Poly[bis(mu-benzene-1,4-dicarboxylato)bis[mu-6-(4-pyridyl)-5H-imidazolo[4,5-f][1,10]phenanthroline]dilead(II)]: an interpenetrating alpha-Po net.

The asymmetric unit of the title compound, Pb(2)(C(8)H(4)O(4))(2)(C(18)H(11)N(5))(2), contains two Pb(II) atoms, two benzene-1,4-dicarboxylate (1,4-bdc) dianions and two 6-(4-pyridyl)-5H-imidazolo[4,5-f][1,10]phenanthroline (L) ligands. Each Pb(II) atom is eight-coordinated by three N atoms from two different L ligands and five carboxylate O atoms from three different 1,4-bdc dianions. The two 1,4-bdc dianions (1,4-bdc(1) and 1,4-bdc(2)) show different coordination modes. Each 1,4-bdc(1) coordinates to two Pb(II) atoms in a chelating bis-bidentate mode. Each carboxylate group of the 1,4-bdc(2) anion connects two Pb(II) atoms in a chelating-bridging tridentate mode to form a dinuclear unit. Neighbouring dinuclear units are connected together by the aromatic backbone of the 1,4-bdc dianions and the L ligands into a three-dimensional six-connected alpha-polonium framework. The most striking feature is that two identical three-dimensional single alpha-polonium nets are interlocked with each other, thus leading directly to the formation of a twofold interpenetrated three-dimensional alpha-polonium architecture. The framework is held together in part by strong N-H...O hydrogen bonds between the imidazole NH groups of the L ligands and the carboxylate O atoms of 1,4-bdc dianions within different alpha-polonium nets.