Proton-transfer supramolecular salts of d-/l-tartaric acid and 1-(2-Pyrimidyl)piperazine

Ionic supramolecular salts 1 and 2 were prepared by single-proton transfer reactions between 1-(2-pyrimidyl)piperazine and d-/l-tartaric acid. An interesting feature in the tartrate is the head-to-tail arrangement and very wide range of anionic substructures observed through hydrogen-bonding interactions, including ring motifs, infinite double zigzag chain and three-dimensional supramolecular framework. Thermal analysis revealed that salts 1 and 2 undergo an irreversible phase transition at about 158 °C, which is ascribed to the loss of water molecule. The temperature- and frequency-dependent dielectric constants in 2 suggested a low-frequency thermal fluctuation above 100 °C.