Identification of a new electron-transfer relaxation pathway in photoexcited pyrrole dimers.
Photoinduced electron transfer is central to many biological processes and technological applications, such as the harvesting of solar energy and molecular electronics. The electron donor and acceptor units involved in electron transfer are often held in place by covalent bonds, π-π interactions or hydrogen bonds. Here, using time-resolved photoelectron spectroscopy and ab initio calculations, we reveal the existence of a new, low-energy, photoinduced electron-transfer mechanism in molecules held together by an NH⋯π bond. Specifically, we capture the electron-transfer process in a pyrrole dimer, from the excited π-system of the donor pyrrole to a Rydberg orbital localized on the N-atom of the acceptor pyrrole, mediated by an N-H stretch on the acceptor molecule. The resulting charge-transfer state is surprisingly long lived and leads to efficient electronic relaxation. We propose that this relaxation pathway plays an important role in biological and technological systems containing the pyrrole building block.
School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Simon P
SP
Neville
Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
Oliver M
OM
Kirkby
Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
Nikolas
http://orcid.org/0000-0003-0293-5742
N
Kaltsoyannis
School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Graham A
GA
Worth
Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
Helen H
HH
Fielding