Transient intermediates in the photolysis of iodonium cations

• Published in: Canadian journal of chemistry Vol. 65; no. 10; pp. 2342 - 2349
• Main Authors: Devoe, R. J, Sahyun, M. R. V, Serpone, N, Sharma, D. K
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.10.1987; National Research Council of Canada
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Solvent effect; Organic cation; Iodonium compounds; Radical mechanism; Visible radiation; Benzenic compound; Chemical decomposition; Counter ion; Pulse photolysis; Aqueous solution; Flash photolysis; Laser photolysis
• ISSN: 0008-4042; 1480-3291
• DOI: 10.1139/v87-391

Pulsed picosecond laser photolysis of the diphenyliodonium cation indicates that excitation of the allowed transition is followed by rapid (ps) deactivation to a homolytically dissociative state, presumably T 1 . Steady-state photolysis yields iodobenzene and biphenyl from the primary radical products. Iodobiphenyl is also observed. We infer in-cage recombination of these radical products, with intervention of a carbocationic intermediate. Laser flash photolysis of diphenyliodonium iodide in its charge transfer band yields an initial transient with a lifetime of ca. 200 ps. A strongly absorbing secondary transient is observed on the nanosecond time scale. Iodobenzene is the exclusive reaction product. We infer that it is not formed directly from the primary photoproduct, but through in-cage recombination of phenyl cation with iodide anion, as in benzenediazonium iodide.