Reversible light-induced magnetization change in an azobenzene-attached pyridylbenzimidazole complex of iron(II) at room temperature

Reversible photomagnetic effects were demonstrated at room temperature by the use of a new iron(II) complex t(100)c(0)-[Fe(1)(3)](BF4)(2)center dot 3H(2)O (1 = phenyl(2-pyridin-2-yl-3H-benzoimidazol-5-yl) diazene), based on the strategy of the so-called ligand-driven light-induced spin change (LD-LISC) effect. The complex showed thermal spin crossover in both solid and solution states, showing a transition temperature T-1/2 = 279(16) K in acetone. trans-cis Photoisomerization of azobenzene moieties using different energy lights afforded reversible photomagnetic effects, which were directly determined using the Evans H-1 NMR method.