Photodissociation dynamics of chlorobenzene and 4‐fluoroiodobenzene in CCl4 probed using time‐resolved infrared spectroscopy

• Published in: Bulletin of the Korean Chemical Society Vol. 43; no. 4; pp. 529 - 537
• Main Authors: Park, Yejin, Park, Seongchul, Shin, Juhyang, Lim, Manho
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley‐VCH Verlag GmbH & Co. KGaA 01.04.2022; 대한화학회
• Subjects: intersystem crossing; phenyl radical; radical of phenyl derivatives; reaction dynamics in solution; time‐resolved vibrational spectroscopy; 화학
• ISSN: 1229-5949; 0253-2964; 1229-5949
• DOI: 10.1002/bkcs.12495

The dynamics of photoexcited chlorobenzene (PhCl) and 4‐fluoroiodobenzne (4‐FPhI) in CCl4 were investigated using time‐resolved infrared spectroscopy. When excited at 267 nm, 50% (70%) of the excited PhCl (4‐FPhI) dissociates the Cl (I) atom immediately, and the remaining molecules relax into the T1 state via intersystem crossing (ISC) with a time constant of 70–80 ps. About half of the dissociated halogen atoms geminately recombine with the nascent radical with a time constant of 100–150 ps, reducing the number of generated radicals that are available to react with other reaction partners. The remaining radicals also recombine with the dissociated halogen atom on a timescale of tens of nanoseconds. Interestingly, the ISC of the light Cl‐atom‐involved PhCl was as efficient as that of the heavy I‐atom‐involved 4‐FPhI. Detailed photoexcitation dynamic studies of PhCl and 4‐FPhI can be utilized to understand the reaction dynamics of Ph and its derivatives. UV‐excited aryl halide dissociates halogen atom producing aryl radical or relaxes via a triplet state.