Redox properties and radical anions of 2-substituted thioxanthen-9-ones and their 2-methyl S-oxide derivatives

The electrochemical reduction of 2-substituted thioxanthen-9-ones in MeCN is a one-electron process with the formation of long-lived radical anions, in which the thioxanthen-9-one fragment is planar according to EPR measurements and UB3LYP/6-31+G* calculations. The electrochemical reduction of 2-methylthioxanthen-9-one sulfoxide and sulfone are EEC and EE processes, respectively, their radical anions are not planar, and the electrochemical oxidation of the title compounds is irreversible with consecutive oxidation of the sulfur atom, except for the sulfone, whose oxidation was not observed at the limit of the anodic potential (2.5V vs. s.c.e.).