Electronic states of the phenoxyl radical

Abstract

The phenoxyl radical and two of its isotopomers were investigated by UV-VIS and IR polarization spectroscopy of molecular samples immobilized in cryogenic argon matrices. Analysis of the combined electronic and infrared linear dichroism data led to determination of absolute transition moment directions and symmetry assignments for four low-lying excited electronic states. The bands observed at 16 000, 25 200, 33 900, and 41 800 cm−1 were assigned to A12, B12, A12, and B12 π–π* states, respectively. A very weak transition observed in the near-infrared close to 8900 cm−1 was assigned to an optically forbidden B22 n–π* state. The electronic transitions predicted by time dependent density functional theory (TD-UB3LYP/cc-pVTZ) were in good agreement with the observed transitions.

An Unprecedented Bridging Phenoxyl Radical in Dicopper(II) Complexes: Evidence for an S=3/2 Spin State

“…+ and 2 . + exhibit similar UV/Vis features: π–π* transitions typical of phenoxyl radicals12 are observed at 440 nm (3330 M −1 cm −1 ) and 600 nm (560 M −1 cm −1 ) for 1 . + (Figure 2), and at 445 nm (4730 M −1 cm −1 )13 and 600 nm (1000 M −1 cm −1 )13 for 2 .…”

Substituent Effects in the Absorption Spectra of Phenol Radical Species: Origin of the Redshift Caused by 3,5‐Dimethoxyl Substitution

“…Similar orbitals were selected for the substituted phenol radical cations, but the active space was augmented by additional lone pair orbitals for oxygen-containing substituents and pseudo-p orbitals for methyl groups. Hence, an [11,9] active space was used for o-, m-and p-methoxyphenol radical cations, a [15,12] active space for 3,5-, 3,4-, 2,6-and 2,5-dimethoxyphenol radical cations, a [9,7] active space for the p-methylphenol radical cation and a [13,10] active space for the 2-methoxy-4-methyl phenol radical cation.…”

“…Spectroscopic studies on phenyl-, alkyl-, hydroxyl-and halogensubstituted phenoxyl radicals were then carried out to determine their basicity (8) and dimerization rate constant (9). Further studies based on electronic and vibrational absorption spectroscopies, as well as electron spin resonance (ESR) spectroscopy, characterized the nature of their electronic states (10)(11)(12), their vibrational spectral signature (13), their kinetics of formation (14,15) and decay (16,17), and their acid-base and redox properties in solution (18). In recent decades, phenoxyl radicals have also been the subject of intense computational research to investigate their ground-state equilibrium geometries (19,20), vibrational frequencies (12,(19)(20)(21)(22)(23), electronic structures (10,12,22,24), ionization potentials (25) and spin-dependent properties (19,20).…”

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

“…Thus, the four observed peaks were attributed to the phenoxy radical. The first peak around 15,800 cm −1 was assigned to the peak that included the origin band, based on the matrix spectrum reported (Radziszewski et al 2001).…”

“…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.…”