Isotropic NMR shifts in transition metal complexes: The calculation of the fermi contact and pseudocontact terms

On the use of pseudocontact shifts in the structure determination of metalloproteins

“…According to Eqn (2), the pseudocontact shift is independent of the specific type of nucleus and depends only on the position of the nucleus relative to the metal ion. Thus, for an amide group in the protein, similar pseudocontact shifts are expected for the amide proton and the amide 15 N nucleus. However, as pointed out previously, 32 -34 the chemical shifts of the 15 N nuclei are considerably more sensitive than the 1 H nuclei to small variations in the backbone torsion angles, the hydrogen bonding and the electric field.…”

“…Furthermore, υ pcs is the pseudocontact shift caused by the dipolar interaction with the unpaired electrons of the paramagnetic metal ion. The pseudocontact shift is given by 15 υ pcs D 0 2 B S S C 1 36 kTr 3 g ax 3 cos 2 Â 1 C 3 2 g eq sin 2 Â cos 2 2 Here, 0 is the permeability of vacuum, B is the Bohr magneton, S is the electron spin number (1/2 for Cu 2C ), k is the Boltzmann constant, and T is the absolute temperature. Furthermore, (r, Â, ) are the spherical coordinates of the nucleus in the principal coordinate system of the g-tensor.…”

“…The pseudocontact shifts were obtained for the amide protons, the˛-protons and the backbone 15 N nuclei in the protein. A total of 150 1 H and 79 15 N pseudocontact shifts were measured.…”

DFT investigation of the effect of spin-orbit coupling on the NMR shifts in paramagnetic solids

“…Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful technique for analysing the local structure in paramagnetic solids, as the unpaired electrons of the TM ions induce a paramagnetic shift and shift anisotropy that provide detailed information concerning the structural and chemical environment of the NMR observed centre (OC) [9][10][11][12][13]. However, the interpretation of these spectra proves very challenging, as the presence of the paramagnetic centres results in multiple effects on the observed NMR lineshapes [14][15][16][17]. The through-bond transfer of unpaired-electron spin density onto the nuclear position of the OC induces a so-called Fermi contact shift, which is a direct measure of the electronic structure of the TM, the electronic spin transfer through the TM-O-OC bond and the degree of interaction between the relevant orbitals [18].…”

“…Substantial progress has been made in the theoretical description of various contributions to the NMR shift of molecular systems with a single paramagnetic centre. After the pioneering work of Kurland and McGarvey [16], Moon and Patchkovski derived a formalism to describe the entire shift tensor including the effects of spin-orbit coupling [19], later ex-tended to the presence of zero-field splitting by Vaara et al [20,21] and Soncini and Van den Heuvel [22], with the consequent extensive study of the NMR shift of paramagnetic molecules [23][24][25][26][27][28]. The shift mechanisms in paramagnetic transition metal-containing extended solids have been studied by Carlier, Grey and co-workers and the effects of multiple paramagnetic centres on the isotropic Fermi contact shift and its relation to the bulk magnetic properties of the solid have been qualitatively [13], and subsequently more quantitatively [29], rationalised.…”