Resonant X-ray photo-oxidation of light-harvesting iron (II/III) N-heterocyclic carbene complexes
Abstract Two photoactive iron N-heterocyclic carbene complexes $${[\hbox {Fe}^{{{\rm{II}}}}(\hbox {btz})_2(\hbox {bpy})]^{2+}}$$ [ Fe II ( btz ) 2 ( bpy ) ] 2 + and $${[\hbox {Fe}^{{\rm{III}}}(\hbox {btz})_3]^{3+}}$$ [ Fe III ( btz ) 3 ] 3 + , where btz is 3,3’-dimethyl-1,1’-bis(p-tolyl)-4,4’-bis(1,...
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| Autores principales: | , , , , , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Nature Portfolio
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/d27330a5170b48d381baf23c66e61dd2 |
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| Sumario: | Abstract Two photoactive iron N-heterocyclic carbene complexes $${[\hbox {Fe}^{{{\rm{II}}}}(\hbox {btz})_2(\hbox {bpy})]^{2+}}$$ [ Fe II ( btz ) 2 ( bpy ) ] 2 + and $${[\hbox {Fe}^{{\rm{III}}}(\hbox {btz})_3]^{3+}}$$ [ Fe III ( btz ) 3 ] 3 + , where btz is 3,3’-dimethyl-1,1’-bis(p-tolyl)-4,4’-bis(1,2,3-triazol-5-ylidene) and bpy is 2,2’-bipyridine, have been investigated by Resonant Photoelectron Spectroscopy (RPES). Tuning the incident X-ray photon energy to match core-valence excitations provides a site specific probe of the electronic structure properties and ligand-field interactions, as well as information about the resonantly photo-oxidised final states. Comparing measurements of the Fe centre and the surrounding ligands demonstrate strong mixing of the Fe $${\hbox {t}_{{\rm{2g}}}}$$ t 2 g levels with occupied ligand $$\pi$$ π orbitals but weak mixing with the corresponding unoccupied ligand orbitals. This highlights the importance of $$\pi$$ π -accepting and -donating considerations in ligand design strategies for photofunctional iron carbene complexes. Spin-propensity is also observed as a final-state effect in the RPES measurements of the open-shell $$\hbox {Fe}^{{\rm{III}}}$$ Fe III complex. Vibronic coupling is evident in both complexes, where the energy dispersion hints at a vibrationally hot final state. The results demonstrate the significant impact of the iron oxidation state on the frontier electronic structure and highlights the differences between the emerging class of $$\hbox {Fe}^{{\rm{III}}}$$ Fe III photosensitizers from those of more traditional $$\hbox {Fe}^{{\rm{II}}}$$ Fe II complexes. |
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