LAUSR

Abstract The syntheses and crystal structures of three anionic water rich phthalates charge balanced by piperazinediium (pipH2)2+ viz. (pipH2)[M(H2O)4(pht)2]·8H2O [M = Ni (1), Co (2) and Cu(3)] (pht = phthalate) are reported. Reaction of 1–3 with imidazole (im) results in the formation of [M(im)6](pht)·H2O [M = Ni (4) and Co (5)] and [Cu2(H2O)(im)4(pht)2]·H2O (6) respectively. Compounds 1–6 have been characterised by spectral, thermal, electrochemical and magnetic studies and their structures determined. The phthalate ligand displays a monodentate binding mode in the bis(phthalato) compounds 1–3. The centroid to centroid distance (Cg⋯Cg) between the adjacent phthalate rings in 1–3 is ∼4.0 A. In the hexaimidazole compounds 4 and 5 phthalate functions as a charge balancing dianion. The H-bonding interactions among lattice water molecules lead to the formation of a water dodecamer cluster in 1–3 with R6 water motif which further extends into a staircase pattern with T4(2)6(2) extended motif. The intra- and intermolecular H-bonding via C H⋯O, N H⋯O, O H⋯N and O H⋯O interactions results in an intricate supramolecular architecture. Thermal studies of 1–3 reveal interesting dehydration and rehydration characteristics. Compounds 1 and 2 undergo crystalline-amorphous-crystalline transformation during de- and rehydration.