In Situ Spectroscopic, Electrochemical, and Theoretical Studies of the Photoinduced Host−Guest Electron Transfer that Precedes Unusual Host-Mediated Alkane Photooxidation

Abstract

In the unusual photooxidation of alkanes within the cavity of a self-assembled M(6)L(4) cage complex (1), the proposed reaction mechanism involves the generation of the host anion radical and guest cation radical via guest-to-host photoinduced electron transfer (PET). In the present study, the postulated host anion radical was elucidated by in situ IR spectroscopy. The difference IR spectrum before and after the irradiation of the clathrate complex 1a [symbol: see text] (2)(4) (2 = adamantane) features a dominant negative peak at approximately 1500 cm(-1), which is attributed to the decrease in the CN stretching vibration and thus indicative of the structural change in the triazine core of the cage. Electrochemical measurements and theoretical calculations show the remarkably great electron-accepting ability of the triazine core. These results strongly support the proposal of guest-to-host PET.