Selenoviologen‐Appendant Metallacycles with Highly Stable Radical Cations and Long‐Lived Charge Separation States for Electrochromism and Photocatalysis

Abstract Two coordinated metallacycles (rhomboid for M1 , hexagonal for M2 ) with selenoviologens (SeV 2+ ) pendants were synthesized via coordination‐driven hierarchical self‐assembly. M1 / M2 with rigid and discrete metallacyclic cores showed tunable optoelectronic properties due to strong π–π stacking and push–pull electron structures. Femtosecond transient absorption (fs‐TA) revealed that the formation of macrocyclic structure can not only enhance the stability of radical cation, but also improve the efficiency of intramolecular charge transfer and produce a long‐lived charge separation state. The electrochromic performances of M1 / M2 ‐based devices were exhibited to show decent radical stabilization. By using M1 / M2 as the photocatalyst, the improved catalytic efficiency (>80 %) of visible‐light‐induced cross‐dehydrogenative coupling (CDC) reactions was achieved due to the highly stable radical cations and long‐lived charge separation states, which were also confirmed by fs‐TA.