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)]3H(2)O}(n) (<bold>1</bold>), where 2,3-H(2)pdc 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 <bold>1</bold> leads to the formation of a perovskite type oxide of brownmillerite series, <bold>2</bold>, with 20.8 % yield. Magnetic studies of <bold>1</bold> 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 <bold>2</bold> (obtained by the controlled heating of <bold>1</bold>) 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.