Supramolecular architectures based on transition metal complexes with 1-(3-pyridyl)-2-(4′-pyrimidyl)ethene

The assemblies of 1-(3-pyridyl)-2-(4′-pyrimidyl)ethene (L ⁴) with transition metal ions lead to different multidimensional supramolecular architectures with interesting net topologies. The ligand tends to assume a monodentate coordination mode through the pyridine group to generate mononuclear [M(L⁴)₂(H₂O)₄] ²⁺ cations [M = Cd (1), Mn (2), Co (3), Ni (4), Zn (5), Cu (6)] with ClO₄^- (1-5) or NO₃^- (6) as the counterion. The uncoordinated pyrimidyl group plays a critical directing role in the supramolecular assembly of the mononuclear species. In 1 and 6, the self-complementary intermolecular O-H⋯N hydrogen bonds involving all pyrimidyl nitrogen atoms and coordinated water molecules assemble the mononuclear species into 2-D sheets, and the sheets are further connected through the O-H⋯O hydrogen bonds between coordinated waters and ClO ₄^- (1) or NO₃^- (6) to generate different 3-D architectures. In 2-5, one of the four pyrimidyl nitrogen atoms in each mononuclear cation is engaged in hydrogen bonding with a lattice water molecule, and consequently the self-assembly of the mononuclear species via the O-H(coordinated water)⋯N hydrogen bonds leads to 1-D tapes instead of 2-D sheets. The tapes are linked into a complicated 3D architecture through the lattice water molecules and ClO₄^- ions. On the other hand, in the compound with SO₄^2- as the counterion (7), the ligand acts as a ditopic bridge to produce 1-D coordination chains of formula [Cu(L⁴)(H₂O)₄]_n²ⁿ⁺. The compound exhibits a very complicated 3D architecture, in which the hydrogen-bonded network of sulfate ions and water molecules is enclosed in the channel surrounded by the coordination chains.