Intramolecular charge transfer with 4-(N-phenylamino)benzoic acid. The N-phenyl amino conjugation effect

4-(N-phenylamino)benzoic acid (PhABA) was synthesized and its fluorescence spectra were recorded. In aprotic polar solvents, PhABA emitted strongly Stokes-shifted single-banded fluorescence with practically the same wavelength as that of 4-(N,N-diphenylamino)benzoic acid (DPhABA), indicative of the ICT character of the emissive state. 4-(N-isopropylamino)benzoic acid (iPrABA) showed single band emission however, sluggish response to the solvent polarity. In alkanols dual fluorescence of PhABA and DPhABA was observed but with different dependencies on alkanol structures. We concluded that ICT occurring with PhABA was due to the N-phenyl/amino conjugation effect. The work could be of help in understanding speciality of anilino moiety as electron donor compared to aliphatic amino group.