Supramolecular diversity in metal–organic hybrids with [VO$_2$(2,6-pydc)]$^–$ anion and piperazine and its derivatives

Ten compounds have been prepared among them six different diox-ido(pyridine-2,6-dicarboxylato)vanadate(V) compounds with piperazinium (H$_2$pip$^{2+}$) (1·6H$_2$O), methylpiperazinium (H$_2$mepip$^{2+}$) (2·5H$_2$O), ethylpiperazinium (H$_2$etpip$^{2+}$) (3·3H$_2$O), isopropylpiperazinium (H$_2$isopip$^{2+}$) (4·H$_2$O), phenylpiperazinium (Hphepip$^+$) (5∙H$_2$O) and thiomorpholinium 1-oxide (HtmorO$^+$) (6·2,6-H$_2$pydc·2H$_2$O) cations as counterions as well as methylpiperazinium (H$_2$mepip$^{2+}$) salt of a mixed valence vanadium [VO(2,6-pydc)-(μ-O)-VO(H$_2$O)(2,6-pydc)]⁻ complex (7), thiomorpholin-4-ium vanadate (Htmor)VO$_3$ (8), hexa(thiomorpholin-4-ium) decavanadate hexahydrate (Htmor)$_6$[V$_{10}$O$_{28}$]·6H$_2$O (9·6H$_2$O) and organic salt cocrystal thiomorpholin-4-ium 6-carboxypicolinate pyridine-2,6-dicarboxylic acid (Htmor)$^+$(2,6-Hpydc)$^–$∙(2,6-H$_2$pydc)·2H$_2$O (10·2H$_2$O) via different pathways starting either from pyri-dine-2,6-dicarboxylic acid or its esters, and were structurally characterized by sin-gle-crystal X-ray diffraction. Extended hydrogen bonding interactions are present due to the presence of organic cations as well as due to diverse roles of water molecules in the hydrogen bonding network. Centrosymmetric hydrogen bonding was found to be an im-portant motif, and diverse supramolecular patterns were observed also due to rich variety of C–H···O and π···π interactions stabilizing the crystal lattices.