Supramolecular framework of a dinuclear cadmium complex with a dianion of xanthurenic acid [Cd2(Xan)2(H2O)4]

Reaction of the sodium salt of xanthurenic acid (8-hydroxy-4-oxo-1 H -quinoline-2-carboxylic acid, H 2 Xan) with cadmium(II) cations in aqueous solution leads to the formation of the dinuclear complex [Cd 2 (Xan) 2 (H 2 O) 4 ]. The structure of this compound was studied by single-crystal X-ray diffraction, IR spectroscopy, and via thermal and elemental analysis. The [Cd 2 (Xan) 2 (H 2 O) 4 ] complex consists of two cadmium(II) ions bridged by a pair of carboxylate oxygen atoms from two Xan 2− ligands. The coordination environments of the two metal atoms are similar—each consists of two Xan 2− ligands and two aqua ligands. Each metal ion is in a pentagonal pyramidal coordination environment, which is highly unusual. An intricate pattern of hydrogen bonds links the molecules in the complex into a three-dimensional structure. Graphical abstract