Chiroptical Chemosensors For Highly Se-lective Recognition Of Mercury(Ⅱ)

The development of selective chemosensors for the detection of toxic heavy-metal ions draws particular interest because of the wide use of these metal ions and their important impact on the environment. Among them, mercury is one of the most prevalent toxic pollutants in the environment because it is widely distributed in water and soil and subsequently bioaccumulates in mammals through the food chain. Even a very low concentration of mercury ions causes a variety of diseases and affects the central nervous system which is reflected in symptoms such as headache, tremors, vision problems, hearing and memory impairments. Therefore, detection of mercury in many fields such as environmental science, life science and medicine has become more and more important. In the past few years, significant efforts have been devoted to develop powerful chemosensors for mercury species, which has the favorable features of operational simplicity, cost-effectiveness, high sensitivity and selectivity.On the basis of the previous studies in our laboratory and oxymercuration of an alkyne, in this thesis we firstly designed and synthesized a chiral molecule, i.e.,(S)-N-(2-hydroxy-l-phenylethyl)-2-(prop-2-ynyloxy)benzamide (HPB). For the model compound, we invesitigated its oxymercuration under various conditions and the corresponding spectroscopic changes in UV-vis and circular dichroism (CD). As expected, in the presence of Hg2+, HPB conducts hydration reaction readily at room temperature in buffer solution and this chemical transformation resulted in a dramatic change in CD spectra. Thus, HPB can used as a chemodosimeter for Hg2+, exhibiting a specific CD responsiveness, excellent resistance to oxidants and sulfur-containing species. A mechanism has been proposed for the interaction between HPB and Hg2+based on the structural analysis of the product.A chiral monomer derived from HPB,(S)-2-phenyl-2-(2-(prop-2-ynyloxy)-benzamido)ethylmethacrylate (PPEMA), was prepared and copolymerized it with N,N-dimethylacrylamide (DMAA) to yield the corresponding copolymer poly(DMAA-co-PPEMA) via RAFT technique. These copolymers bearing optically active benzamide chromophores and propargyl group in the side chain were expored its potential as a new chiraoptical sensor for mercury. The results showed that the water-soluble copolymers exhibited pronounced absorbance and unique circular dichroism responses upon addition of mercury ion. Furthermore, the identification process is also not interfered by sulfur-containing compounds and oxidants. The recognition effect of these copolymers is relatively weaker than that of HPB, which could be explained by the large steric hindrance of polymer chains to the reactive sites.In summary, the chemical reaction-based chiroptical chemosensors developed in this work have potential applications for the highly selective detection of Hg2+in the sulfur-and oxidant-rich environments. Also, the exploration may provide a new path to design chemosensors and expand the application area of chiral function materals.