A six-connected alpha-polonium net based on tetranuclear Cd(II) nodes.

The cadmium(II) coordination polymer poly[[(pyrazino[2,3-f][1,10]phenanthroline-kappa(2)N(8),N(9))cadmium(II)]-mu(3)-naphthalene-1,4-dicarboxylato-kappa(5)O(1):O(1),O(1'):O(4),O(4')], [Cd(C(12)H(6)O(4))(C(14)H(8)N(4))](n), contains two Cd(II) cations, two pyrazino[2,3-f][1,10]phenanthroline (L) ligands and two naphthalene-1,4-dicarboxylate (1,4-ndc) anions in the asymmetric unit. Both Cd(II) ions are in a distorted CdO(5)N(2) monocapped octahedral coordination geometry. Both unique 1,4-ndc ligands are bonded to three Cd(II) ions. In these modes, tetranuclear clusters are formed in which four Cd(II) ions are bridged by the carboxylate groups of the 1,4-ndc ligands to form discrete rods. The tetranuclear cadmium carboxylate clusters act as rod-shaped secondary building units (SBUs) within the structure. The SBUs are connected together by the aromatic backbone of the dicarboxylate ligands, connecting the clusters into a three-dimensional alpha-polonium net. The title compound represents the first alpha-polonium net constructed from rod-like clusters in coordination polymers. The result indicates that an appropriate combination of dicarboxylate and aromatic chelating ligands is critical to the formation of high-dimensional structures based on metal clusters in these systems.