Placing Metal in the Bowl: Does Rim Alkylation Matter?

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.