Visualizing host–guest co-assembly of π-expanded radialene macrocycle with C60

In this study, an electron-rich π-conjugated hexameric radialene macrocycle (HRM) was rationally designed and synthesized to function as a host for the encapsulation of electron-deficient fullerene C60. Owing to the combination of geometric complementarity and cavity size, the HRM selectively accommodated C60 both in solution and at the liquid/solid interface. UV-vis absorption spectroscopy revealed pronounced spectral variations upon the addition of C60, indicative of host-guest complexation in solution. Visual scanning tunneling microscopy imaging further corroborated the formation of a host-guest (HRM-C60) complex at the 1-phenyloctane/highly oriented pyrolytic graphite interface. Collectively, the theoretical calculations and the experimental results established HRM as an effective electron-donating host capable of binding C60 through noncovalent interactions.