Theoretical spectroscopic study of seven zinc(II) complex with macrocyclic Schiff-base ligand

Seven zinc complexes, which are [ZnL1](2+), [ZnL2](2+), [ZnL3](2+), [ZnL4](2+), [ZnL5](2+), [ZnL6](2+) and [ZnL7](2+), are studied as theoretically. Structural parameters, vibration frequencies, electronic absorption spectra and H-1 and C-13 NMR spectra are obtained for Zn(II) complexes of macrocyclic penta and heptaaza Schiff-base ligand. Vibration spectra of Zn(II) complexes are studied by using Density Functional Theory (DFT) calculations at the B3LYP/LANL2DZ. The UV-VIS and NMR spectra of the zinc complexes are obtained by using Time Dependent-Density Functional Theory (TD-DFT) method and Giao method, respectively. The agreements are found between experimental data of [ZnL5](2+), [ZnL6](2+) and [ZnL7](2+) complex ions and their calculated results. The geometries of complexes are found as distorted pentagonal planar for [ZnL1](2+), [ZnL2](2+) and [ZnL3](2+) complex ions, distorted tetrahedral for [ZnL4](2+) complex ion and distorted pentagonal bipyramidal for [ZnL5](2+), [ZnL6](2+) and [ZnL7](2+) complex ions. Ranking of biological activity is determined by using quantum chemical parameters and this ranking is found as: [ZnL7](2+) > [ZnL6](2+) > [ZnL5](2+) [ZnL3](2+) > [ZnL2](2+) > [ZnL1](2+). (C) 2014 Elsevier B.V. All rights reserved.