Cis–trans isomerization equilibrium in hydroquinone in low-temperature argon and xenon matrices studied by FTIR spectroscopy

Akai, Nobuyuki; Kudoh, Shinzoh; Takayanagi, Motowo; Nakata, Munetaka

doi:10.1016/s0009-2614(02)00379-2

Cited by 50 publications

(62 citation statements)

References 24 publications

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“…This is several orders of magnitude a longer time than that found for the spontaneous rotation of the OH groups in compounds such as 1,4-dihydroxybenzene (hydroquinone). 33 The very substantial difference between the speed of the cis → trans tunneling transformation in 1,4-dihydroxybenzene and the time constant of the AH2 → AH1 tunneling in cytosine is obviously related with the depth of the minima of the forms in question and with the height of the barriers separating them. Although for both molecules the isomeric structures differ in rotation of an OH group by ∼180 • , AH1 and AH2 forms of cytosine are stabilized by an attractive interaction of the hydrogen atom of the OH group with the lone electron pairs of the vicinal nitrogen atoms, whereas in cis and trans isomers of 1,4-dihydroxybenzene this stabilizing interaction is replaced by repulsion with the positively loaded hydrogen atoms of the CH groups.…”

Section: Tunneling In the Dark: Conversion Of Ah2 Into Ah1mentioning

confidence: 99%

Spontaneous tunneling and near-infrared-induced interconversion between the amino-hydroxy conformers of cytosine

Reva

Nowak²,

Lapiński³

et al. 2012

The Journal of Chemical Physics

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Spontaneous and near-infrared/infrared (NIR/IR)-induced interconversions between two amino-hydroxy conformers of monomeric cytosine have been investigated for the compound isolated in a low-temperature argon matrix. Combined use of a laser source (which provides narrowband NIR radiation) and a broadband NIR/IR source of excitation light allowed a detailed investigation of mutual conversions of the two conformers in question. The experiments carried out within the current work demonstrated that upon broadband NIR/IR irradiation (with the IR source of FTIR spectrometer) the population ratio of the two amino-hydroxy conformers changes towards a ratio corresponding to a photostationary state. Evolution of the conformer population ratio towards the photostationary ratio occurred independent of the initial ratio of conformers, which could be prepared by a population shift (in favor of one of the forms) induced by narrowband NIR excitation. Moreover, spontaneous tunneling conversion of the higher-energy conformer into a lower-energy form was observed for cytosine isolated in a low-temperature argon matrix kept in the dark. This process is slow and occurs on a time scale of days. The tunneling process, studied for matrix-isolated cytosine, clearly follows a dispersive type of kinetics rather than the classical monoexponential kinetics.

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Section: Tunneling In the Dark: Conversion Of Ah2 Into Ah1mentioning

confidence: 99%

Spontaneous tunneling and near-infrared-induced interconversion between the amino-hydroxy conformers of cytosine

Reva

Nowak²,

Lapiński³

et al. 2012

The Journal of Chemical Physics

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“…The recently published studies on formic acid have further emphasized the importance of tunneling in the isomerization reactions [19,20]. Additionally, isomerization studies performed on hydroquinone and on a halogenated derivative of dihydroxy-benzoquinone isolated in argon matrices [21,22] seem to indicate that the participation of tunneling in isomerization processes involving mainly motion of hydrogen atoms is quite general. Solid-state medium is expected to influence the tunneling rate [23][24][25], which depends also on the temperature due to the participation of the lattice phonons in a dissipative tunneling mechanism [26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Infrared-induced conformational interconversion in carboxylic acids isolated in low-temperature rare-gas matrices

Maçôas

Khriachtchev

Pettersson

et al. 2004

Vibrational Spectroscopy

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An overview of our recent studies dealing with infrared-induced conformational interconversion of carboxylic acids isolated in rare-gas matrices is presented. Extensive rotational photoisomerization studies have been performed on formic acid, which is the simplest organic acid enabling this kind of processes. Formic acid has two conformers and interconversion between them can be induced by vibrational excitation. As such, it is an ideal model system to study the conformational dynamics of the carboxylic group. Formic acid molecules were found to be isolated in different local environments within the rare-gas matrices, as shown by the site splitting of the vibrational bands. Narrowband tunable infrared (IR) radiation was used to induce site-selective isomerization processes. The induced changes in the IR absorption spectra allowed for a detailed analysis of the vibrational properties of both conformers of formic acid isolated in solid argon. In particular, derived from the intermode coupling constants the local environment was shown to affects the intramolecular potential energy surface. Tunneling is involved in the rotamerization of formic acid, with the tunneling rate being affected by the local environment. Additionally, formic acid exhibits isomer-selective photodissociation where narrowband IR excitation can control the conformer-dependent photodissociation channels. Tunable IR radiation was also used to promote rotamerization in a series of matrix-isolated dicarboxylic acids (ethanedioic, propanedioic, and 2-butenedioic acids) by exciting the first overtone of the O-H stretching mode or a suitable combination mode at similar energies. Efficient isomerization involving rotation around the C-O bond was observed in most cases whereas the internal rotation around the C-C bond was found to be constrained for ethanedioic and (Z)-2-butenedioic acids. #

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“…Dihydroxybenzenes, as representatives of a broad class of flexible molecules with two non-coaxial internal tops of low symmetry, having considerable practical importance [1,2], have been the subject of many spectral studies [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and also quantum chemical calculations at different levels [8,14,[17][18][19][20][21][22][23][24][25]. Nevertheless, the problem of interpretation of the torsional IR and Raman spectra of dihydroxybenzenes in the 100-500 cm -1 region is far from resolved.…”

mentioning

confidence: 99%

“…The hydroquinone (1,4-dihydroxybenzene) molecule has two (A (trans) and B (cis)) stable, nonequivalent (C 2h and C 2v ) rotamers [16]. There is no unified opinion in the literature concerning the heights of the potential barriers separating the trans and cis conformers of hydroquinone.…”

mentioning

confidence: 99%

“…The wavefunctions now are localized in one of the minima without appreciable penetration into the other minimum, which also ensures relative stabilization of the rotamers of the molecule when the difference between the energies of the cis and trans configurations is very slight (according to ab initio calculations [20,21,28], ∆E = E B -E A = 10-40 cm -1 ) and a completely surmountable potential barrier. Note that the possibility of such stabilization was discussed in [16].…”

mentioning

confidence: 99%

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Calculation of transition intensities for torsional vibrations in IR and Raman spectra of dihydroxybenzenes

et al. 2007

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Cis–trans isomerization equilibrium in hydroquinone in low-temperature argon and xenon matrices studied by FTIR spectroscopy

Cited by 50 publications

References 24 publications

Spontaneous tunneling and near-infrared-induced interconversion between the amino-hydroxy conformers of cytosine

Spontaneous tunneling and near-infrared-induced interconversion between the amino-hydroxy conformers of cytosine

Infrared-induced conformational interconversion in carboxylic acids isolated in low-temperature rare-gas matrices

Calculation of transition intensities for torsional vibrations in IR and Raman spectra of dihydroxybenzenes

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