Clamshell opening in the mixed-metal supramolecular aggregates formed by fourfold reduced corannulene for maximizing intercalated metal content

The first members of a new class of supramolecular organometallic compounds with mixed-alkali-metal cluster cores, LiK₅ and Li₃K ₃, sandwiched between two four-fold reduced corannulene decks are prepared and fully characterized. The triple-decker supramolecular anions, [(C₂₀H₁₀^4-)(LiK₅) ⁶⁺(C₂₀H₁₀^4-)]^2- and [(C₂₀H₁₀^4-)(Li₃K₃) ⁶⁺(C₂₀H₁₀^4-)]^2-, illustrate a record ability of bowl-shaped and highly charged corannulene to provide all its sites, five benzene rings fused to a central five-membered ring, for binding of six alkali-metal ions. The previously unseen engagement of the hub-site of C₂₀H₁₀^4- in lithium binding is accompanied by unprecedented shifts up to -24 ppm in ⁷Li NMR spectra. The discussion of product formation mechanism, augmented by calculations, is provided. Pearls in a clamshell: A new class of supramolecular organometallic compounds with mixed-alkali-metal clusters, LiK₅ and Li ₃K₃, sandwiched between two highly reduced corannulene decks have been prepared and characterized. They show a coordination record for corannulene tetraanions able to bind six alkali-metal ions. Previously unseen engagement of the hub-site of C₂₀H₁₀^4- in lithium binding is accompanied by unprecedented shifts up to -24 ppm in ⁷Li NMR spectra.