Synthesis And Properties Of Long Wavelength Visible Light Triggered Photochromic Donor-acceptor Stenhouse Adducts

Organic photochromic compounds excited by long-wavelength light are widely used in drug delivery,molecular logic gates and supramolecular chemistry for their fast photoresponse and outstanding photothermal stability.DASAs（Donor-acceptor Stenhouse Adducts）are a new class of negative photochromic compounds which can be triggered by visible light.Upon irradiation with specific wavelengths of visible light,the molecular structure of DASAs is transformed from a hydrophobic linear triene to a hydrophilic cyclopentenone through molecular isomerisation and intramolecular electrocyclisation,leading to a change from coloured to colourless.These compounds are promising for their significant advantage,such as facile synthesis,high contrast,fast light response,and especially the remarkable fatigue resistance.In this paper,a series of multifunctional DASAs have been designed and synthesized to investigate their photochromic properties,and their applications in optical information storage,ions sensing as well as multi-stimulus response are also explored.The detailed works are mainly described as follow.（1）Several DASAs compounds with different absorption wavelengths were synthesized,and the mechanism and factors influencing the response of DASAs compounds to copper ions were preliminary explored.The UV-Vis absorption spectrum and ¹H-NMR titration were used to infer more detail about 1:1 combined ratio between copper ions and DASAs.Besides,the higher temperature and the higher amount of carbonyl groups in the acceptor results in the faster process of isomerization.In addition,the high sensitive and selective of DASAs compounds to copper ions makes it a promising candidate for the detection of Cu²⁺.（2）The fluorophore tetraphenylethylene（TPE）unit with aggregation-induced emission（AIE）effect was modified onto bithienylethene（BTE）.The multiple response photoswitch and combind logic gate were constructed via the combination of BTE and DASAs by benzylamine.The photoswitch showed the outstanding photochromic properties for different stimuli including UV,visible light and heating.Furthermore,the multiple response photoswitch can also realize photofluorescence modulation in aggregation state,making it as a potential optical anti-counterfeit material.（3）Two novel DASAs compounds were designed and synthesized by introducing TPE into the phenazopyridine unit with largeπ-planes.Their photochromic properties and fluorescence properties were investigated by UV-Vis absorption spectroscopy and fluorescence spectroscopy,respectively.Their fluorescence in film could be reversibly switched on/off by alternant visible light/heating,demonstrating potential applications for high contrast reversible fluorescence switching and optical information storage.