Functionalized Corannulene Carbocations: A Structural Overview

A detailed structural overview of a family of bowl‐shaped polycyclic aromatic carbocations of the type [C 20 H 10 R] + with different R functionalities tethered to the interior surface of corannulene (C 20 H 10 ) is provided. Changing the identity of the surface‐bound groups through alkyl chains spanning from one to four carbon atoms and incorporating a different degree of halogenation has led to the fine tuning of the bowl structures and properties. The deformation of the corannulene core upon functionalization has been revealed based on X‐ray crystallographic analysis and compared for the series of cations with R=CH 3 , CH 2 Cl, CHCl 2 , CCl 3 , CH 2 CH 3 , CH 2 CH 2 Cl, and CH 2 CH 2 Br. The resulting carbocations have been isolated with several metal‐based counterions, varying in size and coordinating abilities ([AlCl 4 ] − , [AlBr 4 ] − , [(SnCl)(GaCl 4 ) 2 ] − , and [Al(OC(CF 3 ) 3 ) 4 ] − ). A variety of aggregation patterns in the solid state has been revealed based on different intermolecular interactions ranging from cation–anion to π–π stacking and to halogen⋅⋅⋅π interactions. For the [C 20 H 10 CH 2 Cl] + ion crystallized with several different counterions, the conformation of the R group attached to the central five‐membered ring of corannulene moiety was found to depend on the solid‐state environment defined by the identity of anions. Solution NMR and UV/Vis investigations have been used to complement the X‐ray diffraction studies for this series of corannulene‐based cations and to demonstrate their different association patterns with the solvent molecules.