Computational DFT study on nickel symmetric bis(thiosemicarbazone) complexes: Electronic absorption and redox potentials

This work deals with the performance of density functional theory (DFT) for evaluating one-electron reduction potentials and UV-Vis spectra of nickel complexes containing symmetric bis(thiosemicarbazones). Nine DFT calculation methods in combination with the polarisable continuum solvation model (PCM) were applied to calculate one-electron redox potentials (E-calc) of nickel complexes. The best predicted results were gained by B3PW91/6-311++G(2df,2p)//B3LYP/6-31+G(d) level of theory in DMF. The results revealed that the most important effective thermodynamic factor is the solvation factor. Although the contribution of the electron attachment (EA) energy is more than Delta Delta(solv)G degrees and Delta Delta epsilon(geom), for NiLI, NiL2, NiL3, and NiL4, Delta Delta(solv)G degrees and Delta Delta epsilon(geom) play important roles in redox potentials. The calculated reduction potentials reproduce the tendency in experimental data. The derived error was in the region of -0.342 to -0.051 V. Reduction potentials have correlation with the energy of the frontier molecular orbitals LUMO/HOMO. According to the Natural Population Analysis (NPA), the geometries of nickel complexes remain distorted square planar, after reduction. (C) 2018 Elsevier Ltd. All rights reserved.