Raman spectroscopy of glycolic acid complexes with N2

Abstract

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

“…This indicates the presence of an additional unstable site. Similar conclusions were drawn for bands observed during the Raman spectroscopy study [16] of the GA/N 2 /Ar matrices (see Table 1).…”

“…The first question to answer is whether both AAT and GAC complexes with N 2 are formed in the irradiated/annealed matrices. This question is particularly relevant in the context of the recently published results of the GA…N 2 complexes studied by Raman spectroscopy [16], which indicate that only the AAT…N 2 complex is present in argon matrices. The analysis of the νC=O region of the GA/N 2 /Ar matrices obtained upon irradiation at 1438, 1440, and 1442 nm (Figure S2 and Table S2 in Supporting Information) reveals that both AAT (1806 cm −1 ) and GAC (1784 cm −1 ) carbonyl stretching vibrations were disturbed by the presence of nitrogen, as shown by broadening/shift of the corresponding monomer νC=O bands.…”

“…Also, back reactions were observed. In turn, the high overtone excitation at 532 nm probed in conjunction with Raman spectroscopy [16] induced direct conformational isomerization to both higher energy conformers, GAC and AAT. In the same study, GAC and AAT were found to isomerize back to SSC, resulting finally to photo-induced equilibrium between the conformers.…”

“…Although the overtone-induced isomerisation of the monomeric GA is relatively well known, reports on isomerisation processes upon NIR radiation of its molecular complexes and the influence of complexation on these processes are scarce. 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

“…All of these dimers were formed between SSC conformers: one dimer with hydrogen bonds between the two carboxylic OH groups, one structure with hydrogen bonds between the two alcoholic OH groups and a mixed structure with one OH group from the carboxylic group acting as proton donor and the alcoholic OH group on the other subunit acting as proton acceptor. Molecular complexes between GA and molecular nitrogen were identified in a study applying Raman spectroscopy for argon-trapped species upon high vibrational excitation experiments [22]. In that study, nitrogen was found to form complexes with two GA conformers (SSC and AAT) in low temperature argon environment.…”