Transmission of spin-polarization by π-orbitals : an approach to assessing its effect on NMR spin-spin coupling and EPR hyperfine structure
Abstract
A new approach to assessing the effect of the transmission of spin-polarization by π-orbitals (π-TSP) is presented. In order to switch off the π-TSP effect, we artificially average the α- and β-densities of the valence π-orbitals when calculating the exchange–correlation contribution to the Fock matrix in the unrestricted Kohn–Sham framework. The π-TSP effect is then evaluated as the difference between the results obtained with switched-on and switched-off options. This approach is applied to estimate the π-TSP effect on the Fermi-contact contribution to spin–spin couplings and EPR hyperfine structure coupling constants. The π-TSP effect on the distribution of spin-density, spin–spin coupling pathways and pathways of EPR hyperfine couplings is demonstrated for benzene, naphthalene, 1,3,5,7,9-decapentaene and the 1,3,5,7,9-decapentaen-1-yl radical. The sign alternation of the spin-polarization transmitted by π-orbitals is explained in a theoretical framework based on perturbation theory. However, the delocalized nature of the π-system can interfere with the sign alternation in certain cases, two of which – the cyclobutadiene dication and the cyclooctatetraene dication – are examined, and an explanation for which is provided.
Citation
Malkina , O L , Lemken , F , Asher , J R , Hierso , J-C , Buehl , M & Malkin , V G 2022 , ' Transmission of spin-polarization by π-orbitals : an approach to assessing its effect on NMR spin-spin coupling and EPR hyperfine structure ' , Physical Chemistry Chemical Physics , vol. Advance Article . https://doi.org/10.1039/D2CP03295C
Publication
Physical Chemistry Chemical Physics
Status
Peer reviewed
ISSN
1463-9076Type
Journal article
Description
Funding: We acknowledge the support from Slovak-French PHC Stefanik project “Spin Coupling Advanced Level Perception” (SCALP). OM, VM and JRA acknowledge the support from Slovak grant agencies APVV (grants No. SK-FR-19-0001 and APVV-19-0516) and VEGA (grant No. 2/0135/21). This work was also supported by the CNRS, the Université de Bourgogne, the Conseil Régional BFC (CHIMENE project), the PIA-excellence ISITE-BFC program (COMICS project) and the FEDER, which are all sincerely thanked.Collections
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