Analysis of the paramagnetic spin–orbit transmission mechanism for NMR spin–spin coupling constants using the paramagnetic spin–orbit density distribution

For the analysis of the paramagnetic spin orbit (PSO) term of the NMR spin–spin coupling constant (SSCC), ring current density and PSO density distribution are derived and used to explain magnitude and sign of the isotropic PSO term. Decomposition of the PSO components into orbital contributions helps to identify those orbital pairs (occupied, virtual) dominating the PSO term. The induction of strong ring currents requires low excitation energies and complementing nodal properties of zeroth and first order orbitals. The PSO components for a typical triple, double, and single CC bond are explained.