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Resolving consecutive excited-state evolution in Fe-amido chromophores by wide-band optical transient absorption spectroscopy

Wegeberg, Christina LU ; Sidhu, Baldeep K. ; Chábera, Pavel LU ; Uhlig, Jens LU orcid ; Cowin, Rory A. ; Weinstein, Julia A. ; Persson, Petter LU ; Yartsev, Arkady LU orcid and Herbert, David E. (2026) In Chemical Science 17(12). p.6125-6137
Abstract

A detailed understanding of excited-state evolution is critical to realizing the full potential of abundant-metal coordination complex photosensitizers. Here, we show how wide-band optical transient absorption spectroscopy (oTA) can delineate the complete energy relaxation pathway of the photoexcited state of Fe(ii) polypyridyl complexes supported by benzannulated diarylamido ligands. By covering a broader spectral region from 370 to 1200 nm, we resolve consecutive evolution of a photoexcited Fe-amido chromophore from an initially generated singlet ‘π-antibonding-to-ligand’ charge transfer (1PALCT) excited state to a long-lived metal-centred quintet (5MC) via both a 3PALCT and what we assign as a... (More)

A detailed understanding of excited-state evolution is critical to realizing the full potential of abundant-metal coordination complex photosensitizers. Here, we show how wide-band optical transient absorption spectroscopy (oTA) can delineate the complete energy relaxation pathway of the photoexcited state of Fe(ii) polypyridyl complexes supported by benzannulated diarylamido ligands. By covering a broader spectral region from 370 to 1200 nm, we resolve consecutive evolution of a photoexcited Fe-amido chromophore from an initially generated singlet ‘π-antibonding-to-ligand’ charge transfer (1PALCT) excited state to a long-lived metal-centred quintet (5MC) via both a 3PALCT and what we assign as a 3MC state. Notably, we identify spin-parity transformations by observing photogeneration of the 1PALCT followed by its conversion into a 3PALCT state, and the subsequent 3MC-to-5MC transformation via observation of an isosbestic point in the oTA spectral dynamics. The state-to-state transformations are accompanied by coherent oscillations which are impulsive Raman-induced, originating in the ground state. Combining high-resolution, wide-band oTA experiments with the unique absorptive properties of diarylamido ligand–metal complexes, we are thus able, for the first time, to trace the complete deactivation trajectory of an iron(ii) polypyridyl sensitizer using optical spectroscopy.

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author
; ; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Chemical Science
volume
17
issue
12
pages
13 pages
publisher
Royal Society of Chemistry
external identifiers
  • scopus:105033824063
  • pmid:41640834
ISSN
2041-6520
DOI
10.1039/d5sc06464c
language
English
LU publication?
yes
additional info
Publisher Copyright: This journal is © The Royal Society of Chemistry, 2026
id
b3947725-42bf-4e71-b1a3-935ed9886540
date added to LUP
2026-05-26 22:08:14
date last changed
2026-06-09 23:07:09
@article{b3947725-42bf-4e71-b1a3-935ed9886540,
  abstract     = {{<p>A detailed understanding of excited-state evolution is critical to realizing the full potential of abundant-metal coordination complex photosensitizers. Here, we show how wide-band optical transient absorption spectroscopy (oTA) can delineate the complete energy relaxation pathway of the photoexcited state of Fe(ii) polypyridyl complexes supported by benzannulated diarylamido ligands. By covering a broader spectral region from 370 to 1200 nm, we resolve consecutive evolution of a photoexcited Fe-amido chromophore from an initially generated singlet ‘π-antibonding-to-ligand’ charge transfer (<sup>1</sup>PALCT) excited state to a long-lived metal-centred quintet (<sup>5</sup>MC) via both a <sup>3</sup>PALCT and what we assign as a <sup>3</sup>MC state. Notably, we identify spin-parity transformations by observing photogeneration of the <sup>1</sup>PALCT followed by its conversion into a <sup>3</sup>PALCT state, and the subsequent <sup>3</sup>MC-to-<sup>5</sup>MC transformation via observation of an isosbestic point in the oTA spectral dynamics. The state-to-state transformations are accompanied by coherent oscillations which are impulsive Raman-induced, originating in the ground state. Combining high-resolution, wide-band oTA experiments with the unique absorptive properties of diarylamido ligand–metal complexes, we are thus able, for the first time, to trace the complete deactivation trajectory of an iron(ii) polypyridyl sensitizer using optical spectroscopy.</p>}},
  author       = {{Wegeberg, Christina and Sidhu, Baldeep K. and Chábera, Pavel and Uhlig, Jens and Cowin, Rory A. and Weinstein, Julia A. and Persson, Petter and Yartsev, Arkady and Herbert, David E.}},
  issn         = {{2041-6520}},
  language     = {{eng}},
  month        = {{03}},
  number       = {{12}},
  pages        = {{6125--6137}},
  publisher    = {{Royal Society of Chemistry}},
  series       = {{Chemical Science}},
  title        = {{Resolving consecutive excited-state evolution in Fe-amido chromophores by wide-band optical transient absorption spectroscopy}},
  url          = {{http://dx.doi.org/10.1039/d5sc06464c}},
  doi          = {{10.1039/d5sc06464c}},
  volume       = {{17}},
  year         = {{2026}},
}