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 W P Bebbington, Dave Townsend

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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.

Original languageEnglish
Pages (from-to)8152-8160
Number of pages9
Journal Physical Chemistry Chemical Physics
Volume21
Issue number15
Early online date01 Apr 2019
DOIs
Publication statusPublished - 21 Apr 2019

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Crane, S. W., Ghafur, O., Cowie, T. Y., Lindsay, A. G., Thompson, J. O. F., Greenwood, J. B., Bebbington, M. W. P., & 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