Supramolecular trap for a transient corannulene trianion.

The first structural characterization of the transient triply-reduced state of corannulene (CH) is accomplished. The X-ray crystallographic study reveals that the CH˙ trianions, generated by corannulene reduction with metallic cesium, form a novel type of supramolecular sandwich-type assembly, [Cs//(CH)/4Cs/(CH)//Cs]. In the product, two triply-charged corannulene decks encapsulate a rectangle of four cesium ions with the external concave bowl cavities being filled by one cesium ion each. The structural investigation is augmented by in-depth theoretical calculations to provide insights into the geometrical features and electronic structure of this unique organometallic self-assembly.