Decomposition of nuclear magnetic resonance spin-spin coupling constants into active and passive orbital contributions

The theory for calculating spin-spin coupling constants (SS-CC) was studied using density functional theory (DFT). The mechanism of NMR spin-spin coupling in dependence of the electronic structure of a molecule and its bonding characteristics was also analyzed. A simple form of the new theory for analyzing SSCCs, called decomposition of J into orbital contributions using orbital currents and partial spin polarization (J-OC-PSP), was formulated in terms of one- and two-orbital contributions based on active orbitals. The Fermi contact (FC) coupling mechanism is predominantly based on exchange interactions.