Synthesis, Structural, Spectral, and Photoswitchable Properties of <i>cis</i>- and <i>trans</i>-2,2,2‘,2‘-Tetramethyl-1,1‘-indanylindanes¹

As versatile synthetic intermediates for new photoswitchable molecules with a tetramethylindanylindane (stiff-stilbene) core, the cis and trans isomers of 5,16-dibromo-2,2,13‘,13‘-tetramethylindanylindanes 2 were synthesized by the Barton−Kellogg coupling. The bromine atoms of trans-2 could be readily replaced with alkyl (sp3), aryl (sp2), and ethynyl (sp) groups. The cis isomers of the parent tetramethylindanylindane 1 and its bromo derivative 2 were isolated, and their structural and photophysical properties were examined for the first time. Clean and efficient trans−cis and cis−trans photochemical isomerization processes were observed in 1.以带有四甲基茚满基茚（刚性芪，stiff-stilbene）核心的新型光开关分子的多功能合成中间体为研究对象，研究人员通过巴顿-凯洛格（Barton−Kellogg）偶联反应合成了5,16-二溴-2,2,13',13'-四甲基茚满基茚2的顺式与反式异构体。反式异构体2分子中的溴原子可便捷地被烷基（sp³）、芳基（sp²）及炔基（sp）基团取代。本研究首次分离得到了母体四甲基茚满基茚1及其溴代衍生物2的顺式异构体，并对其结构与光物理性质进行了系统表征。在化合物1中可观测到干净且高效的反式-顺式与顺式-反式光化学异构化过程。