Cucurbituril Complexation Enhances Intersystem Crossing and Triplet Lifetime of 2,4,6-Triphenylpyrylium Ion

Abstract

The crystal structure of two host (cucurbituril, CB)−guest (2,4,6-triphenylpyrylium ion) complexes with 1:1 and 2:1 stoichiometries has been resolved by single-crystal X-ray diffraction and used to rationalize the drastic changes on the photochemistry of the 2,4,6-triphenylpyrylium ion upon encapsulation inside CB[8]. Photophysical data show that because of the influence of cucurbituril carbonyl groups and the conformational immobilization inside the capsule intersystem crossing quantum yields and triplet lifetimes are significantly increased for host−guest complexes of 2,4,6-triphenylpyrylium inside CB[7] and CB[8] with respect to solution.