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Updated: Jun 10, 2026
Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
Published on: July 27, 2022
Density functional theory interpretation of the 1H photo-chemically induced dynamic nuclear polarization enhancements
Emilie Cauët1, Stuart Bogatko, Epiphanie Mugeniwabagara
1Service de Chimie Quantique et Photophysique, CP 160/09, Université Libre de Bruxelles, 50 Avenue F.D. Roosevelt, B-1050 Bruxelles, Belgium.
Abstract:
The unprotonated and protonated monoreduced forms of the polyazaaromatic Ru(II) coordination complexes [Ru(tap)(3)](2+) and [Ru(tap)(2)(phen)](2+) (tap = 1,4,5,8-tetraazaphenanthrene ; phen = 1,10-phenanthroline), that is, [Ru(tap)(3)](*+), [Ru(tap)(2)(phen)](*+), [Ru(tap)(2)(tap-H)](*2+), and [Ru(tap)(tap-H)(phen)](*2+), were studied by Density Functional Theory (DFT). The electron spin density of these radical cations, the isotropic Fermi-contact, and the anisotropic dipolar contributions to the hyperfine coupling constants of the H nuclei were calculated in vacuo and using a continuum model for water solvation. For [Ru(tap)(2)(phen)](*+), as well as for its protonated form, the DFT results show that the unpaired electron is not localized on the phen ligand. For both [Ru(tap)(3)](*+) and [Ru(tap)(2)(phen)](*+), they reveal high electron spin density in the vicinity of tap H-2 and tap H-7 (the H atoms in the ortho position of the tap non-chelating N atoms). These results are in full agreement with recent steady-state (1)H photo-Chemically Induced Dynamic Nuclear Polarization (photo-CIDNP) measurements. The DFT calculations performed for the protonated species also predict major (1)H photo-CIDNP enhancements at these positions. Interestingly, they indicate significantly different polarization for tap H-9,10, suggesting that the occurrence of a photoinduced electron transfer with protonation of the reduced species might be detected by high-precision photo-CIDNP experiments.
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