Photochromism Dependent on Crystal Packing: Photoinduced and Thermal Proton‐Transfer Processes in Single Crystals of 6‐(2,4‐Dinitrobenzyl)‐2,2′‐Bipyridine

Abstract

Despite structural similarities, different photoreactivities are displayed by the two crystalline phases of 6-(2,4-dinitrobenzyl)-2,2′-bipyridine. Whereas one phase (the arrangement of the molecules in the unit cell of this phase is shown on the right) undergoes a photoinduced proton transfer process, the other is photoinert. Deuteration causes a marked increase in the lifetime of the colored phototautomer.