Conformation and photochemical properties of 3-benzoyl-4-benzylamino-7-dimethylaminocoumarin

3-Benzoyl-4-benzylamino-7-dimethylaminocoumarin was synthesized and its conformation in solid state and solution was determined. While the X-ray crystal analysis showed an aromatic π–π stacking interaction in the solid state, the proton NMR studies suggested the presence of an intramolecular hydrogen bonding in solution. Adjacent functional group modifications through N-methylation, reduction of carbonyl group, or replacing the coumarin moiety to dimedone, all resulted in disrupting the π–π stacking conformation. Upon UV irradiation, the 7-methylamino group can be oxidized by molecular oxygen to the corresponding formamide in the absence of any external photosensitizers.