Photophysical Properties of Naphthalene-oxacalix[ m ]arene and Recognition of Fullerene C 60 .

Three different pore sizes of oxacalix[ m ]arene[ n ]pyrimidines modified with a naphthalene substituent were synthesized and characterized by HRMS, 1 H NMR, and single-crystal analysis ( 8OA and 8OA-N ). Steady-state spectroscopy indicates these naphthalene-oxacalix[ m ]arenes exhibit good fluorescence properties, which isattributed to the locally excited (LE) state emission, and electrochemical results show that the photoinduced electron transfer (PET) process occurs from the naphthalene substituent to the linked pyrimidine. Nanosecond transient absorption spectra, singlet oxygen quantum yields (Φ Δ 4OA-N = 45.1%, Φ Δ 6OA-N = 56.6%, and Φ Δ 8OA-N = 65.7%) and theoretical calculations demonstrate that the torsion angle between the donor (naphthalene) and the acceptor (pyrimidine) promotes intersystem crossing (ISC), and the lifetime of the triplet state reaches ca. 8 ms. Interestingly, all three host molecules ( 4OA-N , 6OA-N , and 8OA-N ) showed a high affinity for fullerene C 60 , and significant binding constants in the range of 4.10-6.68 × 10 4 M -1 were obtained by fluorescence titration; in contrast, previous reports indicated that the similar oxacalix[ m ]arene[ n ]pyrimidine scaffold could not efficiently complex with C 60 . In the frontier molecular orbital theory calculations of the supramolecular system of 4OA-N@C 60 , the HOMO is distributed on 4OA-N and the LUMO is localized on fullerene. The calculation results further demonstrated that there are strong interactions between the host and the fullerene guest, which is consistent with the result of the experiments. The characteristic photophysical properties of these novel naphthyl-decorated oxacalix[ m ]arene[ n ]pyrimidines broaden their application field, and the stable host-guest system with fullerene can be applied to supramolecular chemistry.