Wilm Lukas F B, Das Mowpriya, Janssen-Müller Daniel, Mück-Lichtenfeld Christian, Glorius Frank, Dielmann Fabian
Institute of Inorganic and Analytical Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstrasse 28-30, 48149, Münster, Germany.
Institute of Organic Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstrasse 36, 48149, Münster, Germany.
Angew Chem Int Ed Engl. 2022 Jan 17;61(3):e202112344. doi: 10.1002/anie.202112344. Epub 2021 Nov 26.
Using light as an external stimulus to alter the reactivity of Lewis bases is an intriguing tool for controlling chemical reactions. Reversible photoreactions associated with pronounced reactivity changes are particularly valuable in this regard. We herein report the first photoswitchable nitrogen superbases based on guanidines equipped with a photochromic dithienylethene unit. The resulting N-heterocyclic imines (NHIs) undergo reversible, near quantitative electrocyclic isomerization upon successive exposure to UV and visible irradiation, as demonstrated over multiple cycles. Switching between the ring-opened and ring-closed states is accompanied by substantial pK shifts of the NHIs by up to 8.7 units. Since only the ring-closed isomers are sufficiently basic to activate CO via the formation of zwitterionic Lewis base adducts, cycling between the two isomeric states enables the light-controlled capture and release of CO .
利用光作为外部刺激来改变路易斯碱的反应活性是控制化学反应的一种有趣工具。在这方面，与显著反应活性变化相关的可逆光反应特别有价值。我们在此报告了首例基于配备光致变色二噻吩乙烯单元的胍的光开关型氮超强碱。所得到的N-杂环亚胺（NHIs）在连续暴露于紫外光和可见光照射下会发生可逆的、近乎定量的电环化异构化，这在多个循环中都得到了证明。在开环和闭环状态之间切换伴随着NHIs的pK发生高达8.7个单位的显著变化。由于只有闭环异构体具有足够的碱性，能够通过形成两性离子型路易斯碱加合物来活化CO，因此在两种异构状态之间循环能够实现光控捕获和释放CO。
