Synthesis And Properties Of Diarylethene With Pyridine N-oxide/Pyrazole Units

Photochromic diarylethenes,which have drawn considerable interest and concerns benefited from its widespread promising applications for photo-switching,full-displays anti-counterfeiting and optical storage.Among diverse photochromic compounds,diarylethene derivatives are the most promising optically responsive compounds,featuring outstanding fatigue resistance and thermally irreversible properties,high photoisomerization quantum yields,rapid response as well as reactivity in the solid state.Modulation of photochromic properties of diarylethene is vital for the wide variety of practical applications of photochromic systems.In this thesis,the diarylethene compounds were designed and synthesized from two aspects.The first categories contain three new diarylethenes with pyridine N-oxides.The effects of N-O moiety of pyridine N-oxides on their physicochemical properties were investigated in detail.The second categories contain a total of two new diarylethenes with pyrazole units,and studied their optical properties,multifunctional responsive properties and chemical sensing properties.The main contents and results are described briefly as follows:1.Three unsymmetrical isomeric diarylethenes based on the hybrid of benzofuran and pyridine N-oxides bearing N-O moiety at ortho-,meta-,and para-position of the methylpyridyl moiety was synthesized,and their structures were determined by single-crystal X-ray diffraction analysis.The substituent and the position effects of N-O moiety on their properties including photochromism,fatigue resistance,and fluorescence had been systematically discussed in acetonitrile solution and PMMA film.Firstly,compared to the parent diarylethene with pyridine ring DT-1,N-oxidized diarylethenes?DT-4?could lead to an obvious red shift of both absorption maxima of the closed-ring isomer and fluorescence emission peak of the opened-ring isomer,the cycloreversion quantum yield and fluorescence modulation efficiency prominent decreased,and a significant fluorescence decline.Moreover,active carbon of diarylethene located at C-2 and C-4 of pyridine N-oxides lead to higher the cyclization quantum yield,the molar absorption coefficients of closed-ring isomer,the fluorescence emission intensitiy and fluorescence modulation efficiency prominent.In addition,the absorption maxima of the closed-ring isomer red shifted and the cycloreversion quantum yield decreased along with active carbon from the ortho-to para-to meta-position of Pyridine ring.2.A novel diarylethene sensor?DT-7o?modified with a pyrazole carbohydrazide unit had been synthesized.Its multi-addressable behaviors induced by light and chemical stimuli?metal ions,anions,base/acid?had been systematically investigated.The fluorescent sensor showed excellent selectivity and sensitivity with a fluorescence enhancement toward Zn²⁺and CN^-with a low detection limit in aqueous acetonitrile solution.In addition,the diarylethene exhibited notable fluorescence enhancement upon the addition of Na OH into the solution.3.A novel turn-on mode fluorescent diarylethene containing a n indazole unit was developed to fluorescently sense Al³⁺and CN^-.Its multiple-responsive properties induced by Al³⁺/EDTA and ultraviolet/visible lights have been systematically studied.The fluorescent sensor could efficiently detect Al³⁺and CN^-with an enhancement of emission intensity and fluorescent color change.At the same time,it also had a low detection limit.Finally,a molecular logic circuit was fabricated with the emission at521 nm as the output signal and the ultraviolet/visible light and Al³⁺/EDTA as input signals.