Polytriazole bridged with 2,5-diphenyl-1,3,4-oxadiazole moieties: a highly sensitive and selective fluorescence chemosensor for Ag+

Fluorescent conjugated polytriazoles (FCP 1-4) containing both 2,5-diphenyl-1,3,5-oxadiazole (OXD) and 1,2,3-triazole moieties in the main chain were synthesized from aromatic diazide (1) and dialkynes (2-5) via click polymerization, respectively. In the polymers, OXDs (fluorophores) and triazole rings (generated via CuAAC acting as metal ion ligands) comprise a fluorescent system. The polytriazoles displayed relatively strong emission with quantum yields in the range of 0.20-0.28 at room temperature in DMF. The study on their ion-responsive properties showed that, although all four FCPs have good selectivity for Ag+, the integration of alkoxy side groups (methoxy for FCP 2, hexyloxy for FCP 3 and 2-ethylhexyloxy for FCP 4) to the main chains of the polytriazoles decreased their sensitivity for Ag+ via alteration of the polymer aggregation status and electron density of the main chains. Thus FCP 1 is highly sensitive for Ag+, where its K-sv is as high as 1.44 x 10(5) M-1 and its lowest detection limit is in the ppb range (4.22 x 10(-7) M). This study provides an efficient click approach to the synthesis of a novel fluorescence sensor for Ag+ detection, which could expand the application of click polymerization in designing fluorescence sensors based on the triazole unit.