INVESTIGATING THE PHOTOPHYSICAL PROPERTIES OF POTENTIAL ORGANIC LEAD SENSORS

LeadGlow (LG) was reported in 2009 for its ability to both sensitively and selectively detect Pb²⁺ in aqueous solutions. Utilizing the synthetic approach of LG, it is possible to generate a class of novel fluorophores. A derivative of first-generation LG was synthesized and reported here for the first time, intuitively named LG2. Both compounds contain interesting photophysical properties that have not been extensively researched prior to this work. Because of this, photophysical properties of both LG and LG2 are unveiled here for the first time. These properties were investigated by determinations of quantum yield (QY), average fluorescence lifetime, and DFT calculations. LG was found to have a higher QY (0.057) than LG2 (0.011); however, LG2 displays an average fluorescence lifetime (3.186 ns) 5x greater than that of LG. Both LG and LG2 are synthesized via Hg²⁺-facilitated desulfurization of their respective thiocarbonyls, resulting in a turn-on fluorescence feature. The thiocarbonyl-containing fluorophores (SLG and SLG2) display quenched fluorescence compared to their oxo-derivatives (LG and LG2), this work attempts to investigate the mechanism(s) responsible. A whole class of LeadGlow compounds can be synthesized and could be potentially used as fluorescence-based sensors.