A green polymeric zinc(II) complex: Synthesis, structural characterization, and theoretical studies

Synthesis and X-ray structural characterization of a Zn(Il) polymer [Zn(NCS)(2)(L)](n) (1) [L = 4,4'-bipyridine] have been reported. The compound, having a metal [Zn(II)] with d(10) electronic configuration at the centre of each monomeric unit, shows green colour (absorption band at 648 nm). Molecular orbital energy calculations (and the theoretical spectra obtained therefrom) using GAUSSIAN-09 program package show that HOMO-LUMO energy difference gradually decreases from monomeric to tetrameric units. On considering lambda(max) to be 648 nm in the non-linear fit equation (lambda(max) versus molecular units), it is found that 13 molecular units are responsible for the experimentally observed green color of 1.