Tuning the separation and coupling of corannulene trianion-radicals through sizable alkali metal belts

Abstract

The first heterobimetallic sandwich-type aggregate formed by bowl-shaped corannulene trianion-radicals, C₂₀H₁₀˙³⁻, has been synthesized using mixed-metal reduction of C₂₀H₁₀. The product was crystallographically characterized to reveal the self-assembly of [Cs⁺//(C₂₀H₁₀³⁻)/4K⁺/(C₂₀H₁₀³⁻)//Cs⁺], in which two triply-charged corannulene decks encapsulate a rectangle of four potassium ions (the K⋯K separations are 4.212(4) and 5.185(4) Å), with the exterior concave bowl cavities being selectively filled by one cesium ion each. In order to provide insights into the geometrical features and electronic structure of this novel mixed-metal organometallic self-assembly, an in-depth theoretical investigation has been carried out. Specifically, the influence of internal metal binding on the geometry and magnetic coupling of C₂₀H₁₀˙³⁻ radicals is investigated for Group 1 metals. This study reveals that replacement of the sandwiched potassium ions with larger (Cs) and smaller (Li) ions allows variation of the size of the encapsulated metal belts, and thus enables tuning of the coupling of C₂₀H₁₀˙³⁻ radicals.