An Electron Spin Resonance Study of Several 1,4-Dihydro-s-tetrazine Cation Radicals

Abstract

The one-electron oxidation of 1,4-dihydro-s-tetrazines using concentrated iodine solutions of tetrahydrofuran as oxidant gives rise to a new class of relatively stable cation radicals. In the presence of water and air these radical cations in solution are stable for periods of hours to several days. The esr spectra for radical cations of 1,4-dimethyl-, 1,4-diphenyl-, 1,4-dimethyl-3,6-diphenyl-1, ,3,4,6-tetraphenyl-, and 1,4-bis(p-bromopheny1)-3,6- diphenyl-l,4-dihydro-s-tetrazineasr e interpreted and compared with molecular orbital calculations using the CND0/2 method to obtain the molecular orbital parameters. Assignment of the esr nitrogen coupling constants indicates nearly the same value for the five members of the series studied. The formation of the previously unreported 1, 4-dimethyl-1,4-dihydro-s-tetrazine, first identified as its radical cation in several different reactions, is discussed.