Dishi Or, Rahav Yuval, Carmieli Raanan, Gidron Ori
Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel.
Chemical Research Support Unit, Weizmann Institute of Science, Rehovot, 7610001, Israel.
Chemistry. 2022 Nov 7;28(62):e202202082. doi: 10.1002/chem.202202082. Epub 2022 Sep 2.
Macrocyclic furans are predicted to switch between global aromaticity and antiaromaticity, depending on their oxidation states. However, the macrocyclic furans reported to date are stabilized by electron withdrawing groups, which result in inaccessible oxidation states. To circumvent this problem, a post-macrocyclization approach was applied to introduce methylene-substituted macrocyclic furans, which display an extremely low oxidation potential of -0.23 vs. Fc/Fc , and are partially oxidized in ambient conditions. Additional oxidation to the dication results in aromaticity switching to a global 30πe aromatic state, as indicated by the formation of a strong diatropic current observed in the H NMR spectrum. NICS and ACID calculations support this trend and provide evidence for a different pathway for the global current in the neutral and dicationic states. According to these findings, macrocyclic furans can be rendered as promising p-type materials with stable oxidation states.
据预测，大环呋喃会根据其氧化态在全局芳香性和反芳香性之间切换。然而，迄今为止报道的大环呋喃是由吸电子基团稳定的，这导致了难以达到的氧化态。为了解决这个问题，采用了大环化后方法来引入亚甲基取代的大环呋喃，其相对于Fc/Fc显示出极低的氧化电位-0.23，并且在环境条件下会部分氧化。进一步氧化成双阳离子会导致芳香性转变为全局30πe芳香态，这在1H NMR谱中观察到的强抗磁电流的形成中得到了体现。NICS和ACID计算支持这一趋势，并为中性和双阳离子态下全局电流的不同路径提供了证据。根据这些发现，大环呋喃可成为具有稳定氧化态的有前景的p型材料。
