Energy manipulation and metal-assisted photochromism in photochromic metal complex

Over decades of development, functions of photochromic compounds have no longer been as simple as meeting color change demand. Upon photoisomerization, physical and chemical properties can be modulated, leading to exponential growth of related publications. Among a great quantity of publications, photochromic metal complexes are dazzling candidates as for the convenience of achieving all-visible light photochromism. Two photophysical energy transfer processes, from metal to two isomers of photochrome core, make main contribution to metal-sensitized photochromism and luminescence quenching, respectively. Upon light irradiation, photochromic metal complex can be switched between two isomers together with energy manipulation, including energy transfer switching and energy level modulation. Herein, our review focus on the latest six-years development about energy manipulation and metal-assisted photochromism, which mainly refers to metal-sensitized visible light photochromism, in azobenzene/stilbene, spiropyran/spirooxazine and diarylethene metal complexes. Some other issues will also be discussed, such as negative effects of energy/electronic communication on photochromic performance, several applications in bio-sensor/metallogelation/nonlinear optical (NLO) material/rewritable system.