Janus-type emission from a cyclometalated iron(iii) complex
Jakob Steube, Ayla Kruse, Olga S. Bokareva, Thomas Reuter, Serhiy Demeshko, Roland Schoch, Miguel A. Argüello Cordero, Athul Krishna, Stephan Hohloch, Franc Meyer, Katja Heinze, Oliver Kühn, Stefan Lochbrunner, Matthias Bauer
Abstract
Abstract Although iron is a dream candidate to substitute noble metals in photoactive complexes, realization of emissive and photoactive iron compounds is demanding due to the fast deactivation of their charge-transfer states. Emissive iron compounds are scarce and dual emission has not been observed before. Here we report the Fe III complex [Fe(ImP) 2 ][PF 6 ] (HImP = 1,1′-(1,3-phenylene)bis(3-methyl-1-imidazol-2-ylidene)), showing a Janus-type dual emission from ligand-to-metal charge transfer (LMCT)- and metal-to-ligand charge transfer (MLCT)-dominated states. This behaviour is achieved by a ligand design that combines four N -heterocyclic carbenes with two cyclometalating aryl units. The low-lying π * levels of the cyclometalating units lead to energetically accessible MLCT states that cannot evolve into LMCT states. With a lifetime of 4.6 ns, the strongly reducing and oxidizing MLCT-dominated state can initiate electron transfer reactions, which could constitute a basis for future applications of iron in photoredox catalysis.