Resonance Raman spectrum of the allyl-d5 radical and the force field analysis of the allyl radical

Abstract

Resonance Raman spectra of the allyl-d5 radical have been obtained with excitation between 247 and 223 nm. Analysis of the spectra yields the first observation of fundamental frequencies, ν4, ν5, and ν7 and overtone frequencies 2ν9, 2ν10, and 2ν12. The new vibrational data are combined with previously observed frequencies of allyl-h5 and allyl-d5 radical to produce the force field analysis for the allyl radical. This study suggests reassignment of several previously observed infrared (IR) bands. Experimental frequencies and assignments for allyl-h5 and allyl-d5 are compared with results from ab initio calculations. Force constants obtained in the present work are compared with the force constants of other sp2 hybridization molecules such as benzene, allene, and ethylene.

Photoelectron Spectroscopy of the Allyl and 2-Methylallyl Anions

“…The dominant mode observed in the spectra of 1 -and 1D -is ν 7 , the CCC bending mode in the allyl radicals. 17 The values obtained here are in excellent agreement with the values of 427 and 350 cm -1 recommended by Liu et al, 17 based on Raman and IR spectroscopy results. [13][14][15][16][17] Oakes and Ellison 29 obtained values of 395 and 380 cm -1 for these vibrational frequencies from their photoelectron spectra of the allyl and deuterated allyl anions, respectively.…”

“…17 A peak at 1600 cm -1 was also observed in the matrix IR spectrum of allyl radical, 10 and was similarly assigned. The ν 11 fundamental is the most intense peak in the IR spectrum of the allyl radical, [8][9][10][11] with a vibrational frequency of 801 cm -1 .…”

“…The 990 cm -1 vibrational mode (peak D) most likely corresponds to ν 6 of allyl radical, a mixture of symmetric CCC stretching motion, CH 2 scissoring, and CH 2 rocking. 17 This mode has previously been assigned to be 1068 cm -1 by Liu et al 17 on the basis of the results of Table 2. Table 2. resonant Raman spectroscopy studies.…”

Exploring the Excited-State Dynamics of Hydrocarbon Radicals, Biradicals, and Carbenes Using Time-Resolved Photoelectron Spectroscopy and Field-Induced Surface Hopping Simulations

“…The allyl radical is one of the simplest resonance-stabilized hydrocarbons and an important model for the spectroscopy and dynamics of radicals . It is therefore not surprising that it has aroused considerable interest over the years, which resulted in numerous experimental investigations, employing methods such as ESR, IR, Raman, − rotational and rovibrational spectroscopy, , electron diffraction, multiphoton ionization (MPI), ,− and photoelectron spectroscopy. − In parallel, a multitude of theoretical studies has also been performed, covering fundamental aspects such as electron delocalization, spin density distribution, or wave function stability as well as investigating the vibrational spectra, − excited electronic states, − and photochemical reactions . Here we will focus on the influence of a methyl group on the excited-state dynamics by comparing the allyl radical with its 1- and 2‑methylated counterparts (1MA & 2MA).…”

Molecular Spectroscopy at Low Temperatures: A High Resolution Infrared Retrospective

“…It has been theoretically investigated since the 1950s, and experimentally studied by a variety of techniques ranging from ESR 133,139 and electron diffraction 140 to matrix isolation, 141 resonantly enhanced multiphoton ionization (REMPI) 142 and resonance Raman. 143 The first high-resolution infrared study of the CH 2 symmetric wagging mode of the allyl radical was performed by Hirota and co-workers in 1992. 144 However, due to room temperature Doppler broadening and diode laser frequency noise, the excess line widths observed in this ν 11 band were simply attributed to unresolved splitting from spin-rotation interaction.…”