Tetragonal Distortion Parameter of Some Nickel(II) Complexes

Abstract

A macrocyclic ligand viz., 3,8-dimethyl-3,7-diene-5,6-(2',3'-pyridino)-4,7-diaza-2,9- decadihydroxomine (MPAH) was used for complexation with Ni(II) salts. The general formula of the complexes was found NiLX₂ where L = MPAH and X = Cl^–, Br^–, CNS^– and ClO₄^–. The complexes were characterized by their micro analysis, infrared spectra, magnetic moment measurement and electronic spectra. All the complexes except one are found paramagnetic with μeff values 3.15-3.20 BM, higher than μeff value (2.828 BM). Ni(II) is a d8 system with ground term 3F which splits under octahedral crystal field perturbation with ground state crystal field term 3A2g. As it is singly degenerate, orbital contribution to the magnetic moment of the complexes is not possible. So, certainly there is spin-orbit mixing of the ground term with the next excited term. The appearance of four absorption bands in their electronic spectra reveals the tetragonal distortion in the symmetry of complexes. The zero field splitting parameter (D) is found 1.37 to 2.90 cm^-1 while the tetragonal distortion parameter is found 126-183 cm^-1. The ligand field splitting parameter for axial ligands, i.e., DqZ is found 640-870 cm^-1.