SYNTHESIS AND ELECTROCHEMICAL REDUCTION OF 2-METHYL-9H-SELENOXANTHEN-9-ONE

Abstract

2-Methyl-9H-selenoxanthen-9-one (selenoxanthone) 1 was obtained by the reaction of bis-(2-carboxyphenyl)diselenide with toluene in concentrated sulphuric acid. It is demonstrated by means of cyclic voltammetry, EPR spectroscopy and quantum chemical DFT calculations that the electrochemical reduction (ECR) of selenoxanthone 1 in acetonitrile is a one-electron reversible process with the formation of a long-lived radical anion having a similar type of the highest occupied molecular orbital (HOMO) to the radical anions of the thioxanthone series. The ECR potential of selenoxanthone 1 is found to be less negative than the corresponding ECR potential of its related 2-methyl-9H-thioxanthen-9-one, which indicates an increase in the adiabatic electron affinity of selenoxanthone 1 compared to its sulphur-containing analogue. This fact confirms the general nature of the phenomenon of an increase in the adiabatic electron affinity of heterocyclic compounds when a heteroatom is replaced by a heavier one within group VIa of the periodic system of elements.