In this research, a novel supramolecular proton transfer compound was obtained from the reaction between pyridine-2,6- dicarboxylic acid, pydcH2, and piperazine, pipz. According to the crystal structure, the proton transfer compound formulated as (pipzH2)1.5(pydcH)3.3.7H2O. This compound crystallizes in the space group C2/c of the monoclinic system and contains eight molecules per unit cell. The unit cell dimensions are: a=16.9584(9) Å, b=13.4081(7)Å, c=27.2449(2)Å and =94.2140(1)º. The final R value was 0.0448 for 5573 reflections. One of two cations occupies a special position on inversion center. Also, one of water molecules occupies a special position on two-fold axis. All NH2 groups of the cation molecules form with anion molecules the hydrogen bonds as type bifurcate N-H...O and N-H...N. In the crystal structure, hydrogen pyridine-2,6-carboxylate ions, (pydcH)- are connected via hydrogen bonds as zigzag chains. Therefore, the intermolecular forces between cationic and anionic units in this compound consist of ion-pairing, hydrogen bonds and π-π stacking. Hydrogen bonds play a role in the construction of the supramolecular crystal structure. To an aqueous solution of proton transfer compound (pipzH2)1.5(pydcH)3.3.7H2O, was added of a solution of Sr(NO3)2 in 2:1 molar ratio. The resulting complex crystallized in the monoclinic system with space group P21/ c and contains four molecules per unit cell. The unit cell parameters are a=11.995(2)Å, b=13.701(2)Å, c=15.143(2)Å and =90.098(3)º. The final R value was 0.0593 for 3936 reflections. The molecular structure of this complex is built of polymeric units of (pipzH2) [Sr(pydc)2(H2O)2].4H 2O, in which each pyridine-2,6-dicarboxylate moiety has acted as a tridentate ligand. Polymeric chains are connected by hydrogen bonds.
