The acid–base properties of alloxazine (All) and its methyl derivatives have been studied in
their ground and first excited singlet states. The concept of an effective electronic valence
potential was applied to predict the changes in basicity and acidity of heteroatoms upon
excitation and substitution. Changes in the acid–base properties of N (1) and N (10) nitrogen
atoms are particularly important from the point of view of the excited state proton transfer in
alloxazines from N (1) to N (10) to form isoalloxazinic structures. A good linear correlation …