ELECTRON-SPIN-RESONANCE SPECTROSCOPY OF CF3CNSSN. AND C6F5CNSSN. FREE-RADICALS

Solution and powder ESR spectra of the 4-trifluoromethyl-1,2,3,5-dithi adiazolyl and 4-pentafluorophenyl-1,2,3,5-dithiadiazolyl free radicals were analysed. Comparison of the ESR parameters with those obtained f or the protonated equivalents shows that fluorination produces a drift of unpaired electron spin density away from the nitrogen 2p(x) orbita ls towards sulphur 3p(x) orbitals (x is the direction perpendicular to the heterocyclic ring), consistent with an increase in electronegativ ity of the substituent. The fluorinated radicals dimerize more readily than their protonated counterparts.