Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Active repair of a dinuclear photocatalyst for visible-light-driven hydrogen production


The molecular apparatus behind biological photosynthesis retains its long-term functionality through enzymatic repair. However, bioinspired molecular devices designed for artificial photosynthesis, consisting of a photocentre, a bridging ligand and a catalytic centre, can become unstable and break down when their individual modules are structurally compromised, halting their overall functionality and operation. Here we report the active repair of such an artificial photosynthetic molecular device, leading to complete recovery of catalytic activity. We have identified the hydrogenation of the bridging ligand, which inhibits the light-driven electron transfer between the photocentre and catalytic centre, as the deactivation mechanism. As a means of repair, we used the light-driven generation of singlet oxygen, catalysed by the photocentre, to enable the oxidative dehydrogenation of the bridging unit, which leads to the restoration of photocatalytic hydrogen formation.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Visible-light-driven hydrogen production with a PMD.
Fig. 2: UV–vis absorption spectra of the catalytic solution at different irradiation times.
Fig. 3: UV–vis and ultrafast transient absorption spectra of the catalytic solution at different irradiation times.
Fig. 4: UV–vis absorption spectra for the dehydrogenation of the deactivated photocatalyst Ru(tpphzH2)PtI2 by singlet oxygen.
Fig. 5: Repetitive active repair of the Ru(bptz)PtCl2 photocatalyst.

Data availability

Source data are provided with this paper and can also be found via Zenodo ( All other data supporting the findings of this study are available within the paper and its Supplementary Information files.


  1. Acar, C., Dincer, I. & Zamfirescu, C. A review on selected heterogeneous photocatalysts for hydrogen production. Int. J. Energy Res. 38, 1903–1920 (2014).

    Article  CAS  Google Scholar 

  2. Hoffert, M. I. et al. Energy implications of future stabilization of atmospheric CO2 content. Nature 395, 881–884 (1998).

    Article  CAS  Google Scholar 

  3. Lewis, N. S. & Nocera, D. G. Powering the planet: chemical challenges in solar energy utilization. Proc. Natl Acad. Sci. USA 103, 15729–15735 (2006).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  4. Hammarström, L. Towards artificial photosynthesis: ruthenium–manganese chemistry mimicking photosystem II reactions. Curr. Opin. Chem. Biol. 7, 666–673 (2003).

    Article  PubMed  CAS  Google Scholar 

  5. Andreiadis, E. S., Chavarot-Kerlidou, M., Fontecave, M. & Artero, V. Artificial photosynthesis: from Molecular catalysts for light-driven water splitting to photoelectrochemical cells. Photochem. Photobiol. 87, 946–964 (2011).

    Article  CAS  PubMed  Google Scholar 

  6. Balzani, V. Photochemical molecular devices. Photochem. Photobiol. Sci. 2, 459–476 (2003).

    Article  CAS  PubMed  Google Scholar 

  7. Ceroni, P., Credi, A., Venturi, M. & Balzani, V. Light-powered molecular devices and machines. Photochem. Photobiol. Sci. 9, 1561–1573 (2010).

    Article  CAS  PubMed  Google Scholar 

  8. Barber, J. Photosystem II: the water-splitting enzyme of photosynthesis. Cold Spring Harb. Symp. Quant. Biol. 77, 295–307 (2012).

    Article  CAS  PubMed  Google Scholar 

  9. Blankenship, R. E. Molecular Mechanisms of Photosynthesis (Blackwell Science, 2002);

  10. Gamage, D. et al. New insights into the cellular mechanisms of plant growth at elevated atmospheric carbon dioxide concentrations. Plant.Cell Environ. 41, 1233–1246 (2018).

    Article  CAS  PubMed  Google Scholar 

  11. Barber, J. & Andersson, B. Revealing the blueprint of photosynthesis. Nature 370, 31–34 (1994).

    Article  CAS  Google Scholar 

  12. Kato, Y. & Sakamoto, W. Protein quality control in chloroplasts: a current model of D1 protein degradation in the photosystem II repair cycle. J. Biochem. 146, 463–469 (2009).

    Article  CAS  PubMed  Google Scholar 

  13. Kanan, M. W. & Nocera, D. G. In situ formation of an oxygen-evolving catalyst in neutral water containing phosphate and Co2+. Science 321, 1072–1075 (2008).

  14. Kärkäs, M. D., Verho, O., Johnston, E. V. & Åkermark, B. Artificial photosynthesis: molecular systems for catalytic water oxidation. Chem. Rev. 114, 11863–12001 (2014).

    Article  PubMed  CAS  Google Scholar 

  15. Rau, S., Walther, D. & Vos, J. G. Inspired by nature: light driven organometallic catalysis by heterooligonuclear Ru(II) complexes. Dalton Trans. 915–919 (2007).

  16. Kim, D., Whang, D. R. & Park, S. Y. Self-healing of molecular catalyst and photosensitizer on metal–organic framework: robust molecular system for photocatalytic H2 evolution from water. J. Am. Chem. Soc. 138, 8698–8701 (2016).

    Article  CAS  PubMed  Google Scholar 

  17. Elvington, M., Brown, J., Arachchige, S. M. & Brewer, K. J. Photocatalytic hydrogen production from water employing a Ru, Rh, Ru molecular device for photoinitiated electron collection. J. Am. Chem. Soc. 129, 10644–10645 (2007).

    Article  CAS  PubMed  Google Scholar 

  18. White, T. A., Higgins, S. L. H., Arachchige, S. M. & Brewer, K. J. Efficient photocatalytic hydrogen production in a single-component system using Ru,Rh,Ru supramolecules containing 4,7-diphenyl-1,10-phenanthroline. Angew. Chem. Int. Ed. 50, 12209–12213 (2011).

    Article  CAS  Google Scholar 

  19. Manbeck, G. F. & Brewer, K. J. Photoinitiated electron collection in polyazine chromophores coupled to water reduction catalysts for solar H2 production. Coord. Chem. Rev. 257, 1660–1675 (2013).

    Article  CAS  Google Scholar 

  20. Pfeffer, M. G. et al. Palladium versus platinum: the metal in the catalytic center of a molecular photocatalyst determines the mechanism of the hydrogen production with visible light. Angew. Chem. Int. Ed. 54, 5044–5048 (2015).

    Article  CAS  Google Scholar 

  21. Steel, P. J. & Constable, E. C. Synthesis, spectroscopy, and electrochemistry of homo- and hetero-leptic ruthenium(II) complexes of new pyrazole-containing bidentate ligands. J. Chem. Soc. Dalton Trans. 1389–1396 (1990).

  22. Berardi, S. et al. Molecular artificial photosynthesis. Chem. Soc. Rev. 43, 7501–7519 (2014).

    Article  CAS  PubMed  Google Scholar 

  23. Ozawa, H., Haga, M. & Sakai, K. A photo-hydrogen-evolving molecular device driving visible-light-induced EDTA-reduction of water into molecular hydrogen. J. Am. Chem. Soc. 128, 4926–4927 (2006).

    Article  CAS  PubMed  Google Scholar 

  24. Rau, S. et al. A supramolecular photocatalyst for the production of hydrogen and the selective hydrogenation of tolane. Angew. Chem. Int. Ed. 45, 6215–6218 (2006).

    Article  CAS  Google Scholar 

  25. Suneesh, C. V. et al. Mechanistic studies of photoinduced intramolecular and intermolecular electron transfer processes in RuPt-centred photo-hydrogen-evolving molecular devices. Phys. Chem. Chem. Phys. 16, 1607–1616 (2014).

    Article  CAS  PubMed  Google Scholar 

  26. Pfeffer, M. G. et al. Optimization of hydrogen-evolving photochemical molecular devices. Angew. Chem. Int. Ed. 54, 6627–6631 (2015).

    Article  CAS  Google Scholar 

  27. Kaufhold, S., Imanbaew, D., Riehn, C. & Rau, S. Rational in situ tuning of a supramolecular photocatalyst for hydrogen evolution. Sustain. Energy Fuels 1, 2066–2070 (2017).

    Article  CAS  Google Scholar 

  28. Zedler, L. et al. Unraveling the light‐activated reaction mechanism in a catalytically competent key intermediate of a multifunctional molecular catalyst for artificial photosynthesis. Angew. Chem. Int. Ed. 58, 13140–13148 (2019).

    Article  CAS  Google Scholar 

  29. Davidson, R. S. & Trethewey, K. R. Photosensitised oxidation of amines: mechanism of oxidation of triethylamine. J. Chem. Soc. Perkin Trans. 2, 173–178 (1977).

  30. Jiang, G., Chen, J., Huang, J.-S. & Che, C.-M. Highly efficient oxidation of amines to imines by singlet oxygen and its application in Ugi-type reactions. Org. Lett. 11, 4568–4571 (2009).

    Article  CAS  PubMed  Google Scholar 

  31. Alonso, A. M. et al. Generation of strong, homochiral bases by electrochemical reduction of phenazine derivatives. Chem. Commun. 412–413 (2004).

  32. Jackson, M. N. et al. Strong electronic coupling of molecular sites to graphitic electrodes via pyrazine conjugation. J. Am. Chem. Soc. 140, 1004–1010 (2018).

    Article  CAS  PubMed  Google Scholar 

  33. Ji, Z., He, M., Huang, Z., Ozkan, U. & Wu, Y. Photostable p-type dye-sensitized photoelectrochemical cells for water reduction. J. Am. Chem. Soc. 135, 11696–11699 (2013).

    Article  CAS  PubMed  Google Scholar 

  34. Zedler, L. et al. Resonance-Raman spectro-electrochemistry of intermediates in molecular artificial photosynthesis of bimetallic complexes. Chem. Commun. 50, 5227–5229 (2014).

  35. Konduri, R. et al. Ruthenium photocatalysts capable of reversibly storing up to four electrons in a single acceptor ligand: a step closer to artificial photosynthesis. Angew. Chem. Int. Ed. 41, 3185–3187 (2002).

    Article  CAS  Google Scholar 

  36. Konduri, R., de Tacconi, N. R., Rajeshwar, K. & MacDonnell, F. M. Multielectron photoreduction of a bridged ruthenium dimer, [(phen)2Ru(tatpp)Ru(phen)2][PF6]4: aqueous reactivity and chemical and spectroelectrochemical identification of the photoproducts. J. Am. Chem. Soc. 126, 11621–11629 (2004).

    Article  CAS  PubMed  Google Scholar 

  37. Anne, A., Hapiot, P., Moiroux, J., Neta, P. & Saveant, J. M. Dynamics of proton transfer from cation radicals. Kinetic and thermodynamic acidities of cation radicals of NADH analogs. J. Am. Chem. Soc. 114, 4694–4701 (1992).

    Article  CAS  Google Scholar 

  38. Zhang, X. et al. Dynamics of .alpha.-CH deprotonation and .alpha.-desilylation reactions of tertiary amine cation radicals. J. Am. Chem. Soc. 116, 4211–4220 (1994).

    Article  CAS  Google Scholar 

  39. Schmittel, M. & Burghart, A. Understanding reactivity patterns of radical cations. Angew. Chem. Int. Ed. Engl. 36, 2550–2589 (1997).

    Article  Google Scholar 

  40. Pellegrin, Y. & Odobel, F. Sacrificial electron donor reagents for solar fuel production. C. R. Chim. 20, 283–295 (2017).

    Article  CAS  Google Scholar 

  41. McGovern, D. A., Selmi, A., O’Brien, J. E., Kelly, J. M. & Long, C. Reduction of dipyrido-[3,2-a:2′,3′-c]-phenazine (dppz) by photolysis in ethanol solution. Chem. Commun. 1402–1404 (2005).

  42. Juliarena, M. P. et al. On the association and structure of radicals derived from dipyridil[3,2-a:2′3′-c]phenazine. Contrast between the electrochemical, radiolytic, and photochemical reduction processes. J. Org. Chem. 71, 2870–2873 (2006).

  43. Ruiz, G. T., Juliarena, M. P., Lezna, R. O., Feliz, M. R. & Ferraudi, G. On the parallel formation of long-lived excited states of dipyridil[3,2-a:2′3′-c]phenazine, dppz. J. Photochem. Photobiol. A 179, 289–297 (2006).

  44. Guo, W. & Obare, S. O. Tuning the reduction of 9,11,20,22-tetraaza-tetrapyridopentacene (TATPP). Tetrahedron Lett. 49, 4933–4936 (2008).

    Article  CAS  Google Scholar 

  45. Mulazzani, Q. G. et al. The reduction of Ru(bpy)2(dipyridophenazine)2+ in aqueous solution. A radiolytic study. New J. Chem. 13, 441–447 (1989).

    CAS  Google Scholar 

  46. Tschierlei, S. et al. Photophysics of an Intramolecular hydrogen-evolving Ru–Pd photocatalyst. Chem. Eur. J. 15, 7678–7688 (2009).

    Article  CAS  PubMed  Google Scholar 

  47. Creutz, C. & Sutin, N. Electron-transfer reactions of excited states: direct evidence for reduction of the charge-transfer excited state of tris(2,2′-bipyridine)ruthenium(II). J. Am. Chem. Soc. 98, 6384–6385 (1976).

    Article  CAS  Google Scholar 

  48. Anderson, C. P., Salmon, D. J., Meyer, T. J. & Young, R. C. Photochemical generation of Ru(bpy)3+ and O2. J. Am. Chem. Soc. 99, 1980–1982 (1977).

    Article  CAS  Google Scholar 

  49. Mulazzani, Q. G., Emmi, S., Fuochi, P. G., Hoffman, M. Z. & Venturi, M. On the nature of tris(2,2′-bipyridine)ruthenium(1+) ion in aqueous solution. J. Am. Chem. Soc. 100, 981–983 (1978).

    Article  CAS  Google Scholar 

  50. Baron, A. et al. Efficient electron transfer through a triazole link in ruthenium(II) polypyridine type complexes. Chem. Commun. 47, 11011–11013 (2011).

  51. Carolin, M., Friedländer, I., Bagemihl B., Rau, S. & Dietzek-Ivanšić, B. The electron that breaks the catalyst’s back—excited state dynamics in intermediates of molecular photocatalysts. Phys. Chem. Chem. Phys. 23, 27397–27403 (2021).

  52. Wang, C., Li, C., Wu, X., Pettman, A. & Xiao, J. pH-regulated asymmetric transfer hydrogenation of quinolines in water. Angew. Chem. Int. Ed. 48, 6524–6528 (2009).

    Article  CAS  Google Scholar 

  53. Zhang, L. et al. Versatile (pentamethylcyclopentadienyl)rhodium-2,2′-bipyridine (Cp*Rh-bpy) catalyst for transfer hydrogenation of N-heterocycles in water. Adv. Synth. Catal. 357, 3529–3537 (2015).

    Article  CAS  Google Scholar 

  54. Rau, S. et al. Photoinduced ligand transformation in a ruthenium polypyridophenazine complex. Eur. J. Inorg. Chem. 2008, 1031–1034 (2008).

    Article  CAS  Google Scholar 

  55. Chakrabortty, S. et al. Mitochondria targeted protein-ruthenium photosensitizer for efficient photodynamic applications. J. Am. Chem. Soc. 139, 2512–2519 (2017).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  56. Li, M. Y. et al. Quenching of singlet molecular oxygen (1O2) by azide anion in solvent mixtures. Photochem. Photobiol. 74, 760-764 (2001).

  57. Kozak, P. J. & Gesser, H. The photolysis of triethylamine, and reactions of methyl radicals with triethylamine and diethylamine. J. Chem. Soc. 448–452 (1960).

  58. Torriero, A. A. J., Shiddiky, M. J. A., Burgar, I. & Bond, A. M. Homogeneous electron-transfer reaction between electrochemically generated ferrocenium ions and amine-containing compounds. Organometallics 32, 5731–5739 (2013).

    Article  CAS  Google Scholar 

  59. Amthor, S. et al. Tailored protective groups for surface immobilization of ruthenium dyes. Dalton Trans. 49, 3735–3742 (2020).

    Article  CAS  PubMed  Google Scholar 

Download references


We thank the German Science Foundation for funding via the TRR 234 CataLight (project number 364549901; project A1, C.M., B.D.-I. and S.R.; project B4, M.W.; project C5, P.S., S.K. and S.G), the Fonds der Chemischen Industrie (Kekulé-Stipendium, C.M.) and the Studienstiftung des Deutschen Volkes (PhD scholarship, B.B.). We acknowledge the developers of the KiMoPack software employed for global lifetime analysis of the time-resolved spectra. All calculations were performed at the Universitätsrechenzentrum (Friedrich Schiller University Jena, P.S., S.K. and S.G.). The funding organizations had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

Author information

Authors and Affiliations



M.G.P., E.T.E.K. and D.C. performed the catalysis experiments, C.M. performed the steady-state and time-dependent in situ spectroscopic studies, and M.S. and M.W. synthesized and investigated the hydrogenated photocatalyst. M.G.P., A.K.M., B.B., S.F., J.H., D.C., F.L., G.S.H. and S.R. developed the active repair strategies. P.S., S.K. and S.G. conducted the quantum chemical simulations. M.G.P, C.M., L.P., G.S.H., J.G.V., A.K.M., B.D.-I. and S.R. wrote the manuscript with help from all the other authors.

Corresponding authors

Correspondence to Benjamin Dietzek-Ivanšić or Sven Rau.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Chemistry thanks Ken Sakai, Claudia Turro and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–27, Tables 1–4, Discussion and Experimental Details.

Source data

Source Data Fig. 1

Hydrogen turnover numbers and chemical structures.

Source Data Fig. 2

In situ absorption data and chemical structures.

Source Data Fig. 3

In situ absorption and ultrafast transient absorption data, hydrogen turnover numbers (mean, s.d., n = 3) and peak area ratios.

Source Data Fig. 4

Absorption data.

Source Data Fig. 5

Hydrogen turnover numbers and chemical structures.

Rights and permissions

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Pfeffer, M.G., Müller, C., Kastl, E.T.E. et al. Active repair of a dinuclear photocatalyst for visible-light-driven hydrogen production. Nat. Chem. 14, 500–506 (2022).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing