Tautomer Selective Photochemistry in 1-(Tetrazol-5-yl)ethanol

Ismael, A.; Cristiano, Maria Lurdes Santos; Fausto, Rui; Gómez‐Zavaglia, Andrea

doi:10.1021/jp109215q

Cited by 22 publications

(21 citation statements)

References 59 publications

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“…If the molecule exhibits tautomerism, tautomer-selective photochemistry may take place. [19][20][21] The structural features that render tetrazolyl ethers excellent substrates for transfer hydrogenolysis may also influence their photochemistry. Among 1,5-disubstituted tetrazoles, 5-aryloxy-1-phenyltetrazoles appear to be especially interesting, since the central oxygen links an aromatic and an electron-withdrawing heteroaromatic system.…”

Section: Introductionmentioning

confidence: 99%

Structure, vibrational spectroscopy, and photochemistry of 5-phenoxy-1-phenyltetrazole in argon and nitrogen cryomatrices

et al. 2015

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The molecular structure, infrared spectra, and photochemistry of 5-phenoxy-1-phenyltetrazole (5PPT) isolated in argon and N 2 cryogenic matrices were investigated by infrared spectroscopy and theoretical calculations (DFT(B3LYP)/6-311++G(d,p)). Calculations yield two dissimilar minima on the potential energy surface of the molecule, both being eightfold degenerate by symmetry and belonging to the C 1 symmetry point group. Extensive analysis of the potential energy landscape of the molecule was performed. Upon consideration of the zero-point vibrational correction to the energy, the calculations predict that the higher energy minimum shall relax barrierlessly to the lower energy form, leading to conclude that the compound exists in a single conformer in the gas phase. Accordingly, a single conformer was observed and fully characterized spectroscopically upon isolation of the monomer of the compound in argon and nitrogen cryomatrices. UV-laser irradiation ( = 250 nm) of matrixisolated 5PPT leads to photocleavage of the tetrazole ring, with release of N 2 and formation of the corresponding carbodiimide.Résumé : La structure moléculaire, les spectres infrarouges et la photochimie de 5-phénoxy-1-phényltétrazole (5PPT) isolé dans des matrices cryogéniques de l'argon et de N 2 ont été étudiés par spectroscopie d'infrarouges et calculs théoriques (DFT(B3LYP)/ 6-311++G(d,p)). Les calculs donnent deux minima différents sur la surface d'énergie potentielle de la molécule, les deux étant de huit fois dégénéré par symétrie et appartenant au groupe de points de symétrie C 1 . Une analyse approfondie du paysage d'énergie potentielle de la molécule a été effectuée. Après examen des corrections du point zéro de vibration à l'énergie, les calculs prédisent que le minimum d'énergie plus élevée doit détendre sans barrière à la forme d'énergie plus faible, ce qui permet de conclure que le composé existe comme un seul conformère dans la phase gazeuse. En effet, un seul conformère a été observé, et caractérisé entièrement par spectroscopie, après l'isolement du monomère du composé dans des cryomatrices de l'argon et d'azote. Irradiation de 5PPT isolé en cryomatrice de l'argon avec laser UV ( = 250 nm) conduit à photoclivage de l'heterocicle tetrazole avec sortie de N 2 et production de la carbodiimide correspondante.

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Section: Introductionmentioning

confidence: 99%

Structure, vibrational spectroscopy, and photochemistry of 5-phenoxy-1-phenyltetrazole in argon and nitrogen cryomatrices

et al. 2015

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“…Tautomerism has been extensively studied in a great variety of azoles [5][6][7][8] as well as in other similar systems, including tetrazoles. [9][10][11][12][13][14][15][16][17][18][19][20][21][22] In these studies, the preference for a specific a) Author to whom correspondence should be addressed. Electronic mail: reva@qui.uc.pt tautomer or tautomers at different proportions, according to the physical state of the compound, has been established.…”

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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“…Ismail et al, 54 presented a very interesting study where tautomer selective photochemistry was observed for 1-(tetrazol-5-yl)ethanol . The potential energy surface landscapes of the 1H and 2H tautomers of the compound were investigated and the theoretical results were used to help characterize the conformational mixture existing in equilibrium in the gas phase prior to deposition of the matrices, as well as the conformers trapped in the latter.…”

Section: Fragmentation Reactions and Formation Of Complexes Or Weaklymentioning

confidence: 99%

“…18 Simplified scheme showing the observed photoprocesses resulting from UV irradiation (lW 200 nm) of matrix-isolated monomeric 1-(tetrazol-5-yl)ethanol. 54 tetrazole hydrogen to the oxygen atom of substituent. The ring-opening reaction then requires simultaneous cleavage of this bond (Fig.…”

Section: Fragmentation Reactions and Formation Of Complexes Or Weaklymentioning

confidence: 99%