Dibromorhodamine-based photoredox catalysis under visible light for the colorimetric detection of Hg(ll)ion

摘要

We demonstrated a colorimetric readout of Hg(ll)ion through visible-light-induced polymerization,initiated by an Hg(ll)-responsive photoredox initiator/catalyst under aerobic conditions.Thiosemicarbazide-functionalized 4',5'-dibromorhodamine was synthesized as a stimuli-responsive photoredox catalyst.The rhodamine derivatives bearing thiosemicarbazide have been known as fluorogenic probes of Hg(ll)ion with excellent sensitivity and selectivity.In this work,we incorporated a heavy halogen atom(i.e.,Br)onto the xanthene core ring of the rhodamine derivative to improve the photoredox catalytic performance of rhodamine 6G,which exhibits a low catalytic performance,presumably due to the poor quantum yield of intersystem crossing.Thus,this photoredox catalyst led to the formation of a hydrogel with Hg(ll)ion in a concentration of 10 μM,as the catalyst initiated free-radical polymerization of poly(ethylene glycol)diacrylate and A/-vinylpyrrolidone with triethanolamine under visible light for 1 min.