The polarized luminescence and vibrational optical activity of calycanthine

Measurements of the circular intensity differential in the fluorescence of calycanthine, and of the linearly-polarized excitation and emission spectrum, are found to support the exciton analysis of the electronic CD spectrum, upon which the determination of the absolute stereochemical configuration of the molecule is based. The observed vibrational IRCD of the N-H stretching mode of calycanthine is shown to originate principally from chromophore-substituent coupling, and not from the degenerate interchromophore coupling particular to chiral dimers. The general chromophore-substituent coupling mechanism provides a procedure for the determination of absolute configuration from the IRCD associated with a localised characteristic vibrational mode.