TY  - JOUR
A1  - Eckert, Sebastian
A1  - Norell, Jesper
A1  - Jay, Raphael Martin
A1  - Fondell, Mattis
A1  - Mitzner, Rolf
A1  - Odelius, Michael
A1  - Föhlisch, Alexander
T1  - T-1 Population as the Driver of Excited-State Proton-Transfer in 2-Thiopyridone
JF  - Chemistry - a European journal
N2  - Excited-state proton transfer (ESPT) is a fundamental process in biomolecular photochemistry, but its underlying mediators often evade direct observation. We identify a distinct pathway for ESPT in aqueous 2-thiopyridone, by employing transient N1s X-ray absorption spectroscopy and multi-configurational spectrum simulations. Photoexcitations to the singlet S-2 and S-4 states both relax promptly through intersystem crossing to the triplet T-1 state. The T-1 state, through its rapid population and near nanosecond lifetime, mediates nitrogen site deprotonation by ESPT in a secondary intersystem crossing to the S-0 potential energy surface. This conclusively establishes a dominant ESPT pathway for the system in aqueous solution, which is also compatible with previous measurements in acetonitrile. Thereby, the hitherto open questions of the pathway for ESPT in the compound, including its possible dependence on excitation wavelength and choice of solvent, are resolved.
KW  - excited-state proton-transfer
KW  - intersystem crossing
KW  - nitrogen
KW  - photochemistry
KW  - X-ray absorption
Y1  - 2019
U6  - https://doi.org/10.1002/chem.201804166
SN  - 0947-6539
SN  - 1521-3765
VL  - 25
IS  - 7
SP  - 1733
EP  - 1739
PB  - Wiley-VCH
CY  - Weinheim
ER  -