Synthesis Of Coumarin Armed-azacrown Ethers And Their Fragment Molecules And The Study On Their Selective Sensibility On Metal Ions

Molecular recognition is defined as the process that host molecular binds with guest selectively and some special function arise.It is also one of the three basic functions of supramolecular systems.Molecular recognition is regarded as an sensing event that occurs between the microscopic world of molecules and results in the microscopic changes that can be transformed to external signal by a special information system.Optical chemo-sensors is defined that can recognize specific target molecule and be displayed by the optical signal.It includes colorimetric chemo-sensor whose output signal is UV-visible absorption spectrum and fluorescent chemical sensor whose output signal is fluorescent spectrum.Research in molecular recognition based on a variety of optical chemical-sensor have been developed rapidly in recent years and has been applied widely in the field of modern analytical chemistry,environmental sciences and biomedicine.In the thesis,the four kinds of optical chemo-sensor,what are N-(coumarin-7-methyl)-benzoaza-15-crown-5(2L1),N-(4-methyl-coumarin-7-methylene)-benzoaza-15-crown-5(2L2),N-(6-methyl-coumarin-4-formyl acetylhydrazoneyl)-benzoaza-15-crown-5(3L1)and fragmental molecule what is bis(6-methyl-coumarin-4-formyl)azine(4Ll)were designed and synthesized.Their structures were confirmed by melting point determination,elemental analysis,1HNMR,mass spectra.The selective recognition properties of four compounds for 13 kinds of common metal ions were examined by UV-visible and fluorescence spectroscopy and their recognition mechanism were discussed.Details are as follows:1.In order to investigate the influence of selective recognition properties and recognition mechanism that base on the substitution of optical chemo-sensors signal group,N-(coumarin-7-methyl)benzoaza 15-crown-5(2Ll)and N-(4-methyl-coumarin-7-methylene)benzoaza-15-crown-5(2L2)were synthesized in the second chapter of the thesis.The selective recognition properties of crown 2L1 and 2L2 for 13 kinds of common metal ions were examined by UV-visible spectrum method in methanol solvent.The result indicated that the UV-visible spectra of crown 2L1 and 2L2 behaved special recognition and sensitivity to Al3+.Absorption peak intensity of crown 2L1 and 2L2 at 314nm was strengthened in different extent with increasing concentration of Al3+.The linear relationships of crown 2L1 and 2L2 with Al3+ were obtained from the absorption titration profiles using the linear Benesi-Hildebrand expression.Al3+ associates with crown 2L1 and 2L2 in 1:1 stoichiometric complexation and the stability constant were 4.79 and 5.56 respectively.2.In order to investigate the influence of selective recognition properties and recognition mechanism that base on three parts of optical chemosensor,what were the crown ring,linker and coumarin signal groups,crown 3L1 and fragmental molecule 4L1 were synthesized and were examined respectively by UV-visible spectroscopic method and fluorescence spectroscopic method in the third and the fourth chapter of the thesis.The results indicated that the selective recognition properties of crown 3L1 and its fragmental molecule 4L1 for 13 kinds of common metal ions behaved their own characteristics of UV-visible spectra and fluorescence spectra.The study found that insignificant difference of fragmental molecule 4L1 UV-visible spectra when the 13 kinds of common metal ions were added respectively.There are some significant difference of crown 3L1 UV-visible spectra caused by five kinds of ions that were Al3+,Cu2+,Zn2+,Cd2+ and Hg2+.The linear relationships of crown 3L1 with four kinds of ions,what were Al3+,Zn2+,Cd2+ and Hg2+ were obtained from the absorption titration profiles based on Benesi-Hildebrand expression.Crown 3L1 associate with Al3+,Zn2+,Cd2+ and Hg2+ in 1:1 stoichiometric ratio,with Cu.U in 1:2 stoichiometric ratio.Selective recognition properties of the crown 3L1 and fragmental molecule 4L1 for 13 kinds of common metal ions were examined by fluorescence spectrum.The result indicated the crown 3L1 and fragmental molecule 4L1 behaved special recognition and sensitivity to Cu2+.The fluorescence intensity of crown 3L1 was enhance effectively,but molecule 4L1 was quenched efficiently.On the basis of the Stern-Volmer equation,the inhibition process of fragmental molecule 4L1 by Cu2+ belongs to the dynamic quenching of fluorescence.