Synthesis,spectroscopic characterization,X-ray structure and DFT calculations of copper(II) complex with 2-(2-pyridyl)benzimidazole

The reaction of copper(II) nitrate trihydrate and 2-(2-pyridyl)benzimidazole (pybzim) leads to [Cu(pybzim)₂(NO₃)](NO₃). The compound has been studied by IR, UV–Vis spectroscopy and X-ray crystallography. The electronic structure of the [Cu(pybzim)₂(NO₃)]⁺ cation has been calculated with the density functional theory (DFT) method. The spin-allowed doublet–doublet electronic transitions of [Cu(pybzim)₂(NO₃)]⁺ have been calculated with the time-dependent DFT method, and the UV–Vis spectrum of the title compound has been discussed on this basis.     

Synthesis, crystal structure and DFT analysis of a new trinuclear complex of copper

The new trinuclear complex [Cu₂(μ-L)₂CuCl₂] has been synthesized and characterized by elemental analysis, IR, UV-Vis and X-ray spectroscopy, where L is a dianionic tetradentate Schiff base ligand with N₂O₂ donor atoms. The molecular structure of [Cu₂(μ-L)₂CuCl₂] was determined by X-ray crystallography. In the complex, the most remarkable aspect of the trinuclear complex is that it adopts a bent structure for the three copper atoms, with a Cu1Cu3Cu2 intramolecular angle of approximately 90.62(2)°. All three copper atoms are five coordinate, with a slightly distorted square pyramidal geometry. In the two terminals moieties, the basal plane of the square pyramidal is formed by two oxygen atoms and two nitrogen atoms of the Schiff base ligand, and the apical position at the Cu atom is occupied by the bridging Cl1 anion. The Cu1Cl1Cu2 angle is 110.51(5)°. The central copper atom also has a five-coordinate, slightly distorted square pyramidal geometry, with four phenolato oxygens belonging to the Schiff base ligands from Cu(salpn) units describing the square planar base and the Cl anions being apical. The optimized structure of the complex has been studied using the B3LYP/6-31G(d)/LanL2TZf level of theory. The calculation shows that all the copper atoms are five coordinate with distorted square pyramidal structures, which is consistent with experimental data.     

Mn(III) and Cu(II) complexes of 1-((3-(dimethylamino)propylimino)methyl) naphthalen-2-ol): Synthesis,characterization, catecholase and phenoxazinone synthase activity and DFT-TDDFT study

Two new complexes, [MnL₂](ClO₄) (1) and [CuL₂] (2) (where LH = (E)-1-((3-(dimethylamino)propylimino)methyl)naphthalen-2-ol), have been synthesized and characterized by spectroscopic techniques and their molecular structures are established by single-crystal X-ray diffraction study. Complex 1 adopts an octahedral geometry around the central manganese atom which is in + 3 oxidation state, whereas in complex 2, the Cu⁺² ion preferred a square pyramidal environment around it through the ligand donor atoms. Both complexes were tested for catecholase and phenoxazinone synthase activity. Complex 1 catalyzes the oxidation of 3,5-ditertiary-butyl catechol with a k_cat value of 6.8424 × 10² h^?1 in acetonitrile whereas the same for complex 2 is 3.7485 × 10² h^?1 in methanol. Phenoxazinone synthase activity was shown only by complex 2 having k_cat = 74.225 h^?1. Structures of both the title complexes have been optimized by means of DFT calculations. Experimental electronic spectra of the complexes have been corroborated by TDDFT analysis. Electrochemical investigations by means of cyclic voltammetry have been carried out to study the electron transfer processes in the complexes.     

Binuclear terephthalato-bridged copper(II) complex with N2O2 coordinating tripodal ligand: synthesis,structure, magnetic properties,and DFT study

The bluish green binuclear dicarboxylato bridged copper(II) complex [Cu₂(HL)₂(µ-tp)], 1 has been synthesized, where (HL^?) is the monodeprotonated form of N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine and tp = terephthalate dianion. Herein, we report the synthesis, spectral and structural characterization, and magnetic behavior of 1. The coordination geometry of Cu(II) has a distorted square pyramidal geometry (τ = 0.117). The variable temperature magnetic moment reveals that the complex exhibits very weak antiferromagnetic interaction (J _Exp = ?0.30 cm^?1) and the calculated J value (J _Calcd = ?1.05 cm^?1) using broken symmetry DFT method is in agreement with the experimentally observed value.     

Synthesis,characterization, and superoxide dismutase activity of two new copper(II) complexes of benzoylpyridine 4-phenylsemicarbazone

Two mononuclear complexes containing copper(II) and 2-benzoylpyridine 4-phenylsemicarbazone (BPS) and pseudohalides, [Cu(BPS)(N₃)] (1) and [Cu(BPS)(NCS)(H₂O)]NO₃ (2) have been synthesized and characterized by UV-Vis, Fast atom bombardment, electron paramagnetic resonance, and infrared spectroscopy. Crystal structures of these two complexes have been resolved by using single crystal X-ray studies. Complex 1 crystallizes in the triclinic lattice with space group P1 and is a distorted square planar geometry. Complex 2 also crystallizes in the triclinic lattice with space group P1 but is a distorted square pyramidal geometry with N₃O₂ chromophore. Both the complexes have g _∥ > g _┴ > 2.0023 and a G value less than 4, consistent with a d _{x ²? y ²} ground state. Superoxide dismutase activities have also been examined.     

Synthesis,spectroscopic characterization,X-ray structure and DFT calculations of five-coordinated chlorocopper(II) complex with bis(3,5-dimethylpyrazol-1-yl)methane

The reaction of copper dichloride dihydrate and bis(3,5-dimethylpyrazol-1-yl)methane affords [Cu{H₂C(3,5-Me₂pz)₂}₂Cl]Cl · 3H₂O. The compound has been studied by IR, UV–Vis spectroscopy and X-ray crystallography. The electronic structure of the [Cu{H₂C(3,5-Me₂pz)₂}₂Cl]⁺ cation has been calculated with the density functional theory (DFT) method. The spin-allowed doublet–doublet electronic transitions of [Cu{H₂C(3,5-Me₂pz)₂}₂Cl]⁺ have been calculated with the time-dependent DFT method, and the UV–Vis spectrum of the title compound has been discussed on this basis.     

Synthesis,characterization, and electrochemical study of two new macroacyclic Schiff bases and their copper(II) and zinc(II) complexes

Two new potentially octadentate N₂O₆ Schiff-base ligands 2-((E)-(2-(2-(2-((E)-2-hydroxy-3-methoxybenzylideneamino)phenoxy)phenoxy)phenylimino)methyl)-6-methoxyphenol H₂L¹ and 2-((E)-(2-(2-(2-((E)-2-hydroxy-3-methoxybenzylideneamino)phenoxy)-4-tert-butylphenoxy)phenylimino)methyl)-6-methoxyphenol H₂L² were prepared from the reaction of O-Vaniline with 1,2-bis(2′-aminophenoxy)benzene or 1,2-bis(2′-aminophenoxy)-4-t-butylbenzene, respectively. Reactions of H₂L¹ and H₂L² with copper(II) and zinc(II) salts in methanol in the presence of N(Et)₃ gave neutral [CuL¹]?·?0.5CH₂Cl₂, [CuL²], [ZnL¹]?·?0.5CH₂Cl₂, and [ZnL²] complexes. The complexes were characterized by IR spectra, elemental analysis, magnetic susceptibility, ESI–MS spectra, molar conductance (Λ_m), UV-Vis spectra and, in the case of [ZnL¹]?·?0.5CH₂Cl₂ and [ZnL²], with ¹H- and ¹³C-NMR. The crystal structure of [ZnL¹]?·?0.5CH₂Cl₂ has also been determined showing the metal ion in a highly distorted trigonal bipyramidal geometry. The electrochemical behavior of H₂L² and its Cu(II) complex, [CuL²], was studied and the formation constant of [CuL²] was evaluated using cyclic voltammetry. The logarithm value of formation constant of [CuL²] is 21.9.     

Synthesis,crystal structure and magnetic properties of a new binuclear copper(II)-copper(II) complex of a macrocyclic oxamide

The binuclear metal complex [Cu(μ-exoO₂)cyclamCu(bpy)](ClO₄)₂·H₂O (bpy?=?2,2′-bipyridine and (exoO₂)cyclam?=?1,4,8,11-tetraazacyclotradecanne-2,3-dione) has been synthesized and characterized by single-crystal X-ray analysis and spectroscopic and magnetic measurements. The structure consists of homobinuclear [Cu(μ-exoO₂)cyclamCu(bpy)]²⁺ cations, a weakly coordinated water molecule and perchlorate ions. In each binuclear unit, Cu1, coordinated by four nitrogen atoms of the macrocyclic organic ligand is connected to Cu2 via the exo-cis oxygen atoms of the macrocyclic ligand with Cu···Cu separations of 5.151?Å; Cu2 assumes square-pyramidal geometry. Magnetic properties measured at 2–300?K show antiferromagnetic exchange between adjacent copper(II) ions.     

Nickel(II) complex with an asymmetric tetradentate Schiff base ligand: synthesis,characterization, crystal structure,and DFT studies

Abstract

A new asymmetric tetradentate Schiff base, bis(5-methoxysalicylidene)-4-methylbenzene-1,2-diamine), H₂L, and its Ni(II) complex were prepared and characterized using elemental analyses (CHN), FTIR, UV–Vis, ¹H NMR, and ¹³C{¹H} NMR spectroscopic techniques, and crystal structures of both were determined by X-ray crystallography. For both ligand and Ni(II) complex, density functional theory calculations to find geometry parameters, IR frequencies, electronic properties, and natural bond orbital analysis (NBO) were done with M062X method and Def2-TZVP basis set. All calculated data are consistent with the experiments. NBO data for the Ni(II) complex show that the main type of transition in UV-Vis is interligand charge-transfer, which is assigned as π-π*.     

Synthesis,characterization, DFT calculations and antimicrobial activity of pentagonal-bipyramidal Zn(II) and Cd(II) complexes with 2,6-diacetylpyridine-bis(trimethylammoniumacetohydrazone)

Isothiocyanate complexes of Zn(II) and Cd(II) with the condensation product of 2,6-diacetylpyridine and trimethylammoniumacetohydrazide (Girard’s T reagent) were synthesized, characterized, and their antimicrobial activities were evaluated. The structures of the complexes were determined by elemental analysis, IR, and NMR spectroscopy. The crystal structure of the Zn(II) complex was also determined. Quantum-chemical calculations of the geometry and total energy of isomers of 2,6-diacetylpyridine-bis(trimethylammoniumacetohydrazone) were performed in vacuum and methanol solution, with the aim to explain conformational behavior and E/Z isomerism of this compound. DFT calculations of the molecular structures and the relative stabilities of linkage isomers of the Cd(II) complex showed that the isomer with N–Cd–N coordination of SCN^? is the most stable. Complexes of Zn(II) and Cd(II) exhibited low to moderate activity against the tested microbial strains.     

Synthesis and Crystal Structure of a Novel Polymeric Thiocyanato-Bridged Heteronuclear Complex of Copper(II) and Cadmium(II)

The title polymeric complex of Cu(II) and Cd(II) bridged by thiocyanate, Cu(en)₂[Cd(SCN)₃]₂, has been prepared and its structure determined by X-ray diffraction (XRD) methods. The crystal structure reveals that the Cu(II) atom is in an elongated octahedral coordination formed by two SCN^– anions and two en molecules. The Cd(II) atom is in a distorted octahedral coordination formed by six bridging SCN^– anions. Two different bridging thiocyanate anions exist in the complex. Both 1,1--SCN^– and 1,3--SCN^– anion act a role of bridge ligand and link Cu(II), Cd(II) atoms, and adjacent Cd(II). Cd(II) atoms form the three-dimensional (3-D) network polymeric structure. The IR and UV-Vis spectra have also been investigated.     

Copper(II) complexes of bis(pyrazol-1-yl)methane - Synthesis, spectroscopic characterization, X-ray structure and DFT calculations

Two novel copper(II) complexes incorporating bis(pyrazol-1-yl)methane ligand (bpzm) have been synthesized. The compounds [CuCl(bpzm)₂(H₂O)]Cl·H₂O (1) and [Cu(N₃)₂(bpzm)]_n (2) have been studied by IR, UV-Vis spectroscopy and X-ray crystallography. The experimental studies on the compounds 1 and 2 have been accompanied computationally by the density functional theory (DFT) calculations.     

Coordination behavior of 3,4-bis(2-pyridylmethylthio)toluene with copper(II) ions: Synthesis,structural characterization and reactivity,and DNA binding study of the dinuclear copper(II) complex

On reaction of different copper(II) salts with 3,4-bis(2-pyridylmethylthio)toluene (L) having neutral tetradentate NSSN donor set in different chemical environments, two mononuclear copper(II), one dinuclear copper(I) and one dinuclear copper(II) complexes, formulated as [Cu^II(L)(H₂O)₂](NO₃)₂ (1), [Cu^II(pic)₂] (2), [Cu^I₂(L)₂](ClO₄)₂ (3) and [Cu^II₂(L)₂Cl₂](ClO₄)₂ (4), respectively, were isolated in pure form [where pic = picolinate]. All the complexes were characterized by physicochemical and spectroscopic methods. The product of the reactions are dependent on the counter anion of copper(II) salts used as reactant and on the reaction medium. Complexes 1 and 4 were obtained with nitrate and perchlorate copper(II) salts, respectively. On the other hand, C–S bond cleavage was observed in the reaction of L with copper(II) chloride to form in situ picolinic acid and complex 2. Dinuclear complexes 3 and 4 were separated out when copper(II) perchlorate was allowed to react with L in methanol and in acetonitrile, respectively, under aerobic condition. The X-ray diffraction analysis of the dinuclear complex 3 shows a highly distorted tetrahedral geometry about each copper ion. Complex 4 is converted to 3 in acetonitrile in presence of catechol. The spectral study of complex 4 with calf thymus DNA is indicative of a groove binding mode interaction.     

Synthesis and characterization of a stable copper (I) calix[4]dicyano-diimidazole complex

A new calix[4]dicyano-diimidazole ligand was prepared in two steps from a de-tert-butylated calix[4]arene. The corresponding Cu (I) complex was found to be remarkably stable. The X-ray structure of the latter revealed a mixture of both monomeric-mononuclear and dimeric-dinuclear complexes. Detailed investigations on this copper complex, involving NMR (VT and DOSY), Infra-red, and MS analyses, demonstrated that the dimeric-dinuclear complexe does not exist in solution. Despite the presence of two cyano binding groups on the calixarene platform, every attempts to isolate a stable Cu(II) complex failed.     

Synthesis, spectral characterization and crystal structure of copper(II) complexes of 2-benzoylpyridine-N(4)-phenylsemicarbazone

An interesting series of nine new copper(II) complexes [Cu₂L₂(OAc)₂]·H₂O (1), [CuLNCS]·½H₂O (2), [CuLNO₃]·½H₂O (3), [Cu(HL)Cl₂]·H₂O (4), [Cu₂(HL)₂(SO₄)₂]·4H₂O (5), [CuLClO₄]·½H₂O (6), [CuLBr]·2H₂O (7), [CuL₂]·H₂O (8) and [CuLN₃]·CH₃OH (9) of 2-benzoylpyridine-N(4)-phenyl semicarbazone (HL) have been synthesized and physico-chemically characterized. The tridentate character of the semicarbazone is inferred from IR spectra. Based on the EPR studies, spin Hamiltonian and bonding parameters have been calculated. The g values, calculated for all the complexes in frozen DMF, indicate the presence of the unpaired electron in the d_x²-y² orbital. The structure of the compound, [Cu₂L₂(OAc)₂] (1a) has been resolved using single crystal X-ray diffraction studies. The crystal structure revealed monoclinic space group P2₁/n. The coordination geometry about the copper(II) in 1a is distorted square pyramidal with one pyridine nitrogen atom, the imino nitrogen, enolate oxygen and acetate oxygen in the basal plane, an acetate oxygen form adjacent moiety occupies the apical position, serving as a bridge to form a centrosymmetric dimeric structure.     

Dicarboxylate assisted synthesis of the monoclinic heterometallic tetrathiocyanato bridged copper(II) and mercury(II) coordination polymer {Cu[Hg(SCN)4]}n: Synthesis, structural, vibration, luminescence, EPR studies and DFT calculations

The synthesis of the monoclinic polymorph of {Cu[Hg(SCN)₄]}_n is reported. The compound, as determined by X-ray diffraction of a twinned crystal, consists of mercury and copper atoms linked by μ_1,3-SCN bridges. The crystal packing shows a highly porous infinite 3D structure. Diagnostic resonances for the SCN^- ligand and metal-ligand bonds in the IR, far-IR and Raman spectra are assigned and discussed. The electronic band structure along with density of states (DOS) calculated by the DFT method indicates that the compound is an indirect band gap semiconductor. The DFT calculations show that the observed luminescence of the compound arises mainly from an excited LLCT state with small MLCT contributions (from the copper to unoccupied π^? orbital of the thiocyanate groups). The X-band EPR spectrum of the powdered sample at room temperature reveals an axial signal with anisotropic g factors consistent with the unpaired electron of Cu(II) ion in the d_x²−y² orbital.