Oxalate-bridged mixed-valence trinuclear manganese(II)-manganese(III)-manganese(II) complexes: synthesis and magnetism

Abstract

Two novel MnII-MnIII-MnII oxalato complexes have been synthesized and characterized, namely [Mn2Mn(ox)3(L)4](ClO4) [L = 1,10-phenanthroline (phen) or 5-nitro-1,10-phenanthroline (NO2-phen), respectively], where ox stands for the oxalate dianion. Based on i.r., elemental analyses and electronic spectra, these complexes are proposed to have extended oxalatobridged structures consisting of MnII and MnIII ions, in which MnIII and each MnII ion has a distorted octahedral environment. The temperature dependence of magnetic susceptibility for [Mn2Mn(ox)3(phen)4] (ClO4) was measured over the 4.1–300 K range and the observed data were successfully simulated by an equation based on the spin-Hamiltonian operator (Ĥ = -2J(Ŝ1Ŝ2 + Ŝ2Ŝ3)), giving the exchange integral J = -1.57cm−1. This indicates weak antiferromagnetic spin exchange interaction between MnII and MnIII ions.