Syntheses, Structures and Fluorescent Properties of Lead(II) Complexes Based on 5,6-Substituted 1,10-Phenanthroline Derivatives and Benzene Dicarboxylic Acids

Three new coordination polymers, [Pb(1,3-bdc)(MOPIP)(2)](n)center dot nH(2)O (1), [Pb(1,4-bdc)(MOPIP)](n) (2) and [Pb-2(1,4-bdc)(2)(MEDPQ)(2)](n)center dot nH(2)O (3) (MOPIP = 2-(4-methoxyphenyl)-1H-imidazo[4,5-f] [1, 10] phenanthroline, MEDPQ = 2-methyldipyrido [3,2-f:2',3'-h]quinoxaline, 1,3-H(2)bdc = benzene-1,3-dicarboxylic acid, 1,4-H(2)bdc = benzene-1,4-dicarboxylic acid), have been prepared through hydrothermal reactions. The transformation of coordination modes of organic carboxylate ligands and 5,6-substituted 1,10-phen derivatives has a crucial influence on the structures of these series. In compound 1, 1,3-bdc anion adopts a chelating bidentate and bridging monodentate coordination mode, which results in a hepta-coordinated environment of Pb(II) center. However, in complex 2, 1,4-bdc anion acts in the chelating bidentate mode, which results in a hexa-coordinated environment of Pb(II) center. Complex 3 shows face-to-face pi center dot center dot center dot pi interactions between MEDPQ and benzene rings, which are different to that of the complexes 1 and 2. The fluorescence property and thermal stability were also investigated.