Ultrafast Excited-State Dynamics of the Organic Photoredox Catalyst DDQ

Deborin Ghosh; Vera Brieskorn; Charlotte A Smith; Hallam J M Greene; Ria Binyahan; Federico J Hernandez; Alastair J J Lennox; Basile F E Curchod; Andrew J Orr-Ewing

doi:10.1021/acs.jpclett.5c02391

Ultrafast Excited-State Dynamics of the Organic Photoredox Catalyst DDQ

Deborin Ghosh^*, Vera Brieskorn, Charlotte A Smith, Hallam J M Greene, Ria Binyahan, Federico J Hernandez, Alastair J J Lennox, Basile F E Curchod^*, Andrew J Orr-Ewing^*

^*Corresponding author for this work

Research output: Contribution to journal › Article (Academic Journal) › peer-review

Abstract

The electron-deficient oxidant 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has recently emerged as a promising visible-light photoredox catalyst. However, its excited-state behaviour remains poorly understood. Here, we investigate the ultrafast dynamics of photoexcited DDQ in acetonitrile using transient electronic and infrared absorption spectroscopy, supported by quantum chemical calculations. Upon 395 nm excitation, we identify rapid intersystem crossing (ISC) from the singlet to triplet manifold within 1.5 ps, followed by internal conversion and vibrational relaxation on a 10.9 ps timescale. Our findings demonstrate that DDQ exhibits near-unity ISC quantum yield and long triplet lifetime. Together with the high reduction potential of the triplet state, these properties make it a viable metal-free alternative to conventional iridium and ruthenium-based photocatalysts.

Original language	English
Pages (from-to)	9748-9752
Number of pages	5
Journal	Journal of Physical Chemistry Letters
Volume	16
Issue number	37
Early online date	9 Sept 2025
DOIs	https://doi.org/10.1021/acs.jpclett.5c02391
Publication status	E-pub ahead of print - 9 Sept 2025

Bibliographical note

Publisher Copyright:
© 2025 The Authors. Published by American Chemical Society

Research Groups and Themes

Organic & Biological
Physical & Theoretical

Access to Document

10.1021/acs.jpclett.5c02391Licence: CC BY

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OAFI - Basile Curchod - EPSRC Programme Grant - UCL lead: A Universal Approach to Using Quantum Dynamics for Real World Problems: Applying Coherent States for MolecularDynamics Simulations (COSMOS)
Curchod, B. F. E. (Principal Investigator)
1/10/23 → 30/09/29
Project: Research
Ultrafast Photochemical Dynamics in Complex Environments
Orr-Ewing, A. J. (Principal Investigator), Oliver, T. (Principal Investigator) & Curchod, B. F. E. (Principal Investigator)
1/09/21 → 31/08/27
Project: Research
SENF: Selective Electrochemical Nucleophilic Fluorination
Lennox, A. J. J. (Principal Investigator)
1/08/21 → 31/07/26
Project: Research

HPC (High Performance Computing) and HTC (High Throughput Computing) Facilities
Alam, S. R. (Manager), Williams, D. A. G. (Manager), Eccleston, P. E. (Manager) & Greene, D. (Manager)
Facility/equipment: Facility
Various Computer Clusters, Storage Facility
University of Bristol
Facility/equipment: Equipment

Cite this

@article{027d319497d9409ca28fff4741d225f1,

title = "Ultrafast Excited-State Dynamics of the Organic Photoredox Catalyst DDQ",

abstract = "The electron-deficient oxidant 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has recently emerged as a promising visible-light photoredox catalyst. However, its excited-state behaviour remains poorly understood. Here, we investigate the ultrafast dynamics of photoexcited DDQ in acetonitrile using transient electronic and infrared absorption spectroscopy, supported by quantum chemical calculations. Upon 395 nm excitation, we identify rapid intersystem crossing (ISC) from the singlet to triplet manifold within 1.5 ps, followed by internal conversion and vibrational relaxation on a 10.9 ps timescale. Our findings demonstrate that DDQ exhibits near-unity ISC quantum yield and long triplet lifetime. Together with the high reduction potential of the triplet state, these properties make it a viable metal-free alternative to conventional iridium and ruthenium-based photocatalysts.",

author = "Deborin Ghosh and Vera Brieskorn and Smith, \{Charlotte A\} and Greene, \{Hallam J M\} and Ria Binyahan and Hernandez, \{Federico J\} and Lennox, \{Alastair J J\} and Curchod, \{Basile F E\} and Orr-Ewing, \{Andrew J\}",

note = "Publisher Copyright: {\textcopyright} 2025 The Authors. Published by American Chemical Society",

year = "2025",

month = sep,

day = "9",

doi = "10.1021/acs.jpclett.5c02391",

language = "English",

volume = "16",

pages = "9748--9752 ",

journal = "Journal of Physical Chemistry Letters",

issn = "1948-7185",

publisher = "American Chemical Society",

number = "37",

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TY - JOUR

T1 - Ultrafast Excited-State Dynamics of the Organic Photoredox Catalyst DDQ

AU - Ghosh, Deborin

AU - Brieskorn, Vera

AU - Smith, Charlotte A

AU - Greene, Hallam J M

AU - Binyahan, Ria

AU - Hernandez, Federico J

AU - Lennox, Alastair J J

AU - Curchod, Basile F E

AU - Orr-Ewing, Andrew J

PY - 2025/9/9

Y1 - 2025/9/9

N2 - The electron-deficient oxidant 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has recently emerged as a promising visible-light photoredox catalyst. However, its excited-state behaviour remains poorly understood. Here, we investigate the ultrafast dynamics of photoexcited DDQ in acetonitrile using transient electronic and infrared absorption spectroscopy, supported by quantum chemical calculations. Upon 395 nm excitation, we identify rapid intersystem crossing (ISC) from the singlet to triplet manifold within 1.5 ps, followed by internal conversion and vibrational relaxation on a 10.9 ps timescale. Our findings demonstrate that DDQ exhibits near-unity ISC quantum yield and long triplet lifetime. Together with the high reduction potential of the triplet state, these properties make it a viable metal-free alternative to conventional iridium and ruthenium-based photocatalysts.

AB - The electron-deficient oxidant 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has recently emerged as a promising visible-light photoredox catalyst. However, its excited-state behaviour remains poorly understood. Here, we investigate the ultrafast dynamics of photoexcited DDQ in acetonitrile using transient electronic and infrared absorption spectroscopy, supported by quantum chemical calculations. Upon 395 nm excitation, we identify rapid intersystem crossing (ISC) from the singlet to triplet manifold within 1.5 ps, followed by internal conversion and vibrational relaxation on a 10.9 ps timescale. Our findings demonstrate that DDQ exhibits near-unity ISC quantum yield and long triplet lifetime. Together with the high reduction potential of the triplet state, these properties make it a viable metal-free alternative to conventional iridium and ruthenium-based photocatalysts.

U2 - 10.1021/acs.jpclett.5c02391

DO - 10.1021/acs.jpclett.5c02391

M3 - Article (Academic Journal)

C2 - 40926291

SN - 1948-7185

VL - 16

SP - 9748

EP - 9752

JO - Journal of Physical Chemistry Letters

JF - Journal of Physical Chemistry Letters

IS - 37

ER -

Ultrafast Excited-State Dynamics of the Organic Photoredox Catalyst DDQ

Abstract

Bibliographical note

Research Groups and Themes

Access to Document

Handle.net

Fingerprint

Projects

OAFI - Basile Curchod - EPSRC Programme Grant - UCL lead: A Universal Approach to Using Quantum Dynamics for Real World Problems: Applying Coherent States for MolecularDynamics Simulations (COSMOS)

Ultrafast Photochemical Dynamics in Complex Environments

SENF: Selective Electrochemical Nucleophilic Fluorination

Equipment

HPC (High Performance Computing) and HTC (High Throughput Computing) Facilities

Various Computer Clusters, Storage Facility

Cite this