Figure shows the measured rate constants as a function of the tunneling distance. It is evident from Fig. that k 0 of [IrCl 6 ] 3-and [Ru(NH 3 ) 6 ] 3+ , albeit different in absolute value, both decay with the hBN thickness. This is in qualitative agreement with both experiments and predictions for coherent quantum tunneling. The exponential dependence of the electron transfer rate constant between an electrode and redox species (k ET , in s -1 ) on the tunneling distance between the two (x) is described as: 18