4-fluorophenyl)iminomethyl]pyridine-κ2N,N'}mercury(II)

The title complex has been prepared using (4-Fluoro-phenyl)-pyridin-2-ylmethylene-amine bidentate Schiff base ligand (L) and HgCl2. The Hg(II) center in the title compound, [HgCl2(C12H9FN2)], is covalently bonded to three Cl atoms and two N atoms of the diimine ligand. Mercury ion mononuclear fragment that forms a polymeric structure due to bridging chloride ligands is in a distorted trigonal–bipyramidal coordination environment formed by the bis-chelating N-heterocyclic ligand, two bridging Cl ligands and one terminal Cl ligand. One of the bridging Hg—Cl bonds is significantly longer than the other. In the crystal, weak C—H.....Cl hydrogen bonds are observed in addition to π-π stacking interactions. It crystallizes in the Orthorhombic space group P212121 with a = 7.2248 (3) Å, b = 8.7713 (3) Å, c = 20.0217 (7) Å, α = 90.00°, β = 90.00, γ = 90.00°, V = 1268.79(8) Å3, R1 = 0.023 and wR2= 0.062 [I > 2σ(I)] respectively. The antibacterial activities of the complex, ligand and metal salt were tested against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli studied by disk diffusion method.

Bioactive N and O Donor Atom of Bidentate Schiff Base Ligands from Chitosan Biopolymer and its Ruthenium(Iii) Complexes an Enhanced Antioxidant Activity

Bioactive N and O Donor Atom of Bidentate Schiff Base Ligands from Chitosan Biopolymer and its Ruthenium(Iii) Complexes an Enhanced Antioxidant Activity

Synthesis, spectroscopic and antimicrobial studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes derived from benzoic acid bidentate Schiff base ligand

The Schiff base was synthesized by condensation of 2-hydroxy-1-naphthaldehyde with 3- aminobenzoic acid in 1:1 molar ratio. The Schiff base ligand formed complexes with Co (II), Ni (II), Cu (II) and Zn (II) acetate via mechanochemical synthesis. The synthesized compounds were characterized by solubility test, thermal analysis, FT-IR, powder x-ray diffraction, molar conductance measurement, magnetic susceptibility and elemental analysis. The Schiff base has a melting point of 190 oC. The decomposition temperature of complexes was found to be in the range 289 – 302 oC. The Schiff base and its metal (II) complexes were soluble in DMF, DMSO and sparingly soluble in acetonitrile, chloroform, diethyl ether and insoluble in n-hexane which indicate the polar nature of the synthesized compounds. The IR spectral analysis of the free Schiff base shows a band at 1622 cm-1, assigned to v(C=N) stretching vibrations. This band was shifted in the spectra of complexes (1607 – 1633 cm-1), indicating coordination of the Schiff base to the metal ion through the azomethine group. The molar conductance of complexes determined are in the range 9.51 – 14.87 Ohm-1cm2mol-1 which indicate the non-electrolytic nature in DMF. Magnetic susceptibility measurements of Co (II), Ni (II) and Cu (II) complexes exhibit a magnetic moment in the range 1.25 – 3.08 BM. The values correspond to square-planar geometry. The magnetic moment value of Zn (II) complex indicates a diamagnetic behaviour. The elemental analysis of the complexes for C, H and N determined showed that the observed and the calculated percentages of the elements are in good agreement.

Evaluation of in vitro anticancer, antimicrobial and antioxidant activities of new Cu(II) complexes derived from 4(3H)-quinazolinone: Synthesis, crystal structure and molecular docking studies

Present study describes synthesis of a series of Cu(II) metal complexes (C1 - C3) of bidentate Schiff base ligands (L1 - L3) derived from the condensation reaction of 3-amino-2-methyl-4(3H)quinazolinone with 2-chlorobenzaldehyde, 4-bromobenzaldehyde and 2-nitrobenzaldehyde. The structural characterization of synthesized compounds has been analyzed on the basis of FT-IR, UV-Visible, 1H NMR and mass spectroscopy. The orthorhombic structure of the L3 is determined by X-ray crystallographic analysis. In silico analysis of all compounds against various protein targets prove to have better interaction parameters in case of c-MET and VEGFR, thus in accordance with the docking score, the colon cell line (HT-29) was selected for further in vitro analysis and the results revealed that L3, C1, C2 and C3 exhibit important anticancer activity when compared with the standard drug Adriamycin. Further, synthesized compounds have shown excellent activity against Gram-positive (Staphylococcus aureus) and Gram-negative pathogens (Escherichia coli) but exhibited poor activity against fungal strain. Antioxidant activity of the all compounds revealed that the complexes displayed a higher scavenging activity than the corresponding ligands. These studies reveal that the coordination of Cu(II) ion with mixed ligands play a vital role in the enhancement of the biological potential of the complexes.

Syntheses and photocatalytic properties of ruthenium(II) complexes with ferrocenyl-functionalised enaminonate ligands

Treatment of [RuCl2(dmso)4] (dmso = dimethyl sulfoxide) with ferrocenylformyl acetone and ferrocenyl enaminone Fc–C(O)CH=C(CH3)N(H)CH2CH2NH2 (Fc = ferrocenyl, HL1) in a 1:1:1 molar ratio in the presence of CH3ONa in methanol afforded a ruthenium(II) complex [(Fc−C(O)CHC(O)CH3)Ru(dmso)(L1)] (1) with a π-conjugated tridentate Schiff base ligand and a [(Fc−C(O)CHC(O)CH3)]– ligand. Similar reactions between [RuCl2(dmso)4] and Fc–C(O)CH=C(CH3)N(H)Ar (Ar = C6H5, HL2; Ar = 4-ClC6H4, HL3; Ar = 2-MeC6H4, HL4; Ar = 2-OMeC6H4, HL5) afforded corresponding ruthenium(II) complexes [Ru(L2)2(dmso)2] (2), [Ru(L3)2(dmso)2] (3), [Ru(L4)2(dmso)2] (4), and [Ru(L5)2(dmso)2] (5) with π-conjugated bidentate Schiff base ligands. Complexes 1‒5 were well characterized by infrared, UV/Vis and NMR spectroscopies along with their electrochemical properties. The molecular structure of complex 1•Et2O has been established by single-crystal X-ray diffraction. The photocatalytic properties for H2 evolution by reduction of water of complexes 1‒5 were also investigated in the paper.

Preparation, spectroscopic characterization and antitumor-antimicrobial studies of some Schiff base transition and inner transition mixed ligand complexes

Mixed ligand complexes of Mn(II), Ni(II), Zn(II), La(III), Er(III) and Yb(III) metal ions were prepared from bidentate Schiff base ligand (L) as a primary ligand, derived from condensation of benzophenone and 1,8-naphthylenediamine, and 1,10-phenanthroline (Phen) as a secondary ligand. The new Schiff base ligand (N1-(diphenylmethylene)naphthalene-1,8-diamine) and its mixed ligand complexes were characterized by using elemental microanalysis, conductometric measurements, magnetic susceptibility and spectroscopic studies (UV–Vis, mass spectral analysis, IR, 1H NMR and SEM). In addition, their thermal analytical (TG and DTG) behavior has been reported. Measurements of the molar conductivity of the complexes in DMF solvent pointed out the electrolytic nature of all complexes except Mn(II) and Zn(II) complexes were non electrolytes. According to the elemental analyses data, it was observed that the mixed ligand chelates had the general formulae [M(L)(Phen)Cl2]Cl.2H2O (M = La(III), Er(III) and Yb(III)), [M(L)(Phen)Cl2].H2O (M = Mn(II) and Zn(II)) and [Ni(L)(Phen)Cl(H2O)]Cl.H2O. Based on these findings, all mixed ligand complexes had octahedral geometry. The SEM image of the Schiff base ligand illustrated its rods like morphology with and average particle size of 77 nm while, the image of Ni(II) complex showed non-uniform platelets structure with some scattered rods with an average particle size of 54 nm. Considerable applications were done to ensure the biological significance of Schiff base ligand and its new mixed ligand complexes with Phen against Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Bacillus subtilis) and fungal (Aspergillus flavus and Candida albicans) strains and anti-cancer activities against (MCF7 breast cancer cell line). The results obtained revealed that the complexes exhibited promising biological and anticancer activity. Moreover, molecular docking studies were applied to determine the probable binding mode among the Schiff base ligand and the active site of the crystal structure of E. coli YcbB acylated with meropenem (PDB ID: 6NTW) and breast cancer estrogen mutant L536S (PDB ID: 6SBO) receptors.

Synthesis and characterization of cobalt(II) complexes with bidentate Schiff base ligand

The coordination complexes of Co(II) have been prepared from bidentate Schiff base. The Schiff base ligand was synthesized by the condensation of 4- hydroxy-3-methoxybenzaldehyde and 2-aminobenzhydroxamic acid in an alcoholic medium at room temperature. The ligand and cobalt (II) complexes were characterized by elemental analysis, molar conductance, electronic spectra, IR spectra, NMR spectra, electrical conductivity and magnetic susceptibility. The cobalt (II) complexes are colored and stable in air. In the metal complexes, the metal -ligand ratio was found to be 1:2. A sharp band at 1630 cm-1 is characteristics of the azomethine group present in the Schiff base ligand. This band was shifted to lower frequency (1605 – 1620 cm-1) in all the cobalt complexes, indicating the coordination of the azomethine nitrogen to the metal ion in complexes. The ν(N-OH) stretching vibration of the ligand obtained at 1080 cm-1 was raised up by 10-40 cm-1 in the complexes suggesting the deportation of (N-OH) hydrogen and coordination of hydroxy imino nitrogen atom in the bond formation with the Co(II) ions. The molar conductivity data of the complexes in DMF solution indicates that they are of non-electrolytic nature. On the basis of elemental analysis, magnetic susceptibility and electronic spectral data, geometry of complexes was proposed to be octahedral.

Transition‐Metal Complexes of Bidentate Schiff‐Base Ligands: In Vitro and In Silico Evaluation as Non‐Classical Carbonic Anhydrase and Potential Acetylcholinesterase Inhibitors

AbstractSchiff bases display superior features for many areas, such as significant intermediates in industrial biological, pharmacological, catalytic and optical properties, organic synthesis, and coordination chemistry. The pre‐synthesized two Schiff base ligands (HL1andHL2) and their bidentate metal complexes (Co(L1)2,Cu(L1)2,Ni(L1)2,Co(L2)2,Cu(L2)2, andNi(L2)2) were tested for their inhibition activities on acetylcholinesterase (AChE) and human carbonic anhydrase (hCA I andhCA II) isoforms. The transition metal complexes of bidentate Schiff base ligands displayed the potent inhibition effect withKIconstants ranging from 16.39±0.15 to 88.63±0.27 nM and 9.32±0.13 to 33.66±0.57 nM forhCA isoenzymes and AChE, respectively. The compoundCu(L1)2forhCA I andNi(L2)2for AChE andhCA II had the highest inhibitory effect. Besides, the molecular docking analyses of the most active complexes (Cu(L1)2andNi(L2)2) were performed to understand the binding interactions on the enzymes’ binding sites. According to both in vitro and in silico analysis results, all the compounds were potential inhibitors of AChE andhCA I, II isoenzymes.

Investigation of kinetics and thermodynamics in the interaction process between two pyridine derived Schiff base complexes and catalase

In the present study, two new Zn(II) complexes had been prepared by an N2 bidentate Schiff base ligand 4-pyridylimine-1,2-diacetylmonoxime (PIAO) (a: [Zn(PIAO)2]Cl2, b: [Zn(PIAO)Cl2]). Spectroscopic methods were employed to characterize complexes. The antioxidant properties of PIAO and the complexes were studied in vitro by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method. Our findings showed that PIAO binding to the metal center enhances the antioxidant properties with this trend: a > b > PIAO. Biophysical techniques were adopted to study the binding of these complexes with bovine liver catalase (BLC). The catalytic function of BLC decreased after interaction with both complexes (to 66% and 81% in the presence of a and b, respectively). Inhibitory activity of complexes occurs by a mixed-type inhibitory mechanism. Fluorescence results showed that the combination of BLC with both complexes undergoes static quenching mechanism (Kb = 6.1 × 106 M−1 for a and 0.73 × 104 M−1 for b at 310 K). The interaction process was spontaneous, exothermic and van der Waals and hydrogen bonds forces played major roles. UV–Vis, 3D, and synchronous fluorescence measurements indicated the changes in the microenvironment residues in the presence of Zn complexes. Molecular docking studies indicated that a cavity among the wrapping domain, N-Terminal arm and β-barrel is the best binding site of the prepared complexes on BLC. In conclusion, the above complexes in addition to providing antioxidant properties can interact with catalase and so inhibit its catalytic activity.

Synthesis, Spectral, Thermal and Biological Studies of Some Transition and Inner Transition Schiff base Metal Complexes

The new bidentate Schiff base ligand (L) named N1-(diphenylmethylene)naphthalene-1,8-diamine was prepared by the condensation reaction of benzophenone and 1,8-naphthylenediamine. The complexes with Mn(II), Ni(II), Zn(II), La(III), Er(III), and Yb(III) metal ions were prepared and characterized by using elemental analyses (C, H, N and M), FT-IR, 1H NMR, molar conductivity, magnetic moment, UV-Vis, mass and scanning electron microscope (SEM). The temperatures of decomposition of the Schiff base ligand and metal complexes were investigated using thermal analyses. The metal complexes were found to have the formulae [M(L)(H2O)3Cl]Cl.nH2O (M = Mn(II) (n = 4); Ni(II) (n = 2))], [Zn(L)(H2O)2Cl2] and [M(L)(H2O)2Cl2]Cl (M = La(III), Er(III) and Yb(III)) according to the elemental analyses data. The geometrical structure of all complexes was found to be octahedral. The molar conductivity of the complexes in DMF indicated the electrolytic nature of all complexes except Zn(II) complex was non-electrolyte. From the spectroscopic data, the Schiff base ligand acts as NN-bidentate ligand. The biological and anticancer activities of the Schiff base ligand and its complexes were investigated against two bacterial strains, two fungal strains and breast cancer cell line (MCF-7). Docking studies were performed to study the possible interaction between the Schiff base ligand with the active sites of the 3HB5 and 5JPE receptors.

Synthesis, characterization and DFT investigation of new metal complexes of Ni(II), Mn(II) and VO(IV) containing N,O-donor Schiff base ligand

In this work, a bidentate Schiff base ligand (HL) containing N and O as donor heteroatoms has been used to synthesize series of new stable metal complexes of general composition of M(L)2 with M = Mn, Ni and VO. This ligand was obtained from condensation of 2-methoxybenzylamine on 2,3-dihydroxybenzaldehyde in methanolic solutions in which its complexes were obtained by mixing the corresponding metal acetate salt and the ligand in 1:2 molar ratio. The resulting three complexes have been characterized by different analytical techniques like FT-IR, UV-Vis, mass spectroscopy, thermogravimetry and cyclic voltammetry, to identify their molecular structures and redox/electrochemical properties. Moreover, the effect of the metal on the complexes electronic properties with their reactivity has also been studied by Density Functional Theory (DFT). The stable structures were optimized by using the hybrid B3LYP/6–31 G method. The spectroscopic data obtained suggest that the metal is bonded to the ligand through the phenolic-like oxygen and the imine-type nitrogen atoms. Electronic and vibrational absorption spectra of the nickel complex was found to be of square-planar geometry while square-pyramidal and octahedral geometries have been proposed for VO(IV) and Mn(II) complexes, respectively. The thermogravimetric analyses of these complexes confirmed the presence of water molecules in their structures and thermal decomposition led to the formation of metal oxides as the latest residues. The voltammogram of the Ni(II) complex suggests the existence of quasi-reversible redox system in DMSO solution.

Synthesis, crystal structure, theoretical calculation, spectroscopic and antibacterial activity studies of copper(II) complexes bearing bidentate schiff base ligands derived from 4-aminoantipyrine: Influence of substitutions on antibacterial activity

A novel series of Cu(II) complexes, including: [Cu(L1)2]: C1, [Cu(L2)2]: C2, [Cu(L3)2]: C3, [Cu(L4)2]: C4, with four bis-N,O-bidentate Schiff base ligands (HL1: (E)-4-[(2‑hydroxy-3-methoxybenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one; HL2: (E)-4-[(2‑hydroxy-4-methoxybenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one; HL3: (E)-4-[(2‑hydroxy-5-methoxybenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one; HL4: (E)-4-[(2‑hydroxy-6-methoxybenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one have been synthesized and characterized by elemental analyses, FT-IR, 1H NMR and 13C NMR spectroscopic techniques. Furthermore, the crystal structures of HL4 and C2 were determined by single crystal X-ray analysis. Single crystal X-ray analyses, the structure of C2 confirmed the bidentate coordination mode. The metal center possesses a distorted tetrahedral geometry with bis-N,O donor atoms coordinating from Schiff base ligand. Theoretical calculation of the synthesized compounds were carried out by DFT using B3LYP method with employing the Def2-SVPD (for ligands) and Def2-SV(P) (for complexes) basis sets. Calculated data are in good accordance with the experimental investigations. The in vitro biological activities of the synthesized ligands and their copper(II) complexes were evaluated against Staphylococcus aureus and Escherichia coli. The activity data showed that the metal complexes have a promising biological potential comparable with the parent Schiff base ligands against bacterial species.

Antimicrobial Study of Synthesized and Characterized Rhodium, Platinum and Gold Metal Complexes Derived from Bidentate Schiff Base Ligand. (Research Article)

Antimicrobial Study of Synthesized and Characterized Rhodium, Platinum and Gold Metal Complexes Derived from Bidentate Schiff Base Ligand. (Research Article)