High vibrational overtone excitation‐induced conformational isomerization of glycolic acid in solid argon matrix

Abstract

The high overtone‐induced isomerization of glycolic acid in a low‐temperature argon matrix was investigated using Raman spectroscopy. The Raman spectrum of glycolic acid is presented, and the spectral assignment is supported by vibrational anharmonic calculations. The high overtone excitation of the lowest energy conformer (SSC) at 532 nm induced direct conformational isomerization to higher energy conformers (GAC and AAT). Furthermore, upon excitation at 532 nm GAC and AAT isomerized back to SSC and photo‐induced equilibrium was observed between the conformers. Kinetic model was used to describe the observed isomerization and isomerization rate constants were obtained. No experimental evidence of isomerization between GAC and AAT nor other higher energy conformers were observed.

Recent advances in linear and nonlinear Raman spectroscopy. Part XIII

“…Ahokas et al described their study on high vibrational overtone excitation‐induced conformational isomerization of glycolic acid in solid argon matrix . Brambilla and co‐workers synthesized regio‐regular poly(3‐hexylthiophene‐2,5‐diyl) selectively deuterated on the main chain backbone and/or on the hexyl side chain giving the opportunity to record IR and Raman spectra and to carry out a spectroscopic study supported by density functional theory calculations .…”

Complexes of Glycolic Acid with Nitrogen Isolated in Argon Matrices. II. Vibrational Overtone Excitations

“…Experimental IR positions of SSC νOH A and νOH C is 3561.0; GAC: νOH A 3648.0; νOH C 3563.0; AAT: νOH A 3670.0; νOH C 3473.0 cm −1 . Experimental Raman spectra positions of SSC νOH A and νOH C is 3566.0; GAC: νOH A 3652.0, νOH C 3568.0; AAT: νOH A 3675.0, νOH C 3478.0 cm −1 [12].…”

“…The concept of near-infrared photochemistry was suggested by Donaldson et al [1], for example, to describe OH-containing species such as HONO, HNO 3 , carboxylic acid, or alcohols absorbing NIR or visible radiation via vibrational overtones of the OH stretching mode that induced rotamerisation or even dissociation of the molecule. Up-to-now, the majority of overtone excitation studies has been reported for carboxylic acids [4,5,6,7,8,9,10,11,12,13]. As follows, glycolic acid (GA), the smallest α-hydroxycarboxylic acid, is also an advantageous object for such studies due to the presence of two hydroxyl groups with different surroundings in the same molecule.…”

“…Recently, we reported on conformational isomerisation of GA complex with nitrogen induced by high vibrational overtone excitation using green light (532 nm) in a study applying Raman spectroscopy [16]. On the contrary to the GA monomer, where both AAT and GAC conformers could be produced in argon matrices [4,6,12], only AAT…N 2 complexes were identified at the applied experimental conditions [16].…”

Complexes of Glycolic Acid with Nitrogen Isolated in Argon Matrices. I. Structures and Thermal Effects

“…As such, GA is a model species to study in order to understand how competing OH-groups in the molecule affect the chemical reactivity and capability to form molecular complexes. Several reports on monomeric GA isolated in low-temperature matrices as well as its transformations have appeared in the literature [15,16,17,18,19,20]. The structures of the three most stable GA species are presented in Figure 1.…”