Synthesis, Structure, and Fluorescence Property of a Lead Two-dimensional Coordination Polymer Constructed by Cyclohexenedicarboxylate Ligand

Abstract

The reaction of dicarboxylate ligand, cis-4-cyclohexene-2-dicarboxylic acid (H₂ccdca), with Pb(II) in solvothermal condition resulted in the formation of a new coordination polymer (CP) i. e., [Pb(ccdca)]_n. Single crystal X-ray study reveals that this coordination polymer features a two-dimensional network whereas ccdca^2– anions adopt their carboxylate groups to link with five neighboring Pb centers in µ₁:η¹:η¹ and µ₃:η²:η¹ coordination modes. The ccdca^2– ligands display trans-conformation and link with Pb centers to form an interesting 4,4-connected topological network with point symbol of {4³·6³}. In addition, the photoluminescent spectra indicate that free H₂ccdca ligand and [Pb(ccdca)]_n exhibit the emission maxima at 412 and 512 nm and emit blue and green luminescence at room temperature, respectively. Compound [Pb(ccdca)]_n displays a red-shift of 100 nm in emission by comparison with free H₂ccdca ligand, with enhanced emission band, which is attributed to the chelation of ligand to the Pb(II), increasing rigidity and reducing energy loss via nonradiative decay in the excited state.