Structural variation from 1D to 3D: Effects of ligands and solvents on the construction of lead(II)-organic coordination polymers

A series of Pb-II coordination polymers [Pb(ndc)(dpp)] (1), [Pb(ndc)(ptcp)].0.5H(2)O (2), [Pb(ndc)(dppz)] (3), [Pb(ndc)(tcpn)(2)] (4), [Pb-2(ndc)(2)(tcpp)] (5), [Pb(Hndc(2)]-H2O (6), [Pb(ndc)(dma)] (7), [Pb(bdc)(dma)] (8), [Pb(trans-chdc)(H2O)] (9), and [Pb2(cis-chdc)(2)]-NH(CH3)(2) (10), where ndc = 1,4-naphthalenedicarboxylate, dpp = 4,7-diphenyl-1,10-phenanthroline, ptcp = 2-phenyl-1H-1,3,7,8-tetraazacyclopenta[I]phenanthrene, dppz=dipyrido[3,2-a:2',3'-c]phenazine, tcpn = 2(1 H-1,3,7,8-tetraazacyclopenta[l]phenanthren-2-yl)naphthol, tcpp = 4-(1 HI.,3,7,8-tetraazacyclopenta[l]phenanth- ren-2-yl)phenol, dma=NN-dimethylacetamide, Me = 1,4-benzenedicarboxylate, and chdc=1,4-cyclohexanedicarboxylate, have been synthesized from a hydrothermal or solvothermal reaction system by varying the ligands or the solvents. Compounds 1-5 crystallize with an N-donor chelating ligand and an aromatic dicarboxylate linker. Compounds 1-4 are 1D polymers with different pi-pi stacking interactions, whereas compound 5 consists of 2D layers. The structures of compounds 7, 8, and 10 are 3D frameworks formed by connection of the Pb-II centers by organic acid ligands. Compound 7 is chiral although the ndc ligand is achiral, while the framework of 8 is a typical 3D (3,4)-connected net. Compound 10 is the first example of Pb-II wheel cluster [Pb8O8] units bridged by carboxylate groups. Compound 6 contains ID chains which are further extended to a 3D structure by pi-pi interactions. Compound 9 consists of a 2D network constructed by Pb-II centers and trans-chdc ligands. The structural differences between 7 and 8 and between 9 and 10 indicate the importance of solvents for framework formation of the coordination polymers. By varying the solvent the cis and trans conformations of H(2)chdc in 9 and 10 were separated completely. The photoluminescence and nonlinear optical properties of the coordination polymers have also been investigated.