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PreprintCC BY-NC-NDChemRxiv

Enhanced Spin-Forbidden Excitation of Ru(II) Polypyridyl Complexes for the Promotion of Red-Light Photocatalysis

  • Yahya Al Ayi1,2
  • Nathan Grandjean1,2
  • Benjamin Riss-Yaw1,2
  • Annamaria Quaranta1,3
  • Eugénie Romero1,2
  1. 1Université Paris-Saclay
  2. 2SCBM
  3. 3CEA, CNRS, I2BC
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Abstract

Photoredox catalysis, mainly occurring under blue light, has emerged as an indispensable tool in modern organic synthesis. However, some limitations remain, mostly due to the high energy inherent to the irradiation wavelengths used. Red-light excitation of transition-metal photocatalysts is attractive for expanding the synthetic utility of visible-light photochemistry. Here, we report a strategy to enhance spin-forbidden red-light absorption in Ru(II) polypyridyl complexes through ligand tuning. [Ru(Br2-bpy)3](PF6)2 exhibits a substantially intensified spin-forbidden absorption band in the red region, with a molar extinction coefficient approximately 10-fold higher than that of [Ru(bpy)3]2+. The enhanced red-light absorption results in markedly improved photocatalytic activity under 660 nm irradiation in a range of electron- and energy-transfer transformations. Comparison with the parent complex demonstrates that modulation of the spin-forbidden absorption pathway can directly influence red-light photochemical reactivity. These findings support ligand modification as an effective approach for enhancing spin-forbidden excitation and provide a molecular design strategy for redlight-responsive Ru(II) photocatalysts, establishing Ru(II) polypyridyl complexes as an efficient family of photocatalysts activated via a spin-forbidden transition pathway.

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Cite

BibTeXRIS
BibTeX
@misc{ayi2026enhanced,
  title = {{Enhanced Spin-Forbidden Excitation of Ru(II) Polypyridyl Complexes for the Promotion of Red-Light Photocatalysis}},
  author = {Yahya Al Ayi and Nathan Grandjean and Benjamin Riss-Yaw and Annamaria Quaranta and Eugénie Romero},
  howpublished = {ChemRxiv},
  year = {2026},
  month = oct,
  doi = {10.26434/chemrxiv.15010242/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010242/v1},
  note = {CC BY-NC-ND},
}
RIS
TY  - UNPB
TI  - Enhanced Spin-Forbidden Excitation of Ru(II) Polypyridyl Complexes for the Promotion of Red-Light Photocatalysis
AU  - Yahya Al Ayi
AU  - Nathan Grandjean
AU  - Benjamin Riss-Yaw
AU  - Annamaria Quaranta
AU  - Eugénie Romero
PY  - 2026
DA  - 2026/10/11
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15010242/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010242/v1
AB  - Photoredox catalysis, mainly occurring under blue light, has emerged as an indispensable tool in modern organic synthesis. However, some limitations remain, mostly due to the high energy inherent to the irradiation wavelengths used. Red-light excitation of transition-metal photocatalysts is attractive for expanding the synthetic utility of visible-light photochemistry. Here, we report a strategy to enhance spin-forbidden red-light absorption in Ru(II) polypyridyl complexes through ligand tuning. [Ru(Br2-bpy)3](PF6)2 exhibits a substantially intensified spin-forbidden absorption band in the red region, with a molar extinction coefficient approximately 10-fold higher than that of [Ru(bpy)3]2+. The enhanced red-light absorption results in markedly improved photocatalytic activity under 660 nm irradiation in a range of electron- and energy-transfer transformations. Comparison with the parent complex demonstrates that modulation of the spin-forbidden absorption pathway can directly influence red-light photochemical reactivity. These findings support ligand modification as an effective approach for enhancing spin-forbidden excitation and provide a molecular design strategy for redlight-responsive Ru(II) photocatalysts, establishing Ru(II) polypyridyl complexes as an efficient family of photocatalysts activated via a spin-forbidden transition pathway.
ER  -