Design, Synthesis And Anion Recognition Of Triarylimidazole Derivatives

Anions play an important role in chemical, environmental, biological and other processes. So the design and synthesis of chemical sensors toward anions is one of the most intensively studied areas. Triarylimidazole derivatives are very simple organic compounds containing functional groups (N-H) capable of providing binding sites and chromophore group. In addition, the acidity of the NH proton of can be tuned by changing the electronic properties of the imidazole substituents. Hence in this article, we described several triarylimidazole derivatives and investigated how different substituents groups effect on anion recognition. The main contents are as follows:1. We synthesized several triarylimidazole derivatives 1-8 that substituted by different groups and at different position. Results showed that different groups and at different position can affect the selectivity of anion recognition. Because the difference substituted by different groups and at different position have different effect on the acidity increasement and the ability of receptor combined with the anions. But the fluorine atoms substituted at the p-site (the receptor 4) can selectivity recognize the F-. The electron-donating groups, methyl and methoxy these with N-H of imidazole and nitro-phenyl formed a D-Ï€-A system, so the intermolecular charge transfer (ICT) became easily, and the absorbance spectra happened bathochromic-shift. The receptors and anions were formed complexes with 1:2 stoichiometric ratios. So the receptor 4,7,8 can be used as chromogenic sensors for the selectively detection of F-.3. We synthesized 4 new kind of 2-(2-azophenyl)-4,5-biphenyl imidazole 10-13. Results showed that receptor 10-13 can all be used as chromogenic sensors for the selectively detection of F-without any spectroscopic instrument in acetonitrile. In order to investigate the mechanism of receptor recognize the anions, we demonstrate it by the UV-vis titration and 1H NMR experiments. The results showed that:at firstly, the anion and receptor formed complex by hydrogen bond, with the increasement of anion, it may promote the deprotonation of N-H fragment of the imidazole subunit, and increase the electron density on the nitrogen atom, resulting in the enhancement of ICT process and red-shift of the ICT absorption band. At last formed more [HF2]- complex.3. Four kind of 2-(2-hydroxyphenyl)-4,5-biphenyl imidazole receptors (14-17) were synthesized. The interaction between the anions and the receptors were demonstrated by the UV-vis titration experiments. The results showed that the receptors 14 and 15 can be used for detecting the F- by the red-shifted of the absorption spectra. The absorption spectra of receptors 16 and 17 were red-shifted 40 nm compared with the receptors 14 and15. Receptors 16,17 and F- or H2PO4- may form Cu- Receptor- F- or H2PO4- ternary complexes, but the AcO- may decompose the Cu complexes.