Spectral and thermal studies of alloxan complexes

The complexes of alloxan with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) Cd(II), Hg(II), Ti(IV) and Zr(II) have been isolated and characterized on the basis of elemental analysis, molar conductivity, spectral studies (mid infrared, ¹H-NMR and UV/vis spectra), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The thermal decomposition of the metal complexes was studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The kinetic thermodynamic parameters, E*, ΔH*, ΔS* and ΔG*, were calculated using Coats and Redfern and Horowitz and Metzger equations. The ligand and its complexes have been studied for possible biological activity including antibacterial and antifungal activity.     

Phosphorus Schiff base ligand and its complexes: Experimental and theoretical investigations

A phosphorus-containing Schiff base was prepared from bis{3-[2-(4-amino-1,5-dimethyl-2-phenylpyrazol-3-ylideneamino)ethyl]indol-1-ylmethyl}phosphinic acid and paraformaldehyde as a novel antibacterial compound. The reaction of the Schiff base ligand with VO(IV), Ni(II), Co(II), Cu(II), Zn(II), Cd(II), Hg(II), Pd(II) and Pt(IV) led to binuclear species of metal complexes, depending on the ratio of metal ion and ligand. The ligand and its complexes were investigated using elemental analysis, Fourier transform infrared, ¹H NMR, ¹³C NMR, UV–visible and mass spectra, thermogravimetric analysis, conductivity measurements and thermal analysis. The results showed that the Schiff base behaves as a tetradentate ligand; moreover, on the basis of conductance results, of all the prepared complexes are non-electrolytes, excepting the Pt(IV) complex. The metal complexes were found to be formed with a metal-to-ligand ratio of 2:1, except for the Pt(IV) complex with a ratio of 1:1. The activation thermodynamic parameters (ΔE*, ΔH*, ΔS*, ΔG* and K) and the activation energy of thermal decomposition were determined from thermogravimetric analysis using the Coats–Redfern method. The biological activities of the metal complexes were screened against the growth of bacteria and fungi in vitro to assess the antimicrobial potential and study the toxicity of the compounds. The prepared compounds have noteworthy antimicrobial properties.     

Spectroscopic characterization,thermogravimetric and antimicrobial studies of some new metal complexes derived from4-(4-Isopropyl phenyl)-2-oxo-6-phenyl 1,2-dihyropyridine-3-carbonitrile (L)

A new series of Fe (III), Co (II), Zn (II), Y (III), Zr (IV) and La (III) complexes derived from the novel ligand 4-(4-Isopropyl phenyl)-2-oxo-6-phenyl 1,2-dihyropyridine-3-carbonitrile (L) were synthesized and characterized. The mode of bonding of L and geometrical structures of their metal complexes were elucidated by different micro analytical and spectral methods (FT-IR,UV–visible,1H NMR and Mass spectra) as well as thermal analysis (TG and DTG), and differential scanning calorimetry (DSC). The results of analytical and spectroscopic equipments revealed that L acts as bidentate through nitrogen of carbonitrile group and oxygen of keto group. The conductivity measurement results deduced that these chelates are electrolyte with 1:2 for Co (II), Zn (II), and Zr (IV) and 1:3 for Fe (III), Y (III), and La (III). The results of magnetic moment measurements supported paramagnetic for some complexes (Fe (III), Co (II) and Cu (II)) and diamagnetic phenomena for the other complexes (Y (III), Zr (IV) and La (III)). Thermodynamic parameters such as energy of activation E*, entropy ΔS*, enthalpy ΔH* and Gibss free energy ΔG* were calculated using Coats-Redfern and Horowitz-Metzeger methods at n = 1 or n#1. Some results of bioactivity tests for ligands and their metal complexes were recorded against Gram-positive, Gram-negative bacteria and antifungal. The complexes showed significant more than free ligand.     

Spectroscopic study of molecular structures of novel Schiff base derived from o-phthaldehyde and 2-aminophenol and its coordination compounds together with their biological activity

New Schiff base (H₂L) ligand is prepared via condensation of o-phthaldehyde and 2-aminophenol. The metal complexes of Cr(III), Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with the ligand are prepared in good yield from the reaction of the ligand with the corresponding metal salts. They are characterized based on elemental analyses, IR, solid reflectance, magnetic moment, electron spin resonance (ESR), molar conductance, ¹H NMR and thermal analysis (TGA). From the elemental analyses data, the complexes are proposed to have the general formulae [M(L)(H₂O)n]·yH₂O (where M = Mn(II) (n = 0, y = 1), Fe(II) (n = y = 0), Co(II) (n = 2, y = 0), Ni(II) (n = y = 2), Cu(II) (n = 0, y = 2) and Zn(II) (n = y = 0), and [MCl(L)(H₂O)]·yH₂O (where M = Cr(III) and Fe(III), y = 1–2). The molar conductance data reveal that all the metal chelates are non-electrolytes. IR spectra show that H₂L is coordinated to the metal ions in a bi-negatively tetradentate manner with ONNO donor sites of the azomethine N and deprotonated phenolic-OH. This is supported by the ¹H NMR and ESR data. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Fe(III), Co(II) and Ni(II) complexes), tetrahedral (Mn(II), Fe(II) and Zn(II) complexes) and square planar (Cu(II) complex). The thermal behaviour of these chelates is studied and the activation thermodynamic parameters, such as, E*, ΔH*, ΔS* and ΔG* are calculated from the DrTGA curves using Coats-Redfern method. The parent Schiff base and its eight metal complexes are assayed against two fungal and two bacterial species. With respect to antifungal activity, the parent Schiff base and four metal complexes inhibited the growth of the tested fungi at different rates. Ni(II) complex is the most inhibitory metal complex, followed by Cr(III) complex, parent Schiff base then Co(II) complex. With regard to bacteria, only two of the tested metal complexes (Mn(II) and Fe(II)) weakly inhibit the growth of the two tested bacteria.     

Nano‐synthesis and spectral,thermal, modeling,quantitative structure–activity relationship and docking studies of novel bioactive homo‐binuclear metal complexes derived from thiazole drug for therapeutic applications

Seven novel homo‐binuclear Cr(III), Fe(III), Cu(II), ZrO(II), Sn(II), Pb(II) and Ce(III) nanosized complexes of a thiazole drug (H₂L) were synthesized for chemotherapeutic applications. H₂L was prepared via a condensation reaction between 2‐(4‐aminobenzenesulfonamido)thiazole and 2‐hydroxybenzaldehyde. The structures of H₂L and its metal complexes were investigated by various means. These included microanalysis, ¹H NMR, ¹³C NMR, Fourier transform infrared, UV–visible, electron spin resonance and mass spectroscopies, transmission electron microscopy (TEM), powder X‐ray diffraction (XRD), thermogravimetric analysis (TGA) and molar conductivity. The measurements revealed that H₂L coordinates with the metal ions through two chelating centers, indicating its behavior as a dibasic tetradentate ligand. The first center involves the nitrogen of azomethine (CH═N) and the α‐hydroxyl oxygen while the other center is the thiazole nitrogen and the sulfonamide oxygen. From spectroscopic and analytical data, the Cr(III), Fe(III) and Ce(III) complexes have octahedral geometries, whereas the Cu(II), ZrO(II), Sn(II) and Pb(II) complexes have tetrahedral geometries. TEM and XRD measurements unambiguously showed the nanometric particle sizes of the complexes. The activation thermo‐kinetic parameters, E*, ?H*, ?S* and ?G*, of the various decomposition steps of the complexes were determined mathematically from the TGA curves. Gaussian09 and quantitative structure–activity relationship modeling studies were utilized to verify the biological and structural feature relationships. Docking studies were performed to throw more light on the biological priority of the proposed drugs, using microorganism protein receptors. The antitumor and antimicrobial efficiencies of the H₂L drug and its complexes were determined to estimate their potential therapeutic utility. In general, the complexes showed greater antitumor and antimicrobial efficiencies than the H₂L drug. The Fe(III) complex exhibited efficient antimicrobial activities against Candida albicans and Staphylococcus aureus and its efficiency is equivalent to that of standard drugs. The Cu(II) complex showed the greatest cytotoxic activity towards HEPG2.     

Novel Schiff base ligand and its metal complexes with some transition elements. Synthesis,spectroscopic, thermal analysis,antimicrobial and in vitro anticancer activity

A novel Schiff base ligand (H₂L) was prepared through condensation of 2,6‐diaminopyridine and o‐benzoylbenzoic acid in a 1:2 ratio. This Schiff base ligand was characterized using elemental and spectroscopic analyses. A new series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) metal complexes of H₂L were prepared and characterized using elemental analysis, spectroscopy (¹H NMR, mass, UV–visible, Fourier transform infrared, electron spin resonance), magnetic susceptibility, molar conductivity, X‐ray powder diffraction and thermal analysis. The complexes are found to have trigonal bipyramidal geometry except Cr(III), Mn(II) and Fe(III) complexes which have octahedral geometry based on magnetic moment and solid reflectance measurements. The infrared spectral studies reveal that H₂L behaves as a neutral bidentate ligand and coordinates to the metal ions via the two azomethine nitrogens. ¹H NMR spectra confirm the non‐involvement of the carboxylic COOH proton in complex formation. The presence of water molecules in all reported complexes is supported by thermogravimetric studies. Kinetic and thermodynamic parameters were determined using Coats–Redfern and Horowitz–Metzger equations. The synthesized ligand and its complexes were screened for antimicrobial activities against two Gram‐positive bacteria (Bacillus subtilis and Staphylococcus aureus), two Gram‐negative bacteria (Escherichia coli and Neisseria gonorrhoeae) and one fungus (Candida albicans). Anticancer activities of the ligand and its metal complexes against human breast cancer cell line (MCF7) were investigated. Copyright © 2016 John Wiley & Sons, Ltd.     

Physicochemical characterization of nanobidentate ferrocene‐based Schiff base ligand and its coordination complexes: Antimicrobial,anticancer, density functional theory,and molecular operating environment studies

A novel bidentate Schiff base ligand (HL, Nanobidentate Ferrocene based Schiff base ligand L (has one replaceable proton H)) was prepared via the condensation of 2‐amino phenol with 2‐acetyl ferrocene. The ligand was characterized using elemental analysis, mass spectrometry, infrared (IR) spectroscopy, ¹proton nuclear magnetic resonance (H‐NMR) spectroscopy, scanning electron microscopy (SEM), and thermal analysis. The corresponding 1:1 metal complexes with some transition‐metal ions were additionally characterized by their elemental analysis, molar conductance, SEM, and thermogravimetric ana1ysis (TGA). The complexes had the general formula [M(L)(Cl)(H₂O)₃]xCl·nH₂O (M = Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II)), (x = 0 for Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II), x = 1 for Cr(III) and Fe(III)), (n = 1 for Cr(III), n = 3 for Mn(II) and Co(II), n = 4 for Fe(III), Ni(II), Cu(II), Zn(II), and Cd(II)). Density functional theory calculations on the HL ligand were also carried out in order to clarify molecular structures by the B31YP exchange‐correlation function. The results were subjected to molecular orbital diagram, highest occupied mo1ecu1ar orbital–lowest occupied molecular orbital, and molecular electrostatic potential calculations. The parent Schiff base and its eight metal complexes were assayed against four bacterial species (two Gram‐negative and two‐Gram positive) and four different antifungal species. The HL ligand was docked using molecular operating environment 2008 with crystal structures of oxidoreductase (1CX2), protein phosphatase of the fungus Candida albicans (5JPE), Gram(?) bacteria Escherichia coli (3T88), Gram(+) bacteria Staphylococcus aureus (3Q8U), and an androgen‐independent receptor of prostate cancer (1GS4). In order to assess cytotoxic nature of the prepared HL ligand and its complexes, the compounds were screened against the Michigan cancer foundation (MCF)‐7 breast cancer cell line, and the IC₅₀ values of compounds were calculated.     

Coordination modes of multidentate azodye ligand derived from 4,4′‐methylenedianiline towards some transition metal ions: Synthesis,spectral characterization,thermal investigation and biological activity

Nine new azodye metal complexes of Mn(II), Co(II), Ni(II), Cu(II), Cr(III), Fe(III), Ru(III), Hf(IV) and Zr(IV) ions have been prepared via the reaction of 5,5′‐((1E,1′E)‐(methylenebis(1,4‐phenylene))bis(diazene‐2,1‐diyl))bis(6‐hydroxy‐2‐thioxo‐2,3‐dihydropyrimidin‐4(5H)‐one) (H₄L) with the corresponding metal salts affording sandwich (1 L:1 M), mononuclear (2 L:1 M), binuclear (1 L,2 M) and tetranuclear (1 L,4 M) complexes. Elemental analyses, spectral methods, magnetic moment measurements and thermal studies were utilized to confirm the mode of bonding and geometrical structure for the ligand and its metal complexes. Infrared spectral data show that the H₄L ligand chelates with some metal ions in keto–enol–thione or keto–thione manner. It behaves in a neutral/dibasic tetradentate fashion in sandwich and binuclear complexes. Also, it acts as a neutral bidentate moiety in the Cr(III) complex. The spectra reveal that azo group participates in chelation in all complexes. Octahedral geometry was suggested for all chelates but the Cu(II) complex with square planar geometry. The thermal stability and decomposition of the compounds were studied, the data showing that the thermal decomposition ended with metal or metal oxide mixed with carbon as final product. The electron spin resonance spectrum of the Cu(II) complex demonstrates that the free electron is located in the ( ) orbital. Measurements of biological activity against human cell lines Hep‐G₂ and MCF‐7 reveal that the Cu(II) complex has a higher cytotoxicity in comparison to the free ligand and other metal complexes, with IC₅₀ values of 6.10 and 5.2 μg ml^?1, respectively, while the ligand has anti‐tumour activity relative to some of the investigated metal complexes.     

Study of the chemical structure and their nematicidal activity of N2O2 tetradentate Schiff base metal complexes

Coordination compounds of Cu (II), Y (III), Zr (IV) and La (III) with the tetradentate Schiff base (H₂L) obtained through the condensation of p‐phenylenediamine with salicylaldehyde under reflux conditions. The complexes were characterized by elemental analysis, magnetic susceptibility, molar conductance and also, with various spectroscopic techniques such as ¹H NMR, UV–Vis., IR and XRD techniques. Electrolytic nature of complexes was ascertained by molar conductance values. In these four complexes, the ligand chelates act in a tetradentate manner via azomethine nitrogen and oxygen atoms of phenolic groups. Electronic spectroscopic data are in agreement with an octahedral geometrical structure. Thermal degradation analyses in nitrogen gas were used to investigate the number and location of water molecules. The chemical formulae of metal complexes were confirmed by microanalytical data. The activation thermodynamic parameters, such as, E^*, ΔH^*, ΔS^* and ΔG^* were calculated from the DTG curves using Coats Redfern (CR) and Horowitz–Metzeger (HM) methods at n = 1 or n ≠ 1. Nematicidal activities indicate that the ligand exhibit greater activity when compared to its complexes. In addition metal complexes displayed good moderate nematicidal activities.     

Elaborated spectral,modeling, QSAR,docking, thermal,antimicrobial and anticancer activity studies for new nanosized metal ion complexes derived from sulfamerazine azodye

New azodye ligand (H₂L) and its relative Cr(III)-, Mn(II)-, Fe(III)-, Co(II)-, Ni(II)-, Cu(II)-, Zn(II)- and Cd(II)-nanosized complexes were prepared. A new synthesized compounds were characterized using spectral (mass, IR, UV–Vis, XRD, and ESR) and analytical (elemental, molar conductance, thermal and magnetic moment measurements) tools. Infrared spectra showed that the ligand behaves as a monobasic bidentate, coordinating with central atoms through carbonyl oxygen and α-hydroxyl group. The geometrical structures of Cr(III) and Fe(III) complexes were found to be in octahedral configuration, whereas Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes have tetrahedral forms. XRD patterns reflect an amorphous appearance of all investigated complexes. TEM images showed nanosized particles and identical distribution over the complex surface. Molecular modeling for the drug ligand and its metal ion complexes were performed using Gaussian09 program to assert on their structural formulae. Some essential parameters were extracted using HOMO and LUMO energies. AutoDock tools 4.2 was used to simulate the interaction process with infected cell proteins to expect the experimental pathway. The inhibition activity of drug ligand and its metal ion complexes was evaluated towards different types of bacteria and fungi through in vitro antimicrobial activities. The antitumor activities of all compounds are straightened towards human liver carcinoma (HEPG2) cell lines. Fe(III) and Co(II) complexes exhibited IC₅₀ of 2.90 and 4.23 µg mL^?1, respectively, which means they are more potent anticancer drug than the standard (doxorubicin, IC₅₀ = 4.73 µg mL^?1). Therefore, the two complexes may consider promising anticancer drugs.

     

Synthesis,characterization, cyclic voltammetry,and antimicrobial properties of N-(5-benzoyl-2-oxo-4-phenyl-2H-pyrimidine-1-yl)-malonamic acid and its metal complexes

A new heterocyclic compound, N-(5-benzoyl-2-oxo-4-phenyl-2H-pyrimidin-1-yl)-malonamic acid, was synthesized from N-aminopyrimidine-2-one and malonyldichloride. Bis-chelate complexes of the ligand were prepared from acetate/chloride salts of Cu(II), Co(II), Ni(II), Mn(II), Zn(II), Cd(II), Fe(III), Cr(III), and Ru(III) in methanol. The structures of the ligand and its metal complexes were characterized by microanalyses, IR, NMR, API-ES, UV-Vis spectroscopy, magnetic susceptibility, and conductometric analyses. Octahedral geometry was suggested for all the complexes, in which the metal center coordinates to ONO donors of the ligand. Each ligand binds the metal using C=O, HN, and carboxylate. The cyclic voltammograms of the ligand and the complexes were also discussed. The compounds were evaluated for their antimicrobial activities against Gram-positive and Gram-negative bacteria, and fungi using microdilution procedure. The antimicrobial studies showed that Cu(II), Fe(III), and Ru(III) complexes exhibited good antibacterial activity against Gram-positive bacteria with minimum inhibitory concentrations between 20 and 80 µg mL^?1. However, the ligand and the complexes possess weak efficacy against Gram-negative bacterium and Candida strains. As a result, we suggest that these complexes containing pyrimidine might be a new group of antibacterial agents against Gram-positive bacteria.     

Synthesis and spectroscopic studies of Mn(II), Co(II), and Cu(II) complexes of novel 2-[2,4-Dioxo-4-(thiophen-2-yl)butanamido]benzoic acid ligands

Mn(II), Co(II), and Cu(II) complexes with novel heterocyclic ligands derived from anthranilic acid and its 5-bromo derivative with ethyl-2-thionylpyruvate were synthesized and characterized by means of elemental analysis, molar conductivity, spectral methods (IR, ¹H NMR, and UV-Vis spectra) and simultaneous thermal analysis (TG and DTG) techniques. The IR spectra of the two ligands and their complexes were used to identify the type of bonding. The kinetic thermodynamic parameters such as: E*, ΔH*, ΔS*, and ΔG* were estimated from the DTG curves. New ligands and their complexes have been tested for their possible antibacterial and antifungal activity.     

Synthesis,characterization, fluorescence and redox features of new <Emphasis Type="Italic">vic</Emphasis>-dioxime ligand bearing pyrene and its metal complexes

A new vic-dioxime ligand, N,N′-bis(aminopyreneglyoxime) (LH₂), and its copper(II), nickel(II) and cobalt(II) metal complexes were synthesized and characterized by elemental analyses, IR, UVVIS and ¹H and ¹³C NMR spectra (for the ligand). Mononuclear complexes were synthesized by a reaction of ligand (LH₂) and salts of Co(II), Ni(II), and Cu(II) in ethanol. The complexes have the metal-ligand ratio of 1: 2 and metals are coordinated by N,N′ atoms of vicinal dioximes. The ligand acts in a polydentate fashion bending through nitrogen atoms in the presence of a base, as do most vic-dioximes. Detection of a H-bonding in the Co(II), Ni(II), and Cu(II) complexes by IR revealed the square-planar MN₄ coordination of mononuclear complexes. Fluorescent properties of the ligand and its complexes arise from pyrene units conjugated with a vic-dioxime moiety. Fluorescence emission spectra of the ligand showed a drastic decrease in its fluorescence intensity upon metal binding. The electrochemical properties of the complexes were studied by the cyclic voltammetry technique. The nickel complex displayed an irreversible oxidation process while the copper complex exhibited a quasi-reversible oxidation and reduction processes based on the copper Cu(II)/Cu(III) and Cu(II)/Cu(I) couples, respectively.     

Transition metal complexes of Schiff base ligand based on 4,6-diacetyl resorcinol

Novel Schiff base ligand based on the condensation of 4,6-diacetyl resorcinol with 2-amino-4-methylthiazole in addition to its metal complexes with Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) ions have been synthesized. The structure, electronic properties, and thermal behaviour of Schiff base and its metal complexes have been studied by elemental analysis, mass, ¹H NMR, IR spectra, thermal analysis, and theoretically by density function theory. The ligand acted as mononegative bidentate (NO) ligand and all complexes showed octahedral geometry except Cu (II) showed tetrahedral geometry as indicated from the spectral and magnetic studies. The Cu (II), Zn (II) and Cd (II) complexes were non electrolytes while the rest of the complexes were electrolytes. The antibacterial plus anticancer activities of the parent Schiff base and its metal complexes were screened. In addition, the molecular docking study was performed to explore the possible ways for binding to Crystal Structure of Human Astrovirus capsid protein (5ibv) receptor.     

Metal complexes of tetradentate azo-dye ligand derived from 4,4′-oxydianiline: Preparation,structural investigation,biological evaluation and MOE studies

The Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II) and Cd (II) complexes were prepared by reaction of its metal chlorides with new azo-dye ligand (H₂L). The ligand derived from 4,4′-oxydianiline and 2-amino-4-chlorophenol was synthesized in a 1:2 molar ratio. The structure of the ligand and its metal complexes was investigated using different tools such as elemental analysis (C, H, N and M), molar conductivity, IR, UV–vis, ¹H-NMR, mass spectrometry and thermogravimetric and differential thermogravimetric studies. The data showed that the ligand acted as a N,N,O,O-binegative tetradentate ligand. All metal complexes had a octahedral structure as depicted by spectral and elemental analyses. The conductivity data showed the electrolytic nature of the Cr (III) and Fe (III) complexes while the other complexes were nonelectrolytes. Thermal analysis studies showed the decomposition of the complexes in four to five steps with the weight loss of hydrated water in the first decomposition step followed by the coordinated water and ligand molecules. Biological activity was tested for the prepared compounds against four bacterial species (Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa) and against two fungal species (Aspergillus fumigatus and Candida albicans). Also, all complexes were screened for anticancer activities against a breast cancer (MCF-7) cell line. The [Co(L)(H₂O)₂] complex showed the lowest IC₅₀ value. Molecular docking is a key tool in computer drug design. Therefore, investigation of protein receptors and ligand interaction plays a vital role in the design of structurally based drugs. As a result, docking studies were investigated for H₂L ligand, [Mn(L)(H₂O)₂] and [Ni(L)(H₂O)₂] complexes with 5KBC, 3V7B and 4G9M receptors.     

Investigation of mononuclear,dinuclear, and trinuclear transition metal (II) complexes derived from an asymmetric Salamo‐based ligand possessing three different coordination modes

A new asymmetric Salamo‐based ligand H₂L was synthesized using 3‐tert‐butyl‐salicylaldehyde and 6‐methoxy‐2‐[O‐(1‐ethyloxyamide)]‐oxime‐1‐phenol. By adjusting the ratio of the ligand H₂L and Cu (II), Co (II), and Ni (II) ions, mononuclear, dinuclear, and trinuclear transition metal (II) complexes, [Cu(L)], [{Co(L)}₂], and [{Ni(L)(CH₃COO)(CH₃CH₂OH)}₂Ni] with the ligand H₂L possessing completely different coordination modes were obtained, respectively. The optical spectra of ligand H₂L and its Cu (II), Co (II) and Ni (II) complexes were investigated. The Cu (II) complex is a mononuclear structure, and the Cu (II) atom is tetracoordinated to form a planar quadrilateral structure. The Co (II) complex is dinuclear, and the two Co (II) atoms are pentacoordinated and have coordination geometries of distorted triangular bipyramid. The Ni (II) complex is a trinuclear structure, and the terminal and central Ni (II) atoms are all hexacoordinated, forming distorted octahedral geometries. Furthermore, optical properties including UV–Vis, IR, and fluorescence of the Cu (II), Co (II), and Ni (II) complexes were investigated. Finally, the antibacterial activities of the Cu (II), Co (II), and Ni (II) complexes were explored. According to the experimental results, the inhibitory effect was found to be enhanced with increasing concentrations of the Cu (II), Co (II), and Ni (II) complexes.     

Coordination compounds of some transition metal ions with new Schiff base ligand derived from dibenzoyl methane. Structural characterization,thermal behavior,molecular structure,antimicrobial, anticancer activity and molecular docking studies

Series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes were prepared with tetradentate Schiff base ligand derived by condensation of 2‐aminophenol with dibenzoylmethane. The novel Schiff base H₂L (2–2′‐((1Z,1Z’)‐(1,3‐diphenyl propane‐1,3 diylidene) bis (azanylylidene) diphenol) and its binary metal complexes were characterized by physicochemical procedures i.e. elemental analysis, FT‐IR, UV–Vis, thermal analyses (TGA/DTG), mass spectrometry, magnetic susceptibility and conductometric measurements. On the basis of these studies, an octahedral geometry for all these complexes was proposed expect Ni(II) complex which had tetrahedral geometry. Molar conductivity values revealed that the complexes were electrolytes except Mn(II), Zn(II) and Cd(II) complexes were non electrolytes. The ligand bound to the metal ions via two azomethine N and two phenolic OH as indicated from the IR and ¹H NMR spectral study. The molecular and electronic structures of H₂L and its zinc complex were optimized theoretically and the quantum chemical parameters were calculated. The antimicrobial activity against a number of bacterial organisms as Streptococcus pneumonia, Bacillus Subtilis, Pseudomonas aeruginosa and Escherichia coli and fungi as Aspergillus fumigates, Syncephalastrum racemosum, Geotricum candidum and Candida albicans by disk diffusion method were screened for the Schiff base and its complexes. The Cd(II) complex has potent antimicrobial activity. Anticancer activity of the Schiff base ligand and its metal complexes were evaluated in human cancer (MCF‐7 cells viability). The Cr(III) complex exhibited higher activity than other complexes and ligand. Molecular docking was used to predict the binding between Schiff base ligand (H₂L) and its Zn(II) complex and the receptors of RNA of amikacin antibiotic (4P20) and human‐DNA‐Topo I complex (1SC7). The docking study provided useful structural information for inhibition studies.     

Ligational,density functional theory,and biological studies on some new Schiff base 2-(2-hydroxyphenylimine)benzoic acid (L) metal complexes

The metal ions Co(II), Ni(II), Zn(II), Zr(IV), and Hg(II) reacted with synthesized Schiff base (L) in mole ratios 1:2 (M:L) formed metal complexes. The structure of the prepared compounds was identified based on the data obtained from elemental analyses, magnetic measurement, melting point, conductivity, Fourier-transform infrared, UV–Vis., nuclear magnetic resonance spectroscopy, X-ray diffraction (XRD) spectra, and thermal analysis (TG/DTG [thermogravimetric/differential thermal analysis]). The results indicate that the L bound as bidentate through the oxygen atom of the hydroxyl group and nitrogen atom of the azomethine group with the metal ions and the complexes is electrolyte in nature. TG/DTG studies confirmed the chemical formula for complexes. The kinetic and thermodynamic parameters such as E^*, ΔH^*, ΔS^*, and ΔG^* were determined by using Coats–Redfern and Horowitz–Metzger methods at n = 1 and n ≠ 1. The XRD patterns exhibited a semicrystalline nature lying between the amorphous and crystalline nature for L, (D), and (E), but the complexes (A), (B), and (C) possessed a crystalline character. Density functional theory confirmed the structural geometry of the complexes. In vitro antimicrobial activities were performed for L and its metal complexes.     

New biocidal metal complexes of bisphenol-A formaldehyde polymer containing piperazine

The polymeric ligand (BFP) was synthesized by condensation of bisphenol-A, formaldehyde, and piperazine in alkaline medium at 70–80°C. The polymer–metal complexes were synthesized by the reaction of BFP with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) acetates in 1?:?0.5 (ligand?:?metal) molar ratio. All the synthesized polymers were characterized by elemental, spectral (infrared, ¹H-NMR, and UV-Vis), magnetic moment measurements, and thermal (TGA) analysis. The ligand-field and nephelauxetic parameters have been determined from UV-Vis spectra using ligand-field theory. Elemental analyses indicate the association of water with metal for Mn(II), Co(II), and Ni(II), which is also supported by TGA. The antimicrobial activities of the synthesized polymers were studied by agar well diffusion methods against Bacillus subtilis, Bacillus megaterium, Staphylococcus aureus, Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, and Shigella boydii. The antimicrobial activity and thermal stability of Cu(II)–polymer were higher than the other polymer–metal complexes due to the higher stability constant of Cu(II).     

Metal complexes of azo coumarin derivative: synthesis,spectroscopic, thermal,and antimicrobial studies

Cu(II), Co(II), Ni(II), Cd(II), and Zn(II) complexes of 6-(2-phenyldiazenyl)-7-hydroxy-4-methyl coumarin (PAHC) are characterized based on elemental analyses, infrared, ¹H NMR, magnetic moment, molar conductance, mass spectra, UV-Vis analysis, thermogravimetric analysis (TGA), and X-ray powder diffraction. From the elemental analyses, it is found that the complexes have formulae [M(L)₂(H₂O) _n ] ? xH₂O (where M = Cu(II), Co(II), Ni(II), Cd(II), and Zn(II), n = 0–2, x = 1–4). The molar conductance data reveal that all the metal chelates are non-electrolytes. From the magnetic and solid reflectance spectra, it is found that the structures of these complexes are octahedral or tetrahedral. The synthesized ligand and metal complexes were screened for antibacterial activity against some Gram-positive and Gram-negative bacteria.