Stability and conformation of the complexes of riboflavin with aromatic hydroxy compounds in an aqueous medium

Overall equilibrium constants K' for the formation of molecular complexes of riboflavin with the conjugate forms of different aromatic hydroxy compounds are greater in magnitude than those involving the protonated forms of the hydroxy compounds. There is good agreement between the K(B) values determined by using absorption and emission methods. Based on the magnitude of K(B), it is possible to differentiate between the donor capacities of the hydroxy compounds in the charge transfer complexes with riboflavin. Molecular modeling studies indicate stacking interactions for all the systems in an aqueous medium.