Two Pb(II) dicarboxylates constructed by rigid terephthalate or flexible d(+)-camphorate with different 3D motif based on cooperative effect of steric hindrance of ligand and lone pair electrons

Abstract

The hydrothermal preparation via variations of dicarboxylate ligands (terephthalate (bdc) or d(+)-camphorate (ca)) with lead nitrate exhibits two new 3D coordination polymer. In complex 1 [Pb(bdc) 2] n , linear rigid bdc ligands exhibit unique ( μ 5-κO- μ 2:κO′:κO′′,O′′′:κO′′- μ 2) coordination mode. The carboxyl groups of bdc link adjacent lead(II) atoms to form a 2D infinite undulated [Pb(CO 2) 2] n layer, and further linked via the benzene ring of bdc to form a 3D pillared-layer compact framework. In contrast, complex 2 [Pb(ca) 2·H 2O] n exhibits a rod packing 3D sra (Al net in SrAl 2) network with the combination of [Pb(CO 2) 2·H 2O] n rods through ( μ 4-κO,O′:κO′′,O′′′:κO′′- μ 2:κO′′′- μ 2) coordination mode of the bulky chiral ca linkers. Both in 1 and 2, the arrangement of donor atoms suggest the coordination around the lead(II) atoms is hemi-directed. The different steric hindrance of two bridged ligands, and lone pair electrons effect of lead(II) ion cooperatively influence bdc and ca displaying in diverse connecting modes and further result in different packing styles of two 3D motif. Two complexes exhibit an excellent thermal stability with the tolerate temperature ca. 410 °C for 1 and 390 °C for 2, respectively, attributed to the presence of abundant coordination bonds of dicarboxylate ligands and the infinite rod-shaped or layered building blocks in above 3D compact frameworks.