Photoinitiated Processes in Molecules of Schiff Bases Having an NH···N Intramolecular Hydrogen Bond

Study of the absorption and luminescence spectra of Schiff bases derived from o-(p-tolylsulfonylamino)benzaldehyde has shown that these systems, like those derived from salicylaldehyde, are characterized by intramolecular proton transfer in the excited and ground electronic states. This process is responsible for the appearance at 77 K of fluorescence with an anomalous Stokes shift and formation of ketone structures. Unlike o-alkyl(or aryl)iminomethyl]phenols, o-alkyl(or aryl)iminomethyl]anilines do not give rise to acoplanarization of the ketone fragment, which could follow intramolecular proton transfer in the excited state and is responsible for fluorescence with an anomalous Stokes shift and formation of colored structures.