Characteristics of (N-Thiocyanato)chromates(III) of Lanthanides(III) with Pyridine-3-carboxylic Acid

To complete the studies of double complex compounds, (N-thiocyanato)chromates(III) of lanthanide complexes with pyridine-3-carboxylic acid, new compounds of the compositions [LnL(HO)][Cr(NCS)]·nHO (Ln = Pr (I), n = 1.5; Sm (II), Gd (III), Tb (IV), n = 2; L = CHNO). The substances were studied by chemical analysis, IR spectroscopy, and PXRD (CCDC No. 2427051–2427054). In the crystal structures of complexes I–IV, the cation has a chain structure due to the bidentate-bridging function of pyridine-3-carboxylic (nicotinic) acid molecules. The coordination environment of the lanthanide atoms consists of eight oxygen atoms belonging to six nicotinic acid molecules and two coordinated HO molecules, located at the vertices of a distorted square antiprism. In the isolated [Cr(NCS)] anions, the Cr coordination polyhedron consists of the N atoms of six thiocyanate ions and is close to a regular octahedron. In the structures of complexes I–IV, the space between polymeric cations is filled with complex anions and crystallization water molecules. Additionally, the structure is stabilized by intermolecular hydrogen bonds.