Synthesis and characterization of imidazolate-bridged iron(III)–copper(II) and manganese(III)–copper(II) binuclear complexes

Abstract

Imidazolate-bridged iron(III)–copper(II) and manganese(III)–copper(II) binuclear complexes [FeL¹CuL²][BPh⁴](1) and [MnL¹CuL²][BPh₄](2) have been prepared and characterized, where H₂L¹ is 4-methyl-N,N′-bis(salicylidene)-4-azaheptane-1,7-diamine and H₂L² denotes the unsymmetrical quadridentate ligand 4-(6-methyl-8-oxo-2,5-diazanona-1,5-dienyl)imidazole. The magnetic susceptibility data indicated that the spin ground states of the complexes (1) and (2) are S= 2 and respectively, which are produced by antiferromagnetic interaction operating between high-spin iron(III)S₁=5//₂[manganese(III)S₁= 2] and copper(II)S₂=½ ions through the L² imidazolate group. The Mössbauer spectrum of (1) measured at 4.2 K showed a doublet with Δ= 1.30 mm s^–1 and δ_d= 0.49 mm s^–1, consistent with high-spin iron(III). The e.s.r. spectrum of a powdered sample of complex (1) measured at 20 K showed no signals, while that of (2) showed several signals.