Inclusion of [60]fullerene in a self-assembled homooxacalix[3]arene-based dimeric capsule constructed by a Pd-II-pyridine interaction. The Li+-binding to the lower rims can improve the inclusion ability

摘要

A capsule-like cage molecule was constructed by dimerization of pyridine-containing homooxacalix[3]aryl esters utilizing a Pd-II-pyridine interaction. Interestingly, it was found that this molecule can include [60]fullerene in the inner cavity and the exchange rate is slower than the H-1 and C-13 NMR time-scales, giving rise to new separate NMR peaks assignable to the capsule[60]fullerene complex. From the integral intensity ratio the association constant (K-ass) was estimated to be 39 dm(3) mol(-1) (at 30 degrees C). The Delta delta 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 [60]fullerene inclusion. This Lit-induced preorganization enhanced the K-ass up to 2100 dm(3) mol(-1) (at 30 degrees C). Thus, the present study is the first example that [60]fullerene is included in a capsule-like cage molecule and the exchange rate appears to be the slower than the NMR time-scales. (C) 2000 Elsevier Science Ltd. All rights reserved. [References: 38]