Hydrothermal synthesis of a novel μ-dihydroxo-bis(2,6- pyridinedicarboxylatoaquachromium(III)) complex and investigation of its catalytic activity

A new chromium(III) compound [Cr(H ₂O)(OH)(C ₇H ₃NO ₄)] ₂, μ-dihydroxo-bis(2,6- pyridinedicarboxylatoaquachromium(III)), has been successfully synthesized by the hydrothermal reaction of 2,6-pyridinedicarboxylic acid (H ₂pydc) and CrCl ₃·6H ₂O in the alkali medium. This metal complex was characterized by elemental analysis, IR spectroscopy, thermal analysis and single-crystal X-ray diffraction. The X-ray analysis showed that the structure is molecular and consists of units of two Cr(H ₂O)(OH) (C ₇H ₃NO ₄) groups linked through two OH groups. In the complex, each Cr centre is in a distorted octahedral environment, defined by two hydroxyl bridges, an aqua ligand and a tridentate pyridinedicarboxylate anion. The thermal stability and catalytic properties of the complex were also investigated. The complex affected the oxidation of thymol to thymoquinone with 100% selectivity and a conversion rate of 20.25%.