Chemically and Light-Driven Coordination-Induced Spin State Switching (CISSS) of a nonheme-iron complex

Abstract

Abstract The new Fe(II) complex [Fe(trident)(bmik)](ClO4)2 (1) (trident = bis(2-pyridylmethyl)benzylamine and bmik = bis(1-methylimidazole)ketone) exhibits a change of magnetic moment in dichloromethane (DCM) solution upon addition of pyridine which is attributed to the Coordination-Induced Spin State Switching effect (CISSS). By attaching a photoisomerizable azopyridine sidegroup to the tridentate ligand the complex [Fe(azpy-trident)(bmik)](ClO4)2 (2; azpy-trident = [N,N-bis(2-pyridylmethyl)]-3-(3-pyridylazo)benzylamine) is obtained. As detected by Evans NMR spectroscopy, 2 reversibly changes its magnetic moment in homogeneous solution upon photoirradiation which is attributed to intermolecular Light-Driven Coordination-Induced Spin State Switching (LD-CISSS). Further support for this interpretation is inferred from concentration-dependent Evans NMR measurements.