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

ABSTRACT

The benzophenone-3,3'-disulfonyl-4,4'-dicarboxylic acid (H4-BODSDC) ligand and compounds, {(H3O)[Ln(BODSDC)(H2O)2]} n (Ln = Tb(1), Eu(2), and Gd(3)), were synthesized and structurally characterized. The lanthanide centers are bridged by the carboxylate groups of BODSDC4- ligands to give a one-dimensional (1D) chain. The 1D chains are connected by the BODSDC4- ligands to yield a three-dimensional (3D) structure featuring 1D channels. The lanthanide ions are efficiently sensitized by the BODSDC4- 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, {(H3O)[Tb0.93Eu0.07(BODSDC)(H2O)2]} n (abbreviated as Tb0.93Eu0.07-BODSDC), was achieved for use as a ratiometric temperature sensor. The ratio values of Tb(III) emission at 544 nm ( ITb) and Eu(III) emission at 616 nm ( IEu) for Tb0.93Eu0.07-BODSDC linearly vary with temperature over a wide range, which indicates that the Tb0.93Eu0.07-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).