(Iso)Pagodane Radical Cations in Liquid Hydrocarbons: 'Time-Resolved Fluorescence-Detected Magnetic Resonance' Study of Valence Isomeric Radical Cations

摘要

The "tight" (T), cyclobutanoid, and the "extended" (E), pi-complex-like, four-centered--three-electron radical cations (4c/3e) derived from (iso)pagodanes and from the valence isomeric (iso)dienes can be viewed as well-separated stationary points on the reaction coordinate for the ethylene/ethylene radical cation [2 + 1] cycloaddition. So far, experimentally verified examples (ESR, CV, PE) are the extended [1.1.1.1] (2~+) and iso-[2.2.1.1] (4+) ions, persistent in fluid solution at room temperature,and the tight iso-[1.1.1.1]~(+6) and [2.2.1.1]~+ ions, observable only in Freon rnatrix (CFClj, y-rays, 77 K).7 According to calculations, these are the therrnodynamically more stable ones of the respective pairs of valence isomers.