ELECTRON-SPIN-RESONANCE STUDIES OF THE ANIONS OF SOME AZULENE DERIVATIVES - 1-TERT-BUTYLAZULENE, 1,3-DI-TERT-BUTYLAZULENE AND 4,6,8-TRIMETHYLAZULENE

Hyperfine splitting constants are reported for radical anions of the a zulene derivatives 1-tert-butyl-, 1,3-di-tert-butyl- and 4,6,8-trimeth ylazulene. Radical anion geometries are optimized at the Hartree-Fock level of theory using 3-21G and 3-21 + G basis sets. The perimeter bo nd lengths are all approximately 1.40-1.44 Angstrom except for the C-4 -C-5 (and C-7-C-8) bond which, at 1.36 Angstrom, is best described as a double bond. The singly occupied antibonding molecular orbitals are computed to be symmetric with respect to the mirror plane perpendicula r to the molecular plane, consistent with the ESR data.