Organic-acid effect on the structures of a series of Lead(II) complexes

An investigation into the dependence of coordination polymer architectures on organic-acid ligands is reported on the basis of the reaction of Pb(NO3)(2) and eight structurally related organic-acid ligands in the presence or absence of N-donor chelating ligands. Eight novel lead(II)-organic architectures, [Pb(adip)(dpdp)](2) 1, [Pb(glu)(dpdp)] 2, [Pb(suc)(dpdp)] 3, [Pb(fum)(dpdp)]center dot H2O 4, [Pb-2(oba)(dpdp)(2)]center dot 2(dpdp)center dot 2(NO3)center dot 2H(2)O 5, [Pb-2(1,4-bdc)(2)(dpdp)(2)]center dot H2O 6, [Pb(dpdc)(dpdp)] 7, and [Pb(1,3-bdc)(dpdp)]center dot H2O 8, where dpdp = dipyrido[3,2-a:2',3'-c]-phenazine, H(2)adip = adipic acid, H(2)glu = glutaric acid, H(2)suc = succinic acid, H(2)fum = fumaric acid, H(2)oba = 4,4'-oxybis(benzoic acid), 1,4-H(2)bdc = benzene-1,4-dicarboxylic acid, H(2)dpdc = 2,2'-diphenyldicarboxylic acid, and 1,3-H(2)bdc = benzene-1,3-dicarboxylic acid, were successfully synthesized under hydrothermal conditions through varying the organic-acid linkers and structurally characterized by X-ray crystallography. Compounds 1-8 crystallize in the presence of organic-acid linkers as well as secondary N-donor chelating ligands. Diverse structures were observed for these complexes. 1 and 5 have dinuclear structures, which are further stacked via strong pi-pi interactions to form 2D layers. 2-3 and 6-8 feature chain structures, which are connected by strong pi-pi interactions to result in 2D and 3D supramolecular architectures. Compound 4 contains 2D layers, which are further extended to a 3D structure by pi-pi interactions. A systematic structural comparison of these 8 complexes indicates that the organic-acid structures have essential roles in the framework formation of the Pb(II) complexes.