Synthesis of unsymmetrical compartmental oxime nickel(II) and copper(II) complexes: spectral, electrochemical and magnetic studies

A new series of binuclear unsymmetrical compartmental oxime complexes (1–5) [M₂L] [M=Cu(II), Ni(II)] have been synthesized using mononuclear complex [ML] (L=1,4-bis[2-hydroxy-3-(formyl)-5-methylbenzyl]piperazine), hydroxylamine hydrochloride and triethylamine. In this system there are two different compartments, one has piperazinyl nitrogens and phenolic oxygens and the other compartment has two oxime nitrogens and phenolic oxygens as coordinating sites. The complexes were characterized by elemental and spectral analysis. Electrochemical studies of the complexes show two step single electron quasi-reversible redox processes at cathodic potential region. For copper complexes E¹ _pc=−0.18 to −0.62 and E² _pc=−1.18 to −1.25 V, for nickel complexes E¹ _pc=−0.40 to −0.63 and E² _pc=−1.08 to −1.10 V and reduction potentials are sensitive towards the chemical environment around the copper and nickel atoms. The nickel(II) complexes undergo two electrons oxidation. The first one electron oxidation is observed around +0.75 V and the second around +1.13 V. ESR Spectra of the binuclear copper(II) complexes [Cu₂L](ClO₄), [Cu₂L(Cl)], [Cu₂L(NO₃)] shows a broad signal at g=2.1 indicating the presence of coupling between the two copper centers. Copper(II) complexes show a magnetic moment value of μ_eff around 1.59 B.M at 298 K and variable temperature magnetic measurements show a −2J value of 172 cm⁻¹ indicating presence of antiferromagnetic exchange interaction between copper(II) centres.     

Synthesis,structure and spectroscopic study of Cu(II) polypyridine complexes with phenylcyanamide derivative ligands

Several new mononuclear copper(II) complexes, [Cu(phen)₂L]PF₆, where phen = 1,10-phenanthroline and L = monoanions of phenylcyanamide (pcyd), 2,5-dichlorophenylcyanamide (2,5-Cl₂pcyd), 2-dichlorophenylcyanamide (2-Clpcyd) and 4-methylphenylcyanamide (4-Mepcyd), have been prepared and characterized by elemental analysis, UV–Vis, IR and ¹H NMR spectroscopies and cyclic voltammetry. [Cu(phen)₂(2,5-Cl₂pcyd)]PF₆ crystallized with a molecule of acetone with empirical formula of C₃₁H₂₀N₆OF₆Cl₂PCu in a triclinic crystal system and space group P 1 with a = 9.2086(6) Å, b = 13.3117(9) Å, c = 15.5313(10) Å, α = 107.8210(10)°, β = 104.6180(10)°, γ = 104.1670(10)°, V = 1643.21(19) ų and Z = 2. The structure was refined using 7555 Mo-Kα reflections with I > 2σ(I) and R ₁ = 0.0276 and Rw = 0.0692. The results are consistent with a mostly σ bonding interaction between Cu(II) and cyanamide anion. The LMCT band intensity and electrochemical potentials are compared with ruthenium phenylcyanamide analogues.     

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.     

New acyclic Schiff-base copper(II) complexes and their electrochemical,catalytic, and antimicrobial studies

A new series of acyclic mononuclear copper(II) complexes have been prepared by Schiff-base condensation derived from 5-methylsalicylaldehyde, diethylenetriamine, tris(2-aminoethyl) amine, triethylenetetramine, N,N-bis(3-aminopropyl)ethylene diamine, N,N-bis(aminopropyl) piperazine, and copper perchlorate. All the complexes were characterized by elemental and spectral analyses. Electronic spectra of the complexes show a d–d transition in the range 500–800?nm, electrochemical studies of the complexes show irreversible one-electron-reduction process around ?1.10 to ?1.60?V. The reduction potential of the mononuclear copper(II) complexes shifts toward anodic direction upon increasing the chain length of the imine compartment. ESR spectra of the mononuclear copper(II) complexes show four lines, characteristic of square-planar geometry, with nuclear hyperfine spin 3/2. The copper(II) complexes show a normal room temperature magnetic moment value μ _eff?=?1.72–1.76?BM, close to the spin-only value of 1.73?BM. Electrochemical and catalytic studies of the complexes were compared on the basis of increasing the chain length of the imine compartment. All the complexes were screened for antifungal and antibacterial activities.     

Synthesis, X-ray crystal structures, spectroscopic and cyclic voltammetric studies of Cu(II) Schiff base complexes of pyridoxal

Two mononuclear Cu(II) complexes, [Cu(L¹H₂)](ClO₄)_1.25Cl_0.75·1.25H₂O (1) and [Cu(L²H₂)](ClO₄)₂ (2), of the pyridoxal Schiff base ligands N,N′-dipyridoxylethylenediimine (L¹H₂) and N,N′-dipyridoxyl-1,3-propanediimine (L²H₂) are reported. X-ray crystal structures of both complexes are also reported. In both complexes the pyridoxal nitrogen atoms remain protonated. In the solid state, the tetradentate Schiff base ligand is virtually planar in 1, while in 2 the ligand conformation is like an inverted umbrella. In cyclic voltammetry experiments it is found that in these complexes the Cu(III) and Cu(I) states are more easily accessible than in their salen type analogs. The pyridoxal Schiff base complexes are also found to be resistant to oxidative electro-polymerization, unlike their corresponding salicyl aldehyde Schiff base complexes.     

Synthesis,characterization, electrochemical behaviour and X-ray crystal structures of nickel(II) complexes with a N2O4 donor set macrocyclic Schiff base ligand

Two nickel(II) complexes of [1 + 1] macrocyclic Schiff base ligand (L) have been prepared by cyclocondensation reactions between 1,3-diamino-2-propanol and 2-[3-(2-formylphenoxy)-2-hydroxypropoxy] benzaldehyde, using NiX₂ (X = Br, and I) salts as template agents, and characterized by elemental analyses, IR, molar conductivity and electronic spectra in both solid and solution states. The single-crystal X-ray diffractions of the complexes are also reported that contain nickel(II) ion in a distorted octahedral geometry coordination of N₂O₃X (X = Br, I and NO₃). In all complexes the ligand behaves as a pentadentate ligand. Cyclic voltammetric studies of nickel(II) complexes indicate a quasi-reversible redox wave in the negative potential range.     

Synthesis,spectroscopic and electrochemical studies of copper(II) and cobalt(II) complexes of three unsymmetrical vic -dioximes ligands

Cobalt(II) and copper(II) complexes with three dioxime ligands cyclohexylamine-p-tolylglyoxime (L₁H₂), tert-butyl amine-p-tolylglioxime (L₂H₂) and sec-butylamine-p-tolylglyoxime (L₃H₂), have been prepared. The metal to ligand ratios of the complexes were found to be 1?:?2. The Cu(II) complexes of these ligands are proposed to be square planar; the Co(II) complexes are proposed to be octahedral with water molecules as axial ligands. Ligands and complexes are soluble in common solvents such as DMSO, DMF, CHCl₃ and C₂H₅OH. The ligands have been characterized by elemental analysis, IR, UV-VIS, ¹H?NMR, ¹³C?NMR and thermogravimetric analysis (TGA). The complexes were characterized by elemental analysis, IR, UV-VIS, magnetic susceptibility measurements, thermogravimetric analysis (TGA) and electrochemistry. Electrochemical properties of metal complexes show quasi-reversible one-electron redox processes. However, Co(L₁H)₂ and Cu(L₁H)₂ complexes show another oxidation peak in the positive region. This single irreversible oxidation peak is caused by the cyclic ring of the ligand. Data also revealed that the electron transfer rates of metal complexes with L₁H₂ are higher than the other complexes.     

Synthesis,characterization, and structures of nickel(II) and palladium(II) complexes of aromatic thiohydrazides

Nickel(II) and palladium(II) form neutral 1?:?2 chelates with aromatic thiohydrazides, for example. thiobenzhydrazide, o-hydroxythiobenzhydrazide, furan-2-thiohydrazide, and thiophen-2-thiohydrazide. All the compounds are diamagnetic and have been characterized by elemental analysis and spectroscopic methods. o-Hydroxythiobenzhydrazido complexes of nickel(II) and palladium(II) were crystallized from DMSO and their structures were solved by X-ray diffraction. The complexes are isostructural with planar structures. Metal ion is linked to two identical deprotonated ligands through trans hydrazinic nitrogen and sulfur. Hydrogen of OH is involved in intramolecular hydrogen-bonding.     

Synthesis of new ethynylbipyridine-linked mono- and bis-tetrathiafulvalenes: electrochemical, spectroscopic, and Ru(II)-binding studies

Two new ethynylbipyridine-linked mono- and bis-tetrathiafulvalene (TTF) derivatives, together with a Ru(II) complex, were synthesized using Sonogashira coupling reactions and characterized by UV/vis spectroscopy and cyclic voltammetry. They display a clear electrochemically amphoteric behavior consisting of two reversible single-electron oxidation waves (typical for TTF derivatives) and one reversible single-electron reduction wave (bpy) and act as donor-acceptor (D-A) systems. Furthermore, for the Ru(II) complex, a quite intense fluorescence originating from the ³MLCT state is observed.     

Electrochemical, catalytic and antimicrobial activities of N-functionalized cyclam based unsymmetrical dicompartmental binuclear nickel(II) complexes

Five binuclear nickel(II) complexes have been prepared by simple Schiff base condensation of the compound 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-l,4,8,11-tetraazacyclotetradecane (L) with appropriate aliphatic or aromatic diamine, nickel(II) perchlorate and triethylamine. All the complexes were characterized by elemental and spectral analysis. Positive ion FAB mass spectra show the presence of dinickel core in the complexes. The electronic spectra of the complexes show red shift in the d–d transition. Electrochemical studies of the complexes show two irreversible one electron reduction processes in the range of 0 to −1.4 V. The reduction potential of the complexes shifts towards anodically upon increasing chain length of the macrocyclic ring. All the nickel(II) complexes show two irreversible one electron oxidation waves in the range 0.4–1.6 V. The observed rate constant values for catalysis of the hydrolysis of 4-nitrophenyl phosphate are in the range of 1.36 × 10⁻²–9.14 × 10⁻² min⁻¹. The rate constant values for the complexes containing aliphatic diimines are found to be higher than the complexes containing aromatic diimines. Spectral, electrochemical and catalytic studies of the complexes were compared on the basis of increasing chain length of the imine compartment. All the complexes show higher antimicrobial activity than the ligand and metal salt.     

Spectral, thermal, electrochemical and analytical studies on Cd(II) and Hg(II) thiosemicarbazone complexes

The coordination characteristic of the investigated thiosemicarbazones towards hazard pollutants, Cd(II) and Hg(II), becomes the first goal. Their complexes have been studied by microanalysis, thermal, electrochemical and spectral (electronic, IR and MS) studies. The substitutent (salicylaldehyde, acetophenone, benzophenone, o-hydroxy-p-methoxybenzophenone or diacetylmonoxime) plays an important role in the complex formation. The coordination sites were the S for thiosemicarbazide (HTS); NN for benzophenone thiosemicarbazone (HBTS); NS for acetophenone thiosemicarbazone (HATS) and salicylaldehyde thiosemicarbazone (H(2)STS); NNS or NSO for diacetylmonoxime thiosemicarbazone (H(2)DMTS). The stability constants of Hg(II) complexes were higher than Cd(II). The kinetic and thermodynamic parameters for the different thermal decomposition steps in the complexes have been evaluated. The activation energy values of the first step ordered the complexes as: [Cd(H(2)STS)Cl(2)]H(2)O>[Cd(H(2)DAMTS)Cl(2)]>[Cd(HBTS)(2)Cl(2)]2H(2)O>[Cd(HATS)(2)Cl(2)]. The CV of [Cd(H(2)STS)Cl(2)]H(2)O and [Hg(HBTS)Cl(2)] were recorded. The use of H(2)DMTS as a new reagent for the separation and determination of Cd(II) ions from water and some synthetic samples using flotation technique is aimed to be discussed.     

Synthesis and spectroscopic studies of copper(II) and nickel(II) complexes containing hydrazonic ligands and heterocyclic coligand

Two types of copper(II) and nickel(II) complexes derived from benzophenone anthranoylhydrazone (L1), 2-acetonaftanone anthranoylhydrazone (L2), 4-phenylacetonaftonone anthranoylhydrazone (L3), benzophenone salicyoylhydrazone (L4), 2-acetonaftanon salicyoylhydrazone (L5), 4-phenylacetonaftanon salicyoylhydrazone (L6) and bidentate heterocyclic base [1,10-phenanthroline (phen)] with general stoichiometry [ML2] and [ML(phen)]Cl have been synthesized and characterized by elemental analysis, infrared spectra, UV-vis electronic absorption spectra and magnetic susceptibility measurements. The effect of varying pH and solvent on the absorption behavior of both ligands and complexes have been investigated. According to the IR spectra, the ligands act as monobasic bidentate and coordination takes place in the enol tautomeric form.     

Synthesis of new Cu(II), Ni(II) and Co(II) complexes with a bis-amide ligand functionalized with pyridine moieties: Spectral, magnetic and electrochemical studies

Three new copper(II), nickel(II) and cobalt (II) dinuclear complexes with a bis-amide ligand derived from tartaric acid have been prepared and characterized. For this purpose, the ligand (R,R)-(+)-di-N,N′-methylpyridino-tartramide (dmpt) was synthesized via the classical aminolysis of (R,R)-(+)-dimethyltartrate with pyridylmethylamine. The molecular structures of the complexes Na[Cu₂(dmptH₋₃)(CO₃)] · 8H₂O (1) and [Ni₂(dmptH₋₂)₂] · 9.75H₂O (2) were elucidated by X-ray diffraction, and the complex [Co₂(dmptH₋₃)(μ-OH)] · NaClO₄ · 5H₂O (3) by XAS. The crystal structure of (1) shows that the two metallic centres are in a square planar environment. Each copper(II) is bound to pyridyl and deprotonated amidic nitrogen atoms and to the oxygen atoms of hydroxyl and carbonato groups. In complex (2), both nickel atoms are in a distorted octahedral environment with an identical set of donors atoms, N₄O₂, coming from four nitrogen atoms of two pyridylmethylamido moieties and two oxygen donor atoms of alcohol groups. XAS analysis of complex (3) allows us to propose a CoN₂O₄ chromophore, with two nitrogen atoms coming from pyridyl and amidic groups and two bridged oxygen atoms from a deprotonated alcohol group and an hydroxyl group; the hexacoordination is achieved by two water molecules. The spectroscopic, electrochemical and magnetic properties of these complexes were investigated.     

Palladium(II) complexes of 5-substituted isatin thiosemicarbazones: Synthesis,spectroscopic characterization,biological evaluation and in silico docking studies

Substituted heterocyclic (isatin) appended thiosemicarbazone ligands (L1–L3) are synthesized by condensation of substituted isatin molecule with N(4)-phenyl-3-thiosemicarbazide in good yields. The palladium(II) complexes are synthesized from ligands (L1–L3) and PdCl₂, with a general formula [PdCl(X-C₁₅H₁₀N₄OS)] where X?=?5-chloro (1), 5-bromo (2), and 5-nitro (3). Both analytical and spectroscopic methods have been used for the analysis and characterization of the synthesized compounds. The antimicrobial activity results observed that complexes, 1 and 2 have registered potent antibacterial activity against B. subtilis and K. pneumoniae and also complex 2 has shown good antifungal activity against the micro organisms. The antioxidant activity analysis revealed that the complex 3 showed significant activity with IC₅₀ values 7.24?±?0.09?µM. Moreover, the in vitro antiproliferative activity results suggested that complex 3 exhibited high activity against HeLa cell line compared with the standard with the IC₅₀ value 16.52?±?1.08?µM. The docking results correlate well.