Study On Fluorescent Chemosensors For Metal Ions:Synthesis And Properties In Aqueous Solution

Metal is widespread in nature，and has important significance to life, the environment, medicine,and industrial and agricultural production. Many metal ions also play a vital and irreplaceable regulatoryrole in the course of life. What can not be ignored is that, over-exploitation and unreasonable use of metalshas caused serious environmental pollution problems, especially some heavy metal ions and transitionmetal ions also generate considerable harm on living systems. Fluorescent chemosensors can convertidentification information into the fluorescent signals which be easily perceived. Fluorescent chemosensorshave many advantages such as good sensitivity, high selectivity, rapid, and low detection limit, and can bewidely used in biological, environmental testing and sewage treatment. Utilization of fluorescent sensortechnology to identify metal ions attracts great concern.Some “clamp” and “chain” host molecules, bridging with oxygen atom or nitrogen atom, whichhave cavity size adjustable and lone electron pair, attract widespread attention. After introducingfluorophores into the large ring, fluorescent chemosensors can carry out recognition of metal ion effectivelywith the difference of photochemical response.A series of compounds containing naphthalene or phenanthroline were designed and synthesizedin this paper, and their structures were confirmed. Interaction and recognition property between these newcompounds and some common metal ions (Na+, K+, Zn2+, Co2+, Ni2+, Hg2+, Cr3+, Mn2+, Cu2+and Fe3+) wasstudied by1H NMR, MS, UV absorption spectroscopy, fluorescence spectroscopy titration, chemicalcalculations and other methods. The thesis is divided into four chapters, the main contents are as follows:(1) Introduces the research process of recognition and identification between fluorescentchemosensors and transition metal ion or heavy metal ion briefly, puts forward the design thought of thisthesis.(2) Synthesis of six compounds1,2,3,4,5and6based on phenanthroline. UV absorptionspectra showed responsive changes between them and Cu2+and Fe3+, but the results of fluorescencetitration experiments showed no fluorescence intensity change. Compounds1,2,3,4,5and6pairs ofmetal ions Na+, K+, Zn2+, Co2+, Ni2+, Hg2+, Cr3+, Mn2+, Cu2+and Fe3+no ability to identify, probably due to the cavity size inappropriate or energy mismatch.(3) Synthesis of four new compounds1,2,3and4based on naphthalene and study their selectiveidentification of metal ions Na+, K+, Zn2+, Co2+, Ni2+, Hg2+, Cr3+, Mn2+, Cu2+and Fe3+by UV absorptionspectroscopy and fluorescence spectroscopy titration in an aqueous solution.1was significantly superior to2,3and4for the specific recognition of Hg2+, and the calculation results showed that the complex of1:1formation, but did not interact with other metal ions. Conclusion: compound1is a specificity Hg2+fluorescent chemosensor.(4) Synthesis of two clamp compounds1and2based on naphthalene and two Schiff bases alsocyclic compounds3and4, and study their selective identification of metal ions Na+, K+, Zn2+, Co2+, Ni2+,Hg2+, Cr3+, Mn2+, Cu2+and Fe3+by UV absorption spectroscopy and fluorescence spectroscopy titration inan aqueous solution. The results showed that compounds1,2produced identification for Cr3+and Fe3+, thecomplexes of1:1formation and complexation effect on Fe3+much better than Cr3+; compounds3,4produced identification for Hg2+and Fe3+, and the complexes of1:1formation. In other words: compounds1,2were selective recognition sensors for Cr3+and Fe3+, and the identifications of sensors1,2for Fe3+were more efficient than Cr3+; compounds3,4were selective recognition sensors for Hg2+and Fe3+, and theidentifications of sensors3,4for Hg2+and Fe3+were equally efficient.