Magneto-structural correlations of a three-dimensional Mn based metal–organic framework

Abstract

A 3D metal–organic framework, [Na{Mn₃(Hbtc)₂(btc)}·5H₂O]_n (1) (H₃btc = 1,3,5-benzene tricarboxylic acid), was synthesized under hydrothermal conditions. The structure of 1 was established by single crystal X-ray diffraction analysis; 1 crystallizes in the monoclinic space group P2/c, a = 9.753(3) Å, b = 12.751(2) Å, c = 14.174(4) Å, β = 109.41(1)°. The complex 1 is isostructural to previously reported MIL-45 and consists of one dimensional wave like chains of carboxylate bridged hexa-coordinated Mn(II) ions. Variable temperature magnetic susceptibility measurements revealed dominant antiferromagnetic exchange interactions and the intra-chain exchange constants J₁ = -2.4 cm⁻¹ and J₂ = -0.6 cm⁻¹ compare well with literature values for similar materials. Inter-chain interactions are expected to be very small in this compound and there is no indication of magnetic ordering phenomena in the temperature range from 300–2 K.