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).