A comparison of different methods for fitting susceptibility data of cobalt(ii) coordination polymers in a new cobalt(ii)/sulfate 1-D chain

Abstract

The 1-D chain polymer [{Co(μ-SO₄)L₃}_n] (L = 3{5}-tert-butylpyrazole) was prepared by the reaction of CoSO₄·7H₂O with 3 equiv. of L in MeOH. The complex contains trigonal bipyramidal cobalt(II) centres with two axial O,O′-bridging sulfato ligands. The resultant linear chains are arranged into an approximately hexagonal array, the molecules being well-separated from each other by a honeycomb of interdigitated tert-butyl groups. Susceptibility data from [{Co(μ-SO₄)L₃}_n] are consistent with an antiferromagnetic Curie–Weiss chain, which could be well-interpreted using Heisenberg 1-D treatments. Three approaches to model these data were studied to try and separate superexchange and zero-field splitting effects. A recently proposed empirical approach gave g and J values in excellent agreement with a S = Heisenberg chain model, as long as the latter was performed using only high temperature data, which are not affected by zero-field splitting.