Substituent effects on the through-space nuclear magnetic spin-spin coupling in van der Waals dimers

We have investigated the effect of substituents on the donor (benzene) and acceptor (C-H) moieties of CH/pi interacting model systems 1-6 on the through-space nuclear spin-spin coupling J(CH) and J(HH). These couplings were recently predicted by ab-initio and DFT calculations to be of the order of 0.2-0.3 Hz at the equilibrium separation. Electronic effects due to the substitution are found not to increase significantly, and often to decrease, the calculated coupling, since they involve mainly pi orbitals, while the coupling is mainly transmitted through sigma orbitals.