The synthesis of unknown calcium salt of pyridine-2-phospho-4-carboxylic acid (Ca3L2. 7H(2)O) was presented. Interaction between metal and pyridine-2-phospho-4-carboxylic acid was investigated on the basis of the vibrational spectra of the ligand and its salt and confirmed by theoretical simulation (DFT/B3PW91/6-311++G* *). It was determined that the molecule of the acid is completely deprotonated and all oxygen atoms from carboxylic and phosphonic groups bind metal ions. (C) 2007 Published by Elsevier B.V.