Vibrations of the Phenoxyl Radical

Abstract

Phenoxyl radical (C(6)H(5)O) was prepared photochemically in low-temperature argon matrices. The infrared absorption spectra were obtained for C(6)H(5)O and for the isotopically labeled species C(6)D(5)O and 1-(13)C(12)C(5)H(5)O. All but one IR-active fundamental vibrations were detected, most of them not previously observed. Combination of results from IR linear dichroism measurements on photooriented samples, determination of absolute IR intensities with the help of internal standards, analysis of isotopic shifts, and quantum chemical predictions (B3LYP/cc-pVTZ) led to a detailed assignment of phenoxyl radical vibrations. Significant frequency shifts are observed with respect to previously reported data based on resonance Raman studies in polar solutions. For some vibrations, these shifts reflect environment-induced structural changes, such as increase of the quinoid character of the phenoxyl radical in polar media. In particular, the frequency of the CO stretching vibration, readily observable in both IR and Raman experiments, is extremely sensitive to the environment and can thus be used to probe its polarity.

Observation of Mode‐Specific Vibrational Autodetachment from Dipole‐Bound States of Cold Anions

“…The frequencies for modes v 9 and v 18 are in good agreement with the prior infrared absorption measurements in argon matrices (v 9 = 977 cm À1 and v 18 = 635 cm À1 ). [29] However, the frequency we measured for v 10 is lower than the matrix value of 813 cm À1 , but in good accord with the calculated v 10 frequency. [31,35] At certain wavelengths the PE images and spectra are dramatically different, as shown in Figure 2, where the 0 0 0 transition is plotted as the origin so that the vibrational spacing in wavenumbers for the higher binding energy peaks can be directly read off the axis.…”

“…More importantly, in addition to the dominating v 11 vibrational progression, vibrational transitions with weak Franck-Condon factors are observed, that is, modes v 9 , v 10 , and v 18 and their combination bands with mode v 11 . The modes v 9 and v 10 are both totally symmetric with a 1 symmetry, [29,35] similar to mode v 11 , and are allowed transitions. However, mode v 18 has b 1 symmetry and its activity must be due to vibronic couplings, as observed recently in high-resolution PE imaging of other small polyatomic anions.…”

“…Its vibrational spectroscopy has been studied in solution and in argon matrices. [28,29] Photoelectron spectroscopy (PES) of the phenoxide anion (C 6 H 5 O À ) consists of an extensive vibrational progression in the v 11 mode. [30] A recent high-resolution PE imaging study of phenoxide yielded an accurate electron affinity (18 178 AE 7 cm À1 ) and a v 11 vibrational frequency (519 cm À1 ) for the phenoxy radical.…”

The Phenoxy/Phenol/Copper Cation: A Minimalistic Model of Bonding Relations in Active Centers of Mononuclear Copper Enzymes

“…Notwithstanding the fact that various phenol normal modes are complicated mixtures of several contributing internal coordinates we present a gross characterization of key normal modes relevant in the present context in Figure 6. Table 4 shows a comparison of recent experimental results of Spanget-Larsen et al [74] and computed results for the phenoxy radical.…”

Laboratory Optical Spectroscopy of the Phenoxy Radical as a Candidate for Diffuse Interstellar Bands

“…The electronically excited states of A B , and E B 2 1 have been characterized with absorption bands in the regions from 1140 nm to 1310 nm (Gunion et al 1992;Radziszewski et al 2001;Cheng et al 2008), 510 nm to 640 nm (Ward 1968;Pullin & Andrews 1982;Kesper et al 1991;Johnston et al 1993;Yu et al 1995;Radziszewski et al 2001;SpangetLarsen et al 2001), 370 nm to 400 nm (Porter & Wright 1955;Pullin & Andrews 1982;Kesper et al 1991;Radziszewski et al 2001;Spanget-Larsen et al 2001;Tonokura et al 2004), 270 nm to 300 nm (Porter & Wright 1955;Ward 1968;Kajii et al 1987;Berho & Lesclaux 1997;Platz et al 1998;Radziszewski et al 2001;Spanget-Larsen et al 2001;Bayrakceken et al 2003), and 220 nm to 250 nm (Kajii et al 1987;Berho & Lesclaux 1997;Platz et al 1998;Radziszewski et al 2001), respectively, where the z-axis isalong the C-O bond and the x-axis is perpendicular to the plane. Only the A B X B transitions show resolved vibrational structures (Johnston et al 1993;Radziszewski et al 2001;Spanget-Larsen et al 2001;Cheng et al 2008 transition. To compare this transition with DIBs, gas-phase, high-resolution observation of the transition is essential.…”