The Library
Manipulating dynamics with chemical structure : probing vibrationally-enhanced tunnelling in photoexcited catechol
Tools
Tools
Tools
Chatterley, Adam S., Young, Jamie D., Townsend, Dave, Żurek, Justyna M., Paterson, Martin J., Roberts, Gareth M. and Stavros, Vasilios G. (2013) Manipulating dynamics with chemical structure : probing vibrationally-enhanced tunnelling in photoexcited catechol. Physical Chemistry Chemical Physics, Volume 15 (Number 18). pp. 6879-6892. doi:10.1039/c3cp51108a ISSN 1463-9076.
Research output not available from this repository.
Request-a-Copy directly from author or use local Library Get it For Me service.
Official URL: http://dx.doi.org/10.1039/C3CP51108A
Abstract
Ultrafast time-resolved velocity map ion imaging (TR-VMI) and time-resolved ion-yield (TR-IY) methods are utilised to reveal a comprehensive picture of the electronic state relaxation dynamics in photoexcited catechol (1,2-dihydroxybenzene). After excitation to the S1 (1ππ*) state between 280.5 (the S1 origin band, S1(v = 0)) to 243 nm, the population in this state is observed to decay through coupling onto the S2 (1πσ*) state, which is dissociative with respect to the non-hydrogen bonded ‘free’ O–H bond (labelled O1–H). This process occurs via tunnelling under an S1/S2 conical intersection (CI) on a timeframe of 5–11 ps, resulting in O1–H bond fission along S2. Concomitant formation of ground state catechoxyl radicals (C6H5O2(X)), in coincidence with translationally excited H-atoms, occurs over the same timescale as the S1 state population decays. Between 254–237 nm, direct excitation to the S2 state is also observed, manifesting in the ultrafast ([similar]100 fs) formation of H-atoms with high kinetic energy release. From these measurements we determine that the S1/S2 CI lies [similar]3700–5500 cm−1 above the S1(v = 0) level, indicating that the barrier height to tunnelling from S1(v = 0) → S2 is comparable to that observed in the related ‘benchmark’ species phenol (hydroxybenzene). We discuss how a highly ‘vibrationally-enhanced’ tunnelling mechanism is responsible for the two orders of magnitude enhancement to the tunnelling rate in catechol, relative to that previously determined in phenol (>1.2 ns), despite similar barrier heights. This phenomenon is a direct consequence of the non-planar S1 excited state minimum structure (C1 symmetry) in catechol, which in turn yields relaxed symmetry constraints for vibronic coupling from S1(v = 0) → S2 – a scenario which does not exist for phenol. These findings offer an elegant example of how even simple chemical modifications (ortho-hydroxy substitution) to a fundamental, biologically relevant, UV chromophore, such as phenol, can have profound effects on the ensuing excited state dynamics.
| Item Type: | Journal Article | ||||
|---|---|---|---|---|---|
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry | ||||
| Journal or Publication Title: | Physical Chemistry Chemical Physics | ||||
| Publisher: | Royal Society of Chemistry | ||||
| ISSN: | 1463-9076 | ||||
| Official Date: | 2013 | ||||
| Dates: |
|
||||
| Volume: | Volume 15 | ||||
| Number: | Number 18 | ||||
| Page Range: | pp. 6879-6892 | ||||
| DOI: | 10.1039/c3cp51108a | ||||
| Status: | Peer Reviewed | ||||
| Publication Status: | Published | ||||
| Access rights to Published version: | Restricted or Subscription Access |
Request changes or add full text files to a record
Repository staff actions (login required)
 |
View Item |
