Structure and dynamic role of conical intersections in the πσ*-mediated photodissociation reactions

You, Hyeon Sik; Han, Song; Yoon, Jun Ho; Lim, Jae S.; Lee, Jeongmook; Kim, So Yeon; Ahn, Doo‐Sik; Lim, Jean Sun; Kim, Sangkyu

doi:10.1080/0144235x.2015.1072364

Cited by 28 publications

(18 citation statements)

References 154 publications

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“…88,91 These 'dynamic resonances' are pictured as transitions to bound states embedded in the continuum generated by the conical intersection; their identification may provide insights into the nuclear motions that facilitate non-adiabatic coupling at CI-1 and/or CI-2. 92 Not surprisingly, phenol, thiophenol and thioanisole are attracting much interest as test-systems for honing the treatment of non-adiabatic effects in molecular photodissociations. 83,[93][94][95] The remaining panels in Figure 1 show data obtained following 267 nm excitation of these same systems in solution.…”

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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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Molecular Photofragmentation Dynamics in the Gas and Condensed Phases

Ashfold

Murdock

Oliver

2017

Annu. Rev. Phys. Chem.

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“…Phenols are just one of many families of hydrides that decay by X–H (X = O, S, N, etc.) bond fission after coupling to a dissociative 1 πσ* PES [44,56–58]. Parent vibronic mode-dependent tunnelling rates and product quantum state population distributions have been reported for several similar systems including catechol [59,60], thiophenol and several o -substituted thiophenols [61–63].…”

Section: Photoinduced O–h Bond Fission In Phenols Vibronic State Sele...mentioning

confidence: 99%

Non-Born–Oppenheimer effects in molecular photochemistry: an experimental perspective

Ashfold

Kim

2022

Phil. Trans. R. Soc. A.

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Non-adiabatic couplings between Born–Oppenheimer (BO)-derived potential energy surfaces are now recognized as pivotal in describing the non-radiative decay of electronically excited molecules following photon absorption. This opinion piece illustrates how non-BO effects provide photostability to many biomolecules when exposed to ultraviolet radiation, yet in many other cases are key to facilitating ‘reactive’ outcomes like isomerization and bond fission. The examples are presented in order of decreasing molecular complexity, spanning studies of organic sunscreen molecules in solution, through two families of heteroatom containing aromatic molecules and culminating with studies of isolated gas phase H 2 O molecules that afford some of the most detailed insights yet available into the cascade of non-adiabatic couplings that enable the evolution from photoexcited molecule to eventual products. This article is part of the theme issue 'Chemistry without the Born–Oppenheimer approximation'.

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“…Nevertheless, capturing the conical intersection of polyatomic molecules in either a spatial or temporal domain has long been a challenging and important goal for chemists, as figuring out conical intersections has been widely regarded as essential in understanding and controlling ubiquitous nonadiabatic processes in nature. Spectroscopic perturbations in the vicinity of conical intersections had been reported in numerous cases, confirming not only the existence of a conical intersection but its significant role in nonadiabatic dynamic behavior in terms of molecular structure and chemical reactivity. , In the time domain, femtosecond (fs) wavepacket dynamics in the vicinity of the conical intersection have been explored for many interesting chemical or biological systems ranging from a small molecule of NO 2 to a complicated bacterial rhodopsin. − Conical intersection dynamics of several polyatomic molecules have also been studied in the frequency domain, providing a nonadiabatic coupling map in the nuclear configuration space. − Despite many successful experimental studies, however, the spatial and/or temporal description of the conical intersection for polyatomic molecules has not been fully concretized to date, whereas theoretical calculations have been much evolved in terms of both stationary and dynamic aspects of the conical intersection in multidimensional ways. − …”

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confidence: 96%

Real-Time Observation of Nonadiabatic Bifurcation Dynamics at a Conical Intersection

2017

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Looking into temporal dynamics of the reactive flux that is precisely located at the well-characterized conical intersection has been one of chemists' longstanding goals. We report here real-time nonadiabatic bifurcation dynamics in the S-CH bond predissociation of thioanisole (CHSCH) in the first electronically excited state (S). It is found that two distinct adiabatic and nonadiabatic reaction pathways are activated simultaneously only when the vibronic state near the first conical intersection is optically accessed. Our time-resolved measurement of the product state distribution could separate two different dynamic channels unambiguously, unraveling the detailed dynamic mechanism of the nonadiabatic reaction taking place in the vicinity of the conical intersection. The nonadiabatic channel, where the reactive flux funnels through two consecutive conical intersections along the reaction coordinate, is found to be significantly faster than the adiabatic channel along the minimum energy reaction pathway. The kinetic energy release ratio and the nonadiabatic transition probability are found to be much higher for the nonadiabatic channel than those of the adiabatic channel, giving insights into the bifurcation dynamics occurring at the conical intersection.

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Structure and dynamic role of conical intersections in the πσ*-mediated photodissociation reactions

Cited by 28 publications

References 154 publications

Molecular Photofragmentation Dynamics in the Gas and Condensed Phases

Molecular Photofragmentation Dynamics in the Gas and Condensed Phases

Non-Born–Oppenheimer effects in molecular photochemistry: an experimental perspective

Real-Time Observation of Nonadiabatic Bifurcation Dynamics at a Conical Intersection

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