Studies on Copper(II), Cobalt (II) and Nickel (II) Picrate Complexes with the Ligand 1,3-Bis(2-benzimidazyl)- 2-thiapropane

Copper(II) complexes as catalyst for the aerobic oxidation of o-phenylenediamine to 2,3-diaminophenazine

Two new mononuclear copper(II) complexes [Cu (L) (NO3)2] (1) and [Cu (L) Br2] (2) where (L=bis(1-(pyridin-2-ylmethyl)-benzimidazol-2-ylmethyl)ether) are synthesized and characterized by single-crystal X-ray diffraction analysis, elemental analysis, UV-Visible, IR spectroscopy, EPR and cyclic voltammetry. The complexes exhibit different coordination structures; the E1/2 value of the complex (1) is found to be relatively more cathodic than that of complex (2). X-band EPR spectra at low temperature in DMF supports a tetragonally distorted complex (1) while complex (2) shows three different g values suggesting a rhombic geometry. These complexes were utilized as a catalyst for the aerobic oxidation of o-phenylenediamine to 2,3-diaminophenazine assisted by molecular oxygen. The initial rate of reaction is dependent on the concentration of Cu(II) complex as well as substrate, and was found to be higher for the nitrate bound complex, while presence of acetate anion acts as a mild inhibitor of the reaction, as it is likely to pick up protons generated during the course of reaction. The inhibition suggests that the generated protons are further required in another important catalytic step.

Synthesis, Crystal Structure, and Spectra Properties of the Cadmium (II) Complex with Bis(N-allylbenzimidazol-2-ylmethyl)benzylamine

A novel complex of cadmium (II) picrate (pic) with V-shaped ligand bis(N-allylbenzimidazol-2-ylmethyl)benzylamine (babb), with composition [Cd(babb)₂](pic)₂, was synthesized and characterized by elemental analyses and electrical conductivity, IR, and UV/visible spectra. The crystal structure of the complex has been determined by the single-crystal X-ray diffraction. In the complex, the coordination sphere around Cd (II) is distorted octahedral, six nitrogen atoms involved in coordination afforded by two tridentate ligand babb. Moreover, The DNA-binding properties of the ligand babb and Cd (II) complex were investigated by spectrophotometric methods and viscosity measurements, and the results suggest that they bind to DNA via an intercalation binding mode, and the Cd (II) complex shows higher affinity than the ligand.

Dibromido[1,1'-dibenzyl-2,2'-(sulfane-diyl-dimethyl-ene)di-1H-benzimidazole]-cadmium(II) dimethyl-formamide solvate

In the title compound, [CdBr₂(C₃₀H₂₆N₄S)]·C₃H₇NO, both the complex and solvent mol­ecule lie on a crystallographic mirror plane. The Cd^II ion is coordinated in a disorted square-pyramidal CdBr₂N₂S environment with one of the Br atoms in the apical site. In the crystal structure, the benzimidazole ring systems are involved in weak inter­molecular π–π stacking inter­actions [centroid–centroid distances = 3.606 (2) and 3.753 (2) Å]. Further stabilization is provided by weak inter­molecular C—H⋯O hydrogen bonds. The methyl H atoms of the dimethyl­formamide solvent mol­ecule are disordered about a mirror plane.