Hydrogen atom dislocation in the excited state of anthranilic acid: probing the carbonyl stretch fundamental and the effects of water complexation

Abstract

This paper describes further efforts to understand the excited state hydrogen atom dislocation of anthranilic acid. Resonant ion-dip infrared spectroscopy was used to probe the carbonyl stretch fundamental in both the ground and excited states in an effort to observe the excited state behavior of the heavy atoms surrounding the displaced hydrogen. A small peak in the excited state infrared spectrum was tentatively assigned to the carbonyl stretch fundamental, shifted 80 cm⁻¹ to the red of its position in the ground state, indicative of a significant weakening of the CO bond. CASSCF calculations on a prototypical system, 3-amino-2-propenoic acid, were carried out to aid interpretation of vibrational frequencies and intensities. The effects of water complexation on the excited state hydrogen atom dislocation were also investigated. The vibronic spectrum, acquired by resonant two-photon ionization, displayed similar features as the monomer spectrum, as well as a progression in a low frequency intermolecular vibration. The infrared spectrum of the water complex, supported by density functional theory calculations, established that the water binds between the carbonyl oxygen and the acid hydrogen. The NH stretch fundamentals of the water complex in the ground and excited state were quite similar to those of the monomer, indicating complexation to water has little effect on the hydrogen atom dislocation