Abstract The three complexes (pnH2)[Co(pydc)2]4H2O 1, (pnH2)[Cu(pydc)2]4H2O 2, and (pnH2)[Cd(pydc)2] 3.5H2O 3 (pn: propane-1,3-diamine, pydc: pyridine-2,6- dicarboxylate) were prepared using a proton transfer compound (pnH2)(pydc)(pydcH2)2.5H2O, LH2 and corresponding metallic salts. The characterization was carried out using elemental analysis, IR and NMR spectroscopy, and single crystal X-ray diffraction. Complexes 1 and 2 crystallize in space group P1, but complex 3 crystallizes in space group P2/c. Cell parameters of the complexes are a = 8.449(1) A ° , b = 11.668(1) A ° , c = 12.801(1) A ° , a =115.748(2), b = 93.038(2), c = 97.867(2) for 1; a = 7.973(2) A ° , b = 16.632(2) A ° , c = 25.280(5) A ° , a = 94.178(6), b = 95.186(6), c = 91.603(5) for 2 and a = 20.055(1) A ° , b = 13.8161(9) A ° , c = 8.2418(5) A ° , b = 100.086(1) for 3. The three crystal structures illustrate that the metal ion is six-coordinated by two pydc’s. In structures of 2 and 3, it can be seen that propane-1,3-diaminium fragments have different conformations. The complexes have ion-pairing interactions, O–HO, N–HO andC–HOhydrogen bonds, p–p stacking as well as van der Waals forces as the main factors in formation of their supramolecular structures
