Charge-transfer complexation as a general phenomenon in the copigmentation of anthocyanins

Theoretical and experimental evidence is provided for the generality of charge transfer from the copigment to the flavylium cation, as a major driving force for the stabilization of anthocyanin-copigment complexes. Correlations provide a straightforward means of estimating the relative copigmentation strengths of potential copigment molecules based on calculated values of their ionization potentials.