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

Three novel bis-dansyl derivatives bearing a sulfur bridge have been synthesized, fully characterized, and their photophysical characterization 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 better understand the solute-solvent interactions. 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 & mu;M of Hg2+. Considering the solidstate emission of these compounds, the application towards temperature sensing was put forth. L3 was found to quench its emission in a linear relation with temperature up to 170 degrees C. Several doped polymer thin films were fabricated, which served as a platform to establish a linear relation with temperature beyond their melting point. Polymethylmetacrylate (PMMA) films emitted up to temperatures of 218 degrees C, which could be fully restored at room temperature. These results suggest the potential application of these bis-chromophoric compounds as molecular thermometers.

Automated summary

Three novel bis-dansyl derivatives with a sulfur bridge were synthesized and their photophysical properties were studied in solution and in the solid state. The compounds exhibited fluorescence emission with quantum yields up to 60%, which depended on the solvent and molecular structure. Positive solvatofluorochromic behavior was observed, with emission ranging from bluish-green to yellow. The compounds showed high sensitivity to Cu2+ and Hg2+ ions, and one compound (L2) could detect and quantify up to 4 μM of Hg2+. Polymer thin films were fabricated to establish a linear relationship between emission and temperature, suggesting the potential application of these compounds as molecular thermometers.