Synthesis and Magnetization of New Room-Temperature Molecule-Based Magnets: Effect of Stoichiometry on Local Magnetic Structure by X-ray Magnetic Circular Dichroism

The synthesis and the magnetic properties of two new bimetallic chromium−vanadium ferrimagnets, compounds 1 and 2, are reported. They belong to a set of nonstoichiometric Prussian blue analogues C I y V[Cr III (CN) 6 ] z · n H 2 O (C, alkali cation) with T C varying between 295 and 315 K ( T C = 310 K for 1 and 315 K for 2 ). They are obtained through mild chemistry from the molecular precursor [Cr III (CN) 6 ] 3 - and from vanadium V II salts. The synthetic conditions determine (i) the oxidation state of the vanadium (V II, V III, or V IV ), (ii) the stoichiometry, and (iii) hence the magnetic properties. The reported systems present a larger magnetization than the first reported V−Cr analogue (0.36 N A β for 1 and 0.40 N A β for 2 ). Furthermore, X-ray magnetic circular dichroism (XMCD) data demonstrate (i) the short-range antiferromagnetic coupling between the spins borne by the chromium(III) and vanadium ions and (ii) the reversal of the local magnetization on vanadium and chromium when changing the stoichiometry.