Influence of noncovalent interactions on the structures of metal–organic hybrids based on a [VO2(2,6-pydc)]− tecton with cations of imidazole, pyridine and its derivatives†
Seven different dioxido(pyridine-2,6-dicarboxylato)vanadate(V) compounds with pyridinium (Hpy+) (1·2H2O and 1), 2-hydroxypyridinium (H2pyon+) (2·H2O), 4-aminopyridinium (H4apy+) (3·H2O and 3), 4-(dimethylamino)pyridinium (Hdmap+) (4·H2O) and imidazolium (Himd+) (5) cations have been prepared via different pathways starting either from pyridine-2,6-dicarboxylic acid or its esters, and were structurally characterized by single-crystal X-ray diffraction. The vanadium metal center in dioxido(pyridine-2,6-dicarboxylato)vanadate(V) anion is pentacoordinated in all of the compounds: having two oxido oxygen atoms in a mutual cis position and a tridentate pyridine-2,6-dicarboxylic ligand. Study of hydrogen bonds and weak interactions in the compounds revealed the relationship between the type of cation and the hydrogen bonding network in the compounds. While in 1·2H2O, 2·H2O and 4·H2O a one-dimensional (band, pillar or chain) hydrogen bonding network via N/O–H⋯O bonds is preferred, anhydrous 3 and 3·H2O favor a two-dimensional hydrogen-bonded framework, and the Himd+ cation facilitates a three-dimensional hydrogen bonding in 5. The unique vanadium coordination environment with two easily accessible oxido oxygen atoms of the VO2+ unit is suitable for the construction of non-covalent metal–organic hybrids. In 2·H2O, 3·H2O, 4·H2O and 5 both oxido oxygen atoms of the VO2+ unit participate as acceptors, however, in 1·2H2O and 3 only one oxido oxygen atom is involved in classical hydrogen bonding. Besides N/O–H⋯O hydrogen bonding, also other weak non-covalent interactions, such as C–H⋯O, π⋯π and C–H⋯π interactions, play an important role in stabilizing the crystal lattices.