Characterization of the Binding Modes of Cu2+ Ions with Tyrosine and Ado, AMP, ADP, and ATP: A Comprehensive Potentiometric, Spectroscopic, and Computational Approach

We report the mode of interaction of copper(II) ions with tyrosine (Tyr, L) in binary and ternary systems with Ado, AMP, ADP, and ATP (L’) as second ligands in an aqueous solution. The composition and overall stability constants of the complexes formed were determined using the potentiometric method. The coordination sites were identified through spectroscopic (VIS, EPR, IR) methods, as well as DFT and computational–molecular modeling. In the binary Cu(II)/Tyr system, the main reaction centers of the ligand molecule involved in the interactions with copper(II) ions are nitrogen (-NH2 group), as well as oxygen atoms (-COO− group), as confirmed, for example, by comparing the mode of coordination in the CuH2(Tyr)2 species and the [CuH2(Tyr)2(H2O)] × 1.5H2O solid complex obtained. In the ternary Cu(II)/L/L’ systems, MLHxL’ and mixed MLL’ protonated complexes are formed. Only in the ATP system were no MLL’(OH)x hydroxocomplexes found. An increase in the number of phosphate groups in ADP and ATP molecules has no effect on their participation in the coordination in ternary species, and these ligands interact just like in binary species (i.e., in ADP, both α- and β-phosphate groups, and in ATP, only the γ-phosphate group). It was observed that the introduction of a second ligand into the Cu(II)/Tyr system did not change, over the entire pH range studied, the tyrosine coordination mode.