Nanosecond Time-resolved Infrared Spectra and Structure of the Charge-transfer State of 9,9′-Bianthryl in Acetonitrile

Nanosecond time-resolved infrared spectra of photoexcited 9,9′-bianthryl (BA) and its deuterated derivative (BA-d18) were recorded in acetonitrile-d3 and cyclohexane-d12. The charge-transfer (CT) bands observed at the 1200–1400 cm−1 region are contributed mostly by the intra- and inter-ring CC stretch vibrations. The intrinsic frequency of the inter-ring CC stretch falls within the 1200–1400 cm−1 region, which is consistent more with a twisted structure than with a fully conjugated planar structure of the CT state.