Assignment of solid-state 13C and 1H NMR spectra of paramagnetic Ni(II) acetylacetonate complexes aided by first-principles computations

摘要

AbstractRecent advances in computational methodology allowed for first-principles calculations of the nuclear shielding tensor for a series of paramagnetic nickel(II) acetylacetonate complexes, [Ni(acac)2L2] with L?=?H2O, D2O, NH3, ND3, and PMe2Ph have provided detailed insight into the origin of the paramagnetic contributions to the total shift tensor. This was employed for the assignment of the solid-state1,2H and13C MAS NMR spectra of these compounds. The two major contributions to the isotropic shifts are by orbital (diamagnetic-like) and contact mechanism. The orbital shielding, contact, as well as dipolar terms all contribute to the anisotropic component. The calculations suggest reassignment of the13C methyl and carbonyl resonances in the acac ligand [Inorg. Chem.53,2014, 399] leading to isotropic paramagnetic shifts ofδ(13C)?≈?800–1100?ppm and ≈180–300?ppm for13C for the methyl and carbonyl carbons located three and two bonds away from the paramagnetic Ni(II) ion, respectively. Assignment using three different empirical correlations,i.e., paramagnetic shifts, shift anisotropy, and relaxation (T1) were ambiguous, however the latter two support the computational results. Thus, solid-state NMR spectroscopy in combination with modern quantum-chemical calculations of paramagnetic shifts constitutes a promising tool for structural investigations of metal complexes and materials.Graphical abstractDisplay OmittedHighlights?Computational assignment of1,2H and13C MAS NMR spectra of paramagnetic [Ni(acac)2L2], L?=?H2O, D2O, NH3, ND3, and PMe2Ph.?Detailed insight into the different contributions to the paramagnetic shift.]]>