Anion photoelectron spectroscopy of deprotonated ortho-, meta-, and para-methylphenol

Abstract

The anion photoelectron spectra of ortho-, meta-, and para-methylphenoxide, as well as methyl deprotonated meta-methylphenol, were measured. Using the Slow Electron Velocity Map Imaging (SEVI) technique, the Electron Affinities (EAs) of the o-, m-, and p-methylphenoxyl radicals were measured: 2.1991 ± 0.0014, 2.2177 ± 0.0014, and 2.1199 ± 0.0014 eV, respectively. The EA of mmethylenephenol was also obtained, 1.024 ± 0.008 eV. In all four cases, the dominant vibrational progressions observed are due to several ring distortion vibrational normal modes that were activated upon photodetachment, leading to vibrational progressions spaced by ~500 cm -1 . Using the

Anion photoelectron spectroscopy of deprotonated indole and indoline

“…This behavior has been observed in aromatic anion photoelectron spectroscopy previously. 43,44,47,49 Both of these observations are intuitively understandable. Indolide will have the excess charge density primarily localized about the nitrogen group.…”

“…This variation must be due to electron autodetachment in competition with direct photodetachment, a behavior that has been observed in other aromatic systems. 47,[49][50][51] This conclusion is borne out in excited state quantum chemical calculations (TD-DFT) of the indolide anion which predict 9 optically accessible electronic states with term energies ranging from 2.5 to 3.6 eV above the ground vibronic state energy. Due to the density of the available states and the inherent complexity of autodetachment, it is beyond the scope of this work to further investigate this phenomenon theoretically.…”

“…Additionally, this behavior has been observed for many other aromatic anions when photoelectron angular distributions were obtained. 47,49 Upon electron photodetachment from indolide, several vibrational modes are excited; the eigenvectors associated with these vibrational modes may be found in the supplementary material. All of the modes that are activated upon photodetachment share two characteristics.…”

Photoelectron spectroscopy and thermochemistry of o-, m-, and p-methylenephenoxide anions

“…In each case, the primary product arises from deprotonation of the hydroxyl group, generating methylphenoxide. This product has been previously studied via PES, 46 where the photodetachment from methylphenoxide produces signal that spans from approximately 2.1 to 2.7…”

“…[36][37][38][39][40][41][42][43][44][45] Much of their behavior is well understood, and thus they are used as model systems in studies ranging from catalysis to ionic liquids. While a wealth of information exists on cresols, including our own work on methylphenoxide anions and methylphenoxyl radicals, 46 methylenephenoxides are not yet well understood and present an opportunity to study distonic radical anions and diradicals by way of photodetachment. This work is a joint effort across three different experimental setups, using both pulsed and continuous anion PES, as well as FA-SIFT mass spectrometry in conjunction with the acid bracketing procedure.…”