Ten compounds have been prepared among them six different dioxido(pyridine-2,6-dicarboxylato)vanadate(V) compounds with piperazinium (H2pip2+) (1·6H2O), methylpiperazinium (H2mepip2+) (2·5H2O), ethylpiperazinium (H2etpip2+) (3·3H2O), isopropylpiperazinium (H2isopip2+) (4·H2O), phenylpiperazinium (Hphepip+) (5∙H2O) and thiomorpholinium 1-oxide (HtmorO+) (6·2,6-H2pydc·2H2O) cations as counterions as well as methylpiperazinium (H2mepip2+) salt of a mixed valence vanadium VO(2,6-pydc)-(μ-O)-VO(H2O)(2,6-pydc)− complex (7), thiomorpholin-4-ium vanadate (Htmor)VO3 (8), hexa(thiomorpholin-4-ium) decavanadate hexahydrate (Htmor)6V10O28·6H2O (9·6H2O) and organic salt cocrystal thiomorpholin-4-ium 6-carboxypicolinate pyridine-2,6-dicarboxylic acid (Htmor)+(2,6-Hpydc)−∙(2,6-H2pydc)·2H2O (10·2H2O) via different pathways starting either from pyridine-2,6-dicarboxylic acid or its esters, and were structurally characterized by single-crystal X-ray diffraction. Extended hydrogen bonding interactions are present due to the presence of organic cations as well as due to the diverse roles of water molecules in the hydrogen bonding network. Centrosymmetric hydrogen bonding was found to be an important motif, and diverse supramolecular patterns were also observed due to a wide variety of C–H···O and π···π interactions stabilizing the crystal lattices.
Hozjan et al. (Sun,) studied this question.