The relationship between solid-state fluorescence intensity and molecular packing of coumarin dyes

摘要

The solid-state fluorescence intensity of coumarin dyes depends on the substituents present at the 4- and 7-positions. 7-(Dtethylamino)coumarins showed higher solid-state fluorescence quantum yield (Φ_f(ss)=0.29-0.40) than 7-aminocoumarins (0.01). In the case of julolydyl coumarins, a 4-methylte-tramethyljulolydyl derivative also displayed high Φ_f(ss) (0.34), this being greater than that observed for both 4-(perfluoroalkyl)tetramethyljulolydyl (0.09 and 0.10) and 4-methyljulolydyl derivatives (0.01). X-ray crystallographic analysis suggested that coumarin dyes bearing network hydrogen bonds and/or π-π stacking show weak solid-state fluorescence whereas coumarin dyes having isolated monomer- and dimer-type stacking show intense fluorescence. 4-(Perfluoroalkyl)tetrarnethyljulolydyl derivatives displayed medium fluorescence intensity owing to isolated monomer-type packing with little intermolecular interactions operating between adjacent molecules.