Supramolecular complexation studies of [60]fullerene with calix[4]naphthalenes—a reinvestigation

Estimations of equilibrium or association constant (KASSOC) values reported by many other groups for the supramolecular complexation between [60]fullerene (‘C60’) with different macrocyclic hosts, in solvents such as toluene or carbon disulfide, for example, is often conducted by UV–vis absorption and/or 1H NMR spectroscopy. In this paper, the complexation behaviour of two calix[4]naphthalene hosts with C60 in toluene and carbon disulfide has been re-examined, using both of these methods. An analysis is presented of the data newly obtained, in light of recent advances and understanding published by others of the limitations of, in particular, the absorption spectroscopic methods. The discussion presented is also intended to aid those who may be unfamiliar with the nuances and limitations of the analytic models involving C60 supramolecular complexation. Also presented is a general mechanism for C60 supramolecular complexation studies, which lay the groundwork for further experiments.