Paramagnetic NMR of Phenolic Oxime Copper Complexes: A Joint Experimental and Density Functional Study.
1H and13C pNMR properties of bis(salicylaldoximato)copper(II) were studied in the solid state using magic-angle-spinning NMR spectroscopy and, for the isolated complex and selected oligomers, using density-functional theory at the PBE0-1/3 //PBE0-D3 level. Large paramagnetic shifts are observed, up to δ(1H)=272 ppm and δ(13C)=1006 ppm (at 298 K), which are rationalised through spin delocalisation from the metal onto the organic ligand and the resulting contact shifts arising from hyperfine coupling. The observed shift ranges are best reproduced computationally using exchange-correlation functionals with a high fraction of exact exchange (such as PBE0-1/3 ). Through a combination of experimental techniques and first-principles computation, a near-complete assignment of the observed signals is possible. Intermolecular effects on the pNMR shifts, modelled computationally in the dimers and trimers through effective decoupling between the local spins via A-tensor and total spin rescaling in the pNMR expression, are indicated to be small. Addition of electron-donating substituents and benzannelation of the organic ligand is predicted computationally to induce notable changes in the NMR signal pattern, which suggests that pNMR spectroscopy can be a sensitive probe for the spin distribution in paramagnetic phenolic oxime copper complexes.
University of St. Andrews, School of Chemistry and Centre of Magnetic Resonance, North Haugh, St Andrews, Fife, KY16 9ST, Scotland, UK. buehl@st-andrews.ac.uk.
Michael
M
Bühl
University of St. Andrews, School of Chemistry and Centre of Magnetic Resonance, North Haugh, St Andrews, Fife, KY16 9ST, Scotland, UK. sema@st-andrews.ac.uk.
Sharon E
http://orcid.org/0000-0002-4538-6782
SE
Ashbrook
University of St. Andrews, School of Chemistry and Centre of Magnetic Resonance, North Haugh, St Andrews, Fife, KY16 9ST, Scotland, UK.
Daniel M
http://orcid.org/0000-0002-8110-4535
DM
Dawson
University of St. Andrews, School of Chemistry and Centre of Magnetic Resonance, North Haugh, St Andrews, Fife, KY16 9ST, Scotland, UK.
Rachel A
RA
Doyle
Technische Universität Berlin, Institut für Chemie, Strasse des 17. Juni 135, D-10623 Berlin, Germany.
Peter
P
Hrobárik
Technische Universität Berlin, Institut für Chemie, Strasse des 17. Juni 135, D-10623 Berlin, Germany.
Martin
M
Kaupp
University of St. Andrews, School of Chemistry and Centre of Magnetic Resonance, North Haugh, St Andrews, Fife, KY16 9ST, Scotland, UK.
Iain A
IA
Smellie
NMR spectroscopy; chelates; density functional calculations; materials science; quantum chemistry