Design, Synthesis, And Application Of A Series Of Small-molecule Organic Fluorescent Materials

Organic fluorescent materials have a wide range of uses. They are applied to plastic, paper, synthetic detergents, synthetic fibers, printing ink and other traditional industries. At the same time, the materials are also widely used in many emerging areas, such as organic light-emitting materials, organic field-effect transistors, light harvesting system, logic gates, fluorescent probes, fluorescent labeling and so on. With the development of science and social progress, the demand of organic fluorescent materials with special usage is further increased. So it is of great significance to develop new organic fluorescent functional materials. In this dissertation, the main task is to design and modify organic fluorescent molecules, to meet as light-emitting materials, fluorescent probes, fluorescent labeling requirements. The specific contents include the following:(1) In order to deal with the problem of low fluorescence quantum yield of the porphyrin compounds as red emitting materials, by taking advantage of the energy transfer from the coumarin fluorophore to the porphyrin fluorophore to enhance the fluorescence quantum yield of porphyrin compounds, a series of novel coumarin conjugated porphyrins were designed and synthesized. Moreover, we found that the energy transfer from coumarin substituent to the porphyrin core in the synthesized coumarin conjugated porphyrins is more effective in solid films than in THF solution. And when the substituent in the 7 position of coumarin moiety was the strong electron donating diethylamino group, the energy transfer from the coumarin group to porphyrin core is the most effective.(2) To solve the problem of selectivity in the application of fluorescent probes, the high selective organic reactions were chosen to design the fluorescent probes. After the fluorescent probes exclusively reacting with the analyte at physiological conditions, the electronic structure of the fluorescent probe was changed, which result in the alteration of fluorescence signal, and the analyte was detected selectively.Based on the unprecedented copper-mediated dihydrorosamine oxidation reaction, a novel type of fluorescent copper probe was developed. The probe showed high selectivity and sensitivity for the Cu²⁺, and has been successfully applied to detection of Cu²⁺ in newborn calf serum and living cells. We also have investigated the mechanism of the copper-mediated dihydrorosamine oxidation reaction. Via the thiolysis reaction of 2,4-dinitrophenyl ether, we have rationally constructed a novel type of highly selective and sensitive fluorescent probe for benzenethiol. The probe can selectively detect the benzenethiol in the water samples, soil samples, living cells and air.(3) To cancel the problem of artificial signal in the application of fluorescent probes, we designed the fluorescent ratiometric probe to provide a built-in correction for the artificial signal which origins from probe concentration, excitation light intensity, light leakage and other factors.By choosing the phenanthroimidazole as fluorophore and bipyridine as ligand, we have designed and synthesized a new type of Fe³⁺ ratiometric fluorescent probe. Upon treatment with Fe³⁺, the probe displayed a ratiometric fluorescent response, when 30 equiv Fe³⁺ was added, the fluorescence intensity ratio (I440 / I500) increased from 0.36 to 3.24.Based on the fluorescence mechanism of ICT, by choosing the phenanthroimidazole as fluorophore and aldehyde groups as recognition moiety, we designed and synthesized the first fluorescent ratiometric probe for cysteine and homocysteine. Upon introduction of cysteine and homocysteine, the probe displayed a remarkable blue shift (125 nm) in emission. Furthermore, the probe has been successfully employed for quantitatively detecting cysteine in newborn calf serum.Via the deoxime reaction by ClO-, we have designed and synthesized the first ratiometric fluorescent probe for ClO-. The probe exhibited a ratiometric fluorescent response to hypochlorite with the emission intensities ratio (I509/I439) increasing from 0.28 to 2.74. Additionally, the probe showed high selectivity for hypochlorite over other species due to distinct deoximation conditions.(4) We have developed the first caged rosamines fluorophore based on a novel photocaging chemistry, the intramolecular carbon-carbon spirocyclization. By comparison with the reported caged xanthenes fluorophore, our newly constructed caged rosamines clearly exhibited several significant advantages: high photolytic efficiency, photoactivation by visible light instead of UV light, and high photostability of the parent dyes. Moreover, the newly developed caged fluorophore has successfully applied to selective fluorescent labeling of living cells.