Calculating NMR Chemical Shifts for Paramagnetic Metal Complexes from First-Principles

Frédéric Gendron; Kamal Sharkas; Jochen Autschbach

doi:10.1021/acs.jpclett.5b00932

Calculating NMR Chemical Shifts for Paramagnetic Metal Complexes from First-Principles

J Phys Chem Lett. 2015 Jun 18;6(12):2183-8. doi: 10.1021/acs.jpclett.5b00932. Epub 2015 May 29.

Authors

Frédéric Gendron¹, Kamal Sharkas¹, Jochen Autschbach¹

Affiliation

¹ Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260-3000, United States.

PMID: 26266589
DOI: 10.1021/acs.jpclett.5b00932

Abstract

Paramagnetic effects on NMR shifts (pNMR) for paramagnetic metal complexes are calculated from first-principles, without recourse to spin Hamiltonian parameters. A newly developed code based on complete active space (CAS) and restricted active space (RAS) techniques in conjunction with treating spin-orbit (SO) coupling via state interaction is applied to (13)C NMR shifts of actinyl tris-carbonate complexes, specifically [UO2(CO3)3](5-) and [NpO2(CO3)3](4-). The experimental pNMR shifts as well as the sizable difference of the (13)C NMR shift for these iso-electronic species are well reproduced by the calculations. Approximations to the pNMR shift equations using spin Hamiltonian parameters or the magnetic susceptibility are calculated for the same systems at the same level of theory, and it is shown how the approximations relate to the ab initio data.

Keywords: NMR shift; ab initio theory; actinide complexes; hyperfine coupling; paramagnetism; relativistic effects.