Coumarin-derived Probes Based On PET Mechanism:Molecular Design,Synthesis And Recognition Performance

Selective recognition and detection of some heavy metal ions is important because they are widespread in nature and harmful to human health and the biological environment.Fluorimetry is widely used for the detection of metal ions because it is highly sensitive and easy to operate.In this paper,the coumarin-based fluorescent acceptors were designed and studied for several heavy metal ions recognition.Two novel fluorescent probes A1 and A2,comprising a coumarin moiety as fluorophore and a pair of dithiocarbamates as recognition sites,were designed and synthesized as fluorescent probes for Ag⁺Coordination of the silver ion with dithiocarbamate would hinder electron transfer,significantly increasing the fluorescence signal in CH₃CN–HEPES（1:9,v/v）solution.A1 and A2 displayed 7.26-and 12.15-fold fluorescence enhancement for Ag⁺,respectively.These probes could be applied for monitoring of Ag⁺in aqueous solution in the pH range of 5.0–8.0.Two coumarin-based compounds B1 and B2,comprising thioglycollic acid as the recognition site,were designed and synthesized as fluorescent probes for Hg²⁺detection.The probes exhibited high selectivity for Hg²⁺with fluorescence enhancement in pure aqueous media,and the recognition effect of B2 is better than B1.The binding ratio of C-Hg²⁺complex was determined to be 1:1 according to the Job‘s plot and the date of MS.The association constant K_a of Hg²⁺with B2 was 1.41×10⁵ M^-1.The presence of anions has no significant interference with the recognition process and the recoveries of Hg²⁺in water samples were from 96.0%to 101.1%.Two fluorescent probes C1 and C2 containing sulfur atoms and benzocoumarin fluorophores were designed and synthesized.Both compounds exhibit high selectivity for Hg²⁺.The detection limits were calculated to be 2.46×10^-77 M and 5.03×10^-88 M by the quantitative relationship between C1 and C2 with Hg²⁺.Coordination of Hg²⁺with dithiocarbamate in C1 and thioglycollic acid in C2 would hinder electron transfer,significantly increasing the fluorescence signal.The color of C1 changed from colorless to blue and C2 changed from lavender to yellowish-green simultaneously.