TD-DFT Calculation on UV-Vis Spectra of the Complex 8-((Trimethoxysilyl)methylthio)quinoline⋅ZnCl2

Abstract

The electronic structure and absorption spectra properties of the complex 8-((trimethoxysilyl)methylthio)quinoline⋅ZnCl2 in the gas phase and in acetonitrile (MeCN) have been investigated by means of DFT/TD-DFT calculations. Calculation results indicate that the broad and weak experimentally observed absorption bands of the complex in MeCN at 335.6 nm originates from spin-forbidden singlet-triplet transitions, but the other experimentally observed absorption bands at 318.5 nm, 310.6 nm and 237.5 nm arise from spin-allowed singlet-singlet transitions. Inclusion of MeCN as solvent leads to dramatic changes in the electronic structures and energy levels of the frontier molecular orbitals of the complex, and hence transition mechanisms of the absorption bands are also changed. For the complex, whether in the gas phase or in MeCN, the metal Zn does not participate in the transitions involved, in the gas phase the calculated lowest-energy absorption band of the complex comes from π→π ∗ mixed with n→π ∗ transitions with LLCT (ligand-to-ligand charge transfer) character, while in MeCN, the calculated lowest-energy absorption band is of LLCT/ILCT (intra-ligand charge transfer) character.