A test of magnetic field effects on an electron-transfer system: adiabatic or not?

Electron transfer (ET) systems in solution where the rate of transfer can be directly measured could in certain cases be expected to undergo modification by large magnetic fields. This possibility was tested on the classical manganate-permanganate system in solution. Rates were measured by NMR line broadening in significantly different magnitudes of NMR spectrometer magnetic fields. (Field throughout means a magnetic not an electric field.) Any rate changes fell within the bounds of error. This accords with the adiabatic Marcus model of such transfers, corresponding with the Robin-Day Class 2 mixed-valence interaction with a Landau-Zener transition probability of unity. Studies of the solid-state system at low temperatures have implied possibly limited electron delocalization (i.e. Robin-Day Class 1).