Coordination Polymers of Cadmium with Di(pyrazol-1-yl)alkane-4,4'-dicarboxylic Acids: Synthesis, Crystal Structures, and Luminescence Properties

Coordination polymers of cadmium(II) with the di(pyrazol-1-yl)alkane derivatives, bis(3,5-dimethylpyrazol-1-yl)methane-4,4′-dicarboxylic acid (H₂L¹) and 1,3-bis(pyrazol-1-yl)propane-4,4′-dicarboxylic acid (H₂L²), are synthesized. The crystal structures of the products are determined by X-ray diffraction (CIF files CCDC nos. 2172853 (I) and 2172854 (II)). The Cd²⁺ ions and dicarboxylic acid with one methylene group between the pyrazole cycles form a three-dimensional coordination polymer with a single mutual intergrowing of coordination networks, whereas three methylene groups result in the formation of a two-dimensional coordination polymer, the layers of which are linked by hydrogen bonds involving water molecules in the coordination sphere of the Cd²⁺ ions. The luminescence spectra of the synthesized coordination polymers exhibit two bands: with the local intraligand excitation and with the metal–ligand charge transfer.