Switchable Mesomeric Betaines Derived from Pyridinium‐Phenolates and Bis(thienyl)ethane
| Autor: | Jörg Adams, Felix Lederle, Sven Nagorny, Thea Weingartz, Wolfgang Maus-Friedrichs, Viktor Udachin, Andreas Schmidt, Eike G. Hübner, Sebastian Dahle |
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| Rok vydání: | 2021 |
| Předmět: | |
| Zdroj: | European Journal of Organic Chemistry. 2021:3178-3189 |
| ISSN: | 1099-0690 1434-193X |
| DOI: | 10.1002/ejoc.202100279 |
| Popis: | 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, and N-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 an N-methylpyridinium-4-yl and a 4-phenolate substituent (29) displays considerable bathochromic shifts to λmax=724 nm in its closed form. |
| Databáze: | OpenAIRE |
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