Synthesis,crystal structures,and properties of copper(II) complexes with 2,6-bis(benzimidazol-2-yl)pyridine

Three new mononuclear copper(II) complexes, [CuL(2-fca)(CH₃OH)]ClO₄?·?CH₃OH (1), [CuL(m-nba)(CH₃OH)]ClO₄ (2), and [CuL(pic)(ClO₄)]?·?CH₃OH (3), were synthesized and structurally characterized, where L is 2,6-bis(benzimidazol-2-yl)pyridine, while 2-fca, m-nba, and pic are the anions of 2-furoic acid, m-nitrobenzoic acid, and picolinic acid, respectively. All of them were characterized by elemental analysis, infrared, UV-Vis, and X-ray crystallography. In 1 and 2, the Cu(II) resides within a distorted square-pyramidal N₃O₂ coordination sphere with three nitrogens of L, one carboxylate oxygen, and one methanol. In 3, Cu(II) is coordinated with three nitrogens of L, one nitrogen and one oxygen of picolinate, and one oxygen of perchlorate in a distorted octahedral geometry. Two molecules of 1, 2, and 3 are interacted by intermolecular hydrogen-bonding interactions and strong π–π stacking interactions to form a dinuclear structural unit. The dinuclear units are further connected by H-bonds via perchlorate or lattice methanol to form a 1-D chain for 1 and 2-D network structures for 2 and 3. Hydrogen-bonding and π–π stacking interactions are important for the stabilization of the final supramolecular structures of the three complexes.     

Synthesis, structure, and magnetic properties of two 1-D helical coordination polymeric Cu(II) complexes

Two helical coordination polymeric copper(II) complexes bearing amino acid Schiff bases HL or HL′, which are condensed from 2-hydroxy-1-naphthaldehyde with 2-aminobenzoic acid or l-valine, respectively, have been prepared and characterised by X-ray crystallography. In [CuL]_n (1) the copper(II) atoms are bridged by syn-anti carboxylate groups giving infinite 1-D right-handed helical chains which are further connected by weak C-H?Cu interactions to build a 2-D network. While in [CuL′]_n (2) the carboxylate group acts as a rare monatomic bridge to connect the adjacent copper(II) atoms leading to the formation of a left-handed helical chain. Magnetic susceptibility measurements indicate that 1 exhibits weak ferromagnetic interactions whereas an antiferromagnetic coupling is established for 2. The magnetic behavior can be satisfactorily explained on the basis of the structural data.     

Synthesis,characterization, and antimicrobial properties of two Cu(II) complexes derived from a benzimidazole ligand

Two copper(II) complexes, [Cu(L)₂](ClO₄)₂] and [Cu(L)(bipy)](ClO₄)₂, were prepared and characterized by the spectroscopic and analytic methods, where L is N-butylbenzimidazole and bipy is 2,2′-bipyridine. Single crystals of [Cu(L)(bipy)](ClO₄)₂ suitable for X-ray diffraction study were obtained by slow diffusion of diethyl ether into a DMF solution of the complex and the complex was found to crystallize as [Cu(L)(bipy)](ClO₄)₂·DMF. The asymmetric unit contains one [Cu(L)(bipy)]²⁺, two uncoordinated perchlorates, and one DMF solvate. Coordination geometry around Cu(II) is distorted square pyramidal with τ value of 0.31. Thermal properties of the complexes were examined by thermogravimetric analysis, indicating that the complexes are thermally stable to 310?°C. The metal complexes were screened for their in vitro antibacterial and antifungal activities Bacillus subtilis and Bacillus cereus (as Gram(+) bacteria), Escherichia coli, Enterobacter aerogenes, and Klebsiella pneumoniae (as Gram(–) bacteria), and Saccharomyces cerevisiae, Candida utilis, and Candida albicans (as yeasts). The complexes show antibacterial and antifungal activities against bacteria and yeasts.     

Syntheses,structures, and fluorescent properties of three Zn(II) and Cu(II) complexes of different ligands derived from 3,6-bis(2-pyridyl)-1,2-dihydro-1,2,4,5-tetrazine

Three supramolecular complexes [Zn(HL₁ )₂(H₂O)₂(ZnCl₄)₂] (1), [Cu(L₂ )₂Cl₂] (2), and [Zn(L₃ )Cl₂] (3) have been synthesized and characterized by single crystal X-ray diffraction analysis (L₁ = 3,5-di(2-pyridyl)-4-amino-1,2,4-triazole, L₂ = 3,5-di(2-pyridyl)-1,2,4-triazole, and L₃ = 2-pyridinecarboxylic acid (pyridin-2-ylmethylene)-hydrazide). In 1, anion–π interactions between Cl^? and the π-systems of L₁ are observed and anion–π, hydrogen bonding and π–π stacking interactions link the two complex units of [Zn(HL₁ )₂(H₂O)₂]⁴⁺ and [ZnCl₄]^2? to form a 3-D supramolecular network. In 2, π–π stacking interactions between aromatic rings of 1,2,4-triazole and pyridine rings are observed; in 3, hydrogen bonding of Cl ··· H–N and π–π stacking interactions between parallel pyridine rings of L ₃ are observed. The mechanisms of rearrangement reactions of L to L₁ –L₃ are discussed. The fluorescent properties for solid 1 and 3 are also investigated.     

Synthesis and characterization of potassium 1,3-bis(N-methylpiperazino)propan-2-O-xanthate and the complexes of Co(II), Ni(II) and Cu(I) ions

Potassium 1,3-bis(N-methyl piperazino)propan-2-O-xanthate (LK), and its complexes with Co(II), Ni(II) and Cu(I) ions have been prepared and characterized as [CoL₂(H₂O)₂], [NiL₂(H₂O)₂]·2H₂O and CuL·2H₂O by FT-IR, ¹H and ¹³C?NMR spectroscopies, elemental analyses, magnetic susceptibility and TGA techniques.     

Ruthenium monoterpyridine complexes with 2,6-bis(benzimidazol-2-yl)pyridine: Synthesis,spectral properties and structure

Ruthenium monoterpyridine complexes with the tridentate 2,6-bis(benzimidazol-2-yl)pyridine (LH₂), [Ru(trpy)(LH₂)]²⁺, [1]²⁺ and [Ru(trpy)(L²⁻)], 2 (trpy = 2,2′:6′,2″-terpyridine) have been synthesized. The complexes have been authenticated by elemental analyses, UV–Vis, FT-IR, ¹H NMR spectra and their single crystal X-ray structures. Complexes [1]²⁺ and 2 exhibit strong MLCT band near 475 and 509 nm, respectively, and are found to be very much dependent on solution pH. The successive pH dependent dissociations of the N–H protons of benzimidazole moiety of LH₂ in [1]²⁺ lead to the formation of 2. The proton induced inter-convertibility of [1]²⁺ and 2 has been monitored via UV–Vis spectroscopy and redox features. The two pK_a values, 5.75 and 7.70, for complex [1]²⁺ have been determined spectroscopically.     

Synthesis,urease inhibitory activities,and molecular docking studies of two Cu(II) complexes

Two mononuclear copper(II) complexes, [Cu(C₄H₃N₂O₂)₂?·?4H₂O] (1) and [Cu(C₁₂H₁₁N₂O₂Cl₂)₂] (2), were synthesized and structurally characterized by single-crystal X-ray analysis. The copper(II) adopts a square-planar environment in 1, while the geometry in 2 can be described as distorted square-pyramidal. Complexes 1 and 2 were evaluated for their inhibitory activities against jack bean urease in vitro and both were found to have strong inhibitory activities comparable to that of acetohydroxamic acid. A docking simulation was performed to position 2 into the jack bean urease active site to determine the probable binding conformation.     

Synthesis,characterization, molecular modeling,and thermal analyses of bioactive Co(II) and Cu(II) complexes with diacetylmonoxime and different amines

Condensation of diacetylmonoxime with 2-amino-5-mercapto-1,3,4-thiadiazole, 2-amino-1,3,4-thiadiazole or 3-amino-5-methylisoxazole in the presence of Co(II) and Cu(II) salts with different anions produced nine complexes. The synthesized complexes have been characterized by elemental analyses, molar conductivities, thermal analyses, magnetic moments, IR, electron spin resonance, and UV-Vis spectral studies. The spectral data show that sulfur, oxygen, and nitrogen participate in chelation with the metal ions. The complexes are tetrahedral, octahedral, or square planar based on the amine used and the nature of anion. Molar conductance measurements of the complexes in DMF indicate non-electrolytes. CS Chem 3-D Ultra Molecular Modeling and Analysis Program has been used for optimization of the molecular structures of some complexes. In vitro cytotoxicities of the complexes were tested against different carcinoma cell lines. Antimicrobial activities of the complexes were screened against Gram-positive (Staphylococcus aureus), Gram negative bacteria (Escherichia coli), and fungal species (Aspergillus flavus, Candida albicans, and Microsporum canis).     

Synthesis and characterization of two temperature-dependent copper(II) complexes based on 2,6-dimethylpyridine-3,5-dicarboxylate

Two temperature-dependent Cu(II) compounds, [Cu(mpdaH)₂(H₂O)₄] · 4H₂O (1) and [Cu(mpdaH)₂] _n (2) (H₂mpda = 2,6-dimethylpyridine-3,5-dicarboxylic acid), have been synthesized under hydrothermal conditions and characterized by X-ray single crystal diffraction, elemental analysis, thermogravimetric analyses, and IR spectra. The structure at room temperature confirms that 1 is mononuclear with the octahedral coordination geometry. However, on warming to 120°C the same reaction gives 2, in which copper(II) has square planar coordination and is further bridged by mpdaH^? ligands to form extended 2-D layers with parallelogram-like (4,4) topology. Furthermore, in both complexes, through π–π stacking and hydrogen bonding interactions, 3-D supramolecular networks are assembled.     

Synthesis,characterization, and biological evaluation of Cu(II) complexes with the proton transfer salt of 2,6-pyridinedicarboxylic acid and 2-amino-4-methylpyridine

A proton transfer compound, (Hamp)⁺(Hdipic)^??·?1.5H₂O (1), and Cu(II) complexes, [Cu(dipic)(amp)(H₂O)]?·?[Cu(dipic)(amp)]?·?H₂O?·?CH₃COOH (2) and [Cu(dipic)(amp)Cu(dipic)(amp)(H₂O)Cu(dipic)(amp)(H₂O)]?·?3H₂O (3), have been synthesized from 2,6-pyridinedicarboxylic acid (H₂dipic) and 2-amino-4-methylpyridine (amp). They have been characterized by elemental, spectral (¹H-NMR, IR, and UV-Vis), and thermal analyses. In addition, magnetic measurements and single crystal X-ray diffraction have been applied to 2 and 3. The crystal structure of 2 consists of two independent and different cationic sites with Cu²⁺ ions. Cu1 is four-coordinate in a distorted square planar geometry and Cu2 is five-coordinate in a distorted square pyramid. Compound 3 has three independent and different cationic sites of Cu²⁺ ions. Cu1 is four-coordinate in a distorted square planar geometry and Cu2 and Cu3 have five-coordinate, distorted square-pyramidal sites. Inhibitory effects of 1, 2, and 3 have been studied and compared with starting compounds (amp and H₂dipic) on bacterial growth of Staphylococcus aureus and Escherichia coli cultures. Compounds 2 and 3 prevent bacterial growth although 1 has no effect. Compounds 2 and 3 are more effective than amp and H₂dipic, at similar concentrations on preventing bacterial growth for both organisms.     

Syntheses,crystal structures,and DNA-binding properties of two nickel(II) complexes with 1,3-bis(benzimidazol-2-yl)-2-oxapropane derivatives

[Ni(obb)(DMF)₂(H₂O)]·(Pic)₂·0.5DMF (1) and [Ni(Etobb)₂]·(Pic)₂·2DMF (2) (obb = 1,3-bis(benzimidazol-2-yl)-2-oxapropane, Etobb = 1,3-bis(1-ethylbenzimidazol-2-yl)-2-oxapropane, Pic = picrate) have been synthesized and characterized by physicochemical and spectroscopic methods. The structures of both complexes have been determined by X-ray single-crystal diffraction. The coordination geometries of 1 and 2 can be described as distorted octahedra. The interaction of the nickel(II) complexes with calf thymus DNA was investigated by electronic absorption, fluorescence spectroscopy, and viscosity measurements. The experimental results suggest that 1 and 2 bind to DNA in an intercalation mode, and their binding affinity for DNA follows the order 1 > 2. DNA-binding behaviors can be attributed to the large coplanar aromatic rings in the V-shaped ligand and steric hindrance.     

Structure and Photosynthetic Mimicking of Bis(2,6-bis(benzimidazol-2-yl)pyridine)manganese(II)

Introduction　　Manganeseionsplayanimportantroleinthelight in ducedoxidationofwatertomolecularoxygeninphotosys temII (PSII)ofgreenplants.1 3Inrecentyears ,man ganesecomplexesofpolypyridineligands ,suchasbipyri dine ,1,10 phenanthrolineand 2 ,2′:6′,2″ terpyridine ,havehadconsiderableattentionasthecomplexesformedareusefulmodelsformanganese containingbimolecu lars .4 6 Therefore ,synthesisandcharacterizationofman ganeseinitsvariousoxidationstates ,withvariousligandtypesandnuclearities ,hav…     

Synthesis and characterization of mononuclear copper(II) and cadmium(II) complexes with di-(2-picolyl)sulfur

The reaction of Cu(ClO₄)₂·6H₂O and Cd(ClO₄)₂ with di-(2-picolyl)sulfur (dps) leads to the formation of mononuclear complexes [Cu(dps)(H₂O)(ClO₄)](ClO₄) (1) and [Cd(dps)₂](ClO₄)₂ (2). The crystal structure of 1 exhibits a distorted square pyramidal geometry, coordinated by one sulfur and two nitrogen atoms from the dps ligand, one water molecule and one perchlorate oxygen atom. For 2, the environment around cadmium atom is in a distorted octahedron with four nitrogen and two sulfur atoms from the dps ligand. Cyclic voltammetric data show that complexes undergo two waves of a one-electron transfer corresponding to M(II)/M(III) and M(II)/M(I) processes. Spectral and electrochemical behaviors of the complexes are also discussed.     

1,3-Bis(2-alkyltetrazol-5-yl)triazenes and their Fe(II), Co(II) and Ni(II) complexes: Synthesis,spectroscopy, and thermal properties. Crystal structure of Fe(II) and Co(II) 1,3-bis(2-methyltetrazol-5-yl)triazenide complexes

Complexes ML¹₂ and ML²₂, with M = Fe^II, Co^II, Ni^II, and 1,3-bis(2-R-tetrazol-5-yl)triazenide ligands L¹ (R = Me) and L² (R = ^tBu), have been synthesized by the reaction of corresponding 1,3-bis(2-R-tetrazol-5-yl)triazenes with metal(II) salts in basic media and characterized by IR, UV–Vis spectroscopy, thermal and X-ray diffraction analyses. Both 1,3-bis(2-R-tetrazol-5-yl)triazenes were found to deprotonate on coordination and act as tridentate chelating ligands forming distorted MN₆ octahedra around metal(II) cations.     

Synthesis,characterization, and antioxidant activities of three Cu(II) complexes with Schiff-base ligands

Cu(II) complexes of three bis(pyrrol-2-yl-methyleneamine) ligands were synthesized and characterized by elemental analyses, mass spectra, and IR spectra. X-ray diffraction analysis shows that [CuL³]₂ is a dinuclear complex with an extremely distorted square-planar geometry. Furthermore, the antioxidant activities of the compounds have been investigated. The electrochemical properties of the Cu(II) complexes have also been studied by cyclic voltammetry. The Cu(II) complexes show similar superoxide dismutase (SOD) activity compared with that of the native Cu, Zn-SOD.     

Synthesis, structure and non-linear optical property of a copper(II) thiocyanate three-dimensional supramolecular compound

A novel copper(II) thiocyanate complex [Cu(im)₂(NCS)₂] 1 (im=imidazole) has been prepared and characterized by spectroscopic analysis and crystallographic method. This supramolecular compound exhibits a three-dimensional solid state structure constituted by N–HS hydrogen bonds and π–π stacking interactions. The compound in DMF solutions has a very strong third-order non-linear optical (NLO) behavior with absorption coefficient and refractive index ₂=1.18×10⁻¹¹ mw⁻¹, n₂=−9.00×10⁻¹⁶ m²w⁻¹, respectively, and third-order NLO susceptibility χ⁽³⁾ of 7.00×10⁻¹⁰ esu.     

Synthesis and characterization of Cu(II) complexes of pyrazine-2,3-dicarboxylicacid

Four copper(II) coordination polymers, {[Cu(pz(COO)₂)(H₂O)]₄·HBr}_n (1), {[Cu(pz(COO)₂)(NH₃)₂]·H₂O}_n (2), {[Cu₃H₂(pz(COO)₂)₄(H₂O)₃]·2H₂O}_n (3) and {[Cu₂(pz(COO)₂)₂(NH₃)₂(H₂O)₃][Cu(pz(COO)₂)(NH₃)(H₂O)₂][Cu(pz(COO)₂)(NH₃)(H₂O)]·2H₂O}_n (4) were synthesized using pyrazine-2,3-dicarboxylic acid, CuBr₂, 2-(2-aminoethylamino)ethanol/triethanol amine/ammonia in a methanol:water (1:1) solution, and the mixed ligand complexes were characterized by spectroscopic methods, thermal and elemental analysis, and magnetic susceptibility. Complexes 2 and 4 were also characterized by means of single crystal X-ray crystallography. The characterizations show that the complexes have polynuclear molecular structures, except for complex 2, and all of the complex structures form polymeric chains. Complex 4 has a pseudo-merohedral twin structure.     

Benign synthesis of the unsymmetrical ligand N-(quinolin-8-yl)pyrazine-2-carboxamide. Preparation,electrochemistry, antibacterial activity,and crystal structures of Cu(II) and Zn(II) complexes

Hqpzc has been synthesized by a highly efficient procedure using the ionic liquid TBAB as an environmentally benign reaction medium. [Cu(qpzc)(OAc)]·H₂O (1) and [Zn(qpzc)(OAc)(H₂O)] (2), complexes of the deprotonated ligand, qpzc¯ [qpzc¯ = N-(quinolin-8-yl)pyrazine-2-carboxamide], have been synthesized and characterized by elemental analyses, spectroscopic methods, and X-ray crystallography. The coordination geometry around the metal ions in both complexes is distorted square pyramidal. The mono-anionic qpzc¯ is a tridentate unsymmetrical ligand furnishing an N3 set, occupying three of the four basal positions. Acetate is a bidentate ligand in 1 and unidentate in 2. The apical position in 2 is occupied by water. Quite strong O-H…O hydrogen bonds create columns of complexes [rod group p21(11)] in the copper complex, but in conjunction with π-π interactions, a 3D edifice in the zinc complex. The electrochemical behavior of the ligand and its copper and zinc complexes shows that the quinoline ring reduces at more positive potentials in these complexes relative to the free ligand. The in vitro antibacterial activities of these complexes were tested against Escherichia Coli and Staphylococcus Aureus.     

Synthesis,characterization, and DNA-binding of a four-coordinate cobalt(II) complex with 1,3-bis(1-ethylbenzimidazol-2-yl)-2-oxopropane

A new four-coordinate cobalt(II) complex with 1,3-bis(1-ethylbenzimidazol-2-yl)-2-oxopropane (Etobb), Co(Etobb)Cl₂, has been synthesized and characterized by elemental analysis, electrical conductivities, infrared, and UV-Vis spectral measurements. The crystal structure has been determined by single-crystal X-ray diffraction. Cobalt(II) is a distorted tetrahedral geometry, surrounded by two nitrogens from Etobb and two chlorides. DNA-binding properties of Etobb and its Co(II) complex have been investigated by electronic absorption, fluorescence, and viscosity measurements. The experimental results suggest that the ligand and its Co(II) complex bind to DNA via intercalation, and the binding affinity of the Co(II) complex to DNA is greater than Etobb.