Autocatalytic photodegradation of [Ru(ii)(2,2′-bipyridine)2DAD]+(DADH = 1,2-dihydroxyanthracene-9,10-dione) by hydrogen peroxide under acidic aqueous conditions

Lingli Zeng, Dumitru Sirbu, Nikolai V. Tkachenko, Andrew C. Benniston

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

As part of a continuing effort to identify ruthenium agents capable of the photorelease of anthraquinone-based ligands the complexes Δ/Λ-[Ru(bpy)2DAD]+(bpy = 2,2′-bipyridine) were produced by the reaction of 1,2-dihydroxyanthracene-9,10-dione (DADH) with chirally pure Δ/Λ-[Ru(bpy)2(py)2][(+)-O,O′-dibenzoyl-d-tartrate]·12H2O (py = pyridine). A very subtle difference in the chemical shift of the hydroxyl proton in their high-field1H NMR spectra was observed, supporting that the OH proton is susceptible to a small change in environment at the metal centre. The excited state lifetime of the complexes, as measured by femtosecond pump-probe spectroscopy, was 7.1 (±0.8) ps in water (pH 2) and 13 (±1) ps in MeCN. Illumination of a sample of Λ-[Ru(bpy)2DAD]+in water (pH 2) in the presence of hydrogen peroxide resulted in decomposition of the complex. The decay profile, as monitored at several wavelengths, was sigmoidal indicating the reaction was autocatalytic, in which the product formed catalysed decomposition of the starting complex. A mechanism is proposed that relies on participation of the uncoordinated hydroxyl group on the anthraquinone ligand in promoting water loss and radical formation in the excited state. The radical is oxidised by peroxide to generate the ruthenium(iii) complex, which behaves as an oxidant in the autocatalytic process.

Original languageEnglish
Pages (from-to)7640-7646
Number of pages7
JournalDALTON TRANSACTIONS
Volume50
Issue number22
DOIs
Publication statusPublished - 2021
Publication typeA1 Journal article-refereed

Funding

We thank the Royal Society of Chemistry Researcher Mobility Grant for financial support. The National Mass Spectrometry Facility at Swansea University is also thanked for collecting mass spectra.

Publication forum classification

  • Publication forum level 1

ASJC Scopus subject areas

  • Inorganic Chemistry

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