| 总结: | <p>This thesis presents an investigation into diarylethene-based organic photoswitches, with emphasis on optimizing their photoswitching capabilities. The research then progresses to implement these enhanced photoswitches in practical applications, specifically focusing on switchable fluorescence systems and photopharmacology.</p>
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<p><strong>Chapter 1</strong> provides a review of molecular photoswitch research, elucidating fundamental models, quantitative formalisms, and key photoswitching performance parameters. A comparative analysis of various photoswitch classes is presented, highlighting their structural and photochemical features. This analysis identifies diarylethenes as a promising class of photoswitch for further optimization.</p>
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<p><strong>Chapter 2</strong> describes the synthesis and characterization of push-push, pull-pull, and push-pull diarylethenes with varying lengths of conjugation. A comprehensive examination of their photophysical and photochemical properties is presented, with observed trends rationalized through DFT and TD-DFT calculations, and conformational sampling. The chapter culminates in the identification of a water-soluble diarylethene, featuring two N-methylpyridinium groups with alkyne spacers, capable of bidirectional visible light photoswitching with quantitative photostationary state distribution.</p>
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<p><strong>Chapter 3</strong> extends the findings of Chapter 2, utilizing the optimized diarylethene to develop two photoswitchable fluorophores based on a diarylethene-cyanine dyad design. The diarylethene functions as a photocontrollable switch for the fluorophore, enabling reversible transitions between fluorescent and non-fluorescent states. The chapter details the synthesis of these photoswitchable dyads and provides an in-depth characterization of their fluorescence switching properties and fatigue resistance.</p>
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<p><strong>Chapter 4</strong> explores diarylethenes as photoswitchable ligands targeting G-quadruplexes. The synthesis of four diarylethene-based switchable ligands is outlined, followed by an examination of their binding interactions with G-quadruplexes. This chapter reveals that the open and closed isomers of the diarylethenes exhibit distinct affinities for G-quadruplexes and varying degrees of cytotoxicity.</p>
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<p><strong>Chapter 5</strong> summarizes the key findings of the research and provides a critical outlook for future investigations in this field.</p>
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