Equilibrium and kinetic studies of ligand BMXD complexation with copper(II) and glycylglycine

Equilibrium studies of BMXD complexation with copper(II) and glycylglycine were performed by potentiometric and UV–visible titration. The equilibrium constants determined by potentiometry for the ternary system are: [LCu2P3+]/[LCu24+][P−]=8.11(3), [LCu2HP4+]/[LCu2P3+][H+]=5.39(2), [LCu2H−1P2+][H+]/[LCu2P3+]=−6.33(2), [LCu2(OH)H−1P+][H+]/[LCu2H−1P2+]=−8.20(1) and [LCu2(OH)2HH−1P][H+]/[LCu2(OH)H−1P−1]=−10.33(3), which are in good agreement with the values determined by UV–visible titration. The species formed were confirmed by electrospray mass spectrometry. The association constants, determined by kinetic studies, for the association of the second molecule of glycylglycine with the LCu2P complex, for two ionic media, are 1.29 (KCl) and 1.27 (KNO3). These are in good agreement with the values determined by thermodynamic measurements 1.41 (KCl) and 1.26 (KNO3).