Exploratory syntheses, structures, and photoluminescent properties of three lead multi-dimensional frameworks

Three structurally diverse Pb-II coordination complexes, [Pb3O(OH)(4-sphth)](2)(H2O) (1), [Pb(3,5-Hdhb)]H2O (2), and [Pb-3(4-nphth)(2)(OH)(2)] (3) (4-H(3)sphth, 4-sulfophthalic acid; 3,5-H(2)dhb, 3,5-dihydroxybenzoic acid; 4-H(2)nphth, 4-nitrophthalic acid), were synthesized under hydrothermal conditions. X-ray diffraction analyses reveal that 1 is constructed from [Pb4O4] cubanes, based on which ladder-shaped structure is built via 4-H(3)sphth bridge. This is the first Pb4O4-containing polymer. The Pb2O2 units in 2 are bridged by two parallel 3,5-HDHB ligands along the a-axis and two other parallel 3,5-HDHB ligands along the b-axis, forming a 3-D framework. For 3, the crystal structure is built up of a layer motif consisting of corner-sharing pyramidal Pb3O units, which are linked through Pb corners to form a hexagonal unit. Each PbO6 polyhedron is connected to three polyhedra (Pb3O) via sharing an edge (two mu(3)-oxygen atoms) and two faces (three mu(3)-oxygen atoms), thus yielding an infinite 2-D Pb-O-Pb (3,6-net) honeycomb layer. The luminescence of 1-3 demonstrates that they may be good candidates for luminescent materials.