First ligand-driven light-induced spin change at room temperature in a transition-metal molecular compound

Abstract

Applied to the new iron(II) compound Fe(t-msbpy)2(NCS)2 (t-msbpy=4-methyl-4′-trans-styryl-2,2′-bipyridine), a novel strategy based on the so-called '‘ligand-driven light-induced spin change’' (or LD-LISC) effect, which consists in triggering the metal ion electronic spin-state crossover in a complex by a photochemical modification of the ligand, allowed this photomagnetic effect to be observed for the first time at room temperature. The compound, studied in CH3CN or CD3CN, was found to be initially nearly diamagnetic (S=0) by means of NMR experiments. Then, irradiation of a solution to the photostationary state with λexc=334 nm was shown, by using UV-VIS spectrometry, to result in the trans→cis isomerization of the styryl substituent of msbpy and in the subsequent S=0 (low spin)→S=2 (high spin) conversion of a significant fraction of the iron(II) ions.