Novel photosystem involving protonation and deprotonation processes modelled on a PYP photocycle

The synthesis of novel ortho-coumaric acid derivatives, with an amide group linked with an olefin moiety, which introduced photoinduced switching of the intramolecular hydrogen bonds is presented. An intramolecular OH⋯OC hydrogen bond formed in a Z-phenol compound was switched to an intramolecular NH⋯O hydrogen bond in Zphenolate state via deprotonation. The pK_a value of the Z-phenol derivative was lower than that of E-phenol, and a novel photocycle system involving protonation and deprotonation processes was achieved.