Model-independent determination of the degree of charge transfer in molecular and metal complexes

Quantifying charge transfer is a challenging task because it requires that the calculated degree of charge transfer be both consistent with chemical intuition and independent of charge analysis methods. Based on DFT results of molecular and transition metal complexes in organic electronics, we show that both requirements can be fulfilled by choosing a small active space of electrons for the analysis. Our findings hold for inter- and intramolecular processes whether in the ground state or during excitation. Choosing a small active space of electrons for charge analysis allows the model-free determination of the degree of charge transfer.