Combining this insight with eq 1 produces a variant of the Marcus model that accounts for variations in both the reaction driving force (through ∆Er) and the intrinsic activation barrier (through ∆E ‡ int) on the activation energy (eq 3 and Figure , see SI for full derivation). For simplicity, the curvature of the breaking bond parabola is assumed to remain constant, following previous work. To account for the dependence of ∆E ‡ int across a range of similar systems, we introduce a calculated parameter, 𝜒, that captures the physical origin of this variation -in this case proposed to be electron delocalization. The sensitivity constants 𝛼 and β can be determined using multiple linear regression (MLR).