ZnLn Complexes with Carbonate Bridges Formed by the Fixation of Carbon Dioxide in the Atmosphere: Single-molecule Magnet Behaviour and Magnetocaloric Effect

Three novel isostructural ZnLn cluster complexes with carbonate bridging ligands, {ZnLn(μ-CO)L(acacF)}·CHOH [HL = N,N'-dimethyl-N,N'-(2-hydroxy-3-methoxy-5-methyl-benzyl)ethylenediamine; HacacF = hexafluoroacetylacetone; Ln = Dy, 1; Ln = Gd, 2; Ln = Eu, 3], have been prepared by fixing carbon dioxide in the atmosphere. Such carbonate bridging ligands may mediate ferromagnetic exchange between Ln ions. The ZnDy compound (1) displays the properties of a single molecule magnet (SMM), showing slow magnetic relaxation at a 1500 Oe dc field, with an obviously larger U/k value (83 K) with respect to the other carbonate-bridged ZnDy SMMs (≤34 K) and ZnDy dinuclear SMMs derived from the same ligand HL used in this work (≤36.5 K), while the ZnGd compound (2) shows a moderate magnetocaloric effect and can be looked upon as a potential molecular material for low temperature magnetic refrigeration.