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Quantum chemical calculations at the M06L-GD3/def2-TZVPP level were done to investigate hydrogen bonds between amino acid metal complexes and a free water molecule. Octahedral nickel(II) and square planar palladium(II) complexes of glycine, cysteine, phenylalanine, and serine with different charges of metal complexes (+1, 0, and −1) were investigated. The following hydrogen bonds were considered: NH/O (amino acid is a H-donor), O1/HO (coordinated O1 oxygen from amino acid is a H-acceptor), and O2/HO (non-coordinated O2 oxygen from amino acid is a H-acceptor). Amino acid type has a small influence on interaction energies, both for octahedral nickel(II) and square planar palladium(II) complexes. The influence is the largest for NH/O and the smallest for O2/HO hydrogen bonds. For NH/O interaction, palladium(II) complexes showed stronger hydrogen bonds than nickel(II), up to −11.8 kcal mol−1 for singly positively charged complexes. Nickel(II) complexes demonstrated higher O1/HO hydrogen bond strength than palladium(II) with interaction energies up to −8.9 kcal mol−1 for singly negative complexes. With up to −9.0 kcal mol−1 interaction energy for singly negative complexes, O2/HO interactions were also stronger for nickel(II) complexes than palladium(II). [ABSTRACT FROM AUTHOR]

Co(II), Ni(II), Zn(II), and Cd(II) complexes were synthesized from a Schiff base ligand, benzyl-2-(1-(thiophen-2-yl)propylidene)hydrazine-1-carbodithioate (BTPHC), by conventional as well as microwave irradiation methods. The ligand and its metal complexes were characterized by spectroscopic techniques (FT-IR, UV-vis, mass spectrometry, and 1H NMR) and powder X-ray diffraction. Based on magnetic measurements and spectral data, octahedral environments for Co(II) and Ni(II) complexes and tetrahedral environments for Zn(II) and Cd(II) complexes are proposed. The metal(II) complexes were active toward bacterial and fungal strains. Antidiabetic studies showed that the Cd(II) complex possesses greater potential as an antidiabetic agent than the other metal complexes and the ligand. Antioxidant studies indicate that the Zn(II) and Cd(II) complexes possess high radical scavenging activities. The synthesized ligand and metal(II) complexes were screened for their anticancer properties against two human cancer cell lines MCF-7 and HeLa using an MTT cell viability assay. The Ni(II) complex excelled in halting the proliferation of HeLa and MCF-7 cancer cell lines with IC50 values of 46.63 µM and 80.90 µM, respectively, whereas it displayed insignificant cytotoxicity against the human normal embryonic kidney cell line (HEK293) with IC50 = 300.41 µM. [ABSTRACT FROM AUTHOR]

Five copper(II), zinc(II) and nickel(II) complexes, [Cu2L2(μ1,1-N3)2] (1), [Zn2L2(μ2-η1:η1-CH3COO)(NCS)]EtOH (2), [Zn2L2(μ2-η1:η1-CH3COO)(N3)]MeOH (3), [Zn2Cl2L2] (4) and [NiL(HL)]ClO4 (5), were prepared from the Schiff base 3-methyl-2-((pyridin-2-ylmethylene)amino)phenol (HL). The compounds have been characterized by physico-chemical methods including elemental analysis, IR, and UV–Vis spectra. Structures of the five new complexes were determined by single crystal X-ray diffraction. The copper ions in 1 are in square pyramidal, while zinc ions in 2, 3, and 4 are distorted square pyramidal, and the nickel ions in 5 are octahedral. The biological assay indicated that zinc complex 2 has the most effective activity on Jack bean urease with IC50 = 1.7 ± 0.8 μmol·L−1. Molecular docking was performed to study the interaction between the active center of the urease with molecules of the complexes. [ABSTRACT FROM AUTHOR]

Schiff bases are useful pharmacophores and form stable complexes with various metal ions in different oxidation states. Schiff base metal complexes show various biological activities such as antioxidant, antimalarial, antimicrobial, antitumor and anti-inflammatory. Schiff base ligands easily form complexes with rare earth metals and show various biological activities; due to paramagnetic nature of complexes, they are primarily used in medicine as a contrast media for magnetic resonance imaging. This review summarizes the synthesis of Schiff base rare earth metal complexes as well as antimicrobial activities especially antibacterial and antifungal from the last two decades and comparison of the result with standard reference drugs. [ABSTRACT FROM AUTHOR]

Lanthanide complexes of Sm(III), Nd(III), and Dy(III) with a Schiff base ligand, (potassium2-((4-hydroxy-3-methoxybenzylidene)amino)acetate, derived from condensation of 4-hydroxy-3-methoxybenzaldehyde and 2-aminoethanoic acid were synthesized. The compounds were characterized by elemental analysis, IR, UV–Vis, 1H-NMR, ESI-MS, photoluminescence spectra, thermogravimetric analysis, magnetic susceptibility, and molar conductivity measurements. No well-defined peaks were observed in X-ray diffractograms of the synthesized complexes, indicating an amorphous nature. The Schiff base ligand is tridentate and coordinated with the metal ion through phenolic oxygen, azomethine nitrogen, and carboxylic oxygen. Thermal properties of the metal complexes were studied using thermogravimetric analysis (TG/DTG) and revealed good thermal stability. The photocatalytic efficiencies of the complexes were explored using solar water-splitting. The optical band gaps (Eg) were measured and found to be 2.94, 2.86, and 2.82 eV for Sm(III), Nd(III), and Dy(III) complexes, respectively. These values indicated the semi-conducting nature of the investigated complexes. At room temperature, samarium and dysprosium complexes showed characteristic luminescence of the central metal ions ascribed to the efficient transfer of energy from the Schiff base ligand to the metal center under excitation at 390 nm. The binding properties of these complexes with calf-thymus DNA (CT-DNA) have been investigated using absorption spectrophotometry and fluorescence studies. The physicochemical properties such as hydrodynamic size, zeta potential, and stability of the DNA/complexes were also investigated. DNA cleavage activities of the compounds were assayed using the Agarose gel electrophoresis method. In-vitro antimicrobial activities of the compounds were screened against selected pathogenic strains by Agar well diffusion method. [ABSTRACT FROM AUTHOR]

Template condensation between pentane-1,5-dial and triethylenetetramine in the presence of divalent metal salts in methanolic solution resulted in mononuclear 15-membered tetraazamacrocyclic Schiff base metal complexes, [M(C11H22N4)X2], where M = Co(II), Ni(II) and Cu(II), X = Cl− and C11H22N4 is the tetradentate macrocyclic ligand. The bonding and overall geometry of the complexes are inferred through elemental analysis, FT-IR, UV–vis, 1H/13C NMR, ESI-mass, molar conductance, magnetic susceptibility and TG measurements. On the basis of the absorption bands in UV–vis spectra and magnetic moment analyses, a six-coordinate octahedral geometry is proposed for all the metal complexes. The formulation of the metal chelates is compatible with the thermal decomposition profiles. Photocatalytic efficiency of the macrocyclic Ni(II) complex was studied using solar water-splitting. The in vitro antimicrobial activity of metal complexes has been tested against certain bacterial and fungal species. The scavenging ability of DPPH free radicals was used to test the antioxidant activity of the complexes. In addition, MTT assay was used to assess the cytotoxicity of Cu(II) chloro complex against L929 mouse fibroblast cell lines. [ABSTRACT FROM AUTHOR]

This review presents an outline of biological and non-biological applications of transition metal complexes containing Schiff bases as ligands. Schiff bases are prepared by facile condensation of aliphatic and aromatic amino compounds with carbonyl groups to generate an imine or azomethine (–C = N–) functional group. Studies on Schiff base transition metal complexes have been of interest because of a wide range of applications in medicinal chemistry and their catalytic, photoluminiscent and non-linear optical properties. The new advancements of Schiff bases having various donor sets made up of different combinations of N, O, S, or P donor atoms, as well as their metal complexes, are also highlighted in this study. [ABSTRACT FROM AUTHOR]

This review examines the importance of Schiff base ligands and their metal complexes against cancer. The chemotherapeutic action of certain metal complexes especially cisplatin are currently used for treatment of cancer. The main limitation of such cancer related drugs is high toxicity and side effects. The development of new anticancer agents against several cell lines is described in this article. Based on reports from the last decade, we are still awaiting an efficient anticancer candidate. [ABSTRACT FROM AUTHOR]

To investigate how modification in the structure of 1,3-propanediamine chain of 1,3-pdta (1,3-propanediamine-N,N,N′,N′-tetraacetate) ligand affects the structural and biological properties of the corresponding metal complexes, two new octahedral complexes, [Co(H2O)5Co(2,2-diMe-1,3-pdta)]·H2O (1) and [Mg(H2O)5Mg(2,2-diMe-1,3-pdta)]·1.5H2O (2) (2,2-diMe-1,3-pdta = 2,2-dimethyl-1,3-propanediamine-N,N,N′,N′-tetraacetate), were synthesized and characterized by IR spectroscopy and single-crystal X-ray diffraction analysis. Additionally, UV-Vis and NMR spectroscopic methods were applied for the characterization of 1 and 2, respectively. Crystallographic data indicate that these complexes contain 2,2-diMe-1,3-pdta coordinated to the metal ion through 2 N and 4 O atoms forming [M(H2O)5M′(2,2-diMe-1,3-pdta)] complex unit (M, M′ = Co(II), Co(II) (1) and M, M′ = Mg(II), Mg(II) (2)), which is composed of [M′(2,2-diMe-1,3-pdta)]2− and [M(H2O)5O]2+ octahedra bridged by one of the axial carboxylate groups. The antimicrobial activities of 1 and 2 were evaluated against different bacteria and Candida spp., while their cytotoxic effect was tested on the normal human lung fibroblasts (MRC-5). The ability of 1 and 2 to inhibit formation of C. glabrata biofilms was also assessed. The obtained structural parameters and biological properties of the two complexes were compared to Co(II) and Mg(II) complexes with 1,3-pdta ligand. [ABSTRACT FROM AUTHOR]

Three new β-benzylselenated Schiff bases, (S)-L1H, (R)-L2H and (R)-L3H, were synthesized from three chiral β-benzylselenated amines, (S)-2a, (R)-2b and (R)-2c, respectively, on condensation with salicylaldehyde. The corresponding palladium complexes, (S)-1, (R)-2 and (R)-3, were synthesized by reactions of these ligands with Na2[PdCl4]. The ligands and their complexes were characterized by spectroscopic (1H, 13C{1H} NMR and FT-IR), polarimetric and elemental analysis. The crystal structure of (S)-1 was determined by single-crystal X-ray diffraction. The ligands bind palladium(II) as deprotonated ((S)-L1, (R)-L2 and (R)-L3) tridentate (Se,N,O-) chelates resulting in complexes of composition [Pd(L1-3)Cl]. All these compounds have been screened for in vitro DPPH radical scavenging activity using vitamin-C as a reference standard. The DPPH radical scavenging activity was assessed by varying the concentration of each of these compounds. The results of antioxidant activity studies demonstrated that these compounds are good-to-excellent radical scavenging agents. The antioxidant activity was quantitatively expressed as their IC50 values which revealed that the activity of palladium complexes were 50% higher than those of corresponding ligands and very close to that of the standard reference vitamin-C. New tridentate (Se,N,O-) type Schiff bases and their palladium complexes. The crystal structure of a palladium complex determined. Ligands and complexes explored for in-vitro DPPH radical scavenging activity. The antioxidant activity studies revealed that these compounds are promising antioxidants. [ABSTRACT FROM AUTHOR]

1,2,4-Triazine derivatives showed a significant role in the biological and pharmacological fields, which motivated us to study the biological and cytotoxicity activity of its first-row transition metal complexes. Three new complexes of Co(II), 1; Ni(II), 2; and Cu(II), 3 with 3-(2-benzylidenehydrazinyl)-5-(4-isobutylphenyl)-1,2,4-triazine, L were synthesized and characterized by standard physicochemical and theoretical methods. The structure of these complexes was evidenced by IR and 1H NMR spectroscopies, elemental analysis, magnetic measurements, molar conductance, mass spectrometry, and DFT modeling. The ligand behaved as a bidentate chelator that coordinates by triazine nitrogen-2 and azomethine nitrogen in a 2:1 (ligand : metal) ratio. The anticancer activity of the compounds was investigated against breast cancer cells (Mcf7 cell line). The antimicrobial activities of the ligand and its complexes were evaluated against different types of bacteria. Cu(II) was the most efficacious antimicrobial, with greater inhibition zones than the other complexes. The molecular docking studies were implemented to consider the binding attraction of the compounds with the receptors of breast cancer oxidoreductase (PDB:3HB5) and those of the COVID-19 main protease viral protein (PDB ID: 6LU7). The DFT calculations were used to confirm the molecular geometry of the new complexes. [ABSTRACT FROM AUTHOR]

By using a half-salen ligand (HL) and substituted salicylaldehydes, new unsymmetrical salen-type ligands (H2L1, H2L2, and H2L3) and their Ni(II), Zn(II) and Fe(III) complexes were synthesized. The compounds were characterized based on elemental analysis, IR, 1H NMR, X-ray diffraction (for HL), spectroscopy, mass spectrometry, magnetic moment, molar conductance measurements, and thermal analysis (TGA). The unsymmetrical salen ligands, during complexation, are attached to the metal by two imine nitrogen atoms and two phenolic oxygen atoms in all complexes; in the Fe(III) complexes, the fifth coordination is completed by chloride. Square planar geometry or distorted square planar geometry for [NiL1-3], [ZnL1-3], and square pyramidal geometry for [FeL1-3Cl] are proposed. Conductance measurements suggest non-electrolytic nature of the metal complexes. Thermogravimetric analysis showed that the complexes exhibit higher stability than the ligands. The electrochemical properties of the compounds were studied by cyclic voltammetry. HOMO-LUMO energy levels and electrochemical band gaps (E′g) were calculated. The solid state electrical conductivity of the iodine-doped compounds was measured and their semiconductor properties were determined. In addition, fluorescence properties of ligands and Zn(II) complexes were investigated. [ABSTRACT FROM AUTHOR]

From the apocalyptic era of antibiotic resistance, the scientific community around the world is engaged in designing and developing metal-based compounds to inhibit and control continuously rising microbial infections. Metal based triazole-derived compounds are being explored for antimicrobial actions and potentially applicable to provide effective and nontoxic drug candidates having preferred and improved pharmacological activity. Updating the existing literature supporting such details, this review combines the chemistry, synthetic aspects of formation of triazole Schiff bases, mechanism of bioactivity of metal complexes accompanied by the assessment of the biological efficacy including antibacterial, antifungal, enzyme inhibition and antioxidant activity. This review covers bioactive symmetrical and assymmetrical mono and bis-Schiff bases synthesized from condensation involving the amine group of 3-amino-1,2,4-triazole and 3,5-diamino-1,2,4-triazole with the carbonyl group of several aromatic aldehydes and ketones along with their transition metal complexes which were characterized by physical, spectral and chemical properties. In most of the studies highlighting the biomedical assessment of imine functionalized compounds, metal complexes showed outstanding results in comparison to free ligands. [ABSTRACT FROM AUTHOR]

Synthesis of a new series of metal complexes (Co+2, Ni+2, Cu+2, and Zn+2) with novel bioactive Schiff base 5-methyl-3-((3,5-dichlorosalicylidene) amino)-pyrazole which was prepared by condensing 3-amino-5-methylpyrazole with 3,5-dicholorosalicylaldehyde in absolute alcohol under refluxing condition have been carried out. The ligand and its metal(II) complexes were characterized by 1H NMR, IR, mass spectroscopy, UV–vis, fluorescence, ESR, elemental analyses, magnetic moments, and thermogravimetric (TG/DTG) analysis. With the help of different techniques divulged Cu+2 complexes have exhibited square planar geometry and Co+2, Ni+2, and Zn+2 complexes have octahedral geometry. Stability of all the metal complexes has been calculated by spectrophotometric method. All the compounds were studied towards fluorescent, antibacterial and antifungal activity and exhibited significant fluorescence and biological activity as contrasted to Schiff base. [ABSTRACT FROM AUTHOR]

Two new Schiff base cobalt(III) ([Co(LH)Cl2], 1) and nickel(II) ([Ni(LH)ClO4], 2) complexes with a diimine-dioxime ligand, (4,9-diaza-3,10-diethyl-3,9-dodecadiene-2,11-dione bis oxime (LH2)), were synthesized and characterized. The compounds were obtained in MeOH from corresponding metal salts and LH2 in molar ratio 1:1 and further characterized by mass spectrometry, IR spectroscopy, electrochemistry, and elemental analysis. Previously reported copper(II) analog ([Cu2(LH)2]·(ClO4)2, 3) was joined to 1 and 2, and the three metal analogs, 1–3, were further investigated in terms of their electrochemical behavior. Binding studies of the complexes with deoxyribonucleic acid (DNA) and human serum albumin (HSA) were carried out using both spectrophotometric and electrochemical methods. All three complexes exhibit binding affinity towards the DNA chain through intercalative interactions. The binding reaction with HSA showed for 1 and 3 decrease in the peak current obtained in the case of complexes before the addition of HSA, while the Ni complex–HSA possesses the same electroactivity as starting complex. The cytotoxicity of LH2 as well as its metal complexes, and cisplatin were evaluated on CT-26 mouse colon carcinoma and human LS174T cancer cell lines employing MTT assay. The copper(II) complex exhibited very promising anticancer activity compared with cisplatin. [ABSTRACT FROM AUTHOR]

Schiff base macrocycles play a remarkable role in the advancement of modern coordination chemistry in light of their importance to various multidisciplinary research fields. Bioinorganic chemistry has grown tremendously and provides opportunities to use macrocyclic Schiff base metal complexes as therapeutic agents. Macrocyclic Schiff base complexes have been studied on account of their ability to coordinate a variety of metal ions, preparative accessibility and growing applicability in numerous fields. In view of their pharmacological or biological properties, metal complexes of Schiff base macrocycles opened up a new vista of prospects in synthetic organic chemistry. Various methods were embraced to develop macrocyclic Schiff base metal complexes, along with their pharmacological properties. One of the simplest and effective methods for macrocyclic synthesis is an in-situ approach where the appearance of a metal ion in the cyclization reaction increases the yield of the macrocyclic product. This review focuses on the one-pot synthesis of biologically significant Schiff base macrocyclic metal complexes reported from 2005-2021. [ABSTRACT FROM AUTHOR]

The reaction of Schiff base 2-(4-(dimethylamino)benzylideneamino)phenol (DBAP) and diethylenetriamine/ethylenediamine with cobalt(II) and copper(II) metal ion in equimolar ratio afforded mixed ligand complexes [M(DBAP)(L)Cl(H2O)n] (1–4), where M = Co(II) 1, 2; Cu(II) 3, 4; L = diethylenetriamine (1, 3); n = 0 and ethylenediamine (2, 4); n = 1. All the newly synthesized complexes were characterized by elemental analysis, spectroscopic techniques viz., UV-vis, FT-IR, ESR, PXRD and mass spectrometry. The influence of chelation of cobalt(II) and copper(II) ion on nonlinear optical properties of Schiff base (DBAP) were examined with DFT study. The polarizability (α0) and first-order hyperpolarizability (β) of ligand and their metal complexes were calculated and compared with reference molecule p-nitroaniline. The hyperpolarizability of Schiff base and their metal complexes show a good nonlinear optical behavior. Theoretical investigation of the complexes was performed by DFT using B3LYP level of theory on the basis set 6-31 G (d, p)/LanL2DZ. On the basis of spectroscopic data and DFT computation, a six-coordinate geometry is tentatively proposed around the metal ion. In vitro antibacterial activities of these complexes were also screened against V. cholerae and E. coli, and found to have good antibacterial activity. [ABSTRACT FROM AUTHOR]

Three metal complexes, [Cu(L1)]2 (1), [Cu(L2)] (2) and [Ni(L2) (H2O)2]·1.5H2O (3), were synthesized using two different ligands (H2L1=N,N′-bis(2-hydroxy-3-methyl-benzylidene)-2-hydroxy-propane-1,3-diamine and H2L2=N,N′-bis(2-acetyl-indane-1,3-dione)-2-hydroxy-propane-1,3-diamine) and characterized by different spectroscopic methods. Complex 1 was studied by single-crystal X-ray diffraction analysis. In 1, each Cu(II) metal center has distorted square pyramidal structure. Complexes 2 and 3 have square planar and octahedral geometries, respectively. The interaction of calf-thymus DNA (CT-DNA) with H2L2 and the metal complexes (1–3) has been probed by UV–Vis absorption, photoluminescence, cyclic voltammetry and viscosity measurements. [ABSTRACT FROM AUTHOR]

A Schiff base ligand, 3-((2-(-(1-(2-hydroxyphenyl)ethylidene)amino)ethyl)imino)-N-(p-tolyl)butanamide, was synthesized by the condensation of o-hydroxylacetophenone, p-methylacetoacetanilide and 1,2-ethylenediamine and its V(IV)O, Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) complexes have been prepared. The ligand and metal complexes were characterized analytically and spectroscopically by elemental analysis, HRMS, IR, 1H NMR, 13C NMR and UV-vis spectroscopies and molar conductance and magnetic susceptibility measurements. The ligand and its metal complexes have been evaluated for their cytotoxic activity against Dalton's Lymphoma Ascites (DLA) cell line by Trypan blue exclusion method. In vivo anticancer studies using the Cu(II) complex in Swiss Albino female mice showed its potential efficiency against EAC-induced ascites tumor and DLA-induced solid tumor with an IC50 value of 46 µg/mL. Also, the complexes were tested for antibacterial and antifungal properties against some Gram-positive bacteria, Staphylococcus aureus, Bacillus cereus and Streptococcus criceti, and Gram-negative bacteria, Escherichia coli, Klebsilla pneumoniae and Pseudomonas aeruginosa and some fungi, Pencillium expansum, Fusarium oxysporum and Aspergillus niger. The complexes exhibited potential antibacterial and antifungal properties than the ligand, H2L, and in some cases even more than those of standard antibacterial and antifungal drugs. [ABSTRACT FROM AUTHOR]

The Schiff base derived from curcumin and lysine and its Co, Ni, Cu and Zn(II) complexes have been synthesized and characterized by FT-IR, UV-Vis, 1H NMR and elemental analysis. Conductivity measurement showed a non-electrolytic complex. Thermogravimetric (TG/DTG) analyses of Cu complex confirm the stability followed by thermal decomposition in different steps. The UV-Vis and magnetic susceptibility data of the complexes suggest tetrahedral geometry around the central metal ion except the Cu(II) complex which has a square planar geometry. The XRD and SEM studies revealed the nanocrystalline behavior for the complex. The antimicrobial activity of the Schiff base and its metal chelates were screened against bacteria, such as E. coli and P. aeruginosa. The antifungal activity was screened against C. albicans. The result shows that metal chelates have better antimicrobial activity than the Schiff base. The larvicidal activity of the Schiff base and its metal complexes have been studied and the result revealed that the Cu(II) complex shows more activity than the Schiff base. [ABSTRACT FROM AUTHOR]

One new tridentate N-coordinate ligand, N′-phenyl-N″-(phenyl(pyridin-2-yl)methylene)ethane-1,2-diamine (L), has been synthesized and characterized. The tridentate N3-coordinate ligand L has been used in the synthesis of a series of three mononuclear complexes [M(L)Cl2] [M = Cu(II), Co(II), and Zn(II)] and one polynuclear Cd(II) complex [Cd(L)Cl2]n and these complexes were characterized by spectroscopic techniques. The structure of all the complexes has been solved by single-crystal X-ray diffraction studies and the data reveal that all mononuclear complexes have distorted square pyramidal geometry and the polynuclear Cd(II) complex has distorted octahedral geometry. The antimicrobial activity of all complexes was investigated against Gram-positive (Bacillus subtilis, Staphylococcus aureus) and Gram-negative (Escherichia coli, Proteus vulgaris) bacteria by disk diffusion method. The compounds demonstrated significant antimicrobial activity while [Cu(L)Cl2] exhibited the best antibacterial activity among all the synthesized complexes. [ABSTRACT FROM AUTHOR]

A series of new zinc(II) and copper(II) complexes, [Zn2L(μ2-η1:η1-OAc)2(OAc)(CH3OH)] (1), [Zn2Cl2L2] (2), [Zn2Br2L2] (3), [CuL(μ1,3-N3)]n (4) and [Cu3(μ-Cl)2Cl2L2] (5), were prepared from the tridentate Schiff base 5-bromo-2((2-(dimethylamino)ethylimino)methyl)phenol (HL). The complexes were characterized by a variety of physicochemical techniques. Structures of the complexes were further confirmed by single crystal X-ray crystallography. The Zn ions in 1 are in octahedral and tetrahedral coordination. The Zn ions in 2 and 3 are in square pyramidal coordination. The Cu ion in 4 is in square pyramidal coordination. The Cu ions in 5 are in square pyramidal and square planar coordination. The Schiff base ligand coordinates to the metal ions through the phenolate O, and imino and amino N atoms. The complexes were evaluated for their antibacterial (Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas fluorescence) and antifungal (Candida albicans and Aspergillus niger) activities by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. [ABSTRACT FROM AUTHOR]

Mixed-ligand complexes of bivalent metal ions, viz, Co(II), Ni(II), Cu(II), and Zn(II) of the composition [ML(dan)]Cl (where L = Schiff base ligand, dan = 1,8-diaminonaphthalene and M = Co(II), Ni(II), Cu(II), Zn(II)) have been synthesized and characterized. The stoichiometric ratio of the prepared complexes has been estimated using complementary techniques such as elemental analyses, FT-IR, UV-vis and EPR spectra, magnetic and molar conductivity measurements. The study shows that all the complexes have square planar geometry. The synthesized compounds have been tested in vitro against various types of pathogenic bacteria to weigh up their antimicrobial properties. They have lofty activity against the tested bacteria. The complexes have higher activity than the free ligands. The interaction of synthesized complexes with calf thymus DNA (CT-DNA) has been studied by absorption spectroscopic technique and viscosity measurements. The complexes show a successful interaction with CT-DNA via intercalation mode. In addition, molecular docking approach has been performed for predicting the binding free energy of the synthesized compounds with 1BNA receptor. [ABSTRACT FROM AUTHOR]

Metal complexes of Schiff bases synthesized from condensation of an amine with carbonyl compounds are widely used for industrial purposes such as catalysts, pigments and dyes, intermediates in organic synthesis, polymer stabilizers, and corrosion inhibitors. For design and development of various bioactive compounds, Schiff bases carrying imine or azomethine (-C=N-) functional group, are versatile pharmacophores. Medicinal chemists give attention toward new chemotherapeutic Schiff bases and their metal complexes owing to numerous applications in pharmacology as antiviral, antibacterial, antifungal, antimalarial, antituberculosis, anticancer, anti-HIV, anti-inflammatory, and antipyretic agents. This review highlights recently synthesized Schiff bases as well as their metal complexes as potential bioactive core. [ABSTRACT FROM AUTHOR]

Metal complexes have more biological activities than their corresponding ligands. In particular, Schiff base complexes are of great interest due to their stability, electron donating ability, catalytic, photochromic, optical nonlinearity properties and biological activities. These are all based on the coordination of Schiff bases to metal ions. Amino acids are functionally involved in a number of biological processes and have coordinating sites of –NH2 and -COOH which are condensed with aldehydes or ketones to form Schiff bases which are easily coordinated to metal ions. Most amino acid derived Schiff bases and their metal complexes exhibit different pharmacological activities. This review focuses on the research of Schiff base complexes of amino acid derivatives from the past five years. We highlight the antimicrobial, anticancer and antioxidant responses of some Schiff base coordination compounds incorporating amino acids having nitrogen, oxygen and sulfur donors and different metal ions. [ABSTRACT FROM AUTHOR]

New mononuclear Cu(II), Co(II) and Ni(II) complexes of novel azo-dye ligand 4-[(4-hydroxy-7-methyl-1,3-benzothiazol-2-yl)diazenyl]-5-methyl-2-phenyl-2,4-dihydro-3-pyrazol-3-one (L) with O,N-donor site were synthesized and are characterized by various spectroscopic techniques. The quantum chemical parameters were evaluated for all the compounds by ZINDO/1 semi-empirical method and are compared with the experimental data. Spectral investigations suggested the octahedral geometry for Co(II) and Ni(II) complexes and distorted tetrahedral geometry for Cu(II) complex. The antibacterial activity of the compounds was screened against different microbial strains and the results indicated that all the metal complexes exhibited higher activity than the free ligand. The interaction of pUC18 DNA with the synthesized compounds was explored by gel electrophoresis technique. All metal complexes exhibited significant cleavage activity against supercoiled pUC18 DNA. The anticancer activity of the compounds was studied against K562, A549, and MDA-MB-231 by MTT assay and all the metal chelates exhibited good anticancer properties. [ABSTRACT FROM AUTHOR]

The 2-acetylpyridine-ethylcarbazate ligand (HL) formed four metal complexes, [Cu(HL)Cl2]⋅H2O (1), [Cu(HL)Br2]⋅H2O (2), [Zn(HL)Cl2] (3) and [Ni(L)2]⋅H2O (4). The carbazate and their metal complexes have been investigated by single crystal X-ray analysis, physicochemical, and spectroscopic methods. The Schiff base is coordinated to the metal ions as an anionic bi or tridentate ligand with the Z configuration about the imine C = N at the carbazate. Interactions in the crystal structures were analyzed using Hirshfeld surfaces and the 2D-fingerprint plots. Complexes 1, 2, and 3 present π⋅⋅⋅π stacking between the pyridyl rings with inter-centroid separations of 3.664(3)–3.887(2) Å. The water solvent molecules and the halogens allow the formation of intramolecular hydrogen bonds which close supramolecular structures in the molecular packing of the complexes. Free HL and 1–4 have been evaluated for antibacterial and antifungal activity against several multi-resistant bacteria and fungi. Significant antimicrobial activity of the complexes was observed; however, the free ligand and its complexes did not reveal any activity against some of the tested organisms. [ABSTRACT FROM AUTHOR]

A series of binuclear Co(II), Ni(II), Cu(II), and Zn(II) complexes were prepared with a novel bidentate Schiff base ligand derived by condensation of 3,3′-diaminobenzidine with creatinine. The prepared compounds were characterized by elemental analysis, magnetic susceptibility measurements, molar conductivity, FT-IR, UV-vis, 1H NMR, 13C NMR and mass spectra and thermal analysis (TGA/DTG). From spectral analysis, an octahedral geometry was proposed for the complexes except Zn(II) complex which had tetrahedral geometry. The microcrystalline nature of the complexes has been confirmed by powder XRD and SEM analyses. The molecular structures of the Schiff base L and its Zn(II) complex were fully optimized and also their quantum chemical parameters were calculated. The synthesized ligand and their metal complexes were screened against two gram-positive, gram-negative bacterial and fungal species. The results revealed that the metal complexes exhibited higher antimicrobial activity than the free ligand. The antioxidant activity of the synthesized ligand and their metal complexes was carried out by DPPH method. [ABSTRACT FROM AUTHOR]

The napthyl/pyridine-pyrazole-derived complexes, [Mn(L1)Cl2] (1), [Co(L1)Cl2] (2), [Cu(µ-Cl)(Cl)(L)]2 (3), [Cu2(L)2(N3)3(µ2-N3)] (4), and [Co(L2)Cl2] (5) (where L1 = bis-(3,5-dimethyl-pyrazol-1-ylmethyl)-napthalen-1-ylmethyl-amine (L1), L = 5-methyl-pyrazol-1-ylmethyl) -napthalen-1-ylmethyl-amine (L) and L2 = 2-[2-(3,5-dimethyl-pyrazol-1-yl)-1-methyl-ethyl]-pyridine), exhibited phenoxazinone synthase activity in methanol in the range 5–54 h−1. Binuclear copper(II) derivatives 3 and 4 show better catalytic activities than manganese(II) and cobalt(II) derivatives. The kinetic studies reveal that phenoxazinone chromophore is produced via a complex-substrate intermediate. Further, 3 and 4 show catecholase activity in methanol in the presence of oxygen. All the complexes showed potent antimicrobial activity against the tested strains of bacteria and fungi. Complex 1 was synthesized for the first time by mixing L1 and MnCl2 (1:1) and characterized by single-crystal X-ray crystallography, cyclic voltammetry, density functional theory, and thermogravimetry analysis. The present study suggests that napthyl/pyridyl-anchored pyrazole metal complexes are interesting scaffolds for the development of novel model compounds for biochemical reaction and efficient antimicrobial agents. [ABSTRACT FROM AUTHOR]

We present the synthesis of the tridentate Schiff base 2-(1-((pyridine-2-ylmethyl)imino)ethyl)naphtalen-1-ol (LH) providing a NNO coordination environment. Two new Ni(II) and Cu(II) complexes with a ligand to metal stoichiometric ratio of 1:1 and 2:1, respectively, were synthesized from LH. The Cu(II) complex of general formula [Cu(L)(MeOH)](ClO4)·MeOH (2) has a square planar geometry in the central ion completed by a MeOH molecule. In the case of the mononuclear Ni(II) complex [NiL2]·MeOH (3) the central ion has a distorted octahedral geometry. These new compounds were structurally, spectroscopically and electrochemically characterized using X-ray diffraction, UV-vis, IR, 1H NMR, 13C NMR spectroscopies, and cyclic voltammetry. LH is electroactive in the potential window of −1.0 to 1.0 V with one irreversible oxidation at 0.44 V, a quasi-reversible oxidation at 0.60 V, and one irreversible reduction at 0.24 V. For 2, there is a quasi-reversible oxidation at 0.43 V and one irreversible oxidation at 0.64 V. Complex 3 has two quasi-reversible oxidations at 0.19 V and at 0.58 V, one irreversible oxidation at 0.37 V, and one irreversible reduction at 0.38 V. DFT calculations were undertaken to obtain optimized structures and relative stability for 2 and 3 and their intermediates. [ABSTRACT FROM AUTHOR]

A novel series of metal complexes ML2Cl2 [M = Co(II), Ni(II), Cu(II), and Zn(II), L = Schiff base] have been synthesized by the interaction of the ligand derived from the condensation of thiophene-2-carboxaldehyde with 2-amino-6-picoline. Molar conductance measurements indicate that the complexes are non-electrolytes. Infrared data indicate that the ligand is monodentate and binds to the metal ion via azomethine nitrogen atom. Electronic spectral data and magnetic measurements reveal tetrahedral and square planar geometries for the metal complexes. The redox behavior of complex [CuL2Cl2] has been investigated using cyclic voltammetry. Thermal decomposition profiles are consistent with the proposed formulation of the complexes. The XRD and SEM results indicate that ligand and complexes [CuL2Cl2] and [ZnL2Cl2] are nanocrystalline. The metal complexes showed higher photocatalytic efficiency under sunlight as evidenced by photocatalytic studies using methylene blue dye. Molecular structures of the ligand and its complexes have been optimized by DFT computations. Binding affinity of ligand and its complexes with target protein have been examined by molecular docking study. The in vitro antimicrobial activity of the synthesized compounds has been tested against certain bacterial and fungal species. Furthermore, in vitro cytotoxicity of complexes [CoL2Cl2] and [CuL2Cl2] have been tested against L929 fibroblast. [ABSTRACT FROM AUTHOR]

Three Schiff base ligands, L1H = (2-((benzo[d]thiazol-6-ylimino)methyl)-6-nitrophenol), L2H = (2-((benzo[d]thiazol-6-ylimino)methyl)-4,6-diiodophenol), L3H = (2-((benzo[d]thiazol-6-ylimino)methyl)-4-bromo-6-methoxyphenol) and their binary metal complexes, 1 [Cu(L1)2], 2 [Co(L1)2], 3 [Cu(L2)2], 4 [Co(L2)2], 5 [Cu(L3)2] and 6 [Co(L3)2], have been synthesized and characterized by elemental analysis, NMR, ESI mass, FT-IR, ESR, UV–Visible, magnetic susceptibility and TGA studies. The analytical and various spectral data suggested a square-planar geometry around the metal for all complexes with N2O2-donor atoms from the Schiff base ligands. Antimicrobial study was investigated against two Gram-positive, Bacillus amyloliquefaciens and Staphylococcus aureus, and one Gram-negative, Escherichia coli, bacteria as well as against two fungal species, Macrophomina phaseolina and Sclerotium rolfsii, by using Streptomycin and Mancozeb as standard drugs, respectively. The results revealed that metal complexes show more potent activity than free ligands and moderate compared to standard drugs. The free-radical scavenging ability of the complexes was evaluated by DPPH and ABTS assay methods using ascorbic acid as a standard antioxidant, complexes 1 and 2 showed good scavenging activity. DNA-binding titrations were also performed and indicated that all complexes bind to calf-thymus DNA via an intercalation mode. Additionally, the complexes exhibited good cleavage ability against the pBR322 DNA even at low concentrations in the presence of activators, H2O2 as well as UV light. [ABSTRACT FROM AUTHOR]

We have developed complexes [Ni2(L)2(H2O)4]n (1), [Co2(L)2(H2O)4]n (2), [Cd2(L)2(H2O)2Cl2]n (3) and [Cd2(L)2(H2O)2]n (4), where HL = 5-(pyrazol-1-yl) nicotinic acid. All complexes were characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction, showing monoclinic crystal lattice with space group P21/c (1), P21/c (2), P21/c (3), and triclinic crystal lattice with space group P-1 (4), separately. In vitro antitumor screening (MTT method) revealed that 3 exhibited better inhibitory activities than the commercial anticancer drug cisplatin against HeLa tumor cell lines, with IC50 values 9 ± 2. The bindings of these complexes with Fish Sperm DNA were measured by electronic absorption spectra and fluorescence spectroscopy, showing Ksq 0.1867 (1), 0.1589 (2), 0.2332 (3), and 0.1411 (4), with the binding affinities ranked 3 > 1 > 2 > 4. The experimental result showed that these complexes could bind DNA via intercalation. The ability of 1–4 to cleave the pBR322 plasmid DNA was demonstrated by gel electrophoresis assay. The experiment verified that these complexes could induce DNA damage. In addition, flow cytometric analysis showed that 1–4 induced apoptosis of HeLa tumor cell lines; as time increases, the apoptotic impact becomes increasingly significant. The potential of 1–4 as anticancer agents were examined using molecular docking of the complexes with DNA. [ABSTRACT FROM AUTHOR]

Urease catalyzes the decomposition of urea into ammonia, which has harmful effects on both human health and fertile soil. Aiming at exploring novel urease inhibitors, a series of hydrazone compounds and their CoIII, CuII, NiII, and ZnII complexes were prepared from 4-methoxy-N'-(pyridin-2-ylmethylene)benzohydrazide (HL). They are [CoClL(NCS)] (1), [CoL2]·Cl·CH3OH·H2O (2), [CuL(NCNCN)]n·nCH3OH (3), [NiL(HL)]·ClO4·CH3OH (4) and [ZnClL(OH2)]·CH3OH (5). The compounds were characterized by physico-chemical methods. Structures of the complexes were further confirmed by single crystal X-ray diffraction. The metal ions in 1, 3, and 5 display square pyramidal coordination and 2 and 4 display octahedral coordination. The inhibitory effects of the compounds on Jack bean urease were evaluated. The results showed that 3 has effective urease inhibitory activity, with IC50 value of (7.3 ± 1.0) μmol L−1. [ABSTRACT FROM AUTHOR]

Thermal reactions of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Ru(III) metal ions with a novel Schiff base ligand (HL) derived from the condensation of 2-aminothiazole and 2-hydroxy-1-naphthaldehyde resulted in the formation of a series of metal complexes, [Co(L)2(H2O)2]·2H2O (1), [Ni(L)(CH3COO)(H2O)2] (2), [Cu(L)2(H2O)2] (3), [Zn(L)2] (4), [Cd(L)(CH3COO)]·2H2O (5), and [Ru(L)2(H2O)2]Cl (6). The ligand and its complexes were characterized by means of elemental and thermal analyses, molar conductance, and magnetic moment measurements along with different spectroscopic techniques. The structure of the ligand was determined by X-ray crystal structure analysis and revealed that it crystallized in the orthorhombic space group P21cn with a Z value of 4. Theoretical calculations based on accurate DFT approximations were used to verify the structures of ligand and complexes. The relative reactivities were estimated using chemical descriptors analysis. The biological activities of the compounds were examined. The antioxidant activity against DPPH radical was evaluated in vitro by using spectrophotometric methods; the experiments showed potent antioxidant activity. Also, the interaction of the reported compounds with calf-thymus DNA (CT-DNA) by different techniques revealed that the complexes could bind to CT-DNA by intercalative mode. [ABSTRACT FROM AUTHOR]

New air stable N-heterocyclic carbene functionalized Schiff base ligands (L) of the type 2-[-2-[3-(R)imidazol-1-yl]ethyliminomethyl]phenol [R = methyl (2), 2-pyridylmethyl (3)] were synthesized and characterized by NMR, IR, MS, and CHN analysis. Single crystal X-ray structural analysis of their Ni(II) complexes revealed square planar arrangement of the chelating ligands coordinated in tridentate (2, C^N^O) and tetradentate (3, N^C^N^O) modes around the metal. The three new isolated and fully characterized complexes were utilized as catalysts for the catalytic transfer hydrogenation of aliphatic ketones in 2-propanol as solvent and source of hydrogen. Based on 0.2 mol% catalyst concentration, the complexes showed activity for aliphatic ketones and 100% conversion (turnover number of 500) for cyclohexanone and all the aromatic ketones tested. [ABSTRACT FROM AUTHOR]

One new nickel(II) complex, [Ni(L)] (1), was synthesized from the Schiff base ligand derived from pyrrole-2-carboxaldehyde and 1,3-diaminopropane. Complex 1 was characterized by elemental analysis, IR, UV-Vis and ESI mass spectroscopy, cyclic voltammetry, and single-crystal X-ray structure analysis. Crystallographic results show that two Ni(II) monomeric moieties are present with similar structural features but with slightly different bond lengths and bond angles. The geometry around the Ni(II) center is distorted square planar. DNA-binding properties of complex 1 were well explored by employing UV-Vis and fluorescence spectral methods, cyclic voltammetry, and by viscosity measurements. Similarly the protein-binding study was studied by multispectroscopic techniques using both BSA and HSA. The cytotoxicity study of the compound has also been evaluated. Notably, the in vitro cytotoxicity of complex 1 on two cancer cell lines (AGS and A549) demonstrates that complex 1 has very good anticancer activity. MTT assay, cell-cycle analysis, and annexin-V assay have been performed to know the extent of effect of complex 1 as anticancer agent. Further, in silico molecular docking study revealed that the nickel(II) complex fits into the minor groove of duplex DNA by hydrophobic interaction with functional groups of B-DNA. [ABSTRACT FROM AUTHOR]

A new Co(II) complex of general formula [Co(L)2] has been synthesized from a NNO tridentate Schiff base ligand, 2-[(piperidin-2-ylmethylimino)-methyl]-phenol (L). The title complex is characterized by elemental, spectroscopic, antibacterial, and single crystal X-ray structural studies. X-Ray crystallography reveals that the complex shows a distorted octahedral geometry around the Co(II) ion. The complex was tested against several bacteria and shows good antibacterial activities against almost all of the bacteria. The interactions of the title complex with calf thymus deoxyribonucleic acid (CT-DNA) have been investigated by electronic absorption and fluorescence spectroscopy, showing that the complex interacts with CT-DNA via partial intercalation. Thermogravimetric analysis (TGA) of the complex has also been reported and the result shows that the complex is thermally stable up to 134 °C. [ABSTRACT FROM AUTHOR]

In search of effective bioactive compounds, we have synthesized the new Co(II), Ni(II), and Cu(II) complexes of the Schiff base derived from 8-formyl-7-hydroxy-4-methylcoumarin and 2-hydrazino benzothiazole and characterized by analytical, spectroscopic (IR, NMR, UV-vis, Mass), magnetic, powder X-ray diffraction data (PXRD) and TGA studies. Elemental analysis suggests the stoichiometry of the synthesized complexes and the solution electronic spectral study revealed the octahedral geometry of the compounds. Thermal analysis shows the presence of water molecule outside the coordination sphere and powder-XRD patterns have been studied to test the degree of crystallinity of the complexes and unit cell calculations were made. All the synthesized compounds were tested against human ovarian cancer cell line (PA-1). The synthesized metal complexes exhibited enhanced activity against the tested bacterial (Staphylococcus aureus and Escherichia Coli) and fungal strains (Candida albicans and Aspergillus fumigatus) as compared to free ligand (LH). The results of the DNA-cleavage activity suggest that the ligand and its metal complexes can cleave CT-DNA at different degrees. Further, anti-tuberculosis activity was done using microplate almar blue assay. Among all these synthesized compounds, the Cu(II) complex exhibits good cleaving ability compared to other newly synthesized metal complexes. [ABSTRACT FROM AUTHOR]

Three lanthanide complexes (La(III), Er(III), and Yb(III)) derived from ferrocene-based Schiff base ligand (HL) were synthesized from condensation of 2-aminophenol with 2-acetylferrocene. The ligand and metal complexes were characterized based on elemental analyses, IR, 1H NMR, molar conductance, SEM and thermal analyses (TG, DTG). The molar conductance revealed that all the metal chelates were electrolytes having the general composition [M(L)(Cl)(H2O)3]Cl·4H2O. HL and its complexes were screened for their antibacterial and antifungal activity by agar diffusion method. The results of these studies showed that the metal complexes are more effective antibacterial and antifungal agents as compared with the free ligand. The anticancer activity was screened against human breast cancer cell line (MCF-7). Results indicated that metal complexes showed an increased cytotoxicity in proliferation to cell lines as compared to free ligand. Molecular docking studies were performed to identify the binding orientation or conformation of a complex in the active site of the protein. HL and its complexes were docked with crystal structure of DDB1 of breast cancer, crystal structure of HCV, RNA-dependent RNA polymerase, receptors of HBV core protein, crystal structure of the Fab fragment of anti-HAV. [ABSTRACT FROM AUTHOR]

The binuclear Ru(II) complexes with Schiff bases derived from 5-chlorosalicyladehyde and 2-aminopyridine and its 5-substituted salicylideneimine homologues were testedin vitroagainst cervical carcinoma (HeLa), metastatic colorectal adenocarcinoma (SW620), lung adenocarcinoma (A549), breast adenocarcinoma (MCF-7), and human lung fibroblast (WI-38) cell lines. All compounds showed strong antiproliferative activity with extremely low IC50values. The compounds expressed strong activity against gram-positive bacteria,Staphylococcus aureusandEnterococcus faecalis. [ABSTRACT FROM PUBLISHER]

Eight substituted bidentate Schiff base ligands HOC6H4CH=N-R (HL) (HL1: R = 4-ClC6H4, HL2: R = 2-ClC6H4, HL3: R = 4-NO2C6H4, HL4: R = 4-MeC6H4, HL5: R = 2,6-Me2C6H3, HL6: R = 2,46-Me3C6H2, HL7: R = CH2C6H5, and HL8: R = n-Pr) were synthesized by the typical condensation reaction. Interaction ofcis-[Ru(bpy)2Cl2]⋅2H2O (bpy = 2,2′-bipyridine) with one equivalent of HLligand in the presence of KPF6afforded the cationic ruthenium(II) complexes of the type [Ru(bpy)2(L)](PF6) (1–8). The reaction ofcis-[Ru(phen)2Cl2]⋅2H2O (phen = 1,10-phenanthroline) and HL1under similar condition gave complex [(phen)2Ru(L)](PF6) (1a). Treatment ofcis-[Ru(phen)2Cl2]⋅2H2O with two equivalents of HLin the presence of KPF6resulted in isolation of the cationic ruthenium(III) complexes of the type [Ru(phen)(L)2](PF6) (9-16). All complexes have been spectroscopically characterized. The structures of1a⋅CH2Cl2,2⋅½CH2Cl2,3⋅CH3CN,5⋅½H2O,6,12⋅½HOCH2CH2OH,13⋅CH3CN,15⋅H2O, and16have been determined by single-crystal X-ray diffraction. [ABSTRACT FROM PUBLISHER]

A new benzimidazole based Pd(II) Schiff base complex was prepared and its catalytic activity was evaluated for Suzuki cross-coupling reactions in ethyl-methyl imidazolium hexafluorophosphate [EMIM PF6] ionic liquid at ambient temperature. The system provides a stable and reusable method for coupling reactions. Optimization for suitable reaction conditions were studied with respect to the effect of catalyst concentration, effects of additives, solvent and substituents on boronic acid. Good to excellent yields were achieved using a modest amount of the catalyst. The reaction time was less and the yield was more compared to previously reported results. In addition, the catalyst can be easily reused and recycled for six times without much loss in activity; this is an example of sustainable and green methodology. [ABSTRACT FROM PUBLISHER]

Tetradentate Schiff base (H2L) derived from 2,2′-dimethylpropandiamine and its nickel(II) and oxo-vanadium(IV) complexes (NiL, VOL) have been prepared and characterized. The crystal structure of NiL has been determined. The reported structure contains two molecules of the complex revealing slightly different conformation and the coordination sphere around nickel is distorted square planar. The electrochemical properties of the Ni and oxo-vanadium Schiff base complexes were investigated in CH3CN by cyclic voltammetry. The catalytic activities of the complexes were studied in the oxidation of sulfides in ethanol. Under the optimized reaction conditions, in the presence of NiL, 89% and VOL, 100% conversion of methyl phenyl sulfide with 100% selectivity for sulfoxide were obtained. [ABSTRACT FROM PUBLISHER]

Two new Schiff base silver(I) complexes, {[Ag(L1)][H2O]}∞(1) and {[Ag(L2)][H2O]}∞(2), where L1 = 4-((2-diethylaminoethylimino)methyl)phenecarboxylate and L2 = 4-([3-(morpholin-4-yl)propyl]iminomethyl)phenecarboxylate, have been synthesized and characterized. X-ray crystallographic analysis reveals that silver ions in1are bridged by L1to form a one-dimensional zigzag chain, while three silver ions in2are linked by L2to produce a two-dimensional coordination polymer. Guest water molecules in1generate a one-dimensional hydrogen-bonded chain. Both1and2offer high antibacterial activity against Gram-positive bacteriaStaphylococcus aureuswith MIC values of 0.26 and 0.24 mM and to exhibit good inhibitory activity against urease with the respective IC50values of 3.5 ± 0.1 and 3.8 ± 0.2 μM. [ABSTRACT FROM AUTHOR]

A series of new mononuclear heteroleptic derivatives of aluminum(III), {[(CH3COCHCOCH3)AlL] (1and4)}, {[(C6H5COCHCOC6H5)AlL] (2,5, and7)}, and {[(C9H6NO)AlL] (3and6)}, have been synthesized by reacting Al(OPri)3with tridentate Schiff base H2Lx(H2L1 = C13H10BrNO2; H2L2 = C14H13NO3; H2L3 = C17H13NO2) and β-diketone/8-hydroxyquinoline (β-diketone = acetylacetone/dibenzoylmethane) in 1 : 1 : 1 stoichiometry using anhydrous benzene and ethanol. All the complexes were characterized by elemental analysis, FTIR, and NMR (1H and13C) spectral studies. Molecular structures obtained from single-crystal XRD of aqua1(1a) and DMSO coordinated2(2a) authenticate their existence. Further, nanostructured α-alumina was synthesized from1by well-established sol–gel method and was characterized by powder XRD, TEM, and EDX analyses. [ABSTRACT FROM AUTHOR]

Oxoperoxo tungsten(VI) complex immobilized on Schiff base-modified Fe3O4super paramagnetic nanoparticles were synthesized and appropriately characterized using FT-IR, XRD, SEM, TEM, EDX, BET, and VSM analysis. The synthesized nanoparticles efficiently catalyzed oxidation of benzylic alcohols with H2O2as oxidant in high yields, with high to excellent selectivity. The catalyst can be recovered using an external magnetic field and recycled for subsequent oxidation reactions without any appreciable loss of efficiency. The simple preparation, high activity, excellent selectivity, and simple recoverability of the catalyst are advantageous. [ABSTRACT FROM AUTHOR]

A series of Cu(II) complexes have been synthesized from bidentate Schiff base ligands (by condensation of Knoevenagel condensate of acetoacetanilide (obtained from substituted benzaldehydes and acetoacetanilide) and 2-aminobenzothiazole). They were characterized by elemental analysis, IR,1H NMR,13C NMR, UV–vis., molar conductance, magnetic moment, ESR spectra and electrochemical studies. Based on the magnetic moment, ESR, and electronic spectral data, a distorted square planar geometry has been suggested for the complexes. Antibacterial and antifungal screening of the ligands and their complexes reveal that all the complexes show higher activities than the ligands. The antioxidant activities of the ligands and complexes were determined by superoxide and hydroxyl radical scavenging methodsin vitro, indicating that the complexes exhibit more effective antioxidant activity than the ligands alone. The results show that the Cu(II) complexes also have similar superoxide dismutase activity to that of native Cu, Zn-SOD. All complexes exhibit suitable Cu(II)/Cu(I) redox potential (E1/2) to act as synthetic antioxidant enzyme mimics. [ABSTRACT FROM AUTHOR]

A nickel(II) Schiff base complex immobilized on multi-wall carbon nanotubes (MWCNTs) surface as a highly efficient heterogeneous catalyst was synthesized and characterized by IR, X-ray diffraction patterns, scanning electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma, elemental analysis, and thermal gravimetric analysis. Then a facile and environmentally benign procedure was developed for synthesis of polyhydroquinoline derivatives via Hantzsch one-pot condensation reaction of aromatic aldehydes, 1,3-diones, ethyl acetoacetate, and ammonium acetate in the presence of above synthesized catalyst under solvent-free conditions. This protocol has the advantages of stability, easy availability, recyclability and eco-friendly nature of catalyst, simple experimental and work-up procedure, and also high to excellent yields. Considering the solvent-free condition and also temperature, time, and yield of the model reaction, the nanocatalyst reported here is among the best catalysts reported so far for synthesis of polyhydroquinolines. [ABSTRACT FROM AUTHOR]

A six-coordinate Mn(IV) complex, [Mn(H2L)2] (1) [H4L = 2-methoxy-6-(tris(hydroxymethyl)methyliminomethyl)phenol], was synthesized and characterized by elemental analysis, single-crystal X-ray crystallography, FTIR, UV–Vis electronic absorption, and EPR spectroscopy. The single-crystal structural determination reveals that the complex crystallizes in tetragonal space groupP41212 and the tridentate Schiff base ligands are arranged inmerconfiguration chelating manganese, which exhibits as slightly distorted octahedral coordination sphere with a N2O4chromophore. Weak hydrogen bonding interactions of uncoordinated hydroxyl groups result in a 2-D supramolecular structure. The UV–Vis electronic absorption and IR spectral data of1have been compared with the results obtained by employing DFT and time-dependent density functional theory calculation using B3LYP, B3PW91, and MPW1PW91 functionals, with 6-31G (d-p) and LanL2MB basis sets. The results of these calculations are functional-dependent and, among those used, B3PW91 proved to better reproduce the experimental results. [ABSTRACT FROM AUTHOR]