2D molecular square grid of Cobalt(II) with tridentate phenylglycinate and mandelate: structure and magnetism

The hydrothermal synthesis, single crystal X-ray structures and magnetic properties of two layered cobalt-carboxylate complexes, _∞²[Co^II(O₂C^∗CH(OH)C₆H₅)₂] (1) and _∞²[Co^II(O₂C^∗CH(NH₂)C₆H₅)₂] (2), where O₂CCH(OH)C₆H₅ is mandalate and O₂CCH(NH₂)C₆H₅ is phenylglycinate, are described. Pale pink crystals of 1 and 2 were obtained by the reaction of cobalt nitrate and the enantiomer-pure acids at 120 °C. In each case, the structure consists of stacks of quasi square-grid polymeric sheets consisting of carboxylato- bridges, M-O-C-O-M, and the presence of both d- and l-enantiomers of the ligands segregated on each face of the layer. The ligands exhibit both chelating and bridging functions with the carboxylate group adopting an anti-anti mode. The magnetic properties are characteristic of weakly interacting paramagnets where the moments are elevated by an important orbital contribution via spin-orbit coupling.