Crystal Structures and EPR Spectra of Cu2+-Doped Magnesium(II) and Cadmium(II) Methoxyacetates

Magnesium methoxyacetate crystallizes from aqueous solution as a dihydrate, isomorphous with its nickel(II) and copper(II) counterparts, the six-coordinate metal atoms being disposed on crystallographic inversion centres in space group P2(1)/n. The cadmium complex is anhydrous, the six-coordinate metal atoms being linked into a two-dimensional polymer parallel to the ab plane in space group P2(1)/c by bridging coordination through carboxylate oxygen atoms. The powder EPR spectra of traces Of Cu2+ doped into the magnesium(II) and cadium(II) compounds show slight temperature dependences, with the higher two g-values converging as the temperature is raised from similar to 77 K to 290 K. This is analysed in terms of an equililibrium between complexes having similar geometries, but with the long and intermediate bond directions interchanged. The behaviour is in contrast to that of the pure copper(II) complex, where the thermal properties appear to be influenced by cooperative interactions.