Supramolecular cobalt(II), copper(II) and cadmium(II) complexes obtained from a proton transfer compound including pyridine-2,6-dicarboxylate and propane-1,3-diaminium ions; synthesis, characterization and crystal structure

The three complexes (pnH(2))[Co(pydc)(2)]center dot 4H(2)O 1, (pnH(2))[Cu(pydc)(2)]center dot 4H(2)O 2, and (pnH(2))[Cd(pydc)(2)]center dot 3.5H(2)O 3 (pn: propane-1,3-diamine, pydc: pyridine-2,6-dicarboxylate) were prepared using a proton transfer compound (pnH(2))(pydc)center dot(pydcH(2))center dot 2.5H(2)O, LH (2) 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 P (1) over bar, but complex 3 crystallizes in space group P2/c. Cell parameters of the complexes are a = 8.449(1) angstrom, b = 11.668(1) angstrom, c = 12.801(1) angstrom, alpha = 115.748(2)degrees, beta = 93.038(2)degrees, gamma = 97.867(2)degrees for 1; a = 7.973(2) angstrom, b = 16.632(2) angstrom, c = 25.280(5) angstrom, alpha = 94.178(6)degrees, beta = 95.186(6)degrees, gamma = 91.603(5)degrees for 2 and a = 20.055(1) angstrom, b = 13.8161(9) angstrom, c = 8.2418(5) angstrom, beta = 100.086(1)degrees 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-H center dot center dot center dot O, N-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds, pi-pi stacking as well as van der Waals forces as the main factors in formation of their supramolecular structures.