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

Self-assembly of pyridine-2,6-dicarboxylic acid (H(2)py-2,6-dc) and CrCl3 center dot 6H(2)O 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)]center dot 2H(2)O (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-H center dot center dot center dot O, N-H center dot center dot center dot O, and C-H center dot center dot center dot O hydrogen bonding as well as C-O center dot center dot center dot pi, C-H center dot center dot center dot pi, and pi-pi stacking interactions to produce extended 2-D architectures. We have analyzed the pi-pi stacking interactions by DFT calculations focusing our attention on the influence of the anionic/cationic nature of the complex.