Two new Pb(II) coordination polymers derived from fatty dicarboxylates and phenanthroline derivatives: syntheses, structures, and properties

Two new Pb(II) coordination polymers, [Pb(3-pdip)(L1)]center dot 0.5H2O (1) and [Pb(4-pdip)(L2)] (2) [L1 = heptane diacid, L2 = hexane diacid, 3-pdip = 2-(3-pyridyl)imidazo[4,5-f]1,10-phenanthroline, 4-pdip = 2-(4-pyridyl)imidazo[4,5-f]1,10-phenanthroline], have been obtained from hydrothermal reactions of Pb(II) nitrate with two flexible fatty carboxylic acids and two phenanthroline derivatives. Single-crystal X-ray diffraction analysis reveals that 1 is a 1-D staircase-like double chain coordination polymer extended by binuclear [Pb2N4O8] subunits and pairs of L-1 ligands. Compound 2 exhibits a 2-D (4,4) network based on bi-metallic [Pb2N6O8] units and (L-2)(2)/(4-pdip)(2) double linkers. Furthermore, adjacent chains of 1 and layers of 2 are extended into 3-D supramolecular networks by pi-pi stacking interactions between aromatic rings of phenanthroline groups. The organic carboxylic acids with different lengths show great influence on the shapes of Pb(II)-carboxylate double chains. Phenanthroline derivatives possessing different sites of N-donors (3-pyridyl and 4-pyridyl) determine the final coordination frameworks of 1 and 2. Photoluminescence and thermal stabilities of 1 and 2 were also investigated.