Spectroscopic and DFT studies of nonclassical and classical radical cations of 7-benzhydrylidenenorbornene analogues: contrasting molecular geometry and electronic structures originating from the different patterns of electronic coupling

Nanosecond time-resolved UV/vis absorption spectroscopy on laser flash photolysis and calculations based on (time-dependent) density functional theory for radical cations of 7-benzhydrylidenebenzonorbornene (3) and 7-benzhydrylidene-2,3-dimethylenenorbornane (4) indicated their contrasting molecular geometry and electronic structures, suggesting the nonclassical and classical nature of 3•+ and 4•+, respectively, which originated from the different patterns of electronic coupling between the C-7–C-8 and C-2–C-3 subunits.