Cobalt complexes based on 2-(1H-benzimidazol-2-yl)-phenol derivatives: preparation,spectral studies,DFT calculations and catalytic behavior toward ethylene oligomerization

In this study, five novel Co(II) complexes of 2-(1H-benzimidazol-2-yl)-phenol derivatives (HL_x: x = 1–5) have been synthesized and characterized. The general formula for complexes C1 and C2 is K₂[Co(HL_1,2)₂Cl₂]·H₂O, for complex C3 K₂[Co(HL₃)₂Cl₂], and for complexes C4 and C5 [Co(HL_4,5)₂]. In all complexes, the ligands are coordinated as bidentate, via one imine nitrogen and the phenolate oxygen atoms. The structures of the compounds were characterized by FT-IR, UV–vis, ¹H, ¹³C NMR spectroscopies, ICP and elemental analysis (C, H, and N). The purity of these compounds was ascertained by melting point (m.p.) and TLC. Geometry optimization of the studied complexes was done by Gaussian09 software at B3LYP/TZVP level of theory and satisfactory theoretical–experimental agreement was achieved for NMR and IR spectra of the compounds. Based on the combined experimental and theoretical studies, six-coordinate octahedral structures have been proposed for complexes C1–C3, while complexes C4 and C5 had distorted tetrahedral geometry. All complexes were activated with diethylaluminum chloride (Et₂AlCl), cobalt(II) complexes containing bulky methyl groups in the aryl moiety show high catalytic activities (1774 kg?mol^?1(Co)?h^?1) for ethylene oligomerization. The oligomers obtained from the cobalt complexes exhibit good selectivity for linear 1-butene and 1-hexene. Results revealed that both the steric and electronic effects of ligands strongly affect the catalytic activities and the properties of the catalytic products.     

Chemical and Electrochemical Preparation for Co(II) Complexes of Some Novel Pyridine-2-(1H)-Thione Ring Fused Cycloalkane Derivatives

Anodic oxidation of cobalt and copper metals in an anhydrous acetone solution of pyridine-2-(1H)-thione-3-cyano-4-(2-bromophenyl)-5,6-ring fused cycloheptane (HL¹) and its derivatives, (HL²), (HL³), (HL⁴), (HL⁵), (HL⁶), (HL⁷), (HL⁸), and (HL⁹) yields complexes of composition [M(L)₂·(H₂O)₂]·n H₂O and [M(L)₂·(acetone)₂], where M = Co(II) or Cu(II) and L is the ligand. Also, reaction of an aqueous ethanolic solution of Co(Ac)₂·2H₂O with the previous ligands was prepared. Elemental analysis, and infrared and electronic spectral data are presented to confirm the formulation of the amorphous complexes. The spectral data indicate that the ligands are coordinated to the metal via the thioenol sulfur atom and the nitrogen atom of cyano groups. The ligands reacts in the enol form through the anodic dissolution of the ligands or during the reaction with metal salts. The ligand field parameters and crystal field splitting energies, Δ_o, for different cobalt metal complexes were calculated.     

Synthesis,characterization, DNA-binding,and antioxidant activities of four copper(II) complexes containing N-(3-hydroxybenzyl)-amino amide ligands

Four new substituted amino acid ligands, N-(3-hydroxybenzyl)-glycine acid (HL₁), N-(3-hydroxybenzyl)-alanine acid (HL₂), N-(3-hydroxybenzyl)-phenylalanine acid (HL₃), and N-(3-hydroxybenzyl)-leucine acid (HL₄), were synthesized and characterized on the basis of ¹H NMR, IR, ESI-MS, and elemental analyses. The crystal structures of their copper(II) complexes [Cu(L₁)₂]·2H₂O (1), [Cu(L₂)₂(H₂O)] (2), [Cu(L₃)₂(CH₃OH)] (3), and [Cu(L₄)₂(H₂O)]·H₂O (4) were determined by X-ray diffraction analysis. The ligands coordinate with copper(II) through secondary amine and carboxylate in all complexes. In 2, 3, and 4, additional water or methanol coordinates, completing a distorted tetragonal pyramidal coordination geometry around copper. Fluorescence titration spectra, electronic absorption titration spectra, and EB displacement indicate that all the complexes bind to CT-DNA. Intrinsic binding constants of the copper(II) complexes with CT-DNA are 1.32?×?10^6?M^?1, 4.32?×?10^5?M^?1, 5.00?×?10^5?M^?1, and 5.70?×?10^4?M^?1 for 1, 2, 3, and 4, respectively. Antioxidant activities of the compounds have been investigated by spectrophotometric measurements. The results show that the Cu(II) complexes have similar superoxide dismutase activity to that of native Cu, Zn-SOD.     

Synthesis,structures, and urease inhibition of nickel(II), zinc(II), and cobalt(II) complexes with similar hydroxy-rich Schiff bases

Four new nickel(II), zinc(II), and cobalt(II) complexes, [Zn(L¹)₂]?·?H₂O (1), [Ni(L¹)₂]?·?H₂O (2), [Ni(L²)₂] (3), and [Co(L³)₂]?·?H₂O (4), derived from hydroxy-rich Schiff bases 2-{[1-(5-chloro-2-hydroxyphenyl)methylidene]amino}-2-methylpropane-1,3-diol (HL¹), 2-{[1-(2-hydroxy-3-methoxyphenyl)methylidene]amino}-2-ethylpropane-1,3-diol (HL²), and 2-{[1-(5-bromo-2-hydroxyphenyl)methylidene]amino}-2-methylpropane-1,3-diol (HL³) have been synthesized and characterized by elemental analyses, infrared spectroscopy, and single-crystal X-ray determination. Each metal in the complexes is six-coordinate in a distorted octahedral coordination. The Schiff bases coordinate to the metal atoms through the imino N, phenolate O, and one hydroxyl O. In the crystal structures of HL¹ and the complexes, molecules are linked through intermolecular O–H···O hydrogen bonds, forming 1-D chains. The urease inhibitory activities of the compounds were evaluated and molecular docking study of the compounds with the Helicobacter pylori urease was performed.     

Theoretical,antimicrobial, antioxidant,in vitro cytotoxicity,and cyclin-dependent kinase 2 inhibitor studies of metal(II) complexes with bis(imidazol-1-yl)methane-based heteroscorpionate ligands

Abstract

A series of C-centered heteroscorpionate-based homoleptic manganese(II), nickel(II), and copper(II) complexes of type [M(L^1–3)₂] (1–9) have been synthesized by using the ligands (2-hydroxyphenyl)bis(imidazol-1-yl)methane (HL¹), (4-diethylamino-2-hydroxyphenyl)bis(imidazol-1-yl)methane (HL²) and (5-bromo-2-hydroxyphenyl)bis(imidazol-1-yl)methane (HL³). The geometric parameters of the complexes were determined using UV-vis and theoretical studies suggesting distorted octahedral geometry around metal(II) ion. Frontier molecular orbital analysis supports bioefficacy of the complexes. Antimicrobial activity of the metal(II) complexes were determined against two Gram(–ve) (Escherichia coli and Klebsiella pneumoniae) and two Gram(+ve) (Bacillus cereus and Staphylococcus aureus) bacteria, and three fungal (Candida albicans, Candida glabrata, and Candida krusei) strains. Antioxidant activity of nickel(II) and copper(II) complexes were evaluated against ABTS, DPPH, and H₂O₂ free radicals. In vitro cytotoxicity activity of nickel(II) and copper(II) complexes against human breast adenocarcinoma (MCF-7), cervical (HeLa), and lung (A549) cancer cell lines along with one normal human dermal fibroblasts (NHDF) cell line were carried out by MTT assay, which shows the potent activity of copper(II) complex 8 with respect to the standard drug cisplatin. Molecular docking studies evidence the interaction of complexes with cyclin-dependent kinase 2 receptor (CDK2).     

Zinc(II) and mercury(II) complexes with Schiff bases: syntheses,spectral, and structural characterization

Schiff bases o-vanilidene-1-aminobenzene (HL¹) and o-vanilidene-2-methyl-1-aminobenzene (HL²) lead to the formation of mono- and bis-[(Cl)Zn(L¹)] (1), [(Cl)Zn(L²)] (2), [(Cl)Hg(L¹)] (3), [(Cl)Hg(L²)] (4), [Zn(L¹)₂] (5), [Zn(L²)₂] (6), [Hg(L¹)₂] (7), and [Hg(L²)₂] (8) complexes by reactions of zinc(II) and mercury(II) chlorides in different mole ratio(s). Complexes 1–8 have been characterized by elemental analyses (Zn, Hg, C, H, Cl, and N), melting point and spectral (IR, ¹H-NMR), PXRD, molar conductivity measurement, and TGA. Conductivity measurements suggest non-electrolytes. Structural compositions have been assigned by mass spectral studies. Four-coordinate geometry may be assigned to these complexes tentatively. Structural study reveals that in 1–4 two metal centers are held together by two bridged (μ₂-Cl) chlorides, whereas 5–8 contain two bidentate Schiff-base ligands around one metal-producing monomers.     

Synthesis,crystal structure and fluorescence properties of two dinuclear zinc(II) complexes incorporating tridentate (NNO) Schiff bases

Reactions of hydrated zinc(II) trifluoroacetate and sodium azide with two tridentate Schiff bases HL¹ (2-((E)-(2-(dimethylamino)ethylimino)methyl)-4-chlorophenol) and HL² (2-((E)-(2-(dimethylamino)ethylimino)methyl)-4-bromophenol) under the same reaction conditions yielded two dinuclear isostructural zinc(II) complexes, [Zn(L¹)(N₃)]₂ (1) and [Zn(L²)(N₃)]₂ (2), respectively. The complexes were characterized systematically by elemental analysis, UV–Vis, FT-IR, and ¹H NMR spectroscopic methods. Single-crystal X-ray diffraction studies reveal that each of the dinuclear complexes consists of two crystallographically independent zinc(II) ions connected by double bridging phenoxides. All zinc(II) ions in 1 and 2 are surrounded by similar donor sets and display distorted square–pyramidal coordination geometries. The ligands and complexes reveal intraligand ¹(π → π*) flourescence. The enhancement of the fluorescence intensities for the complexes compared to the ligands indicates their potential to serve as photoactive materials.     

Synthesis,characterization, molecular docking,biological activity and density functional theory studies of novel 1,4‐naphthoquinone derivatives and Pd(II), Ni(II) and Co(II) complexes

Two novel heterocyclic ligands, 2‐[(5‐fluoro‐1,3‐benzothiazol‐2‐yl)amino]naphthalene‐1,4‐dione (HL¹) and 2‐[(5‐methyl‐1,3‐benzothiazol‐2‐yl)amino]naphthalene‐1,4‐dione (HL²), and their Pd(II), Ni(II) and Co(II) complexes were prepared and characterized using ¹H NMR, ¹³C NMR, infrared and UV–visible spectroscopic techniques, elemental analysis, magnetic susceptibility, thermogravimetry and molar conductance measurements. The infrared spectral data showed that the chelation behaviours of the ligands towards the transition metal ions were through one of the carbonyl oxygen and deprotonated nitrogen atom of the secondary amine group. Molar conductance results confirmed that the complexes are non‐electrolytes in dimethylsulfoxide. The geometries of the complexes were deduced from magnetic susceptibility and UV–visible spectroscopic results. Second‐order perturbation analysis using density functional theory calculation revealed a stronger intermolecular charge transfer between ligand and metal ion in [NiL¹(H₂O)₂(CH₃COO‐)] and CoL¹ compared to the other complexes. The in vitro antibacterial activity of the compounds against some clinically isolated bacteria strains showed varied activities. [NiL¹(H₂O)₂(CH₃COO‐)] exhibited the best antibacterial results with a minimum inhibitory concentration of 50 μg mL^?1. The molecular interactions of the compounds with various drug targets of some bacterial organisms were established in a bid to predict the possible mode of antibacterial action of the compounds. The ferrous ion chelating ability of the ligands indicated that HL¹ is a better Fe²⁺ ion chelator, with an IC₅₀ of 29.79 μg mL^?1, compared to HL² which had an IC₅₀ of 98.26 μg mL^?1.     

New Ni(II) complexes involving symmetrical bidentate N,O-donor Schiff base ligands: synthesis at ambient temperature,crystal structures,electrochemical study,antioxidant and cytotoxic activities

A new series of Ni(II) complexes, [Ni(L¹)₂] (1), [Ni(L²)₂] (2), [Ni(L³)₂] (3), and [Ni(L⁴)₂] (4), were synthesized at ambient temperature. The bidentate Schiff base ligands HL^1?4 have been obtained by the condensation reaction of 2-hydroxybenzaldehyde, 5-bromo-2-hydroxybenzaldehyde, 3-methoxy-2-hydroxy-benzaldehyde, and 4-methoxy-2-hydroxy-benzaldehyde, respectively, with 2-methoxyethylamine. The newly synthesized complexes were characterized by elemental analyses, FT-IR and UV–vis spectroscopy. The crystal structures of mononuclear Ni(II) complexes 2 and 3 were determined by the single-crystal X-ray diffraction technique. Electrochemical properties of the complexes were investigated in acetonitrile. The antioxidant properties of the Schiff base ligands and complexes were evaluated by two in vitro tests, DPPH radical scavenging and reducing power. The compounds were screened for their in vitro anticancer potential using gastric cancer cell lines by MTT assay. All ligands and complexes showed considerable cytotoxic activity against cancer cell lines (IC₅₀ = 0.2516–5.468 μg·mL^?1). The most promising result was achieved for complex 1 with the best IC₅₀ value of 0.2516 μg·mL^?1. It was found that the proliferation rate of MKN-45 cells decreased after treatment with the complexes in a dose-dependent way.     

Heteronuclear complexes of oxorhenium(V) with Fe(III), Co(II), Ni(II), Cu(II), Cd(II) and UO2(VI) and their biological activities

Heteronuclear complexes containing oxorhenium(V), with Fe(III), Co(II), Ni(II), Cu(II), Cd(II) and UO₂(VI) ions were prepared by the reaction of the complex ligands [ReO(HL¹)(PPh₃)(OH₂)Cl]Cl (a) and/or [ReO(H₂L²)(PPh₃)(OH₂)Cl]Cl (b), where H₂L¹?=?1-(2-hydroxyphenyl)butane-1,3-dione-3-(5,6-diphenyl-1,2,4-triazine-3-ylhydrazone) and H₃L²?=?1-(2-hydroxyphenyl)butane-1,3-dione-3-(1H-benzimidazol-2-ylhydrazone), with transition and actinide salts. Heterodinuclear complexes of ReO(V) with Fe(III), Co(II), Ni(II), Cu(II) and Cd(II) were obtained using a 1?:?1 mole ratio of the complex ligand and the metal salt. Heterotrinuclear complexes were obtained containing ReO(V) with UO₂(VI) and Cu(II) using 2?:?1 mole ratios of the complex ligand and the metal salts. The complex ligands a and b coordinate with the heterometal ion via a nitrogen of the heterocyclic ring and the nitrogen atom of the C=N⁷ group. All transition metal cations in the heteronuclear complexes have octahedral configurations, while UO₂(VI)?complexes have distorted dodecahedral geometry. The structures of the complexes were elucidated by IR, ESR, electronic and ¹H NMR spectra, magnetic moments, conductance and TG-DSC measurements. The antifungal activities of the complex ligands and their heteronuclear complexes towards Alternaria alternata and Aspergillus niger showed comparable behavior with some well-known antibiotics.     

Copper(II), nickel(II) and cobalt(II) complexes of 5,5-dimethylcyclohexane-1,2,3-trione-2-arylhydrazones

Summary Copper(II), nickel(II) and cobalt(II) perchlorate complexes of 5,5-dimethylcyclohexane-1,2,3-trione-2-(p-nitrophenyl-hydrazone) (HL¹), 5,5-dimethyl-cyclohexane-1,2,3-trione-2-(p-chlorophenylhydrazone) (HL²), 5,5-dimethylcyclohexane-1,2,3-trione-2-(o-chlorophenylhydrazone) (HL⁴), 5,5-dimethylcyclohexane-1,2,3-trione-2-(o-methylphenyl-hydrazone) (HL⁵) and 5,5-dimethylcyclohexane-1,2,3-trione-2-(m-methylphenylhydrazone) (HL⁶) have been prepared, and characterized using analytical, spectral and magnetic measurements. The data reveal that the reaction of Cu(ClO₄)₂ (1 mol) in EtOH, with all ligands, produces complexes of the type CuL(ClO₄)(H₂O).nH₂O. Nickel(II) and cobalt(II) perchlorates react only with HL¹ and HL² to produce the complexes ML(ClO₄)(H₂O)₃ (where M = Ni^II, L = L^– and L², M = Co^II, L = L¹) and Co(HL₂)₂-(ClO₄)₂.2H₂O. The spectral data show that the ligands behave as monobasic bidentate in their azo forms, except HL² which reacts with cobalt(II) as a neutral bidentate ligand in its hydrazone form.     

In-vitro antibacterial activity of Ni(II), Cu(II), and Zn(II) complexes incorporating new azo-azomethine ligand possessing excellent antioxidant,anti-inflammatory activity and protective effect of free radicals against plasmid DNA

Azo Schiff base ligand 2-hydroxy-3-methoxy-5-(tolyldiazenyl)benzaldehyde oxime (HL¹) and 2-hydroxy-3-methoxy-5-(methoxyphenyl)benzaldehyde oxime (HL²) were prepared along with their transition metal complexes of Ni(II), Cu(II), and Zn(II). Ligands and their metal complexes were characterized by several analysis techniques. In- vitro antibacterial, antioxidant and anti-inflammatory activities of synthesized ligands and their metal complexes have been studied. Biological study showed that amongst all the synthesized compounds, Cu(II) complexes possessed excellent antibacterial activity than standard antibiotic Chloramphenicol. Ligands (HL¹) and (HL²) showed excellent antioxidant as well as anti-inflammatory activity. Both the ligands were tested for their protective effect of free radicals against plasmid DNA and it was found that both the ligands showed good DNA nicking activity.     

Crystal structures,electrochemical properties,antioxidant screening and in vitro cytotoxic studies on four novel Cu(II) complexes of bidentate Schiff base ligands derived from 2-methoxyethylamine

Four novel Schiff base ligands and their copper(II) complexes, [Cu(L¹)₂] (1), [Cu(L²)₂] (2), [Cu(L³)₂] (3), and [Cu(L⁴)₂] (4), were synthesized and characterized by elemental analyses, FT-IR, and UV–Vis spectroscopy. The ligands were synthesized from the condensation of 2-methoxyethylamine with various salicylaldehyde derivatives (x-salicylaldehyde for HLⁿ, x = H (n = 1), 5-Br (n = 2), 3-OMe (n = 3), and 4-OMe (n = 4)). The molecular structures of 1, 2, and 3 were determined by the single crystal X-ray diffraction technique. The redox behavior studies of the complexes in acetonitrile display the electronic effects of the groups on the redox potential. The antioxidant activity of the Schiff base ligands and their Cu(II) complexes was evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method and FRAP assay. Furthermore, the in vitro anticancer activity of compounds was screened, including MTT and migration assays against gastric cancer cell line (MKN-45). The results show that all ligands and complexes have antioxidant and anticancer activity in a concentration-dependent way.     

Synthesis,crystal structures,antimicrobial activities,and DFT calculations of two new azido nickel(II) complexes

Two new complexes, [Ni(HL¹)(N₃)(μ_1,1N₃)]₂ (1) [HL¹: NC₅H₄CH₃C=NNH (C=O) NH₂] and [Ni(L²)N₃] (2) [HL²: NC₅H₄HC=N NH(C=S)NH₂], have been synthesized by reaction of Ni(OAC)₂·4H₂O and sodium azide with HL¹ and HL² and characterized by elemental analysis, FT-IR, and UV–vis spectral studies. Single-crystal X-ray diffraction reveals that 1 is dinuclear with nickel(II) in an octahedral environment of NNO donors of HL¹, two nitrogens of azide bridges and one nitrogen of terminal azide; 2 is mononuclear containing nickel(II) in a distorted square-planar environment of NNS donors of HL² and one terminal azide. The structures of 1 and 2 have been optimized by density functional theory. The results of antimicrobial activities of ligands, 1 and 2 demonstrated that HL² and 2 have good antimicrobial activity in contrast with HL¹ and 1, related to the presence of sulfur donor in HL².     

Ruthenium(II) complexes containing 4‐methoxybenzhydrazone ligands: synthesis,characterization, DNA binding,DNA cleavage,radical scavenging and in vitro cytotoxic activity

Three ruthenium(II) hydrazone complexes of composition [RuCl(CO)(PPh₃)₂L] were synthesized from the reactions of [RuHCl(CO)(PPh₃)₃] with hydrazones derived from 4‐methoxybenzhydrazide and 4‐formylbenzoic acid (HL¹), 4‐methylbenzaldehyde (HL²) and 2‐bromobenzaldehyde (HL³). The synthesized hydrazone ligands and their metal complexes were characterized using elemental analysis and infrared, UV–visible, NMR (¹H, ¹³C and ³¹P) and mass spectral techniques. The hydrazone ligands act as bidentate ones, with O and N as the donor sites, and are predominantly found in the enol form in all the complexes studied. The molecular structures of the ligands HL¹, HL² and HL³ were determined using single‐crystal X‐ray diffraction. The interactions of the ligands and the complexes with calf thymus DNA were studied using absorption spectroscopy and cyclic voltammetry which revealed that the compounds could interact with calf thymus DNA through intercalation. The DNA cleavage activity of the complexes was evaluated using a gel electrophoresis assay which revealed that the complexes act as good DNA cleavage agents. In addition, all the complexes were subjected to antioxidant assay, which showed that they all possess significant scavenging activity against 2,2‐diphenyl‐2‐picrylhydrazyl, OH and NO radicals. The in vitro cytotoxic effect of the complexes examined on cancerous cell lines (HeLa and MCF‐7) showed that the complexes exhibit substantial anticancer activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Copper(I) and copper(II) complexes with pyrazine-containing pyridylalkylamide ligands N-(pyridin-2-ylmethyl)pyrazine-2-carboxamide and N-(2-(pyridin-2-yl)ethyl)pyrazine-2-carboxamide

Four copper(II) complexes and one copper(I) complex with pyridine-containing pyridylalkylamide ligands N-(pyridin-2-ylmethyl)pyrazine-2-carboxamide (HL^pz) and N-(2-(pyridin-2-yl)ethyl)pyrazine-2-carboxamide (HL^pz?) were synthesized and characterized. The X-ray crystal structures of [Cu₂(L^pz)₂(4,4?-bipy)(OTf)₂] (1, OTf?=?trifluoromethanesulfonate, 4,4?-bipy?=?4,4?-bipyridine) and [Cu(L^pz)(py)₂]OTf·H₂O (2, py?=?pyridine) revealed binuclear and mononuclear molecular species, respectively, while [Cu(L^pz)(μ₂-1,1-N₃)]_n (3), [Cu(L^pz?)(μ₂-1,3-N₃)]_n (4), and [Cu(HL^pz)Cl]_n (5) are coordination polymer 1-D chains in the solid state.     

Synthesis,structure, and properties of coordination compounds of copper(II) acetate with substituted 2-{[2-(2-hydroxyethylamino)ethylimino]methyl}phenol

Salicylic, 5-chloro-5-bromo-5-nitro-, 3-methoxysalicylic, 2-hydroxy-1-naphthoic aldehydes and 2,3-, 2,4-, and 2,5-dihydroxybenzaldehyde were shown to react in ethanol with 2-(2-aminoethylamino)ethanol in the presence of copper acetate hydrate forming coordination compounds Cu(L^1-9)CH₃COO {HL^1-8, 2-([2-(2-hydroxyethylamino)ethylimino]methyl}phenol (HL¹) and respective chloro(HL²), bromo- (HL³), nitro- (HL⁴), methoxy- (HL⁸), or hydroxy-substituted (HL^5-7); HL⁹, 2-{[2-(2-hydroxyethylamine)ethylimino] methylnaphthol)}. Structure of the complex Cu(L³)CH₃COO was determined by X-ray diffraction analysis. Coordination polyhedron of its central atom is a distorted tetragonal bipyramid with (4+1+1) modes of coordinating the copper atom. The bipyramid base is formed by the atoms of phenol oxygen and of azomethine and imine nitrogen atoms of the ligand (HL³) and the oxygen atom of the acetate ion. Axial apices of the bipyramid are occupied by the alcohol oxygen atoms of the azomethine (HL³) and the second oxygen atom of the acetate ion. Other complexes are also of monomer structure. Azomethines (HL^1-9) behave as monodeprotonated tetradentate O,N,N,O ligands. The thermolysis of substances includes a stage of complete thermal decomposition (360–530°C). Synthesized complexes show selective antimicrobial activity against a series of standard strains of Staphylococcus aureus and E. coli at the concentration in the range of 75–300 μg ml⁻¹.     

Coordination compounds of copper with 2-formylpyridine 4-(dimethylphenyl)thiosemicarbazones

2-Formylpyridine 4-(2,6-dimethylphenyl)-(HL¹), 4-(2,5-dimethylphenyl)-(HL²), 4-(3,4-dimethylphenyl)-(HL³), and 4-(2,4-dimethylphenyl)thiosemicarbazones (HL⁴) react with copper chloride and nitrate to form coordination compounds CuL^1–4X·nH₂O [X = Cl^?, NO ₃ ^? ; n = 1, 2]. All compounds have a polynuclear structure. Azomethines HL^1–4 act as the bridging monodeprotonated tridentate N,N,S-ligands. The thermolysis of the complexes includes the dehydration (70–90°C) and total thermal decomposition (350–520°C). The complexes synthesized exhibit a selective antimicrobial activity against a series of standard strains of Staphylococcus aureus and Escherichia coli in the concentration range of 0.009–37.5 μg ml^?1.     

Heteroscorpionate‐based heteroleptic copper(II) complexes: Antioxidant,molecular docking and in vitro cytotoxicity studies

Three new heteroscorpionate ligands, (2‐hydroxyphenyl)bis(imidazol‐1‐yl)methane (HL¹), (4‐diethylamino‐2‐hydroxyphenyl)bis(imidazol‐1‐yl)methane (HL²) and (5‐bromo‐2‐hydroxyphenyl)bis(imidazol‐1‐yl)methane (HL³), and their heteroleptic copper(II) complexes of the type [Cu(L^1–3)diimine]ClO₄ ( 1 – 6 ; where diimine =2,2′‐bipyridyl or 1,10‐phenanthroline) have been synthesized and characterized using spectroscopic methods. The molecular structure of ligand HL¹ was determined by single‐crystal X‐ray diffraction. UV–visible, electron paramagnetic resonance and theoretical studies suggest a distorted square pyramidal geometry around copper(II) ion. Analyses of highest occupied and lowest unoccupied molecular orbitals have been used to explain the charge transfer taking place within the complexes. The antioxidant activities of the heteroscorpionate ligands and their heteroleptic copper(II) complexes were determined using ABTS, DPPH and H₂O₂ free radical scavenging assays with respect to standard antioxidant ascorbic acid. In molecular docking studies, the complexes showed π–π, hydrogen bonding, van der Waals and electrostatic interactions with fibroblast growth factor receptor kinase. In vitro cytotoxicity activities of ligands and copper(II) complexes were examined on human breast adenocarcinoma (MCF‐7), cervical (HeLa) and lung (A549) cancer cell lines and normal human dermal fibroblast cell line using MTT assay. Complex 4 exhibited higher anticancer activity than the other complexes against all three cancer lines, being more potent than the standard drug cisplatin.     

Synthesis and characterization of new lead(II) complexes of Schiff bases derived from amino acids

Some new lead(II) complexes of the general formula Pb(L)₂, where HL = Schiff bases derived from the condensation of isatin and chloroisatin with phenylalanine (HL¹/HL⁴), isoleucine (HL²/HL⁵), and glycine (HL³/HL⁶), have been synthesized and characterized by elemental analysis, molar conductance, electronic, infrared, and multinuclear magnetic resonance (¹H and ¹³C) studies. In all cases, the Pb atom is in a four-coordinated environment with two bidentate deprotonated Schiff bases binding as monoanionic ligands through the oxygen and azomethine nitrogen. The 3D molecular modeling and analysis for bond lengths and bond angles have also been carried out for one of the representative compounds, [Pb(L³)₂] to substantiate the proposed structures.