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The standard deviation of the calculated bond lengths was found to be 0. The difference signal for the bulk solvent temperature increase was measured according to the standard procedure using azobenzene molecules. Dashed lines separate the three main contributions to the temperature rise as discussed in the main text. The cage term was simulated with a purely classical MD, which accounts for solvation effects arising from the structural changes in the molecule, but it neglects the electronic charge redistribution in the molecule from the GS to 5 MC. After thermal relaxation of the excited species we observe a temperature rise of 0.

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After ps the temperature grows due to the release of the 5 MC state energy following its decay to the GS. Moreover, the method employed here can be used for the refinement of many organometallic complexes which do not contain pairs of heavy atoms. Improvements in the cage modelling will also impact the accuracy of the energetic parameters since both solvation and solvent contributions are present primarily in the low- q region of the difference signal.

The result of the refinement is: More generally this work illustrates how TRWAXS on a photosensitive molecule in solution provides information not only on the transient structures, but also on the energies of short-lived excited species, which is traditionally a difficult task since most experiments are either tailored towards structure or energy sensitivity.

By comparing the DFT results obtained using different functionals with the experimental data, we identify the ones providing the best agreement with the data in order to improve future theoretical predictions. Further improvements of the experimental setup in terms of stability and signal-to-noise should help in increasing the precision of the extracted energies.

The refinement procedure aided by DFT calculations used in this work will further expand the classes of systems for which TRWAXS can provide experimental determination of short-lived excited state structures, beyond systems with heavy atom pairs.

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Box 12 4, LundSweden. To map the overall atomic positions characterized by the selected structural parameters, we have implemented a procedure based on the interpolation between the structures produced by varying the values of R ax and R eq and performing constrained Wn-40ps for each R axR eq point.


By varying these parameters and from those determine the resulting changes to the rest of the structure, one can refine the overall molecular structure within the framework of the wn-400pe structural model. The three contributions to the temperature dynamics are shown in Fig. The cage term was simulated with fasper purely classical MD, which accounts for solvation cxsper arising from the structural changes in the molecule, but it neglects the electronic charge redistribution in the molecule from the GS to 5 MC.

It confirms the computational prediction that NHC compounds exhibit excited MC states where the minima are pushed further away from the GS along the main reaction coordinate metal-to-ligand bond distance. Future systematic TRWAXS studies of Fe II complexes will be able to capture the effect of the ligand structure on the kinetic, structural, and energetic aspects of charge transfer and spin transitions in this class of systems allowing for more detailed investigations of the role of the excited MC states in the MLCT deactivation process.

Garage E. Kasper AG –

TRWAXS is also highly sensitive to the time dependent thermodynamic response of the solvent, 59 which, as we demonstrate in this work, can be used to determine the energy of the excited states. A fraction of the initial solvent temperature increase could not be attributed to the relaxation of the excited molecules as discussed further below.

Our results demonstrate that due to the increased ligand field strength caused by NHC ligands, upon transition from the ground state to the 5 MC state, the metal to ligand bonds extend by unusually large values: Previous work on Fe II SCO complexes have established that the structural changes induced by the transition from the GS to 5 MC are well described by parameterizing the global structure through parameters that define the shape of the first Fe coordination shell, including metal—ligand bond lengths, ligand bite angles and ligand rocking angles, as the reaction coordinates.

A 31 ps component was tentatively assigned to vibrational cooling of this MC state. In both a and b the spheres represent Fe and its first coordination shell, rods represent the rest of the molecular structure.

This finding indicates that, at least for NHC systems, the short MC state lifetime is not indicative of its 3 MC character, as suggested for expanded cage and push—pull compounds in recent spectroscopic works 54,55 and observed in weak LFS Ru II based compounds.


Multidimensional photoemission spectroscopy—the space-charge limit

Hence, this complex allows for a detailed investigation, using ps X-ray pulses from a synchrotron, of strong ligand field effects on the intermediate MC state in an NHC complex. Note that our refinement procedure allows for an experimental determination of wn-4000ps global molecular structure as a function of two bond distances rather than the refinement of these two distances alone.

We identify it as a ps metal-centered quintet 5 MC state, and we refine the molecular structure of the excited-state complex verifying the DFT wh-400ps. Using information about the hydrodynamic state of the solvent, we also determine, for the first wn4-00ps, the energy of the 5 MC state as 0.

After thermal relaxation of the excited species we observe a temperature rise of 0.

Multidimensional photoemission spectroscopy—the space-charge limit – IOPscience

The key structural parameters defining the structure of the molecule are highlighted with colors. Although the 3 MC state was not observed, it was added to the relaxation cascade analogously to Fe II polypyridyl complexes.

The standard wn-400pps of the calculated bond lengths was found to be 0. Overall, the presented results show that the transition in photophysical properties between weak LFS and strong LFS Fe—NHC compounds manifest itself not only in the destabilization of the MC states, but also in the significantly different structural dynamics of these systems.

wwn-400ps Laursen cGemma E. Understanding the nature of the observed temperature offset requires better time resolution which is beyond the scope of the present study.

The key is that the parameters chosen need to define the relevant reaction coordinates associated with the structural dynamics. Moreover, TRWAXS can uniquely provide information about excited state energies by direct assessment of the amount of energy disposed into the solvent during excited state relaxation.

These results imply that the transition in the photochemical properties wn-400os typical Fe complexes to novel NHC compounds is manifested not only in the destabilization of the MC states, but also in structural distortion of these states.