Photoinduced proton transfer in a pyridine based polymer gel.

We describe an experimental and theoretical consideration of photoexcited proton transfer in a poly(4-vinyl pyridine)/pyridine gel. Evidence was found for two states of a multiple state process analyzed by DFT modeling. According to the latter, following irradiation at 385 nm, the proton donor is the CH group of the polymer main chain and the proton acceptor is the nitrogen of the polymeric pyridine side chain. Proton transfer is made possible through the assistance of a mobile pyridine solvent molecule acting as a transfer vehicle. Proton transfer promotes both a geometrical rearrangement of the vinyl side chain as well as electronic density redistribution. The photoproduct intermediate—the hydrogen-bonded complex between the protonated solvent pyridine molecule and the deprotonated polymeric pyridine side chain—is identified by its Curie law magnetic susceptibility, ESR spectrum, and fluorescence lifetime measurements. The proton transfer from the nitrogen of the solvent pyridine molecule to the pyridin...