Heteroleptic Fe(II) Complexes with N4S2 Coordination as a Platform for Designing Spin-Crossover Materials

Abstract

Heteroleptic complexes [Fe(bpte)(bim)]X2 and [Fe(bpte)(xbim)]X2 (bpte = S,S′-bis(2-pyridylmethyl)-1,2-thioethane, bim = 2,2′-biimidazole, xbim = 1,1′-(α,α′-o-xylyl)-2,2′-biimidazole, X = ClO4-, BF4-, OTf-) were prepared by reacting the corresponding Fe(II) salts with a 1:1 mixture of the ligands. All mononuclear complexes exhibit temperature-induced spin crossover (SCO) with the onset above room temperature. The SCO is rather gradual, due to low cooperativity of interactions between the cationic complexes, as revealed by crystal structure analyses. These complexes expand the range of the recently discovered Fe(II) SCO materials with {N4S2} coordination environment.