Molecular complexes between methoxyamphetamines and riboflavin derivatives.

Molecular complexes in the ratio 1:1 were formed in aqueous solution between various methoxysubstituted phenylisopropylamine (amphetamine) hydrochloride or oxalate salts and riboflavin deri­ vatives (flavin mononucleotide and flavin adenine dinucleotide). The association constants for these complexes were determined by the fluorescence quenching method as well as by the absorption method. The nature of the complex formation may be due to charge-transfer, electron-transfer, electrostatic and hydrophobic forces. The steric effect also plays an important role in the complex formation. The absorption wavelength and association constant of the complexes are correlated with the published biological activities of the methoxyamphetamines.