Switchable Mesomeric Betaines Derived from Pyridinium‐Phenolates and Bis(thienyl)ethane
Switchable Mesomeric Betaines Derived from Pyridinium‐Phenolates and Bis(thienyl)ethane
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DOI：
10.1002/ejoc.202100279
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发表时间：
2021-06
影响因子：
2.8
通讯作者：
Sven Nagorny;Felix Lederle;V. Udachin;Thea Weingartz;E. Hübner;S. Dahle;W. Maus‐Friedrichs;J. Adams;A. Schmidt
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文献类型：
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作者：
Sven Nagorny;Felix Lederle;V. Udachin;Thea Weingartz;E. Hübner;S. Dahle;W. Maus‐Friedrichs;J. Adams;A. Schmidt
描述了具有中心全氟环戊烯核的推拉式取代的非对称双（噻吩基）乙烯（BTE）的合成。苯甲醚、苯酚和苯酚盐以及吡啶、吡啶鎓和N-甲基吡啶鎓取代基分别通过它们的3-或4-位连接到中心BTE核上的取代基效应涵盖了标题内消旋甜菜碱中从非常强的供电子[σ（4-苯酚盐）=-1.00]到非常强的吸电子[σ（4-吡啶鎓基）=+2.57]的范围。具有4-基/4-基、4-基/3-基和3-基/3-基取代基的不同异构体代表共轭和交叉共轭部分结构的不同组合，并导致不同的光谱性质。此外，可以观察到噻吩的2-和2′-位之间的通过空间共轭，这避免了通过键交叉共轭的电荷分离。具有由3-苯甲醚和4-吡啶取代基组成的推拉发色团的BTE（24）在本文所述的一系列化合物中显示出最好的消光系数（λ =33.8/15.7 L/mol·cm），而具有N-甲基吡啶-4-基和4-酚盐取代基的内消旋甜菜碱（29）在其封闭形式中显示出相当大的红移至λmax=724 nm。
Syntheses of push–pull substituted non‐symmetric bis(thienyl)ethenes (BTEs) possessing a central perfluorocyclopentene core are described. The substituent effects of anisole, phenole, and phenolate as well as pyridine, pyridinium, andN‐methylpyridinium substituents, joined through their 3‐ or 4‐positions to the central BTE core, respectively, cover the range from very strongly electron‐donating [σ(4‐phenolate)=−1.00] to extremely strongly electron‐withdrawing [σ(pyridinium‐4‐yl)=+2.57] in the title mesomeric betaines. The different isomers possessing 4‐yl/4‐yl, 4‐yl/3‐yl and 3‐yl/3‐yl substituents represent different combinations of conjugated and cross‐conjugated partial structures and cause different spectroscopic properties. In addition, through‐space conjugation between the 2‐ and 2′‐position of the thiophenes can be observed which circumvents the charge‐separation of through‐bond cross‐conjugation. The BTE possessing the push–pull chromophore consisting of 3‐anisole and 4‐pyridinium substituents (24) displays the best extinction coefficients within the series of compounds described here (ϵ=33.8/15.7 L/mol ⋅ cm), while the mesomeric betaine possessing anN‐methylpyridinium‐4‐yl and a 4‐phenolate substituent (29) displays considerable bathochromic shifts to λmax=724 nm in its closed form.