Conformational Transformation in Squaric Acid Induced by Near-IR Laser Light

Lapiński, Leszek; Reva, Igor; Rostkowska, Hanna; Halasa, Anna; Fausto, Rui; Nowak, Maciej J.

doi:10.1021/jp402128g

Cited by 34 publications

(41 citation statements)

References 38 publications

(51 reference statements)

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“…In 2013, Nowak et al. trapped squaric acid in solid argon by matrix isolation techniques inducing conformational changes by using a near‐IR laser …”

Section: Introductionmentioning

confidence: 99%

“…In 2013, Nowak et al trapped squaric acid in solid argonb ym atrix isolation techniques inducing conformational changes by using an ear-IRlaser. [9] Squaric acid standsa sachallenging problem for high-resolution rotational studies, remaining unexplored in the isolation conditions of the gas phase. Fouriert ransform (FT) microwave spectroscopy is extremely sensitivet om olecular geometry and has been proved to be ac rucial tool in the conformational analysis.…”

Section: Introductionmentioning

confidence: 99%

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The Shape of the Archetypical Oxocarbon Squaric Acid and Its Water Clusters

Sanz-Novo

Alonso

León

2019

Chemistry A European J

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Herein, a full structural description is presented for the archetypical supramolecular synthone squaric acid (3,4‐dihydroxy‐3‐cyclobutene‐1,2‐dione), placed in the gas phase by laser ablation and characterized by chirped pulse Fourier transform microwave technique. Free from natural environmental disturbances, two different anti‐anti and syn‐anti planar forms and the corresponding water clusters have been revealed in a supersonic expansion. The substitution structure of the most stable anti‐anti conformer has also been extracted from the analysis of the rotational spectra of the 13C and 18O isotopic species in their natural abundance. The interplay between inter‐ and intramolecular interactions involving hydroxy and carbonyl groups has been analyzed by QTAIM (quantum theory of atoms in molecules) methods for squaric acid and its water clusters to understand their chemical behavior and further rationalize their role in the stabilization of these molecular systems.

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“…In 2013, Nowak et al. trapped squaric acid in solid argon by matrix isolation techniques inducing conformational changes by using a near‐IR laser …”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Shape of the Archetypical Oxocarbon Squaric Acid and Its Water Clusters

Sanz-Novo

Alonso

León

2019

Chemistry A European J

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“…In this approach, in situ vibrational excitation using narrowband laser light, tuned at a vibrational transition of a chosen conformer, consumes that form, which undergoes a conformational isomerization, while the populations of the other conformers remain intact. 39,40 As described in detail below, this strategy was applied successfully in this study to produce high-energy conformers of TAA, whose populations in the gas phase are negligible.…”

Section: Introductionmentioning

confidence: 99%

Tetrazole acetic acid: Tautomers, conformers, and isomerization

Araujo-Andrade

Reva

Fausto

2014

The Journal of Chemical Physics

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Monomers of (tetrazol-5-yl)-acetic acid (TAA) were obtained by sublimation of the crystalline compound and the resulting vapors were isolated in cryogenic nitrogen matrices at 13 K. The conformational and tautomeric composition of TAA in the matrix was characterized by infrared spectroscopy and vibrational calculations carried out at the B3LYP/6-311++G(d,p) level. TAA may adopt two tautomeric modifications, 1H- and 2H-, depending on the position of the annular hydrogen atom. Two-dimensional potential energy surfaces (PESs) of TAA were theoretically calculated at the MP2/6-311++G(d,p) level, for each tautomer. Four and six symmetry-unique minima were located on these PESs, for 1H- and 2H-TAA, respectively. The energetics of the detected minima was subsequently refined by calculations at the QCISD level. Two 1H- and three 2H-conformers fall within the 0-8 kJ mol(-1) energy range and should be appreciably populated at the sublimation temperature (∼330 K). Observation of only one conformer for each tautomer (1ccc and 2pcc) is explained in terms of calculated barriers to conformational rearrangements. All conformers with the cis O=COH moiety are separated by low barriers (less than 10 kJ mol(-1)) and collapse to the most stable 1ccc (1H-) and 2pcc (2H-) forms during deposition of the matrix. On the trans O=COH surfaces, the relative energies are very high (between 12 and 27 kJ mol(-1)). The trans forms are not thermally populated at the sublimation conditions and were not detected in matrices. One high-energy form in each tautomer, 1cct (1H-) and 2pct (2H-), was found to differ from the most stable form only by rotation of the OH group and separated from other forms by high barriers. This opened a perspective for their stabilization in a matrix. 1cct and 2pct were generated in the matrices selectively by means of narrow-band near-infrared (NIR) irradiations of the samples at 6920 and 6937 cm(-1), where the first OH stretching overtone vibrations of 1ccc and 2pcc occur. The reverse transformations could be induced by irradiations at 7010 and 7030 cm(-1), transforming 1cct and 2pct back to 1ccc and 2pcc, also selectively. Besides the NIR-induced transformations, the photogenerated 1cct and 2pct forms also decay in N2 matrices back to 1ccc and 2pcc spontaneously, with characteristic decay times of hours (1H) and tens of minutes (2H). The decay mechanism is rationalized in terms of the proton tunneling. In crystals, TAA exists exclusively as 1H-tautomer. By contrast, the tautomeric composition of the matrix-isolated monomers was found to consist of both 1H- and 2H-tautomers, in comparable amounts. A mechanistic discussion of the tautomerization process occurring during sublimation, accounting also for the observed minor decomposition of TAA leading to CO2 and 5-methyl-tetrazole, is proposed.

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“…This is the only case, where the isomerization back to the SSC conformer from the higher energy conformer is observed after near‐IR induced overtone excitation. The success of the SST formation in nitrogen matrix instead of the GAC and AAT is explained by the stabilization of the OCO c H dihedral angle of carboxylic acids to trans position in a nitrogen matrix . The SST conformer also observed to decay back to the SSC conformer via tunneling .…”

Section: Introductionmentioning

confidence: 99%

“…The success of the SST formation in nitrogen matrix instead of the GAC and AAT is explained by the stabilization of the O¼C-O c -H dihedral angle of carboxylic acids to trans position in a nitrogen matrix. [22][23][24][25][26] The SST conformer also observed to decay back to the SSC conformer via tunneling. [13] The tunneling reactions are typically slower in a nitrogen matrix than in rare gas matrices.…”

Section: Introductionmentioning

confidence: 99%

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

Ahokas

Kosendiak

Krupa

et al. 2018

J Raman Spectroscopy

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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.

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Conformational Transformation in Squaric Acid Induced by Near-IR Laser Light

Cited by 34 publications

References 38 publications

The Shape of the Archetypical Oxocarbon Squaric Acid and Its Water Clusters

The Shape of the Archetypical Oxocarbon Squaric Acid and Its Water Clusters

Tetrazole acetic acid: Tautomers, conformers, and isomerization

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

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