| Autor: |
Justin Earley, Anna Zieleniewska, Hunter Ripberger, Megan Lazorski, Zachary Mast, Hannah Sayre, Robert Knowles, James McCusker, Gregory Scholes, Obadiah Reid, Garry Rumbles |
| Rok vydání: |
2021 |
| Popis: |
We report evidence of excited-state ion pair reorganisation in a cationic iridium (III) photoredox catalyst in 1,4-dioxane. Microwave-frequency dielectric-loss measurements allow us to assign both ground and excited-state molecular dipoles and excited-state polarizability volumes. These measurements show significant changes in ground-state dipole moment between [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]PF_{6} (10.74 Debye) and [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]BAr^{F}_{4} (4.86 Debye). Photoexcitation of each complex results in population of highly mixed ligand centered and metal-to-ligand charge transfer states. Relaxation to the lowest lying excited-state leads to a negative change in the dipole for [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]PF_{6}, and a positive change in dipole for [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]BAr^{F}_{4}. These observations are consistent with a sub-nanosecond reorganization with the PF_{6}^{-} counter-ion. Taken together, these observations suggest contact-ion pair formation in [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]PF_{6}. The ion pair reorganisation we observe with the PF_{6}^{-} may modify both the thermodynamic potential available for electron transfer and inhibit oxidative catalysis, providing a possible mechanism for recently observed trends in similar complexes. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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