Synthesis And Studies Of Properties Of Diarylethenes Based On Imidazole And Benzothiazole Moiety

So far,the new group imidazole ring unit has been incorporated into the traditional photochromic dithienylethene with a view to optimizing the invisible photochromism and giving rise to fluorescence "turn on" novel properties reported rarely,which is a breakthrough.The introduction of imidazole ring unit at the side of dithienylethene or benzothiazole unit at the end of aromatic aldehyde expect better modulation the photochromic properties of the diarylethenes in structure and performance is the focus of this thesis research.This thesis mainly studies the influence of diarylethenes in the electron-withdrawing substituent,conjugate effect,acid effect or the response of ions and so on.The main research results are generalized as follows:This article were designed and synthesized seven kinds of novel diarylethenes containing imidazole group and two kinds of novel asymmetric photochromic diarylethenes containing benzothiazole group.Their structures were characterized by NMR,IR,MS-ESI,Crystal structure and elemental analysis.Photochromic properties of these diarylethenes in acetonitrile were studied.The result shows that the compounds DT-1?7 are exhibited invisible photochromism and fluorescence "turn on" in acetonitrile.The compounds DT-8 and DT-9 are exhibited good photochromic properties in acetonitrile.Especially the DT-8 underwent reversible cyclization and cycloreversion reactions upon alternating irradiation with lower energy UV?297 nm,25 ?W/cm2?and visible light,while it could induce intramolecular proton transfer reaction upon irradiation with higher energy UV light?254 nm,92 ?W/cm2?with distinct color change.The different substituents and length of the conjugated chain have notable effects on the properties of these diarylethenes containing imidazole group were investigated in detail.The substituents effect results suggest that no matter replacing the hydrogen atom at the para-position of the therminal benzene ring with electron-withdrawing substituent or electon-donating substituent the cycloreversion reaction???-o?of the diarylethenes had clearly decreased compared with traditional diarylethenes.What's more,the fluorescence has been significantly enhanced during the photocyclization of diarylethenes.Along with the compounds of the ? conjugate chain extended,the maximum absorption wavelength increases obviously.It's worth noting that there is no obvious color changes during the photocyclization reaction because the absorption band locates at the ultraviolet region.The effects of acid were studied.Addition of TFA to DT-1c?7c in acetonitrile resulted in the absorption maximum decreased.The protonated DT-1c'?7c' couldn't return to the initial state of DT-1c?7c by neutralizing with TEA.What's more,when TFA was added to the acetonitrile solution containing DT-7o,the emission intensity was remarkably enhanced.Then,the fluorescence spectrum of DT-7o' could return to the initial state DT-7o by neutralizing with TEA.Similarly,the photochromism and fluorescence of DT-8 and DT-9 also exhibited multi-addressable behaviors by the stimulation of both light irradiation and acid/base.The metal cation respond was studied.The fluorescence of DT-7o showed remarkably increase when Fe³⁺,Al³⁺,and Cr³⁺ were added in the solution.The diarylethene DT-8 can serve as a chemosensor for highly selective recognition of Cu²⁺.While Cu²⁺ could efficiently quench its fluorescence intensity with significant absorption and fluorescence changes,which makes the 'naked-eye' detection of Cu²⁺possible.