Design, Synthesis And Application Of Organic Fluorescent Probes Based On ICT Mechanism

Organic luminescent small molecules are generally composed of conjugate structure for small organic molecular, with advantages of simple structure, easy to modify, easy purification; which have a wide range of applications in many emerging areas, such as field-effect transistors, organic light-emitting materials, light harvesting system, logic gates, fluorescent probe and so on. Chemodosimetric fluorescent probe has attracted much attention in the environmental and biological relevant system because of its simple operation, high sensitivity and selectivity, developed an active area in supramolecular chemistry. In this paper, based on intramolecular charge transfer, three types of chemodosimetric fluorescent probe were designed and prepared, and this usually irreversible reaction-based approach relies on the strong nucleophilicity of CN'/Cys, which has been successfully observed remarkable optical properties and color change. Thus, we could high sensitivity and selectivity detect analytes in environmental and biological relevant systemThe main contents and results are focused as following:1. The outline and the major sensing principles of the fluorescent probes are simply introduced. The latest progresses of reaction-based chemodosimetric fluorescent probe sensing anions, metal ions, neutral molecule and biothiols are reviewed.2. A colorimetric and fluorescent cyanide chemodosimetric probe based on7-(trifluoroacetamino) coumarin has been prepared. This structurally simple probe displays rapid response and high selectivity for cyanide over other common anions in the CH3CN/H2O=4:1(v/v) solution. The detection limit of the fluorescent assay for cyanide is as low as0.29?M in a rapid response of less than30s. The sensing of cyanide was performed via the nucleophilic attack of cyanide anion to carbonyl of the probe with a1:1binding stoichiometry, which could be confirmed by Job's plot,'H NMR, and MS studies. DFT/TDDFT calculations support that the fluorescence enhancement of the probe is mainly due to the ICT process improvement. In the end, we were successfully applied to a practical system for the monitoring of cyanide concentrations in aqueous samples with relative standard deviation lower than2%.3. Based on ICT mechanism, six chemososimetric fluorescent probes (CM1, CM2, CB1, CB2, CTB1and CTB2) which own a coumarin unit as the fluorophore coupling to Meldrum's acid or1,3-dimethybarbituric acid or1,3-diethythiolbarbituric acid activation moiety were designed and synthesized, and the crystal structure of some compounds, and their optical behaviors toward aqueous solution were investigated. The probe CM2, CB2, and CTB2were hydrolyzed easily to produce the starting3in a same solution, because the crystal structure of CM2was also studied and showed a distorted conjugation between the coumarin and Meldrum's acid. The probes (CM1, CB1and CTB1) display rapid response and high selectivity for cyanide over other common anions, and biothiols, and a maximal fluorescent signal is achieved in the presence of only1equiv. of cyanide, and caused a fluorescence change, which provides a facile method for visual detection of cyanide by the naked eye in the DMSO/Tris-HCl (10mM pH7.4,90%DMSO) solution. Importantly, they presented linearly proportional to cyanide concentrations (from5×10-7to5×10-6mol/L) with detection limit down to11,23and18nM, respectively. Thus, this analytical method can be applied to the quantitative and qualitative determination of cyanide anion in drinking water sample and biomimetic system with high precision. In addition, the highly reactive nature on ?-site was verified by H-NMR, absorption spectral, and DFRT calculations.4. We designed and developed a novel fluorescence probe based on benzothiazolium-quinoline hemicyanine dye with an acrylate group as a functional trigger moiety. The probe exhibited rapid response and high specificity for the detection of Cys over other structurally and functionally similar amino acids and thiols. The remarkable red-shift (179nm) of probe1with Cys was implemented by forming the intermolecular charge-separated hemicyanine dyes. Thus, the proposed probe can serve as an optical probe and a "naked-eye" probe for the detection of Cys at the nanomole level. In addition, a maximal fluorescent signal is achieved in the presence of only1equiv. of cys, and they presented linearly proportional to cys concentrations (from1×10-7to1×10-6mol/L) with detection limit down to8.5nM. The kinetic analysis results of probe1and control compound6show that the stabilization of the resultant hydroxyhemi-cyanine dye (2-anion) has an important role in the rapid response and high sensitivity of the probe toward Cys. Furthermore, this fluorescent probe was successfully applied for the fluorescent detection of Cys34in BSA and the bioimaging of Cys in HeLa cancer cells.