Spectroscopic Studies of Zinc Benzenethiolate Complexes: Electron Transfer to Methyl Viologen

Abstract

Mononuclear and tetranuclear zinc benzenethiolate complexes are studied by both spectroscopic and electrochemical methods.
Zn(SPh)4 2- and Zn4(SPh)10 2- represent tetrahedral fragments of the cubic zinc sulfide lattice. The structured absorption spectra of the zinc benzenethiolate complexes are ascribed to intraligand transitions for the mononuclear complex and to a composite of both intraligand and ligand-tc-metal charge-transfer (LMCT) transitions for the tetranuclear species. The mononuclear complex
does not emit, while the tetranuclear compound displays a short-lived metal-to-ligand charge-transfer (MLCT) emission. Photodegradation of both zinc complexes yields thianthrene, dibenzothiophene, and benzenethiol. Zn4(SPh)10 2- forms a ground-state charge-transfer complex with the dicationic electron acceptor methyl viologen in CH3CN. Excitation of the charge-transfer absorption band with a 30-ps laser pulse leads to the formation of the methyl viologen radical cation showing a lifetime of 2 +- 0.4 ni.