RADICAL CATIONS OF DITHIASELENARADIALENE AND TETRASELENARADIALENE WITH RESTRICTED DELOCALIZATION OF THE UNPAIRED ELECTRON

The radical cations of the permethylated dithia[6]radialene 1 and the tetraselena[8]radialene 2 have been investigated by ESR- and ENDOR-spe ctroscopy. It is shown that in the radical cation of 1 the unpaired el ectron is delocalized only in one half of the molecule. The magnitude of the S-33 coupling constant suggests a restricted localization withi n the 2,3-dithiatetramethyl-butadiene unit. We ascribe the slow electr on transfer from one part of the molecule to the other to steric effec ts. The analysis of the ESR spectrum of 2(.+) shows that only two of t he four selenium atoms are involved. The delocalization of the unpaire d electron is restricted to only one of the divinyl diselenide moietie s with a slow electron transfer rate to the other one.