Photochemistry of acetylacetone isolated in parahydrogen matrices upon 266 nm irradiation

Lozada‐Garcia, Rolando Rafael; Čeponkus, Justinas; Chevalier, Michèle; Chin, W.; Mestdagh, J. M.; Crépin, C.

doi:10.1039/c2cp23913b

Cited by 17 publications

(45 citation statements)

References 22 publications

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“…The large red shift of νOD is due to the internal hydrogen bond. In particular, the OH stretching band of AcAcH8 was not clearly observed in neon matrices at 4 K. 14 One can see in Fig. 4 and Table I).…”

Section: A Acacd2 CCC Conformermentioning

confidence: 90%

“…1 -and seven open conformers * . 9,10,14,22,23 The highly stabilizing hydrogen bond interaction in the CCC form prevents isomerization in the electronic ground state and an electronic excitation is required to access to the open forms. 1, and are denoted XYZ, where letters X, Y and Z stand for C or T depending on the cis or trans positions of the groups around the C-C, C=C and C-O bonds, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…10,11,21 They are obtained by rotations around three bonds, two CC bonds and one CO bond as shown in Fig. 11,14,[24][25][26] Photo-isomerization in matrices was probed in previous works by electronic and vibrational spectroscopy. The chelated enol (CCC) is the most stable form and the only one observed in the gas phase.…”

Section: Introductionmentioning

confidence: 99%

“…1, and are denoted XYZ, where letters X, Y and Z stand for C or T depending on the cis or trans positions of the groups around the C-C, C=C and C-O bonds, respectively. 9,10,12,14,23 The stabilization of different open conformers depends on the host. In cryogenic matrices, it is also the most stable but several open conformers can be produced by UV irradiation.…”

Section: Introductionmentioning

confidence: 99%

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Double deuterated acetylacetone in neon matrices: infrared spectroscopy, photoreactivity and the tunneling process

Gutiérrez-Quintanilla

Chevalier

Crépin

2016

Phys. Chem. Chem. Phys.

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The effect of deuteration of acetylacetone (C5O2H8) is explored by means of IR spectroscopy of its single and double deuterated isotopologues trapped in neon matrices. The whole vibrational spectra of chelated enols are very sensitive to the H-D exchange of the hydrogen atom involved in the internal hydrogen bond. UV excitation of double deuterated acetylacetone isolated in neon matrices induces the formation of four open enol isomers which can be divided into two groups of two conformers, depending on their formation kinetics. Within each group, one conformer is more stable than the other: slow conformer interconversion due to a tunneling process is observed in the dark at low temperature. Moreover, IR laser irradiation at the OD stretching overtone frequency is used to induce interconversion either from the most stable to the less stable conformer or the opposite, depending on the excitation wavelength. The interconversion process is of great help to assign conformers which are definitively identified by comparison between experimental and calculated IR spectra. Kinetic constants of the tunneling process at play are theoretically estimated and agree perfectly with experiments, including previous experiments with the totally hydrogenated acetylacetone [Lozada García et al., Phys. Chem. Chem. Phys., 2012, 14, 3450].

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Section: A Acacd2 CCC Conformermentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Double deuterated acetylacetone in neon matrices: infrared spectroscopy, photoreactivity and the tunneling process

Gutiérrez-Quintanilla

Chevalier

Crépin

2016

Phys. Chem. Chem. Phys.

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“…7,10 The reason for the stabilization of the enolic form is an intramolecular H-bond, coupled with a π-electronic delocalization over the O−C−C−C−O pseudocycle (see Scheme 1). The two simplest and smallest structures exhibiting the central six membered ring closed by the intramolecular Hbond in the chelated enol (CE) form are the compounds malonaldehyde (MA) and acetylacetone (AA; Scheme 1).…”

Section: ■ Introductionmentioning

confidence: 99%

Ultrafast UV-Induced Photoisomerization of Intramolecularly H-Bonded Symmetric β-Diketones

et al. 2014

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In photoinduced molecular reaction dynamics, the effects of electronic charge redistribution can lead to multiple pathways that are determined by the nature of the initial structures involved and the environment the molecule of interest is studied in. The β-diketones are a common example of this complexity. They show keto−enol tautomerism that is almost totally shifted toward the enolic form. However, compared to the gas phase, the photochemistry proceeds completely differently by virtue of the solvent environment for these compounds, which are used in commercial sunscreen agents due to a high absorption in the ultraviolet (UV) and fast deactivation processes. We disclose these dynamics by investigating three symmetrical β-diketones in various solvents. To observe these effects on an ultrafast time scale directly in the UV spectral region where the relevant electronic transitions take place, we have developed and employed femtosecond transient absorption with detection capability in the deep UV. Our studies confirm that electronic excitation of the chelated enol form does not lead to any ultrafast photochemistry other than proton transfer followed by rotamerization. The formation of the nonchelated conformers takes place on a picosecond time scale through a dark state, whereas the recovery to the stable chelated enol form is a comparably slow process. ■ INTRODUCTIONDerivatives of β-diketones are of great importance in diverse research fields by virtue of several remarkable chemical features that lead to a variety of applications. 1 For example, they are widely employed as chelating agents due to their binding affinity for transition metals, 1 or they are even contained in commercial sunscreen products 2−4 owing to the fast deactivation processes after ultraviolet (UV) irradiation. The most prominent property of β-diketones is their keto−enol tautomerism that is shifted almost totally toward the enolic form. 5−7 With structural similarities to relevant biomolecules and photochromic substances on the one hand, and the molecules' own versatility in combination with their structural simplicity on the other hand, small β-diketones are prototypical candidates for a systematic study of the photoinduced processes and the subsequent deactivation channels upon which the wide applicability of β-diketones is based.C o m p o u n d s l i k e β -d i k e t o n e s o f t y p e R−C(O)−CH 2 −C(O)−R, where R = H, CH 3 , have drawn continuous attention from chemists and physicists of different research areas because of the pronounced keto−enol tautomerism that is observable (and exploitable) in the gas 5,8 and the liquid phase 6,9 and even in isolated cryogenic matrices. 7,10 The reason for the stabilization of the enolic form is an intramolecular H-bond, coupled with a π-electronic delocalization over the O−C−C−C−O pseudocycle (see Scheme 1). The two simplest and smallest structures exhibiting the central six membered ring closed by the intramolecular Hbond in the chelated enol (CE) form are the compounds malonaldehyde (M...

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Nuclear Spin Conversion to Probe the Methyl Rotation Effect on Hydrogen‐Bond and Vibrational Dynamics

et al. 2012

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Acetylaceton ist ein bemerkenswertes Beispiel für ein Molekül, in dem Bewegungen mit großer Amplitude gekoppelt sind (Methylgruppentorsion und intramolekulare Wasserstoffbrücken). Für die Untersuchung des Protonentunnelns wurde dieses Molekül in festem Parawasserstoff isoliert. Eine beobachtete Kernspin‐Umkehr in den Methylgruppen belegt in Kombination mit IR‐Spektren die Kopplung zwischen hochfrequenten Moden und Bewegungen mit großer Amplitude.

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Photochemistry of acetylacetone isolated in parahydrogen matrices upon 266 nm irradiation

Cited by 17 publications

References 22 publications

Double deuterated acetylacetone in neon matrices: infrared spectroscopy, photoreactivity and the tunneling process

Double deuterated acetylacetone in neon matrices: infrared spectroscopy, photoreactivity and the tunneling process

Ultrafast UV-Induced Photoisomerization of Intramolecularly H-Bonded Symmetric β-Diketones

Nuclear Spin Conversion to Probe the Methyl Rotation Effect on Hydrogen‐Bond and Vibrational Dynamics

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