NMR of Nuclei Bound to a Paramagnetic Metal Centre: The Case of S = 1 Square-Planar Ruthenium(II) [data]

This has been achieved by the planar tridentate ligand, which combines hard and soft donor atoms, giving rise to a very large zero-field splitting (D > 200cm−1). The electronic structure and systematic influence of the fourth (halogenido) ligand has been explored theoretically via DFT and CASSCF calculations as well as experimentally via UV-VIS spectroscopy and SQUID Magnetometry.

Analysis of the strikingly well-resolved pNMR spectra allowed the detection of the directly bound 31P nuclei at around −3900 ppm for all discussed complexes, as well as the 19F resonance of the fluorido complex at over +3900 ppm chemical shift, which are a direct probe for the the sign and magnitude of the hyperfine coupling constants Aiso. Simulation of the room temperature spectra based on DFT and CASSCF calculations allowed for full assignment of the observed resonances and experimental determination of the axial zero-field splitting parameter 𝐷 from VT-NMR experiments.