Mechanistic Insight into Catalyst-Controlled Photodegradation of Ru(II) Polypyridyl Complexes
Keywords:
(Ruthenium(II) polypyridyl complexes, ; Photodegradation mechanism, MLCT states, PtI₂ coordination, UV–Vis spectroscopy, Solvent effects)Abstract
Understanding the mechanisms governing the photodegradation of Ru(II) polypyridyl complexes is essential for the rational design of stable photoactive systems. In this study, mechanistic insight into the catalyst-controlled photodegradation of Ru(II) complexes bearing tbbpy ligands is presented through a comparative investigation of systems with and without a peripheral PtI₂ unit. Photodegradation under visible-light irradiation was monitored by time-dependent UV–Vis spectroscopy and analyzed under pseudo-first-order kinetic conditions in acetonitrile and methanol. Complementary HPLC and ¹H NMR analyses verified that the observed spectral changes arise from irreversible chemical degradation rather than transient photophysical processes. Coordination of the PtI₂ unit significantly modulates the MLCT excited state, leading to a reduced optical gap and prolonged excited-state lifetime, as supported by TD-DFT calculations. Solvent-dependent kinetic behavior further reveals the role of medium coordination in stabilizing the photoexcited state. Collectively, these results provide mechanistic insight into how catalyst coordination governs photodegradation pathways in Ru(II) polypyridyl complexes
References
Cotic, A., Ramírez-Wierzbecki, I., & Cadranel, A. (2024). Harnessing high-energy MLCT excited states for artificial photosynthesis. Coordination Chemistry Reviews, 514, 215878.
https://doi.org/10.1016/j.ccr.2024.215878
Di Pietro, M. L., La Ganga, G., Nastasi, F., & Puntoriero, F. (2021). Ru(II)-Dppz Derivatives and Their Interactions with DNA: Thirty Years and Counting. Applied Sciences, 11(7), 3038.
https://doi.org/10.3390/app11073038
Fennes, A., Montesdeoca, N., Papadopoulos, Z., & Karges, J. (2024). Rational design of a red-light absorbing ruthenium polypyridine complex as a photosensitizer for photodynamic therapy. Chemical Communications,60,10724–10727.
https://doi.org/10.1039/D4CC04126G
García-Camacho, F., Martín-Diana, A. B., Nicasio, M. C., & López-García, M. (2021).
Excited-state lifetime tuning in transition metal complexes: From fundamentals to applications. Chemical Society Reviews, 50(15), 8452–8487.
https://doi.org/10.1039/D1CS00233A
Khanduja, D., Singh, A., Sharma, P., Gupta, R., Verma, S., & Kumar, V. (2023). Enhanced photostability and photoactivity of ruthenium polypyridyl-based photocatalysts by covalently anchoring onto reduced graphene oxide. ACS Omega, 8(15), 13821–13833.
https://doi.org/10.1021/acsomega.3c08800
Lanquist, A. P., Piechota, E. J., Wickramasinghe, L. D., Marques Silva, A., Thummel, R. P., & Turro, C. (2023). New Tridentate Ligand Affords a Long-Lived 3MLCT Excited State in a Ru(II) Complex: DNA Photocleavage and 1O2 Production. Inorganic chemistry, 62(39), 15927–15935.
https://doi.org/10.1021/acs.inorgchem.3c01990
Milenković, D. P., & Zarić, S. (2020). Stacking interactions between indenyl ligands of transition metal complexes: Crystallographic and density functional study. Crystal Growth & Design, 20(7), 4491–4502.
https://doi.org/10.1021/acs.cgd.0c00303
Mohammed, H. A., & Younis, H. A. (2025, November 30). Investigation of solvent effects on the spectroscopic and photochemical properties of ruthenium(II) polypyridyl complexes [Paper presentation]. Proceedings of the Environmental Pollution and Challenges of Environmental Sustainability Conference (EPESC). Sirte University Institutional Repository.
http://dspace-su.server.ly:8080/xmlui/handle/123456789/3595
Ruslanova J, Decurtins S, Rusanov E, Stoeckli-Evans H, Delahaye S, Hauser A. Ruthenium(II) complex of bis(2,2′-bipyridine)(6,7-dicyanodipyrido[3,2-a:2′,3′-c]phenazine): synthesis, structure, electrochemical and luminescence studies. J Chem Soc Dalton Trans. 2002;(23):4318–4320. https://doi.org/10.1039/B210440G
Sun, Y., El Ojaimi, M., Hammitt, R., Thummel, R. P., & Turro, C. (2010). Effect of ligands with extended π-system on the photophysical properties of Ru(II) complexes. The journal of physical chemistry. B, 114(45), 14664–14670.
https://doi.org/10.1021/jp102613n
Suneesh, C. V., Balan, B., Ozawa, H., Nakamura, Y., Katayama, T., Muramatsu, M., Nagasawa, Y., Miyasaka, H., & Sakai, K. (2014). Mechanistic studies of photoinduced intramolecular and intermolecular electron transfer processes in RuPt-centred photo-hydrogen-evolving molecular devices. Physical Chemistry Chemical Physics, 16(4), 1607–1616.
https://doi.org/10.1039/c3cp54630f
Wei, H., Li, R., & Zhang, X. (2020).
Recent advances in ruthenium(II) polypyridyl complexes: Photophysics, photochemistry and applications. Coordination Chemistry Reviews, 416, 213338.
