An ESR and MO study of the butatriene and tetramethylbutatriene radical cations

The radical cations of butatriene (BT +• ) and tetramethylbutatriene (TMBT +• ) have been stabilized in low-temperature halocarbon matrices and studied by ESR spectroscopy. The spectra of BT +• and TMBT +• exhibit isotropic hyperfine splittings of 8.3 G (4H) and 13.0 G (12H), respectively. The skew angles of BT +• (25°) and TMBT +• (50°) are estimated by comparing the experimental hyperfine splittings with those obtained by semiempirical MO calculations.