Design and synthesis of fluorescence "turn-on" chemosensors based on photoinduced electron transfer in conjugated polymers

A new approach to fluorescence "turn-on" chemosensors based on a photoinduced electron transfer (PET) strategy involving conjugated polymers has been developed. Two new conjugated polymers dea-PPETE and tmeda-PPETE were synthesized and characterized. These two polymers use diethylamino and N,N,N '-trimethylethylenediamino as receptors, respectively, on a poly [p-(phenyleneethylene)-alt-(thienyleneethynylene)] (PPETE) fluorescent conjugated polymer backbone. The polymers were found to be relatively weakly emissive at lambda(max) similar to 488 mn with quantum yields of 0.11 and 0.09, respectively, at room temperature in THF solution. Initial investigations show that the tmeda-PPETE selectively detects some metal cations by an observed increase in fluoresence. In particular, Hg2+ in aqueous solution causes the fluorescence of tmeda-PPETE to increase by a factor of 2.7 at less than micromolar concentrations. The photophysical results are consistent with a PET mechanism for fluorescence quenching, which is removed upon binding of the analyte.