Syntheses, crystal structures, and photophysical properties of two 2-D coordination polymers with different geometries of lead(II)

Two complexes constructed from aromatic acid and N-heterocyclic ligands have been synthesized by hydrothermal reaction: [Pb(cipt)(NDC)](n) (1) [cipt=2-(3-chlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, NDC=naphthalene-1,4-dicarboxylic acid] and [Pb(ipm)(BDC)(2)](n) (2) [BDC=terephthalic acid, ipm=5-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-2-methoxyphenol]. Single-crystal X-ray analysis shows that 1 exhibits an interesting arm-shaped chain structure. 1-D ladder chain structure is formed by N-H center dot center dot center dot O bonding interactions and further into a 2-D network by N-H center dot center dot center dot O hydrogen bonds and interchain pi-pi stacking interactions. Complex 2 shows a 2-D butterfly wings structure, which has been rarely reported. The structure in 2 has intermolecular N-H center dot center dot center dot O interactions, which help in construction of the 3-D framework. In 1, the coordination sphere of Pb(II) is hemi-directed, whereas the Pb(II) geometry in 2 is holo-directed. The solid-state fluorescence spectra of 1 and 2 are also investigated, as well as the ligands cipt and ipm.