We observe a remarkable resemblance when comparing the electron affinity and wave function behavior of the copper subsystem with the charge transfer for the bi-centered molybdenum-copper model system. Such resemblance is neither unexpected nor accidental. It was hinted by the similarities in the experimental spectra of the multi-center complex and its sub parts, described by Herrera et al., and this division has also been explored by Graaf et al. in the geometry optimization of the model system. Plotting the MMCT energy as explored by Graaf et al., we observe a similar, almost linear pattern between the usual SA-CASSCF values and the relative weight chosen among states. This is shown in Figure ), for both the literature result 8 and our calculations. To reduce the computational cost we used a smaller basis set, but we can see from Figure ) that the results change only slightly. In the same way as the copper subsystem, Figure ), the energy variation with the weight is larger than 10 eV at both CASSCF and NEVPT2 levels of theory. To decide which weight is the appropriate, we can generalize the criterion used for the electron affinity of the copper subsystem, Equations ( ) and (9). In this case, the relative energies calculated with the reference wave function and for the correlated calculation should be the same. These relative energies cross each other at the weight of 60% for the MMCT state, in an energy of 3.8 eV, for the smaller basis set. For the results from reference 8 with the larger basis set, extrapolation of the results suggests that CASSCF and NEVPT2 curves cross each other around 67%, in an energy of 3.1 eV. This energy is very close to the MMCT experimental transition for the original system (between 2.99 and 3.05 eV 1 ).