The Synthesis And Properties Of Copper Ion And Cyanide Probe Based On Benzimidazole

Fluorescent probes are valuable tools for environmental, chemistry, bioanalysis and materials science due to their high sensitivity, low detection limit and easy for implementation. They can selectively transfer chemical information of the analyte into fluorescence signals which can be detected by analytical instruments. Nowdays,fluorescent probes have been used widely in environmental and biological systems for the detection of certain substances.There are two sp2 hybrid N atoms in the imidazole ring of benzimidazole. One could be a metal-ion coordination sites, the other one could be a reactivity sites which makes the probe easy to be covalented and modified on the surface of materials. By connecting benzimidazole to flurescent(such as coumarin, triphenylamine), it can be easily obtained a functionalized fluorescent probe whcih provide a convenience for materialization. In this paper, a general introduction to structural characteristics of benzimidazole and the research progresses on those complexes of copper and cyanide probe were presented. And some fluorescent probes were developed on basis of previous work. The main contributions are listed as follows.1. A new reactive pyrazine heterocyclic-based probe R was designed and synthesized. No fluorescence was detected from the solution of R(CH3CN: CH2Cl2).With the addition of 5 equip. Cu2+, 22-fold fluorescence enhancement was observed.At the same time the color of the solution was also changed from light brown to yellow. Studies showed that a new compound R-P was formed and its structure was confirmed by 1H NMR, 13 C NMR and MS. Other common ions did not interfere with the detection of Cu2+. The results showed that probe R has a high selectivity and sensitivity of recognizing Cu2+.2. A novel fluorescence enhancement probe N was designed and synthesized based on water-soluble benzimidazole and coumarin. Probe N showed orange fluorescence in C2H5OH/ water(v: v=9: 1)(λem=442 nm). Upon the addition of 10 equiv. of Cu2+, it turned to a blue fluorescencet(λem=494 nm) with other metal ions exhibited no obvious change. The results showed that probe N coordinated with Cu2+in a 1:1 stoichiometric ratio and the calculated binding constant is 4.03 × 106 M-1.Moreover, the fluorescence emission increases linearly with Cu2+ concentration in the range 3-25 μM and the detection limit reaches 0.068 μM.3. A novel probe L based on the phenazine-imidazole-coumarin conjugate was designed and synthesized. Probe L could be used to detection both copper and fluoride ions in one system. The color of solution is orange and it shows orange fluorescent(λem=565 nm) in acetonitrile. With the addition of 10 equiv. of Cu2+, an obvious fluorescence quenching was observed at the maximum emission wavelength while other metal cations exhibited no obvious changes. It could be used in recognized copper ions among other metal cations. Meanwhile, upon the addition of10 equiv. of F- ion, other common anions exhibited no obvious change except F- that can induce a fluorescence quenching. The result showed that probe L has potential application in detecting F- in common anions.4. A probe M was synthesized with triphenylamine as the raw materials. Studies showed that probe M exhibits purplish red in C2H5OH/ water(v: v=9: 1). Upon the addition of 10 equiv. of CN-, cyanide has strongly nucleophilic which could nucleophilic addition with C=N bond of probe M lead to the interruption of π-electron conjunction, and an obvious change in color was very easily observed with naked eye and the solution emited strong blue fluorescence at the excitation wavelength as set at355 nm. The results showed that probe M could detect CN- selectively without any interference with other anions.