The interaction between di- and tripeptide hydroxamic acids and Pd(ii) (as a Pt(ii) model but with faster ligand exchange reactions) was studied in aqueous solution in the presence of chloride ions by pH-potentiometric and NMR methods revealing ligand-dependent competition between the coordinative and hydrolytic processes.

The combined use of various techniques reveals the binding preference of Pd(ii) to the N donors of the title ligand paving the way for the synthesis of heterobimetallic Co/Pd(Pt) complexes with anticancer potential.

Copper­(II) complexes of pyridine-based ligands functionalized with alanine (PydiAla) and tyrosine (PydiTyr) moieties have been synthesized as novel superoxide dismutase mimics. The complexes were characterized by pH-potentiometric, spectroscopic (UV–vis, circular dichroism, mass spectrometry, electron paramagnetic resonance spectroscopy), computational (DFT), and X-ray diffraction methods. Both ligands form high stability copper­(II) complexes via the (Npy,N–,N–) donor set supported by the binding of the carboxylate pendant arms. Although the coordination mode is the same for the two systems, the tyrosine containing counterpart exhibits increased copper­(II) binding affinity, which is most likely due to the presence of the aromatic moiety of the side chains. Both copper­(II) complexes are capable of binding N-methylimidazole, and the formation of the corresponding ternary species was observed at physiological pH. The binary and ternary copper­(II) complexes exhibit high SOD activity. The PydiTyr complex exhibits about 1 order of magnitude higher activity than the PydiAla complex. This is probably due to the presence of the phenolic OH group in the former species, which promotes the binding of the superoxide anion radical to the metal center. The results serve as a basis for designing highly efficient copper­(II) mimics for medical and practical applications.

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