Dynamics of electronically excited states in the eumelanin building block 5,6-dihydroxyindole

Stuart W. Crane, Omair Ghafur, Thomas Y. Cowie, Anita G. Lindsay, James O.F. Thompson, Jason B. Greenwood, Magnus Bebbington, Dave Townsend

Research output: Contribution to journalArticleResearchpeer-review

Abstract

We report the first excited state dynamics study of gas-phase 5,6-dihydroxyindole (5,6-DHI), a key building block of eumelanin pigments that are found throughout nature and serve as important photo-protective compounds. Time-resolved ion-yield measurements over the 241-296 nm ultraviolet photoexcitation region revealed non-adiabatic processes occurring on up to three distinct timescales. These reflect ultrafast (i.e. sub-picosecond) internal conversion within the excited state singlet manifold, and much longer-lived processes ranging from 10 ps to in excess of 1 ns. Our investigation paves the way for precisely targeted future studies of 5,6-DHI that exploit more differential measurement techniques. The work was facilitated by the use of soft laser-based thermal desorption to introduce 5,6-DHI samples into the gas phase. This approach, based on low-cost, readily available diode lasers, is straightforward, easily controllable and potentially applicable to a wide range of non-volatile molecular species.

Original languageEnglish
Pages (from-to)8152-8160
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume21
Issue number15
DOIs
StatePublished - 1 Jan 2019

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Excited states
vapor phases
internal conversion
pigments
Gases
photoexcitation
excitation
Thermal desorption
Photoexcitation
desorption
semiconductor lasers
heat transfer
Pigments
Semiconductor lasers
Ions
lasers
ions
Lasers
eumelanin
5,6-dihydroxyindole

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Crane, S. W., Ghafur, O., Cowie, T. Y., Lindsay, A. G., Thompson, J. O. F., Greenwood, J. B., ... Townsend, D. (2019). Dynamics of electronically excited states in the eumelanin building block 5,6-dihydroxyindole. Physical Chemistry Chemical Physics, 21(15), 8152-8160. https://doi.org/10.1039/c9cp00620f
Crane, Stuart W. ; Ghafur, Omair ; Cowie, Thomas Y. ; Lindsay, Anita G. ; Thompson, James O.F. ; Greenwood, Jason B. ; Bebbington, Magnus ; Townsend, Dave. / Dynamics of electronically excited states in the eumelanin building block 5,6-dihydroxyindole. In: Physical Chemistry Chemical Physics. 2019 ; Vol. 21, No. 15. pp. 8152-8160.
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abstract = "We report the first excited state dynamics study of gas-phase 5,6-dihydroxyindole (5,6-DHI), a key building block of eumelanin pigments that are found throughout nature and serve as important photo-protective compounds. Time-resolved ion-yield measurements over the 241-296 nm ultraviolet photoexcitation region revealed non-adiabatic processes occurring on up to three distinct timescales. These reflect ultrafast (i.e. sub-picosecond) internal conversion within the excited state singlet manifold, and much longer-lived processes ranging from 10 ps to in excess of 1 ns. Our investigation paves the way for precisely targeted future studies of 5,6-DHI that exploit more differential measurement techniques. The work was facilitated by the use of soft laser-based thermal desorption to introduce 5,6-DHI samples into the gas phase. This approach, based on low-cost, readily available diode lasers, is straightforward, easily controllable and potentially applicable to a wide range of non-volatile molecular species.",
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Crane, SW, Ghafur, O, Cowie, TY, Lindsay, AG, Thompson, JOF, Greenwood, JB, Bebbington, M & Townsend, D 2019, 'Dynamics of electronically excited states in the eumelanin building block 5,6-dihydroxyindole', Physical Chemistry Chemical Physics, vol. 21, no. 15, pp. 8152-8160. https://doi.org/10.1039/c9cp00620f

Dynamics of electronically excited states in the eumelanin building block 5,6-dihydroxyindole. / Crane, Stuart W.; Ghafur, Omair; Cowie, Thomas Y.; Lindsay, Anita G.; Thompson, James O.F.; Greenwood, Jason B.; Bebbington, Magnus; Townsend, Dave.

In: Physical Chemistry Chemical Physics, Vol. 21, No. 15, 01.01.2019, p. 8152-8160.

Research output: Contribution to journalArticleResearchpeer-review

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Crane SW, Ghafur O, Cowie TY, Lindsay AG, Thompson JOF, Greenwood JB et al. Dynamics of electronically excited states in the eumelanin building block 5,6-dihydroxyindole. Physical Chemistry Chemical Physics. 2019 Jan 1;21(15):8152-8160. https://doi.org/10.1039/c9cp00620f