A binucleariron(III) complexbridged by trans-1,2-bis(4-pyridyl)ethylene, [LFeIII(vibpy)FeIIIL](BPh4)2, showed a gradual two-step spin crossover behavior, where H2L is bis(3-methoxysalicylideneami...
Two binuclear iron(III) complexes, [(LFeIII)-Fe-1(bpy)(FeL1)-L-III](BPh4)(2) (1) and [(LFeIII)-Fe-2(bpy)(FeL2)-L-III](BPh4)(2) (2), were synthesized and characterized, where H2L1 and H2L2 denote bis(salicylicdeneaminopropyl)methylamine and bis(3-methoxysalicylideneaminopropyl)methylamine, respectively, and bpy denotes 4,4'-bipyridine and BPh4 - denotes tetraphenylborate. Complexes 1 and 2 consist of one and two crystallographically unique Fe sites, respectively, while they have a similar binuclear complex-cation [(LFeIII)-Fe-n(bpy)(FeLn)-L-III](2+) (n = 1, 2) bridged by 4,4'-bipyridine and two tetraphenylborate ions as the counter anions. The magnetic susceptibility measurements of 1 and 2 showed one-step and two-step spin crossover (SCO), respectively. The four saturated six-membered chelate rings at the aminopropyl moieties of 1 exhibit disorder throughout one-step SCO. The two chelate rings of one Fe site of 2 exhibit disorder but the other two of another Fe site do not. The different SCO behaviors of 1 and 2 were ascribed to one and two crystallographically unique Fe sites and the order/disorder at the saturated six-membered chelate rings of aminopropyl moieties. (C) 2011 Elsevier B.V. All rights reserved.