A capsule-like cage molecule was constructed by dimerization of pyridine-containing homooxacalixaryl esters utilizing a Pd(II)-pyridine interaction. Interestingly, it was found that this molecule can include fullerene in the inner cavity and the exchange rate is slower than the 1H and 13C NMR time-scales, giving rise to new separate NMR peaks assignable to the capsulefullerene complex. From the integral intensity ratio the association constant (K(ass)) was estimated to be 39 dm3 mol-1 (at 30°C). The Δδ(H) between H(ax) and H(eq) in the ArCH2O methylene protons gave a sign that when Li+ cations are bound to the ionophoric lower rims, the capsule molecule is changed to a more flattened conformation which is more suitable to fullerene inclusion. This Li+-induced preorganization enhanced the K(ass) up to 2100 dm3 mol-1(at 30°C). Thus, the present study is the first example that fullerene is included in a capsule-like cage molecule and the exchange rate appears to be the slower than the NMR time-scales.
All Science Journal Classification (ASJC) codes
- Drug Discovery
- Organic Chemistry