The first mixed-ligand coordination compound involving 8-aminoquinoline and pyridine-2,6-dicarboxylate: synthesis, X-ray crystal structure, and DFT studies

Abstract

Self-assembly of pyridine-2,6-dicarboxylic acid (H2py-2,6-dc) and CrCl3·6H2O in the presence of 8-aminoquinoline as a N-donor co-ligand leads to the formation of a supramolecular coordination compound in which the cationic and anionic complexes differ in composition, namely [Cr(py-2,6-dc)(8-aq)(H2O)][Cr(py-2,6-dc)2]·2H2O (1). Single-crystal X-ray analysis reveals that the coordination sphere around Cr in the cationic complex consists of one (py-2,6-dc)2−, one 8-aq, and one H2O while the anionic complex is more symmetrical and has two (py-2,6-dc)2− ligands in its coordination environment. Both Cr centers are six coordinate with distorted octahedral geometries. The ionic coordination motifs in 1 are held together by intermolecular O–HO, N–HO, and C–HO hydrogen bonding as well as C–Oπ, C–Hπ, and π–π stacking interactions to produce extended 2-D architectures. We have analyzed the π–π stacking interactions by DFT calculations focusing our attention on the influence of the anionic/cationic nature of the complex.