Transmission mechanisms of spin–spin coupling constants within the CHF approximation: Their study using inner projections of the polarization propagator

A new method for separating differently transmitted components of spin–spin coupling constants is introduced which is suitable when couplings are calculated using the coupled Hartree–Fock (CHF) approximation via the polarization propagator. Contributions transmitted through different electronic subsystems are found choosing different subsets of orbitals with their corresponding virtual spaces for their description. Examples for two different channels of transmission are given, which are very well known among NMR spectroscopists, namely, components trasmitted via π‐electron systems, and “through‐space” interactions. In the first case a set of canonical orbitals is chosen, while in the latter noncanonical ones are used. For both cases, numerical results are given within the INDO approximation. These results are compared with others obtained previously by means of the partially restricted molecular orbitals approach. The possibility of using this method of inner projections of the polarization propagator in decomposing other second orther properties is suggested.