Chiroptical switching based on photoinduced proton transfer between homopolymers bearing side-chain spiropyran and azopyridine moieties

A novel optically-active polymeric methacrylate, bearing the (S)-3-hydroxy pyrrolidinyl group linked through the nitrogen atom to an azopyridine chromophore, was synthesized and investigated in combination with a polymeric methacrylate incorporating the photoisomerizable spiropyran chromophore in the sidechain. In the presence of acid, this system can be operated in solution to modulate the protonation of the azopyridine moieties by photoisomerizing the spiropyran component. In addition to UV-vis spectroscopy, the proton transfer process occurring between the macromolecular components can be also followed by CD spectroscopy, thus behaving as a chiroptical switch.