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

School of Life Sciences and Pharmaceutical Engineering, West Anhui University, Lu’an, 237000 China
Journal of Solution Chemistry (Impact Factor: 1.08). 01/2011; 40(1):147-153. DOI: 10.1007/s10953-010-9630-x

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 335.6nm originates from
spin-forbidden singlet-triplet transitions, but the other experimentally observed absorption bands at 318.5nm, 310.6nm and
237.5nm 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.

-TD-DFT-Solvent effect-Transition mechanism

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