Synthesis and photophysical properties of models for twisted PRODAN and dimethylaminonaphthonitrile

The synthesis and photophysical properties of 7-cyano-3,4-dihydro-2H-1,4-ethano-benzo[g]quinoline and 3,4-dihydro-2H-1,4-ethano-7-propionyl-benzo[g]quinoline are reported. These compounds possess a quinuclidine substructure that locks the tertiary amino group perpendicular to the naphthalene ring. Their excited states are models for the twisted excited states of 2-(dimethylamino)-6-naphthonitrile (DMANN) and 6-propionyl-2-(dimethylamino)naphthlene (PRODAN). In contrast to DMANN and PRODAN, the fluorescence of these twisted derivatives is strongly deactivated in polar solvents. Neither DMANN nor PRODAN likely emit from TICT excited states.