Synthesis and magnetic properties of tetrabromophthalato-bridged manganese(II) binuclear complexes

Abstract

Four novel MnII binuclear complexes have been prepared and characterized, namely: [Mn2(TBPHTA)(L)4](ClO4)2 [L = 2,2′-bipyridyl (bipy), 1,10-phenanthroline (phen), 4,4′-dimethyl-2,2′-bipyridyl (Me2bipy) and 5-nitro-1,10-phenanthroline (NO2-phen), respectively], and TBPHTA = the tetrabromophthalate dianion. Based on i.r. spectra, elemental analyses and conductivity measurements, extended tetrabromophthalato-bridged structures consisting of two MnII ions, in which each MnII ion has a distorted octahedral environment, are proposed for these complexes. The temperature dependence of the magnetic susceptibility for [Mn2(TBPHTA)(phen)4] (ClO4)2·H2O was measured over the 4–300 K range and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator (Ĥ = -2JŜ 1 Ŝ 2), giving the exchange integral J = -1.22 cm−1. This result indicates a weak antiferromagnetic spin exchange interaction between the metal ions.