Structural investigations on bis-(semicarbazido)dihydrazine nickel(II) complex synthesized by using uracil and hydrazine hydrate

A mixed-ligand bis-(semicarbazido) dihydrazine nickel(II) complex, [Ni(sem)(2)(Hz)(2)] (Hsem = semicarbazide, Hz = hydrazine) has been synthesized by unusual ring opening of uracil reacting with hydrazine hydrate in the presence of nickel(II) chloride. The complex was characterized by elemental analyses, IR, UV-Vis spectral studies and magnetic susceptibility measurement. The molecular structure of the complex was finally determined by single crystal X-ray diffraction study. The complex acquires a six coordinate distorted octahedral geometry in which semicarbazide ligand binds through hydrazinic - NH2 and a deprotonated C-O group whereas, hydrazine coordinates through one of the -NH2 group to nickel(II) centre. The structure was stabilized by the presence of strong inter-molecular hydrogen bonding interactions N-H . . . N and N-H . . . O forming a huge supramolecular network. Further, the structure was satisfactorily modeled by density functional theory calculations (DFT). UV-Vis and IR spectra are analyzed in depth with the help of time dependent-DFT. The theoretical analyses of electronic structure and molecular orbitals have suggested that the high-energy absorption bands in UV-Vis spectrum are mainly pi -> pi(*) ligand-to-ligand charge transfer transitions (LLCT) and lower energy absorption bands are pi -> (d(z)(2) or d(x)(2) y(2), d(yz)) ligand-to-metal charge transfer transitions (LMCT) in nature. (C) 2013 Elsevier B.V. All rights reserved.