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

The article of record as published may be found at http://dx.doi.org/10.1021/ja01038a007The 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.Director of Naval LaboratoriesOffice of Naval Researc

The Cation Radical of Tetramethyl-2-tetrazene

The article of record as published may be found at http://dx.doi.org/10.1021/ja00967a002The reaction between tetramethyl-2-tetrazene and tetranitromethane in various solvents gives a relatively long-lived paramagnetic species which has been identified by its electron paramagnetic resonance spectrum as the cation radical of tetramethyl-2-tetrazene. Although the complexity of the spectrum precluded analysis by inspection, spin-coupling constants were determined by least-squares analysis of a portion of the spectrum. These parameters agreed with values obtained for similar radicals. The coupling constants (in gauss) for the radical in acetone are a(N) (2,3 positions) = 1.07 ± 0.05, a(N) (1,4 positions) = 10.93 ± 0.06, a(H) (six equivalent protons) = 10.45 ± 0.05, and a (H) (six equivalent protons) = 11.72 ± 0.05; the line width is 0.39 gauss at -30˚. The free electron spin density is estimated to be 0.42 on the 1,4 positions and 0.08 on the 2,3 positions. The relatively small nitrogen coupling constant in the 1,4 positions compared to that predicted for tetrahedral nitrogen atoms is evidence for sp² hybridization on the terminal nitrogen atoms. It is found that reactions of tetranitromethane with other materials result in paramagnetic positive ions of the oxidized species.Office of Naval Researc