Photochromic Organometallics, A Stimuli-Responsive System: An Approach to Smart Chemical Systems

Recent progress of photochromic metal complexes is summarized with emphasis on photochromic organometallics with a M-C(photochromic unit) bond. Stimuli-responsive systems including the photochromic system are essential components of smart chemical systems, where the system recognizes changes of the environment so as to trigger a chemical function required for the smart chemical system. Combination with metal components, which exhibit unique properties such as redox and photophysical properties and catalysis, should lead to more sophisticated systems. Photophysical properties (e.g., luminescence) have been the major research subject of photochromic coordination compounds, whereas for photochromic organometallics, a limited number of studies on switching of catalytic activity of metal-catalyzed organic transformation and application to molecular devices have been reported. Intriguing switching systems (e.g., performance of organometallic molecular wire and multimodal stimuli-responsive system) have been realized by the use of dithienylethene, a representative photochromic molecule. Future prospects of photochromic organometallics are discussed in the final part.