Resonant inelastic X-ray scattering of a Ru photosensitizer: Insights from individual ligands to the electronic structure of the complete molecule

Temperton, Robert H.; Skowron, Stephen T.; Handrup, Karsten; Gibson, Andrew; Nicolaou, A.; Jaouen, N.; Besley, Elena; O’Shea, James N.

doi:10.1063/1.5114692

“…It is noteworthy that vibronic coupling was previously evidenced by RIXS at the N K‐edge in aqueous ammonia, [ 44 ] spin‐liquid insulator, [ 22 ] and on small organic molecules with other vibrational modes. [ 45,46 ] Our work demonstrates that RIXS can also be used to probe vibronic interactions in polymeric material.…”

Section: Resultsmentioning

confidence: 92%

Role of Dopants on the Local Electronic Structure of Polymeric Carbon Nitride Photocatalysts

Ren

¹

,

Lin

²

,

Lieutenant

³

et al. 2020

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Polymeric carbon nitride (PCN) is a promising class of materials for solar‐to‐chemical energy conversion. The increase of the photocatalytic activity of PCN is often achieved by the incorporation of heteroatoms, whose impact on the electronic structure of PCN remains poorly explored. This work reveals that the local electronic structure of PCN is strongly altered by doping with sulfur and iron using X‐ray absorption spectroscopy (XAS) and resonant inelastic X‐ray scattering (RIXS). From XAS at the carbon and nitrogen K‐edges, sulfur atoms are found to mostly affect carbon atoms, in contrast to iron doping mostly altering nitrogen sites. In RIXS at the nitrogen K‐edge, a vibrational progression, affected by iron doping, is evidenced, which is attributed to a vibronic coupling between excited electrons in nitrogen atoms and C–N stretching modes in PCN heterocycling rings. This work opens new perspectives for the characterization of vibronic coupling in polymeric photocatalysts.

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“…Many recent studies utilizing RIXS have targeted nitrogen-conjugated heterocycles as fundamental building blocks of larger biomolecules 18 − 20 and as ligands in metal-complexes 21 used for catalysis and energy harvesting. 22 In this context, we report on a quantitative combined experimental and theoretical investigation of the RIXS spectra of aqueous pyrimidine, as a prime example of the interplay between the two symmetry breaking mechanisms. Pyrimidine belongs to the C 2 v point group, containing two identical nitrogens, which are acceptors of strong solute–solvent hydrogen bonds, 23 − 26 via their in plane lone-pair orbitals.…”

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confidence: 99%

Breaking the Symmetry of Pyrimidine: Solvent Effects and Core-Excited State Dynamics

Eckert

¹

,

Cruz

²

,

Ochmann

³

et al. 2021

J. Phys. Chem. Lett.

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Symmetry and its breaking crucially define the chemical properties of molecules and their functionality. Resonant inelastic X-ray scattering is a local electronic structure probe reporting on molecular symmetry and its dynamical breaking within the femtosecond scattering duration. Here, we study pyrimidine, a system from the C 2 v point group, in an aqueous solution environment, using scattering though its 2a 2 resonance. Despite the absence of clean parity selection rules for decay transitions from in-plane orbitals, scattering channels including decay from the 7b 2 and 11a 1 orbitals with nitrogen lone pair character are a direct probe for molecular symmetry. Computed spectra of explicitly solvated molecules sampled from a molecular dynamics simulation are combined with the results of a quantum dynamical description of the X-ray scattering process. We observe dominant signatures of core-excited Jahn–Teller induced symmetry breaking for resonant excitation. Solvent contributions are separable by shortening of the effective scattering duration through excitation energy detuning.

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“…Several metal complexes have been studied with RPES, including the Ru centred light-harvesting complexes “N3” 40 , 41 and “N719” 42 . RPES has also been used to probe the metal centre of the ferricyanide and ferrocyanide model complexes 43 .…”

Section: Introductionmentioning

confidence: 99%

“…The similar ligand environments in the two complexes allow a good comparison of and oxidation states. Additionally, it is noteworthy that the valence-ionised final state in RPES distinguishes this technique from the related technique of Resonant Inelastic X-ray Scattering (RIXS), which has successfully been used to investigate transition metal complexes 41 , 45 , including the highly relevant ferrous and ferric hexacyanide 46 . The RIXS process is the photon-in/photon-out analogue of RPES (photon-in/electron-out), and as such the final state is not oxidised.…”

Section: Introductionmentioning

confidence: 99%

Resonant X-ray photo-oxidation of light-harvesting iron (II/III) N-heterocyclic carbene complexes

Temperton

¹

,

Guo

²

,

D’Acunto

³

et al. 2021

Sci Rep

Self Cite

2

0

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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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Resonant inelastic X-ray scattering of a Ru photosensitizer: Insights from individual ligands to the electronic structure of the complete molecule

Cited by 13 publications

References 30 publications

Role of Dopants on the Local Electronic Structure of Polymeric Carbon Nitride Photocatalysts

Role of Dopants on the Local Electronic Structure of Polymeric Carbon Nitride Photocatalysts

Breaking the Symmetry of Pyrimidine: Solvent Effects and Core-Excited State Dynamics

Resonant X-ray photo-oxidation of light-harvesting iron (II/III) N-heterocyclic carbene complexes

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