Lanthanide-benzophenone-3,3'-disulfonyl-4,4'-dicarboxylate Frameworks: Temperature and 1-Hydroxypyren Luminescence Sensing and Proton Conduction.

The benzophenone-3,3'-disulfonyl-4,4'-dicarboxylic acid (H-BODSDC) ligand and compounds, {(HO)[Ln(BODSDC)(HO)]} (Ln = Tb(1), Eu(2), and Gd(3)), were synthesized and structurally characterized. The lanthanide centers are bridged by the carboxylate groups of BODSDC ligands to give a one-dimensional (1D) chain. The 1D chains are connected by the BODSDC ligands to yield a three-dimensional (3D) structure featuring 1D channels. The lanthanide ions are efficiently sensitized by the BODSDC ligand with an appropriate triplet excited state to generate characteristic Tb(III) and Eu(III) emissions in Tb(1) and Eu(2), respectively. Thus the binary compound, {(HO)[TbEu(BODSDC)(HO)]} (abbreviated as TbEu-BODSDC), was achieved for use as a ratiometric temperature sensor. The ratio values of Tb(III) emission at 544 nm ( I) and Eu(III) emission at 616 nm ( I) for TbEu-BODSDC linearly vary with temperature over a wide range, which indicates that the TbEu-BODSDC is a thermometer for ratiometric fluorescence sensing of temperature. Additionally, Tb(1) is a fluorescent probe for detecting 1-hydroxypyrene (1-HP) by luminescence quenching. The uncoordinated sulfonate oxygens exposed on the channel surfaces serve as the binding sites for 1-HP. Finally, the enrichment of the solvent water molecules in the channels decorated by high-density hydrophilic sulfonate groups resulted in a high proton conductivity for Tb(1).