Photodetachment of Deprotonated R-Mandelic Acid: The Role of Proton Delocalization on the Radical Stability

F. L. MOLINA; R. A. JARA-TORO; J. A. NOBLE; C. DEDONDER-LARDEUX; C. JOUVET; G. A. PINO

Chemphyschem

WILEY-V C H VERLAG GMBH

Año: 2022 p. 1 - 8

1439-4235

The photodetachment and stability of R-Mandelate, the deprotonated form of the R-Mandelic acid, was investigated by observing the neutral species issued from either simple photodetachment or dissociative photodetachment in a cold anions set-up. R-Mandalate has the possibility to form an intramolecular ionic hydrogen-bond between adjacent hydroxyl and carboxylate groups. The potential energy surface along the proton transfer (PT) coordinate between both groups (O-?H+?-OCO) features a single local minima, with the proton localized on the O- group (OH?-OCO). However, the structure with the proton localized on the ?OCO group (O-?HOCO) is also observed because it falls within the extremity of the vibrational wavefunction of the OH?-OCO isomer along the PT coordinate. The stability of the corresponding radicals, produced upon photodetachment, is strongly dependent on the position of the proton in the anion: the radicals produced from the OH?-OCO isomer decarboxylate without barrier, while the radicals produced from the O-?HOCO isomer are stable.