Synthesis, Structures, and Properties of Tropone-Fused Coumarin Dyes
Synthesis, Structures, and Properties of Tropone-Fused Coumarin Dyes
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DOI：
10.1246/bcsj.20220264
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发表时间：
2022-12-01
影响因子：
4
通讯作者：
Mazaki, Yasuhiro
中科院分区：
文献类型：
--
作者：
Amishiro, Sae;Ueda, Masafumi;Mazaki, Yasuhiro
通过香豆素衍生物的转环反应和二溴和三溴前体的脱氢溴化反应，设计并成功合成了一种非苯基芳香环，trop1 -fused - 7-甲氧基香豆素染料（1a）及其氯化产物（1b）。x射线晶体学显示，与典型的3,4环pi-延伸香豆素染料不同，1a和1b在环状的tropone骨架上扭曲，并伴有键的交替。与平面型的3,4-苯并-7-甲氧基香豆素染料相比，这些tropo -fused香豆素染料具有红移的吸收和发射光谱。尽管这些化合物具有弯曲的骨架，但它们表现出相对有效的荧光发射（Phi(F) = 2-10%），并且由于激发态中的分子内电荷转移而依赖于溶剂。一项计算研究表明，化合物1在激发态下转变为包含tropylium单元的扁平结构。此外，在三氟乙酸作用下的1a荧光光谱中，由于与tropylium阳离子形成电荷分离结构，发射强度急剧增加至Phi(F) = 19%。
A nonbenzenoid aromatic ring, tropone-fused 7-methoxy-coumarin dye (1a) and its chlorinated product (1b) were designed and successfully synthesized via transannulation of a coumarin derivative and dehydrobromination of the dibromoand tribromoprecursors. X-ray crystallography revealed that 1a and 1b are distorted at the annulated tropone skeleton with bond alternation, unlike typical 3,4-annulated pi-extended coumarin dyes. These tropone-fused coumarin dyes exhibited redshifted absorption and emission bands compared with that of planar 3,4-benzo-7-methoxycoumarin. These compounds demonstrated relatively efficient fluorescence emission (Phi(F) = 2-10%) despite their curved skeletons, and solvent dependency owing to the intramolecular charge transfer in the excited state. A computational study clarified that compound 1 changes to a flat structure including the tropylium unit in the excited state. Furthermore, in the fluorescence spectra of 1a with trifluoroacetic acid, the emission intensity increased dramatically to Phi(F) = 19% owing to the formation of a charge-separated structure with the tropylium cation.