Synthesis,crystal structure,fluorescence, electrochemical property,and SOD-like activity of an unexpected nickel(II) complex with a quinazoline-type ligand

An unexpected mononuclear Ni(II) complex, [Ni(L²)₂]·CH₃OH (HL² = 1-(2-{[(E)-3,5-dichloro-2-hydroxybenzylidene]amino}phenyl)ethanone oxime), has been synthesized via complexation of Ni(II) acetate tetrahydrate with HL¹. HL¹ and its corresponding Ni(II) complex were characterized by IR, ¹H-NMR spectra, HRMS, as well as by elemental analysis, UV–vis, and emission spectroscopy. The crystal structure of the complex has been determined by single-crystal X-ray diffraction. Each complex links two other molecules into an infinite 1-D chain via intermolecular hydrogen bonds. Moreover, the electrochemical properties of the nickel complex were studied by cyclic voltammetry. Superoxide dismutase-like activities of HL¹ and Ni(II) complex were also investigated.     

Two two‐dimensional supramolecular copper(II) and cobalt(III) complexes derived from a new quinazoline‐type ligand: Syntheses,structures, and spectral,thermal, electrochemical and antimicrobial activity studies

Two two‐dimensional supramolecular copper(II) and cobalt(III) complexes, Cu(L¹)₂ ( 1 ; HL¹ = 2‐hydroxy‐3‐methoxybenzaldehyde oxime) and [Co(L²)₂]₂⋅2CH₃COOCH₂CH₃ ( 2 ; HL² = 1‐(2‐{[(E )‐3‐methoxy‐2‐hydroxybenzylidene]amino}phenyl)ethanone oxime), have been synthesized via complexation of Cu(II) nitrate trihydrate and Co(II) acetate tetrahydrate with HL. A plausible reaction mechanism for the formation of HL¹ is proposed. HL was synthesized and characterized using infrared, ¹H NMR and ¹³C NMR spectra, as well as elemental analysis. Complexes 1 and 2 were investigated using single‐crystal X‐ray diffraction and have a 2:1 ligand‐to‐metal ratio. Different geometric features of both complexes are observed. In their crystal structures, 1 and 2 form infinite two‐dimensional structures and 2 forms a three‐dimensional supramolecular framework. Electron paramagnetic resonance spectra of 1 and 2 were also investigated. Moreover, thermal and electrochemical properties and antimicrobial activity of 2 were also studied. In addition, the calculated HOMO and LUMO energies show the character of complex 1 .     

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.     

两种1,2,3-三唑衍生物的配合物合成策略:晶体结构和表面分析

在不同反应条件下反应得到了两种1,2,3-三唑衍生物的配合物[Co（H₂O）₆][Co（L¹）₃]₂·4H₂O（1）和Cu（L²）₂（2）（HL¹=5-methyl-1-phenyl-1H-1,2,3-triazole-4-carboxylic acid;HL²=1-（4-iodophenyl）-5-methyl-1H-1,2,3-triazole-4-carboxylic acid）。通过X射线单晶衍射和红外光谱确定了晶体结构,同时对配合物1和2进行了表面作用分析（Hirshfeld surface analysis）,在二维指纹图谱中可以清楚的看到配合物中的主要分子间作用。     

Synthesis,structural characterization and substituent effects of two copper(II) complexes with benzaldehyde ortho-oxime ligands

Two new Cu(II) complexes, [Cu(L¹)₂] (1) and [Cu(L²)₂] (2) (HL¹ = (E)-3-bromo-5-chloro-2-hydroxy benzaldehyde O-methyl oxime; HL² = (E)-3-bromo-5-chloro-2-hydroxy benzaldehyde O-ethyl oxime), have been synthesized and characterized by physicochemical and spectroscopic methods. X-ray crystallographic analyses show that complexes 1 and 2 have similar structures, consisting of one Cu(II) atom and two L⁻ units. In both complexes, the Cu(II) atom, lying on an inversion center, is four-coordinated in a trans-CuN₂O₂ square-planar geometry by two phenolate O and two oxime N atoms from two symmetry-related N,O-bidentate oxime ligands. Moreover, both complexes form an infinite three-dimensional supramolecular structure involving intermolecular C–H···Br hydrogen bonds and π···π stacking interactions between the metal chelate rings and aromatic rings. Substituent effects in the two complexes are discussed.     

Synthesis, structural characterization and thermal properties of three copper(II) complexes based on aryl hydrazide ligands

The thiosemicarbazide and hydrazide Cu(II) complexes, [Cu₃L₂¹(py)₄Cl₂] (1), [Cu(HL²)py] (2) and [Cu(HL³)py] (3), (H₂L¹ = 1-picolinoylthiosemicarbazide, H₃L² = N′-(2-hydroxybenzylidene)-3-hydroxy-2-naphthohydrazide, H₃L³ = 2-hydroxy-N′-((2-hydroxy-naphthalen-1-yl)methylene)benzohydrazide) have been prepared and characterized through physicochemical and spectroscopic methods as well as X-ray crystallography. Complex 1 has a centrosymmetric structure with –N–N– bridged Cu₃ skeleton. Neighboring molecules are linked into a 3D supermolecular framework by π–π stacking interactions, N–H···Cl and C–H···Cl hydrogen bonds. Complexes 2 and 3 have similar planar structures but different dimers formed by concomitant Cu···N and Cu···O interactions, respectively. Solvent accessible voids with a volume of 391 ?³ are included in the structure of complex 2, indicating that this complex is a potential host candidate. Thermogravimetric analysis shows that the three complexes are stable up to 100 °C.     

Three new coordination complexes of cobalt(III), manganese(II), and copper(II) with N,N,O-donor hydrazone ligands: syntheses and structural characterizations

Three new coordination complexes, 2{[Co(L¹)₂]ClO₄} · 0.5CH₃OH (1), [Mn(L²)₂] (2), and [Cu(HL²)(L²)]ClO₄ · 2H₂O (3) have been synthesized from two tridentate N,N,O-donor hydrazone ligands HL¹, 2-acetylpyridine-salicyloylhydrazone, and HL², 2-benzoylpyridine-salicyloylhydrazone, respectively and thoroughly characterized by elemental analysis, FT-IR, UV–Vis, electrochemical, and room temperature magnetic susceptibility measurements. Structures of the complexes have been unequivocally established by single crystal X-ray diffraction technique. Structural analysis reveals that 1 consists of two chemically similar but crystallographically independent cationic [Co(L¹)₂]⁺ units and 2 consists of a neutral [Mn(L²)₂] molecule while 3 consists of a cationic [Cu(HL²)(L²)]⁺ unit. Metal ions display distorted octahedral geometry in 1 and 2 while in 3 it shows a distorted square pyramidal geometry. Ligand conformations around the metal ions are stabilized by the presence of intra-ligand hydrogen bonding in all the complexes. Structure of 3 reveals that a perchlorate ion linked to the complex by hydrogen bonding via a water molecule.     

Crystal structures and DNA cleavage activities of two mononuclear nickel(II) complexes

Two new nickel complexes, [Ni(L₁)₂]?·?2(CH₃OH) (1) and [Ni(L₂)₂]?·?2(CH₃OH) (2), where HL₁ is 4-chloro-2-((2-hydroxy-ethylimino)methyl)phenol and HL₂ is 4-fluoro-2-((2-hydroxy-ethylimino)methyl)phenol, have been synthesized and characterized by single-crystal X-ray diffraction and UV-Vis absorption spectra. The coordination polyhedron of nickel(II) in each complex can be described as distorted octahedral. The interactions between the complexes and calf thymus (CT)-DNA/DNA were investigated by UV-Vis spectra and agarose gel electrophoresis. The results show that the complex transforms supercoiled to nicked form and exhibits effective DNA cleavage activity via hydrolytic cleavage mechanism.     

Ni(II) complexes with pyrazole-derived ligands. Crystal structures of [Ni(HL0)2ClH2O][Ni(HL0)2(H2O)2]Cl3·CH3OH·H2O and [Ni(HL1)2(H2O)2]Br2·2.5DMF (HL0=3-phenyl-5-(2-pyridyl)pyrazole and HL1=3-phenyl-5-(6-methyl-(2-pyridyl))pyrazole

The reaction of 3-phenyl-5-(2-pyridyl)pyrazole (HL⁰) and 3-phenyl-5-(6-methyl-(2-pyridyl))pyrazole (HL¹) with nickel(II) salts produces mononuclear coordination compounds. The new complexes have been characterised by elemental analyses, conductivity measurements and infrared and electronic spectroscopies.Two different forms of mononuclear nickel(II) complexes have been prepared and structurally characterised by X-ray crystallography: [Ni(HL⁰)₂Cl(H₂O)][Ni(HL⁰)₂(H₂O)₂]Cl₃·CH₃OH·H₂O and [Ni(HL¹)₂(H₂O)₂]Br₂·2.5DMF. In the cationic complexes, the coordination of the Ni(II) is octahedral with two bidentate HL⁰ or HL¹ neutral ligands in a cis disposition. The degree of distortion from regular octahedral geometry is compared to closely related structures. In the solid state, cations and anions are bonded by hydrogen bonding.     

Manganese(II) complexes of hydrazone based NNO-donor ligands and their catalytic activity in the oxidation of olefins

The reaction between tridentate NNO donor hydrazone ligands, (E)-2-cyano-N′-(phenyl(pyridin-2-yl)methylene)acetohydrazide (HL¹) and (E)-2-cyano-N′-(1-(pyridin-2-yl)ethylidene)acetohydrazide (HL²), with MnCl₂·4H₂O in methanol resulted in [Mn(HL¹)Cl₂(CH₃OH)] (1) and [Mn(HL²)Cl₂(CH₃OH)] (2). Molecular structures of the complexes were determined by single-crystal X-ray diffraction. All of the investigated compounds were further characterized by elemental analysis, FT-IR, TGA, and UV–Vis spectroscopy. These complexes were used as catalysts for olefin oxidation in the presence of tert-butylhydroperoxide (TBHP) as an oxidant. Under similar experimental conditions with equal manganese loading, the presence of [Mn(HL²)Cl₂(CH₃OH)] (2) resulted in higher conversion than [Mn(HL¹)Cl₂(CH₃OH)] (1).     

Synthesis,spectral, thermal and crystallographic investigations on oxovanadium(IV) and manganese(III) complexes derived from heterocyclic β-diketone and 2-amino ethanol

Novel mononuclear oxovanadium(IV) and manganese(III) complexes [VO(L¹)₂·H₂O] (1); [VO(L²)₂·H₂O] (2); [VO(L³)₂·H₂O] (3); [Mn(L¹)₂]ClO₄·H₂O (4); [Mn(L²)₂] ClO₄·H₂O (5); [Mn(L³)₂]ClO₄·H₂O (6) were prepared by condensation of 1 mol of VOSO₄·5H₂O or Mn(OAc)₃· 2H₂O with 2 mol of ligand HL¹, HL² or HL³ (where HL¹ = 4-[(2-hydroxy-ethylamino)-methylene]-5-methyl-2- phenyl-2,4-dihydro-pyrazol-3-one; HL²=4-[(2-hydroxy-ethylamino)-methylene]-5-methyl-2-p-tolyl-2,4-dihydro-pyrazol-3-one; HL³=4-{4-[(2-hydroxy-ethyl-amino)-methyl]-3-methyl-5-oxo-4,5-dihydropyrazol-1-yl} benzene sulfonic acid). The resulting complexes were characterized by elemental analyses, molar conductance, magnetic and decomposition temperature measurements, electron spin resonance, FAB mass, IR and electronic spectral studies. From TGA, DTA and DSC, the thermal behaviour and degradation kinetic were studied. Electronic spectra and magnetic susceptibility measurements indicate distorted octahedral stereochemistry of oxovanadium(IV) complexes and regular octahedral stereochemistry of manganese(III) complexes. Hamiltonian and bonding parameters found from ESR spectra indicate the metal ligand bonding is partial covalent. The X-ray single crystal determination of one of the representative ligand was carried out which suggests existence of amine-one tautomeric form in the solid state. The ¹H-NMR spectra support the existence of imine-ol form in solution state. The LC-MS studies sustain the¹H-NMR result. The electronic structure of the same representative ligand was optimized using 6-311G basis set at HF level ab initio studies to predict the coordinating atoms of the ligand.     

Synthesis and structure of amide oxygen-bridged polymeric and monomeric copper(II) complexes with aroylhydrazones

The synthesis and structure of two Cu(II) complexes, {[Cu₂(L¹)₂]?·?DMF} _n (1) and [CuL²(phen)] (2), are described. The dinegative hydrazones are obtained by deprotonation of both phenolic and amide moieties of N′-(5-bromo-2-hydroxybenzylidene)-3,5-dimethoxybenzohydrazide (H₂L¹) and N′-(2-hydroxybenzylidene)pyrazine-2-carbohydrazide (H₂L²). In each complex the planar ligand binds the metal ion via phenolate-O, imine-N, and amide-O. Complex 1 is a polymer in which phenoxo-bridged binuclear Cu(II) units are further joined by equatorial–apical amide-O bridges. The Cu···Cu separations are 3.0306 and 3.8217?Å for the phenolate-O bridged pair and the amide-O bridged pair, respectively. Complex 2 is a monomer where chelating phen displays axial–equatorial bonding, with square-pyramidal Cu(II).     

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,crystal structure and catalytic performance of bis (imino)pyridyl nickel complexes

Two new Ni(II) complexes of 2,6-bis[1-(2,6-diethylphenylimino)ethyl]pyridine (L¹), 2,6-bis[1-(4-methylphenylimino)ethyl]pyridine (L² ) have been synthesized and structurally characterized. Complex Ni(L¹)Cl₂?·?CH₃CN (1), exhibits a distorted trigonal bipyramidal geometry, whereas complex Ni(L¹)(CH₃CN)Cl₂ (2), is six-coordinate with a geometry that can best be described as distorted octahedral. The catalytic activities of complexes 1, 2, Ni{2,6-bis[1-(2,6-diisopropyl-phenylimino)ethyl]pyridine} Cl₂?·?CH₃CN (3), and Ni{2,6-bis[1-(2,6-dimethylphenylimino) ethyl]pyridine}Cl₂?·?CH₃CN (4), for ethylene polymerization were studied under activation with MAO.     

Synthesis,crystal structure and antibacterial activity of manganese(III) and cobalt(III) complexes containing pentadentate Schiff bases of a common amine and thiocyanate

Abstract

Four new mononuclear Schiff base manganese(III) and cobalt(III) complexes viz. [Mn(L¹)(NCS)] (1), [Mn(L²)(NCS)] (2), [Co(L³)(NCS)] (3), and [Co(L⁴)(NCS)]·0.5CH₃OH·0.5H₂O (4), containing thiocyanate as a common pseudohalide ion are reported. The pentadentate Schiff base ligands H₂L¹, H₂L², H₂L³, and H₂L⁴ were obtained by the condensation of substituted salicylaldehydes with N-(3-aminopropyl)-N-methylpropane-1,3-diamine. The syntheses of the complexes have been achieved by the reaction of manganese(II) perchlorate or cobalt(II) perchlorate with the respective Schiff bases in the presence of thiocyanate in methanol medium. Complexes 1–4 have been characterized by microanalytical, spectroscopic, single-crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1–4 adopt nearly similar structures containing the MN₄O₂ (M?=?Mn, Co) chromophore in which each central M(III) ion adopts a distorted octahedral geometry. Weak intermolecular H-bonding interactions are operative in these complexes to bind the molecular units. The antibacterial activity of 1–4 and their constituent Schiff bases has been tested against some common bacteria.     

Altering the Activity of Catechol Oxidase Model Compounds by Electronic Influence on the Copper Core

The catecholase activity of the dicopper(II) complexes [Cu₂(L¹)(μ‐OCH₃)(NCCH₃)₂](PF₆)₂·H₂O·CH₃CN ( 1 ), [Cu₂(L²)(μ‐OH)(MeOH)(NCCH₃)](BF₄)₂ ( 2 ), [Cu₂(L³)(μ‐OMe)(NCCH₃)₂](BF₄)₂·2CH₃CN·H₂O ( 3 ), [Cu₂(L²)(μ‐OAc)₂]BF₄·H₂O ( 4 ), [Cu₂(L⁴)(μ‐OAc)₂]ClO₄ ( 5 ) and [Cu₂(L⁵)(μ‐OMe)(NCCH₃)₃(OH₂)](ClO₄)₂·2CH₃OH·CH₃CN ( 6 ) consisting of varying para‐substituted phenol ligands HL¹ = 4‐trifluoromethyl‐2,6‐bis((4‐methylpiperazin‐1‐yl)methyl)phenol, HL² = 4‐bromo‐2,6‐bis((4‐methyl‐1,4‐diazepan‐1‐yl)methyl)phenol, HL³ = 4‐bromo‐2‐((4‐methyl‐1,4‐diazepan‐1‐yl)methyl)‐6‐((4‐methylpiperazin‐1‐yl)methyl)phenol, HL⁴ = 2,6‐bis((4‐methylpiperazin‐1‐yl)methyl)‐4‐nitrophenol and HL⁵ = 4‐tert‐butyl‐2,6‐bis((4‐methylpiperazin‐1‐yl)methyl)phenol was studied. The main difference within the six complexes lies in the individual copper–copper separation that is enforced by the chelating side arms of the phenolate ligand entity and more importantly in the exogenous bridging solvent, hydroxide, methanolate or acetate ions. The distance between the copper cores varies from 2.94Å in 1 to 3.29Å in 5 . The catalytic activity of the complexes 1 – 6 towards the oxidation of 3,5‐di‐tert‐butylcatechol was determined spectrophotometrically by monitoring the increase of the 3,5–di‐tert‐butylquinone characteristic absorption band at about 400 nm over time saturated with O₂. The complexes are able to oxidize the substrate 3,5‐di‐tert‐butylcatechol to the corresponding o‐quinone with distinct catalytic activity (k_cat between 92 h^?1 and 189 h^?1), with an order of decreasing activity 6 > 5 > 1 , 2 , 4 ≥ 3 . A kinetic treatment of the data based on the Michaelis‐Menten approach was applied. A correlation of the catecholase activities with the variation of the para‐ substituents as well as other effects resulting from the copper core distances is discussed. [Cu₂(L⁵)(μ‐OMe)(NCCH₃)₃(OH)₂](ClO₄)₂·2CH₃OH·CH₃CN ( 6 ) exhibited the highest activity of the six complexes as a result of its high turnover rate.     

Zn(II) Complexes with Quinoline Supported Amidate Ligands: Synthesis,Fluorescence, and Catalytic Activity

Zn(II) complexes of N-(quinolin-8-yl)picolinamide (HL¹) (1) and N²,N⁶-di(quinolin-8-yl)pyridine-2,6-dicarboxamide (H₂L²) (2) have been synthesized by deprotonation of the ligands and characterized by IR, NMR, and Single crystal X-ray crystallography. The mononuclear [Zn(L¹)₂] (3) and homodinuclear [Zn₂(L²)₂] (4) complexes are characterized by distorted octahedral geometries stabilized by hydrogen bonding and weak π···π interaction. The complexes demonstrate intense fluorescence bands in comparison with their corresponding ligands with well-distinguished intensity. The complexes act as efficient catalysts in various transesterification reactions. Among those, the best results have been achieved with complex 3 in conversion of 4-nitrophenylacetate into methyl acetate within 3 h.

     

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.