Development of fluorochromic polymer doped materials as platforms for temperature sensing using three dansyl derivatives bearing a sulfur bridge.

Abstract

Three novel bis-dansyl derivatives bearing a sulfur bridge have been synthesized and fully characterized. Their photophysical characterization has been studied in solution as well as in the solid state. All compounds exhibit fluorescence emission with quantum yields up to 60%, which vary significantly depending on the solvent used, and the inherent molecular structure. Moreover, these compounds demonstrate positive solvatofluorochromic behaviour emitting from bluish-green to yellow. Kamlet-Taft studies were performed to understand the solute-solvent interactions better. Due to the intrinsic characteristics of the compounds, efforts were made to understand their potential usefulness for environmental remediation, and thus metal ion sensing studies were investigated. Compounds L1 and L2 showed high sensitivity to Cu2+ and Hg2+ ions and were found to modulate their emission extensively, with L2 capable of detecting and quantifying up to 4 µM of Hg2+. Considering the solid-state emission of these compounds, the application towards temperature sensing was put forth. L3 was found to quench its emission linearly with temperatures up to 170 ºC. Several doped polymer thin films were fabricated, which served as a platform to establish a linear relation with temperature beyond their melting point. Polymethylmethacrylate (PMMA) films emitted up to temperatures of 218 ºC, which could be fully restored at room temperature. These results suggest the potential application of these bis-chromophoric compounds as molecular thermometers.