Design,Synthesis And Properties Of Al³⁺、Zn²⁺、Cd²⁺ Sensors Based On Diarylethene

Compared with traditional analytical methods,such as ion selective electrodes,voltammetric methods and colorimetric sensors,the development of fluorescent chemosensors for sensing and recognition metal ions of importance to the environment and health has attracted considerable attention,due to their simplicity,high sensitivity,good selectivity and rapid response time.Zinc ion plays an important part in many biological processes and the metabolic imbalance.In contrast,cadmium ion is known as an extremely toxic and potentially carcinogenic metal.Moreover,they have similar properties and it is difficult to eliminate serious interference from each other.So,it’s still a challenge to develop fluorescent chemosensors that can selectively recognize Zn²⁺and/or Cd²⁺.Aluminium is the third most prevalent metal in the earth’s crust,and it is noteworthy that excessive intake of aluminium can lead to severe health problems of human.Therefore,exploring Al³⁺sensors with high sensitivity and excellent selectivity signaling mechanisms has attracted widespread attention.Compared with the former single recognition of Zn²⁺/Cd²⁺/Al³⁺chemical sensors,the design and synthesis with multiple response diarylethenes Zn²⁺/Cd²⁺/Al³⁺chemical sensor has become a hot spot.However,diarylethene compounds as chemical sensors detecting metal ions,especially Al³⁺,Zn²⁺,Cd²⁺,still have some shortcomings such as poor selectivity,short emission wavelength and low fluorescence quantum yield.Based on the above reasons,eight kinds of fluorescent chemical sensors were designed and identified to identify Al³⁺,Zn²⁺,Cd²⁺.In this paper,the main contents are as follows:In chapter 1,the research background of the chemical sensors and Al³⁺,Zn²⁺,Cd²⁺chemical sensors,the applied research of diarylethene,the research progress of Al³⁺,Zn²⁺,Cd²⁺diarylethene chemical sensors were reviewed.Finally,the research content was proposed.In chapter 2,two diarylethenes based on a 6-（hydroxymethyl）picolinohydrazide unit were designed and synthesized.When irradiated with higher UV light,DT-1O could be induced by intramolecular proton transfer reaction.In addition,acid-base could control the ultraviolet absorption spectrum of DT-1O.The differences in the fluorescence behavior of the compounds DT-1O and DT-2O are mainly manifested in the identification of metal ions.Compound DT-1O could specifically recognize Al³⁺,while compound DT-2O could specifically recognize Zn²⁺.In chapter 3,three diarylethenes based on a 2-hydrazinoquinoline group were designed and synthesized,and the photochromic behavior and fluorescence behavior of diarylethenes were measured.Among them,DT-3O exhibited the superior fatigue resistance.DT-3O not only could selectively detect and differentiate Zn²⁺、Cd²⁺,but also could detect HSO₄^-as a multiplex recognition chemical sensor.Interestingly,DT-4O specifically recognized Zn²⁺,while DT-5O was a recognition of the trivalent metal ions Fe³⁺,Al³⁺,Cr³⁺.In chapter 4,two diarylethenes based on quinoline formaldehyde base were designed and synthesized.DT-6O could be used as a selective and distinguish fluorescence sensor for Zn²⁺and the fluorescence quantum yields of DT-6O-Zn²⁺was determined to be 0.89.In chapter 5,a highly selective fluorescent sensor for Cd²⁺based on a new diarylethene with a 1,8-naphthyridine unit was successfully synthesized and the single crystal of DT-8O was obtained by slow evaporation of methanol solution.Base not only promoted the enhancement of closed-ring quantum yield of DT-8,but also promoted fluorescence emission peak red-shifted to 685nm.The experiments about pH effect on the complexation of DT-8O with Cd²⁺and competitive experiment indicated DT-8O could specifically identify Cd²⁺.Finally,the complexation sites and methods of DT-8O with Cd²⁺were further determined by NMR and MS.