Synthesis Of The Phenylaza-crown Ethers Luminescent Chemosensors And Studies On Their Properties For Selective Recognition Ions

Based on the special importance in chemistry,biology and environmental processes,the design and synthesis of luminescent chemical sensors with high selectivity and sensitivity to metal ions has become the focus of many supramolecular studies.The superiority of the crown ring ether has the advantages of selective capture of metal ions as one of the ideal options for designing chemical sensor receptors.The synthesis of crown ether luminescent chemosensors and their effects on the selectivity and mechanism of metal ions have special and important value in theory and application.In this paper,three phenyl-aza crown ethers luminescent chemical sensors were designed and synthesized: p-aza-15-crown-5-benzaldehyde-2-?4'-methylcoumarin-7'-yloxy?acetylhydrazone?C1?,Bis-[4-?N-aza-15-crown-5?benzaldehyde]?C2?and p-N-aza-15-crown-5-benzaldehyde salicylaldehyde azine?C3?.The composition and structure of the compounds were characterrized by melting point determination,elemental analysis,1HNMR and mass spectrometry techniques.The identification and sensing properties of these three kinds of photochemical sensors for various important metal ions were also investigated by UV-visible and fluorescence spectroscopy methods.Specific studies are as follows: 1.In the second chapter,C1 was synthesized,and the selectivity and bonding stability of the 16 kinds of metal ions such as K⁺,Ba²⁺,Al³⁺,Ca²⁺,Cd²⁺,Co²⁺,Cu²⁺,Fe³⁺,Hg²⁺,Li⁺,Mg²⁺,Na⁺,Ni²⁺,Sr²⁺,Tb³⁺ and Zn²⁺ in the solvent of ethanol were studied by fluorescence spectroscopy.There were 4-fold and 2-fold fluorescence enhancement of C1 at ?em,max=406 nm upon the addition of 5 equiv of K⁺ and Ba²⁺,respectively.Whereas Fe³⁺ and Al³⁺ induced fluorescence quenching and enhancement respectively,and both were simultaneous with fluorescence peak a blue-shift of C1,other metal ions has no such significant effect on the fluorescence of C1.The experimental results showed that the interaction of C1 with K⁺ was not affected by other metal ions,and the the interaction of C1 with Ba²⁺ was affected by K⁺,while the recognition of Fe³⁺ and Al³⁺ by crown ether C1 was affected by K⁺ and Ba²⁺.The 1:1 and 1:2 stoichiometric binding mode of K⁺ and Ba²⁺,Fe³⁺ and Al³⁺ were supported by the results of fluorescence titration and Benesi-Hildebrand analysis.2.In order to investigate the role of the sensor system's connection system and the signal system in the selection of metal ions,the third chapter has synthesized Bis-[4-?N-aza-15-crown-5?benzaldehyde]?C2?,and observed the effects of the crown ether C2 on the 15 kinds of metal ions(K⁺,Ba²⁺,Al³⁺,Ca²⁺,Cd²⁺,Co²⁺,Cu²⁺,Fe³⁺,Tb³⁺,Mg²⁺,Na⁺,Ni²⁺,Mn²⁺,Pb²⁺ and Zn²⁺)in the ethanol solvent by UV-Vis and fluorescence spectroscopy.The results of UV-Vis spectraum showed that both Al³⁺ and Fe³⁺ decreased the absorbance of compound C2 at 393 nm,at the same time,a new absorption peak was generated at 493 nm,and it was observed that when the addition of Al³⁺ and Fe³⁺ the color of the solution of the crown ether C2 was changed from colorless to orange.Fluorescence spectra showed that both Al³⁺ and Fe³⁺ can effectively redistribute the fluorescent peaks at 464 nm to about 600 nm.The fluorescence intensity of the crown ether C2 at 600 nm was significantly enhanced upon the addition of 10 equiv of Al³⁺ and Fe³⁺.Under the same conditions,other metal ions did not cause significant fluorescence spectral changes.The experimental results showed that the recognition of Al³⁺ by crown ether C2 was not affected by other metal ions,but the recognition of Fe³⁺ by crown ether C2 was affected by Al³⁺.The 1:2 stoichiometric binding mode of Al³⁺ and Fe³⁺ were supported by Benesi-Hildebrand analysis and the results of UV-visible and fluorescence titration.3.In order to investigate the effect of luminescent groups on the selection and sensing mechanism of metal ions in the sensor molecule,the fourth chapter has synthesized p-N-aza-15-crown-5-benzaldehyde salicylaldehyde azine?C3?.The UV-Vis spectra and fluorescence spectra were used to investigate the effect of crown ether C3 on the reaction of 15 different metals(K⁺,Ba²⁺,Al³⁺,Ca²⁺,Co²⁺,Cu²⁺,Fe³⁺,Pb²⁺,Mn²⁺,Mg²⁺,Na⁺,Ni²⁺,Li⁺,Tb³⁺ and Zn²⁺).The results showed that the crown ether C3 had a UV absorption peak at 389 nm in the ethanol solvent and a fluorescence emission peak at 532 nm.The UV-Vis spectra showed that Fe³⁺ and Cu²⁺ reduced the absorption intensity of about 3/4 at 389 nm when 10 equiv the metal ions of crown ether C3 were added,Zn²⁺,Co²⁺ and Ni²⁺ reduced the absorption intensity of about 1/4,Fe³⁺ and Cu²⁺ produced some new absorption peak at 340 nm,500 nm and 340 nm,respectively.Fluorescence spectroscopy showed that Cu²⁺ could strongly quench the fluorescence of crown ether C3 at 532 nm,and Fe³⁺,Co²⁺ and Ni²⁺ had some quenching effect,while Zn²⁺ could strongly enhance the fluorescence of crown ether C3 and transmit it from 532 nm blue to 500 nm.The results from the UV-Vis spectra and fluorescence spectra of the competitive experiments showed that the crown ether C3 had preferential selectivity to Cu²⁺,and without interference from other metal ions,followed by Fe³⁺ and then Zn²⁺.So the order of preference was Cu²⁺> Fe³⁺> Zn²⁺.The 1:1 stoichiometric binding mode of Fe³⁺,Cu²⁺ and Zn²⁺,and 1:2 stoichiometric binding mode of Co²⁺ and Ni²⁺ were supported by Benesi-Hildebrand analysis and the results of UV-visible and fluorescence titration,respectively.