Heterometallic Co–Sr −2,3-pyridinedicarboxylate complex and its related perovskite oxide: Synthesis, structural characterization and magnetic properties

A new heterometallic complex {[CoSr(2,3-pdc)2(H2O)5]3H2O}n (1), where 2,3-H2pdc stands for 2,3-pyridinedicarboxylic acid, has been synthesized and investigated by single crystal X-Ray diffractometry, IR spectroscopy and thermal analysis. The compound is self-organized in a polymeric structure forming a 2D framework. The 2,3-pyridinedicarboxylic acid is fully deprotonated performing several types of coordination: monodentate, bridging chelating, bidentate bridging. Thermal decomposition of the heterometallic 2,3-pyridinedicarboxylate 1 leads to the formation of a perovskite type oxide of brownmillerite series, 2, with 20.8 % yield. Magnetic studies of 1 show the paramagnetic behavior of Co(II) ions with a significant influence of a ground state zero-field splitting at low temperatures. Variable field and temperature magnetic studies of the oxide product 2 (obtained by the controlled heating of 1) indicate the presence of the Sr6Co5O15, detected by the diffraction method. Also, trace amounts of SrCoO2.75 and SrCoO2.5 were revealed by magnetic and DSC methods, respectively.