NMR Scalar Couplings and Molecular Interactions

Abstract

In this work, a description is given of the possibilities that, at present, can be envisioned for using NMR scalar spin–spin couplings for studying molecular systems. Such possibilities are based both on the application of computational chemistry approaches to calculate them and on the using of modern experimental techniques to measure them. This article intends to be useful to scientists who are not familiar with the theoretical background of scalar couplings. The organization of this work proceeds as follows: First, a short description is given of the nucleus–electron magnetic interactions that originate these spectral parameters. Second, some comments on the current approaches to calculate them are quoted, and adequate references are given for readers interested in deepening their theoretical background. Third, the potential of scalar couplings to study inter‐ and intramolecular interactions is illustrated. This is accomplished by discussing how the Fermi contact contribution to ${}^{1}J_{\rm CH}$ as well as to several types of geminal scalar couplings is influenced by hyperconjugative interactions. A qualitative analysis is presented for geminal couplings involving nuclei of lone‐pair–bearing atoms in order to explain under which conditions their paramagnetic spin‐orbital contribution could be substantial. Two different examples are presented in which, for similar configurations of lone pairs, the roles played by such lone pairs in coupling transmission are quite different.

Magnetism in Graphene Systems

“…48,51 Native doping elements are boron and nitrogen. Keeping in mind that BN zigzag nanoribbons have the similar structures with C, 49,50 we designed a new hybrid structure named as C/BN nanoribbons in our recent research. 48 Our structures constitute C i BN, ( i= 1,2,3).…”

Critique of the Multipath Model for 1J(C,C) Nuclear Spin–Spin Coupling via Electron Current Induced by 13C Nuclear Magnetic Dipoles

“…[39] The performance of the CHF method for evaluating spinspin coupling constants is known to be quite poor in general, for example, the experimental values of saturated hydrocarbons are systematically overshot. [40][41][42][43] Post-Hartree-Fock approaches are required to account for electron correlation via accurate calculations. However, we expect that the essentials of the underlying physics are correctly represented by CHF wavefunctions for the systems considered here.…”