Recent advances in crystalline hybrid photochromic materials driven by electron transfer

Photochromic materials have broad application prospects in the fields of molecular switching, detection, biological, and molecular machines. Crystalline hybrid photochromic materials (CHPMs) can not only preserve the intrinsic features of photochromic materials but also coin new photoresponsive functionality derived from the synergy of each components. The crystalline characteristics feature unique advantages in understanding structure–property relationships and mechanisms, which provides the possibility to explore potential photoresponsive mechanisms. This review summarizes the recent advances in CHPMs driven by electron transfer (ET) with focus on molecular design, assembly strategy and structure-related photoresponsive properties. The first unit offers a short discussion of CHPMs and the general ET strategies for the design of CHPMs. The following sections give overviews of CHPMs based on pyridinium-derivatives, CHPMs based on naphthalene diimide-derivatives, CHPMs based on conjugated N-heterocycle units, CHPMs based on metallocyanate. Finally, we will give the conclusions and perspectives of CHPMs. The trends identified in this review could propel the design and application of CHPMs and photoresponsive materials.