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Electronic structures of transition metal complexes-core level spectroscopic investigation
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Uppsala: Uppsala University, The Department of Chemistry The Ångström Laboratory , 2016. , 40 p.
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-275074OAI: oai:DiVA.org:uu-275074DiVA: diva2:898659
Presentation
2016-02-25, Å64119, Ångström Laboratory, Uppsala, 22:52 (English)
Opponent
Supervisors
Available from: 2016-02-05 Created: 2016-01-28 Last updated: 2016-11-08Bibliographically approved
List of papers
1. Restricted active space calculations of L-edge X-ray absorption spectra: From molecular orbitals to multiplet states
Open this publication in new window or tab >>Restricted active space calculations of L-edge X-ray absorption spectra: From molecular orbitals to multiplet states
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2014 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 141, no 12, 124116Article in journal (Refereed) Published
Abstract [en]

The metal L-edge (2p -> 3d) X-ray absorption spectra are affected by a number of different interactions: electron-electron repulsion, spin-orbit coupling, and charge transfer between metal and ligands, which makes the simulation of spectra challenging. The core restricted active space (RAS) method is an accurate and flexible approach that can be used to calculate X-ray spectra of a wide range of medium-sized systems without any symmetry constraints. Here, the applicability of the method is tested in detail by simulating three ferric (3d(5)) model systems with well-known electronic structure, viz., atomic Fe3+, high-spin [FeCl6](3-) with ligand donor bonding, and low-spin [Fe(CN)(6)](3-) that also has metal backbonding. For these systems, the performance of the core RAS method, which does not require any system-dependent parameters, is comparable to that of the commonly used semi-empirical charge-transfer multiplet model. It handles orbitally degenerate ground states, accurately describes metal-ligand interactions, and includes both single and multiple excitations. The results are sensitive to the choice of orbitals in the active space and this sensitivity can be used to assign spectral features. A method has also been developed to analyze the calculated X-ray spectra using a chemically intuitive molecular orbital picture.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-236075 (URN)10.1063/1.4896373 (DOI)000342844100021 ()25273421 (PubMedID)
Note

Correction in: Journal of Chemical Physics, vol. 141, issue 4, article number: 149905, DOI: 10.1063/1.4908043 ISI: 000349847000064

Available from: 2014-11-12 Created: 2014-11-12 Last updated: 2017-12-05Bibliographically approved
2. Cost and sensitivity of restricted active-space calculations of metal L-edge X-ray absorption spectra
Open this publication in new window or tab >>Cost and sensitivity of restricted active-space calculations of metal L-edge X-ray absorption spectra
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2015 (English)In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987XArticle in journal (Refereed) Published
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-272445 (URN)
Available from: 2016-01-13 Created: 2016-01-13 Last updated: 2017-11-30
3. Simulations of iron K pre-edge X-ray absorption spectra using the core restricted active space method
Open this publication in new window or tab >>Simulations of iron K pre-edge X-ray absorption spectra using the core restricted active space method
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2016 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 4, 3250-3259 p.Article in journal (Refereed) Published
Abstract [en]

The intensities and relative energies of metal K pre-edge features are sensitive to both geometric and electronic structures. With the possibility to collect high-resolution spectral data it is important to find theoretical methods that include all important spectral effects: ligand-field splitting, multiplet structures, 3d-4p orbital hybridization, and charge-transfer excitations. Here the restricted active space (RAS) method is used for the first time to calculate metal K pre-edge spectra of open-shell systems, and its performance is tested against on six iron complexes: [FeCl6](n-), [FeCl4](n-), and [Fe(CN)(6)](n-) in ferrous and ferric oxidation states. The method gives good descriptions of the spectral shapes for all six systems. The mean absolute deviation for the relative energies of different peaks is only 0.1 eV. For the two systems that lack centrosymmetry [FeCl4](2-/1-), the ratios between dipole and quadrupole intensity contributions are reproduced with an error of 10%, which leads to good descriptions of the integrated pre-edge intensities. To gain further chemical insight, the origins of the pre-edge features have been analyzed with a chemically intuitive molecular orbital picture that serves as a bridge between the spectra and the electronic structures. The pre-edges contain information about both ligand-field strengths and orbital covalencies, which can be understood by analyzing the RAS wavefunction. The RAS method can thus be used to predict and rationalize the effects of changes in both the oxidation state and ligand environment in a number of hard X-ray studies of small and medium-sized molecular systems.

National Category
Theoretical Chemistry
Research subject
Chemistry with specialization in Quantum Chemistry
Identifiers
urn:nbn:se:uu:diva-243571 (URN)10.1039/c5cp07487h (DOI)000369506000108 ()26742851 (PubMedID)
Funder
Marcus and Amalia Wallenberg FoundationSwedish Research CouncilCarl Tryggers foundation Knut and Alice Wallenberg Foundation, KAW-2013.0020Swedish National Infrastructure for Computing (SNIC), snic2013-1-317Swedish National Infrastructure for Computing (SNIC), snic2014-5-36
Available from: 2015-02-10 Created: 2015-02-10 Last updated: 2017-12-04Bibliographically approved
4. Molecular orbital simulations of metal 1s2p resonant inelastic X-ray scattering
Open this publication in new window or tab >>Molecular orbital simulations of metal 1s2p resonant inelastic X-ray scattering
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2016 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 120, no 29, 5848-5855 p.Article in journal (Refereed) Published
Abstract [en]

For first-row transition metals, high-resolution 3d electronic structure information can be obtained using resonant inelastic X-ray scattering (RIXS). In the hard X-ray region, a K pre-edge (1s -> 3d) excitation can be followed by monitoring the dipole-allowed K alpha (2p -> 1s) or K beta (3p -> 1s) emission, processes labeled 1s2p or 1s3p RIXS. Here the restricted active space (RAS) approach, which is a molecular orbital method, is used for the first time to study hard X-ray RIXS processes. This is achieved by including the two sets of core orbitals in different partitions of the active space. Transition intensities are calculated using both first- and second-order expansions of the wave vector, including, but not limited to, electric dipoles and quadrupoles. The accuracy of the approach is tested for 1s2p RIXS of iron hexacyanides [Fe(CN)(6)](n-) in ferrous and ferric oxidation states. RAS simulations accurately describe the multiplet structures and the role of 2p and 3d spin-orbit coupling on energies and selection rules. Compared to experiment, relative energies of the two [Fe(CN)(6)](3-) resonances deviate by 0.2 eV in both incident energy and energy transfer directions, and multiplet splittings in [Fe(CN)(6)](4-) are reproduced within 0.1 eV. These values are similar to what can be expected for valence excitations. The development opens the modeling of hard X-ray scattering processes for both solution catalysts and enzymatic systems.

National Category
Theoretical Chemistry
Research subject
Chemistry with specialization in Quantum Chemistry
Identifiers
urn:nbn:se:uu:diva-302165 (URN)10.1021/acs.jpca.6b05139 (DOI)000380730400008 ()27398775 (PubMedID)
Funder
Marcus and Amalia Wallenberg FoundationSwedish Research CouncilKnut and Alice Wallenberg Foundation, KAW-2013.0020
Available from: 2016-08-31 Created: 2016-08-31 Last updated: 2017-11-21Bibliographically approved

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