Synthesis and Properties of Bis-corannulenes

Corannulenecarbaldehyde and corannulenylmethyl triphenylphosphonium bromide are combined through the Wittig olefination reaction to furnish dicorannulenylethene with 70% yield. A subsequent oxidative photocyclization leads to annulation of the corannulene nuclei to produce a C₄₂H₁₈ nanographene structure in 59% yield. Interestingly, only the trans isomer of the dicorannulenylethene forms cocrystals with fullerene C₆₀ through concave–convex and convex–convex π–π stacking interactions. The Mallory photocyclization could be extended to a phenanthrene-based diarylethene precursor to yield a large bicorannulene system.