Direct Observation of Hydrogen Tunneling Dynamics in Photoexcited Phenol

Roberts, Gareth M.; Chatterley, Adam S.; Young, Jamie D.; Stavros, Vasilios G.

doi:10.1021/jz2016318

Cited by 130 publications

(202 citation statements)

References 33 publications

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“…This study returns a 2-FPhOH(S1) lifetime  = 2.3±0.2 ns, in reasonable accord with previous estimates from high resolution linewidth studies of the syn-conformer ( = 4.60.2 ns and 2.8±0.2 ns 31 ) and similar to that found when exciting bare phenol at its S1-S0 origin. 5,30 As with phenol, the 2-FPhOH(S1) decay time constant was seen to decrease on tuning to shorter excitation wavelengths (e.g.  =…”

Section: Ultrafast Pump-probe Studiesmentioning

confidence: 96%

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A Multipronged Comparative Study of the Ultraviolet Photochemistry of 2-, 3-, and 4-Chlorophenol in the Gas Phase

et al. 2015

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The S1( 1 *) state of the (dominant) syn-conformer of 2-chlorophenol (2-ClPhOH) in the gas phase has a sub-picosecond lifetime, whereas the corresponding S1 states of 3-and 4-ClPhOH have lifetimes that are, respectively, ~2 and ~3-orders of magnitude longer. A range of experimental techniques -electronic spectroscopy, ultrafast time-resolved photoion and photoelectron spectroscopies, H Rydberg atom photofragment translational spectroscopy, velocity map imaging and time-resolved Fourier transform infrared emission spectroscopyas well as electronic structure calculations (of key regions of the multidimensional ground (S0) state potential energy surface (PES) and selected cuts through the first few excited singlet PESs) have been used in the quest to explain these striking differences in excited state lifetime. The intramolecular OH ---Cl hydrogen bond specific to syn-2-ClPhOH is key. It encourages partial charge transfer and preferential stabilisation of the diabatic 1 * potential (relative to that of the 1 * state) upon stretching the C-Cl bond, with the result that initial C-Cl bond extension on the adiabatic S1 PES offers an essentially barrierless internal conversion pathway via regions of conical intersection with the S0 PES. Intramolecular hydrogen bonding is thus seen to facilitate the type of heterolytic dissociation more typically encountered in solution studies.3

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Section: Ultrafast Pump-probe Studiesmentioning

confidence: 96%

“…30 The temporal decay of the various chlorophenol isomers following excitation to their respective S1 states was also investigated by time resolved, 266 nm pump, 800 nm (multiphoton) probe photoelectron imaging (TRPEI) methods. Sample images are shown in the ESI.…”

Section: Ultrafast Pump-probe Studiesmentioning

confidence: 99%

A Multipronged Comparative Study of the Ultraviolet Photochemistry of 2-, 3-, and 4-Chlorophenol in the Gas Phase

et al. 2015

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“…Such fragmentation dynamics have been demonstrated in phenol [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] and thiophenol, [24][25][26][27][28][29][30] in a range of substituted phenols [31][32][33][34][35][36] and thiophenols, [37][38][39] and in the methylated analogues anisole 40,41 and thioanisole, [42][43][44][45][46] in both the gas and condensed [47][48][49][50] phase. The present study focusses on thiophenols and, particularly, how the much-studied S-H bond fission process is affected by asymmetric substitution (i.e., in the 2-and 3-positions) of the aromatic ring.…”

Section: Introductionmentioning

confidence: 99%

The near ultraviolet photodissociation dynamics of 2- and 3-substituted thiophenols: Geometric vs. electronic structure effects

Marchetti

Karsili

Cipriani

et al. 2017

The Journal of Chemical Physics

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The near ultraviolet spectroscopy and photodissociation dynamics of two families of asymmetrically substituted thiophenols (2- and 3-YPhSH, with Y = F and Me) have been investigated experimentally (by H (Rydberg) atom photofragment translational spectroscopy) and by ab initio electronic structure calculations. Photoexcitation in all cases populates the 11ππ* and/or 11πσ* excited states and results in S–H bond fission. Analyses of the experimentally obtained total kinetic energy release (TKER) spectra yield the respective parent S–H bond strengths, estimates of ΔE(A∼−X∼), the energy splitting between the ground (X∼) and first excited (A∼) states of the resulting 2-(3-)YPhS radicals, and reveal a clear propensity for excitation of the C–S in-plane bending vibration in the radical products. The companion theory highlights roles for both geometric (e.g., steric effects and intramolecular H-bonding) and electronic (i.e., π (resonance) and σ (inductive)) effects in determining the respective parent minimum energy geometries, and the observed substituent and position-dependent trends in S–H bond strength and ΔE(A∼−X∼). 2-FPhSH shows some clear spectroscopic and photophysical differences. Intramolecular H-bonding ensures that most 2-FPhSH molecules exist as the syn rotamer, for which the electronic structure calculations return a substantial barrier to tunnelling from the photoexcited 11ππ* state to the 11πσ* continuum. The 11ππ* ← S0 excitation spectrum of syn-2-FPhSH thus exhibits resolved vibronic structure, enabling photolysis studies with a greater parent state selectivity. Structure apparent in the TKER spectrum of the H + 2-FPhS products formed when exciting at the 11ππ* ← S0 origin is interpreted by assuming unintended photoexcitation of an overlapping resonance associated with syn-2-FPhSH(v33 = 1) molecules. The present data offer tantalising hints that such out-of-plane motion influences non-adiabatic coupling in the vicinity of a conical intersection (between the 11πσ* and ground state potentials at extended S–H bond lengths) and thus the electronic branching in the eventual radical products.

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“…76,85 Long wavelength excitation of PhOH thus populates exclusively the * state which, again, can decay by tunnelling through a (much larger) barrier under CI-1, but on an orders of magnitude longer 8 (nanosecond) timescale, 86 and subsequent non-adiabatic coupling at CI-2 to yield H + PhO( X ) products in a limited number of vibrational levels.…”

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confidence: 99%

Molecular Photofragmentation Dynamics in the Gas and Condensed Phases

Ashfold

Murdock

Oliver

2017

Annu. Rev. Phys. Chem.

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This is the submitted manuscript. The final published version (version of record) is available online via Annual Review of Physical Chemistry at http://www.annualreviews.org/doi/10.1146/annurev-physchem-052516-050756 . Please refer to any applicable terms of use of the publisher University of Bristol -Explore Bristol Research General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms 1 Molecular Photofragmentation Dynamics in the Gas and Condensed PhasesMichael N.R. Ashfold, Daniel Murdock and Thomas A.A. Oliver School of Chemistry, University of Bristol, Bristol, U.K., BS8 1TS AbstractExciting a molecule with a UV photon often leads to bond fission, but the final outcome of the bond cleavage is typically both molecule and phase dependent. The photodissociation of an isolated gasphase molecule can be viewed as closed system: energy and momentum are conserved, and the fragmentation is irreversible. The same is not true in a solution-phase photodissociation process.Solvent interactions may dissipate some of the photoexcitation energy prior to bond fission, and will dissipate any excess energy partitioned into the dissociation products. Products that have no analogue in the corresponding gas-phase study may arise by, for example, geminate recombination. Here we illustrate the extents to which dynamical insights from gas-phase studies can inform our understanding of the corresponding solution-phase photochemistry and how, in the specific case of photoinduced ring-opening reactions, solution-phase studies can in some cases reveal dynamical insights more clearly than the corresponding gas-phase study.Keywords photochemistry, photodissociation, photoinduced ring opening, non-adiabatic dynamics, conical intersections. 2 HISTORICAL CONTEXTCiamician is recognised as a pioneer of (organic) photochemistry and an early advocate for fuel production by means of artificial photo'synthesis'. 1 His studies were performed in solution and usually driven by sunlight, at a time when the concept of the photon was yet to be fully accepted.Identifying the ultimate reaction products was in itself a major achievement, and any ideas regarding reaction mechanism were rudimentary. Even the concatenation of ideas like ground and excited electronic states, radiative and non-radiative transitions, spin multiplicity, etc, into what would later be termed a Jablonski diagram 2 still lay far in the future.A potentially more fruitful path at that time for those curious about the mechanisms of photochemical reactions was to focus on very simple molecular systems -diatomic and 'diatomic-like' molecules. generally polychromatic) light sources were now available, and the development of grating spectrometers enabled the recording of electronic absorption spectra for many small gas-phase molecules. Vibrational and even rotational fine structure was resolved and interpreted in many such ...

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Direct Observation of Hydrogen Tunneling Dynamics in Photoexcited Phenol

Cited by 130 publications

References 33 publications

A Multipronged Comparative Study of the Ultraviolet Photochemistry of 2-, 3-, and 4-Chlorophenol in the Gas Phase

A Multipronged Comparative Study of the Ultraviolet Photochemistry of 2-, 3-, and 4-Chlorophenol in the Gas Phase

The near ultraviolet photodissociation dynamics of 2- and 3-substituted thiophenols: Geometric vs. electronic structure effects

Molecular Photofragmentation Dynamics in the Gas and Condensed Phases

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