Synthesis Of Several Small-molecule Fluorescent Probes And Its Application

Molecular probe is a tool that can transfer the molecular recognition events into the optical signals. Because of its specific selectivity, high sensitivity and simple operation and so on, molecular probes have caused the researchers’interest in recent years, and have been widely used in medicine, chemical and biological science. The dyes like benzoxazole, fluorene and cyanine have been widely used as fluorophores in molecular probes construction due to their excellent optical and physical properties including high fluorescent quantum yields, good stability. In this paper, molecular probes for cysteine, mercury ion and hydrazine hydrate have been constructed using benzoxazole, fluorene and cyanine as fluorophores respectively. The concrete contents are as follows:(1) based on specificity cyclization mechanism of aldehyde group and cysteine, a new turn-on fluorescent probe, was designed and synthesized. This probe is based on the principle of Intramolecular Charge Transfer (ICT). First, the probe was weakly fluorescent. While reaction between aldehyde group and cysteine taken after adding cysteine, the molecular structure of the probe was changed, the process of ICT was off, and fluorescence intensity was enhanced significantly. The probe exhibited good sensitivity and selectivity toward cysteine with a detection limit of9.84x10-8M.(2) In order to avoid the disadvantages of hard purification of the fluorescent probes based on polyfluorene, in this work, small molecule fluorene was used as fluorophore. Novel polyamide reeeptor containing heteroatoms N, S and O was synthesized through amide reaction between carboxyl and thiophene methylamine. Which can selectively detect Hg. First, the probe showed strong fluorescence. While adding Hg2+, the π-electron of fluorophore fluorene ring took interaction with Hg because of complexation heteroatomic O, S with Hg2+, which reduced the electron cloud density of conjugate system and led to the fluorescence quenching. Accordingly, a new fluorescence quenching probe based on Hg2+was designed and synthesized, which exhibited high selectivity, low detection limit and short response time. Moreover, the probe could be employed to monitor Hg in water samples.(3) In order to the deal with the problem of low selective probes constructed by the single functional group transformation strategy, a molecular probe based on double functional group transformation strategy was designed and synthesized. In this paper, a NIR molecular probe has been constructed by linked near-infrared Cy7-C1cyanine dye that used as fluorophore and trifluoroacetylacetone with a phenol linker. The probe taken Hantzsch reaction with hydrazine. Then the conjugate structure of probe reduced, which lead to probe absorption declind at760nm. Therefore, this probe can colorimetrically detect hydrazine hydrate, and be employed to monitor hydrazine hydrate in water samples.