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)]·H2O 4, [Pb2(oba)(dpdp)2]·2(dpdp)·2(NO3)·2H2O 5, [Pb2(1,4-bdc)2(dpdp)2]·H2O 6,
[Pb(dpdc)(dpdp)] 7, and [Pb(1,3-bdc)(dpdp)]·H2O 8, where dpdp = dipyrido[3,2-a:2‘,3‘-c]-phenazine, H2adip =
adipic acid, H2glu = glutaric acid, H2suc = succinic acid, H2fum = fumaric acid, H2oba = 4,4‘-oxybis(benzoic
acid), 1,4-H2bdc = benzene-1,4-dicarboxylic acid, H2dpdc = 2,2‘-diphenyldicarboxylic acid, and 1,3-H2bdc = 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 π−π interactions to form 2D
layers. 2−3 and 6−8 feature chain structures, which are connected by strong π−π interactions to result in 2D and
3D supramolecular architectures. Compound 4 contains 2D layers, which are further extended to a 3D structure by
π−π 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.