Bifunctional photochromism based on photoinduced nitro-assisted proton transfer

The preparation, spectroscopy, structure, and solid-state photochromism of the first photoactive bifunctional molecule based on the ortho-nitrobenzyl- pyridine (NBP) unit was carried out. NBP was found capable of nitro-assisted proton transfer (NAPT) and could serve as a prototypic compound for a new concept of design of nitro-based polystable switching materials. The visible absorption maximum of the colored form of the dimer is strongly red-shifted from the respective monomer and appeared at the highest wavelength. The low-temperature photactivity of the monoclinic form, whose molecular conformation was unfavorable for proton transfer, was due to latent photochromism caused by radical reactions.