Exploring quantum phenomena and vibrational control in σ* mediated photochemistry

Roberts, Gareth M.; Hadden, David J.; Bergendahl, L. Therese; Wenge, Andreas M.; Harris, Stephanie J.; Karsili, Tolga N. V.; Ashfold, Michael N. R.; Paterson, Martin J.; Stavros, Vasilios G.

doi:10.1039/c2sc21865h

Cited by 65 publications

(88 citation statements)

References 32 publications

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“…mainly in the excited Ã state), on a nanosecond timescale. 89,90 These observations accord with expectations that the PECs along R S-Me are qualitatively similar to those shown in Figure 1a. Fragmentation starts with an initial, rate limiting, coupling to the * PES via CI-1.…”

supporting

confidence: 82%

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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supporting

confidence: 82%

Molecular Photofragmentation Dynamics in the Gas and Condensed Phases

Ashfold

Murdock

Oliver

2017

Annu. Rev. Phys. Chem.

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“…Such behavior is unsurprising and has been observed previously in studies of tetramethylethylene, 31 pyrrole, 36 and thioanisole. 5 Vibrational excitation in the A 2 (πσ * ) state should decrease upon going from 236.2 to 241.5 nm, consistent with the observed increase in excited state lifetimes. These vibrationally excited states are prepared either through vibronic transitions originating from the S 0 (ν = 0) level or, potentially, through transitions starting from vibrationally excited states (hot bands) of low frequency modes of the S 0 electronic state, due to the incomplete cooling of the vibrational degrees of freedom within the supersonic expansion of the molecular beam.…”

Section: B Excited State Non-adiabatic Dynamicssupporting

confidence: 67%

“…[1][2][3][4][5][6] Such molecules have vanishingly small fluorescence quantum yields, implying the existence of ultrafast non-radiative decay mechanisms connecting the excited and ground electronic states. A general mechanism for non-radiative decay in heteroaromatics was proposed by Domcke et al and invokes the population of low-lying singlet states of π(3s/σ * ) character.…”

Section: Introductionmentioning

confidence: 99%

Excited state non-adiabatic dynamics of N-methylpyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

Neville

Schalk

et al. 2016

The Journal of Chemical Physics

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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 Excited state non-adiabatic dynamics of N-methylpyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study The dynamics of N-methylpyrrole following excitation at wavelengths in the range 241.5-217.0 nm were studied using a combination of time-resolved photoelectron spectroscopy (TRPES), ab initio quantum dynamics calculations using the multi-layer multi-configurational time-dependent Hartree method, as well as high-level photoionization cross section calculations. Excitation at 241.5 and 236.2 nm results in population of the A 2 (πσ * ) state, in agreement with previous studies. Excitation at 217.0 nm prepares the previously neglected B 1 (π3p y ) Rydberg state, followed by prompt internal conversion to the A 2 (πσ * ) state. In contrast with the photoinduced dynamics of pyrrole, the lifetime of the wavepacket in the A 2 (πσ * ) state was found to vary with excitation wavelength, decreasing by one order of magnitude upon tuning from 241.5 nm to 236.2 nm and by more than three orders of magnitude when excited at 217.0 nm. The order of magnitude difference in lifetimes measured at the longer excitation wavelengths is attributed to vibrational excitation in the A 2 (πσ * ) state, facilitating wavepacket motion around the potential barrier in the N-CH 3 dissociation coordinate. C 2016 AIP Publishing LLC. [http://dx

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“…It is well-known that the vibrational quantum state on a reactant surface can severely influence the ensuing excited state dynamics. [30][31][32][33][34] Indeed, we find in our ultrafast experiments that the CSSs are formed on two distinct timescales representing ET from a hot 3 MLCT ( 3 MLCT*) ( hot = 3.6 ps) and a relaxed 3 MLCT ( cool = 14.7 ps). Note however that we do not find any evidence of (C C) v>0 population in the TRIR data beyond the instrument-limited time resolution of ca.…”

Section: Excited State Dynamics Without Ir Excitationmentioning

confidence: 99%

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

et al. 2017

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Ultrafast electron transfer in condensed-phase molecular systems is often strongly coupled to intramolecular vibrations that can promote, suppress and direct electronic processes. Recent experiments exploring this phenomenon proved that light-induced electron transfer can be strongly modulated by vibrational excitation, suggesting a new avenue for active control over molecular function. Here, we achieve the first example of such explicit vibrational control through judicious design of a Pt(II)-acetylide charge-transfer Donor-Bridge-Acceptor-Bridge-Donor "fork" system: asymmetric 13 C isotopic labelling of one of the two -C≡C-bridges makes the two parallel and otherwise identical Donor→Acceptor electron-transfer pathways structurally distinct, enabling independent vibrational perturbation of either. Applying an ultrafast UV pump (excitation)-IR pump (perturbation)-IR probe (monitoring) pulse sequence, we show that the pathway that is vibrationally perturbed during UV-induced electron-transfer is dramatically slowed down compared to its unperturbed counterpart. One can thus choose the dominant electron transfer pathway. The findings deliver a new opportunity for precise perturbative control of electronic energy propagation in molecular devices. Main TextControlling the function of future advanced materials demands a profound understanding of energymatter interactions in molecular systems at the quantum level. 1 There is a growing consensus that energy-and electron-transfer processes occurring far away from equilibrium in condensed-phase systems on femto-to-picosecond timescales do not conform to the Born-Oppenheimer approximation. Indeed, nuclear and electronic wave functions often strongly interact with each other, leading to exotic phenomena whereby vibrational motion can mediate and dictate the rate and efficiency of electronic transitions. [2][3][4][5] With overwhelming evidence that nuclear-electronic (vibronic) interactions play a crucial role in a broad range of systems, including light harvesting and conversion in photosynthetic organisms, 6-11 this phenomenon represents a tremendous opportunity to acquire deeper knowledge and control over the structural traits that govern molecular function and reactivity.Recent efforts led by Rubtsov et al.,12,13 Bakulin et al., 14 and our group 15,16 have shown that one way to experimentally exploit vibronic coupling to modulate molecular function is to introduce targeted vibrational excitation along specific reaction co-ordinates using ultrafast mid-infrared (IR) pulses. This approach enables promoting or suppressing electronic transitions, notably photo-induced electron transfer (ET), an elementary process that pervades the natural world. Although the demonstrated excited state modulations have been remarkably efficient, up to 100% suppression in one case, 15 predictive and directive control of electron transfer in the condensed phase has not been achieved yet.

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Exploring quantum phenomena and vibrational control in σ* mediated photochemistry

Cited by 65 publications

References 32 publications

Molecular Photofragmentation Dynamics in the Gas and Condensed Phases

Molecular Photofragmentation Dynamics in the Gas and Condensed Phases

Excited state non-adiabatic dynamics of N-methylpyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

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