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Placing Metal in the Bowl: Does Rim Alkylation Matter?

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posted on 04.01.2019, 19:21 authored by Andrey Yu. Rogachev, Shuyang Liu, Qi Xu, Jingbai Li, Zheng Zhou, Sarah N. Spisak, Zheng Wei, Marina A. Petrukhina
In-depth theoretical analysis of the consequences of methylation of the rim sites of corannulene is completed. The full set of derivatives ranging from parent C20H10 to fully substituted C20(CH3)10 has been evaluated, revealing consistent trends along the series. The controlled one-electron chemical reduction of selected methylated corannulenes, such as monomethyl- (C20H9(CH3)), sym-pentamethyl- (1,3,5,7,9-C20H5(CH3)5), and decamethylcorannulene (C20(CH3)10) has also been investigated. Cesium metal was used as a reducing agent to access endo complexes having cesium ion placed inside the concave cavity of the monoreduced bowls. Two products, [{Cs+(18-crown-6)}­{C20H9(CH3)}] (1) and [{Cs+(18-crown-6)}­{C20H5(CH3)5}] (2), have been crystallized in the presence of 18-crown-6 ether and crystallographically characterized to confirm the concave cesium ion coordination. The direct structural comparison of 1 and 2 with the complex of unsubstituted corannulene, [{Cs+(18-crown-6)}­{C20H10}] (3), has been conducted. Furthermore, the nature and strength of metal binding for the series of concave cesium complexes with methyl-substituted corannulene bowls has been evaluated using different theoretical methods.