Feasibility of ground state spin switching in a molecular analogue of the mixed-metal oxides with the perovskite structure

Abstract

The carboxylate substitution reaction between the reported all-benzoate complex [Ce3Mn8O8(PhCO2)18(PhCO2H)2] (1) and 2-Cl-benzoic acid has led to isolation of [Ce3Mn8O8(2-Cl-PhCO2)15.3(PhCO2)2.7(H2O)2] (2). The structures of 1 and 2 are very similar, both containing a tetragonally-elongated MnIII8 cuboid with a CeIV at its center and two CeIII attached to opposite faces, but 2 shows extensive disorder in the ligands and the Cl atom positions and occupancies. Variable-temperature (T) solid-state dc and ac magnetic susceptibility data for 2 are significantly different from those for 1 and are assigned as due to small ligand-induced structural perturbation of the core that has brought an A-type antiferromagnetic (AF) excited state much closer to the C-type AF ground state. Fits of the dc χMT vs T data support this interpretation but due to the ligand disorder in 2, a more definitive description of the lowest energy spin states of 2 is not possible. Nevertheless, these results provide important support for the feasibility of ground state spin switching by ligand-induced core perturbation (‘chemical pressure’) in this family, and they encourage further studies.