Two metal–organic coordination polymers based on a salt, (pydcH)3·(pipzH2)1.5·(H2O)3.7, between pyridine-2,6-dicarboxylic acid, pydcH2, and piperazine, pipz, formulated as (pipzH2)[Sr(pyd- c)2(H2O)2]n·4H2O and [Ce(pydc)2(H2O)2]n·4H2O were prepared. The synthesis, IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, supramolecular synthons, and potentiometric measurements were investigated. The chemical environment around each Sr(II) or Ce(IV) was a dis- torted tricapped trigonal prism. The butter!y- and ladder-like structures of these complexes were bridged by oxygens of (pydc)2– and M–O(pydc)–M bonds. In the crystal structure, intermolecular O–H!O, N–H!O, and C–H!O hydrogen bonds result in the formation of supramolecular struc- tures. The stoichiometry and stability of the pydc–pipz system with Sr(II) in aqueous solution were investigated by potentiometric titration. The stoichiometry of complex species in solution was found to be similar to the cited crystalline metal ion complexes.
