Electron spin resonance studies of the anions of some azulene derivatives: 1‐tert‐butyl‐, 1,3‐di‐tert‐butyl‐ and 4,6,8‐trimethylazulene

Hyperfine splitting constants are reported for radical anions of the azulene derivatives 1‐tert‐butyl‐, 1,3‐di‐tert‐butyl‐ and 4,6,8‐trimethylazulene. Radical anion geometries are optimized at the Hartree‐Fock level of theory using 3–21G and 3–21 + G* basis sets. The perimeter bond lengths are all approximately 1.40–1.44 Å except for the C‐4C‐5 (and C‐7C‐8) bond which, at 1.36 Å, is best described as a double bond. The singly occupied antibonding molecular orbitals are computed to be symmetric with respect to the mirror plane perpendicular to the molecular plane, consistent with the ESR data. Copyright © 1995 John Wiley & Sons Ltd.