A tetragonal core with asymmetric iron environments supported solely by bis(μ-OH){μ-(O-H···O)} bridging and terminal pyridine amide (N, O) coordination: a new member of the tetrairon(III) family

Abstract

Room-temperature aerobic reaction of [Fe(MeCN)₄][ClO₄]₂ with 1,3-bis(2-pyridinecarboxamido)propane (H₂bpp) yields the tetrairon(III) complex [Fe₄(H₂bpp)₄(μ-OH)₂(μ-OHO)][ClO₄]₇·2H₂O·xMeCN (1·xMeCN, 0≤x≤3). Crystal structure determination reveals that 1·3MeCN is a new member of the tetrairon(III) family, bridged solely by two hydroxido ligands and a localized {O-H···O}^3- bridging unit. The properties of the "tetragonal" core [Fe₄(μ-OH)₂{μ-(O-H···O)}]⁷⁺ have been investigated by variable-temperature magnetic and Mossbauer spectroscopic measurements. Successful modeling of the data has revealed asymmetric iron environments and three types of magnetic exchange interactions [through μ-OH and μ-O/μ-OH of μ-(O-H···O) bridges]. This tetragonal core is a valuable addition to the tetrairon(III) cluster family from inorganic and bioinorganic perspectives.