Impact of Molecular Geometry and Functionalization on Solution Complexation of Coronene-Based Buckybowls and Fullerenes

Contorted polycyclic aromatic molecules, such as corannulenes and sumanenes, have been studied as host molecules for fullerenes due to their complementary geometries. It has been suggested that stronger associations with fullerenes can be attained by extending their π surface or by incorporating heteroatoms, as unsubstituted corannulene and sumanene do not readily complex with fullerenes in solution. Here, we design and synthesize π-extended buckybowls derived from contorted hexabenzocoronene and pentabenzocoronene with either pentyl or butoxy side chains. These coronene-based buckybowls have approximately twice the π surface compared to unsubstituted corannulene and sumanene. Buckybowls with pentyl side chains complex with C₆₀ in a preferred 1:1 buckybowl-to-C₆₀ stoichiometry, with association constants on the order of 10³ M^-1. Complexation with C₆₀ further strengthens with the addition of heteroatoms in buckybowls bearing butoxy side chains. We find a preferred 1:2 association stoichiometry with fullerene and association constants on the order of 10⁴ M^-1. Density functional theory calculations suggest the larger dipole moment on the butoxy-substituted buckybowls relative to their pentyl-substituted counterparts is responsible.