2D s-d Mixed-Metal Coordination Polymer Containing Potassium, Chromium(III) and Dipicolinate Ions: Preparation and Crystal Structure

The reaction of pyridine-2, 6-dicarboxylic acid (dipicolinic acid, dipicH2) with potassium tetraperoxochromate(V) in the mixture of water and ethanol led to the formation of a 2D s-d mixed-metal coordination polymer of {; ; ; ; K[Cr(dipic)2]}; ; ; ; n (1). The compound was characterized by spectroscopic methods (IR, Raman, UV/Vis). Single crystal X-ray diffraction analysis revealed that dipicolinate ligand is coordinated to the chromium(III) ion in a O, N, O’- tridentate fashion, while its uncoordinated and coordinated carboxylate O atoms (with respect to Cr(III) ion) are in turn bound to potassium ions. Therefore, each dipicolinate ligand bridges two potassium ions and a chromium(III) ion between them, giving rise to a 2D coordination network. The coordination of chromium(III) ions is octahedral, while the coordination number of potassium ions is 8. The coordination networks are in turn assembled only by π–π stacking interactions into a 3D structure.