| BORA, Pankaj Lochan, Jan NOVOTNÝ, Kenneth RUUD, Stanislav KOMOROVSKY a Radek MAREK. Electron-Spin Structure and Metal-Ligand Bonding in Open-Shell Systems from Relativistic EPR and NMR: A Case Study of Square-Planar Iridium Catalysts. Journal of Chemical Theory and Computation. American Chemical Society, 2019, roč. 15, č. 1, s. 201-214. ISSN 1549-9618. Dostupné z: https://dx.doi.org/10.1021/acs.jctc.8b00914. |
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@article{1473118,
author = {Bora, Pankaj Lochan and Novotný, Jan and Ruud, Kenneth and Komorovsky, Stanislav and Marek, Radek},
article_number = {1},
doi = {http://dx.doi.org/10.1021/acs.jctc.8b00914},
keywords = {EPR; NMR; relativistic DFT; g-tensor; A-tensor; metal-ligand bond},
language = {eng},
issn = {1549-9618},
journal = {Journal of Chemical Theory and Computation},
title = {Electron-Spin Structure and Metal-Ligand Bonding in Open-Shell Systems from Relativistic EPR and NMR: A Case Study of Square-Planar Iridium Catalysts},
url = {http://dx.doi.org/10.1021/acs.jctc.8b00914},
volume = {15},
year = {2019}
}
TY - JOUR
ID - 1473118
AU - Bora, Pankaj Lochan - Novotný, Jan - Ruud, Kenneth - Komorovsky, Stanislav - Marek, Radek
PY - 2019
TI - Electron-Spin Structure and Metal-Ligand Bonding in Open-Shell Systems from Relativistic EPR and NMR: A Case Study of Square-Planar Iridium Catalysts
JF - Journal of Chemical Theory and Computation
VL - 15
IS - 1
SP - 201-214
EP - 201-214
PB - American Chemical Society
SN - 15499618
KW - EPR
KW - NMR
KW - relativistic DFT
KW - g-tensor
KW - A-tensor
KW - metal-ligand bond
UR - http://dx.doi.org/10.1021/acs.jctc.8b00914
L2 - http://dx.doi.org/10.1021/acs.jctc.8b00914
N2 - Electron and nuclear magnetic resonance spectroscopies are indispensable and powerful methods for investigating the molecular and electronic structures of open-shell systems. We demonstrate that the NMR and EPR parameters are extremely sensitive quantitative probes for the electronic spin density around heavy-metal atoms and the metal-ligand bonding. Using relativistic density-functional theory, we have analyzed the relation between the spin density and the EPR and NMR parameters in paramagnetic iridium(II/IV) complexes with a PNP pincer ligand. As the magnetic-response parameters for compounds containing 5d transition metal(s) are heavily affected by spin-orbit coupling, relativistic effects must be included in the calculations. We have used a recent implementation of the fully-relativistic Dirac-Kohn-Sham (DKS) method employing the hybrid PBE0 functional and an implicit solvent model to calculate EPR parameters and hyperfine NMR shifts. The modulation of the metal–ligand bond by the trans substituent (-Cl or -N) and the electronic spin structure around the central metal atom and ligands are shown to be reflected in the “long-range” through-bond Fermi-contact (FC) contributions to the ligand 13C and 1H hyperfine couplings. Interestingly, the hyperfine coupling constant of the ligand atom L (A_L) bonded directly to the iridium center changes its sign because of the dominating role of the paramagnetic spin-orbit (PSO) term. Furthermore, the electronic g-shift and the PSO contribution to the ligand A_L are shown to invert their signs when nitrogen is substituted for chlorine, reflecting the different formal metal oxidation states and the change in metal–ligand bond character. A full understanding of the substituent effects is provided by using chemical bond concepts in combination with a molecular-orbital (MO) theory analysis of the second-order perturbation theory expression for the EPR parameters. Our findings are easily transferable to other systems containing d-block elements and beyond. Relativistic DFT calculations of magnetic-resonance parameters are expected to frequently assist in future experimental observations and the characterization of hitherto unknown unstable or exotic species.
ER -
BORA, Pankaj Lochan, Jan NOVOTNÝ, Kenneth RUUD, Stanislav KOMOROVSKY a Radek MAREK. Electron-Spin Structure and Metal-Ligand Bonding in Open-Shell Systems from Relativistic EPR and NMR: A Case Study of Square-Planar Iridium Catalysts. \textit{Journal of Chemical Theory and Computation}. American Chemical Society, 2019, roč.~15, č.~1, s.~201-214. ISSN~1549-9618. Dostupné z: https://dx.doi.org/10.1021/acs.jctc.8b00914.
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