Mononuclear and Tetranuclear Copper(II) Complexes Bearing Amino Acid Schiff Base Ligands: Structural Characterization and Catalytic Applications

Two new glycine-Schiff base copper(II) complexes were synthesized. Single crystal X-ray diffraction (SCXRD) allowed us to establish the structure of both complexes in the solid state. The glycine-Schiff base copper(II) complex derived from 2′-hydroxy-5′-nitroacetophenone showed a mononuclear hydrated structure, in which the Schiff base acted as a tridentate ligand, and the glycine-Schiff base copper(II) complex derived from 2′-hydroxy-5′-methylacetophenone showed a less common tetranuclear anhydrous metallocyclic structure, in which the Schiff base acted as a tetradentate ligand. In both compounds, copper(II) had a tetracoordinated square planar geometry. The results of vibrational, electronic, and paramagnetic spectroscopies, as well as thermal analysis, were consistent with the crystal structures. Both complexes were evaluated as catalysts in the olefin cyclopropanation by carbene transference, and both led to very high diastereoselectivity (greater than 98%).

Weakly Non-Covalent Docking of Amino-Acid Schiff Base Zn(II) Complex to Lysozyme

Artificial metal enzymes that combine proteins with synthesized unnatural metal complexes as cofactors are attracting attention. The preparation of artificial metal enzymes not only clarifies the behavior of metal ions in biology, but also leads to the development of synthetic chemistry fields such as the discovery of new catalytic reactivity and substrate selectivity that are not observed in nature. In addition, a certain Schiff base zinc (II) complex is known to exhibit antioxidant and anticancer activity, too. Therefore, in this study, we investigated a rapid synthesis method of two known amino acid Schiff base zinc (II) complexes using microwave method and the complexation of zinc (II) complex with chicken egg white lysozyme, which is a relatively low molecular weight protein. Furthermore, investigation of weakly non-covalent intermolecular interaction features between the zinc (II) complexes and lysozyme was also carried out using some spectroscopic measurements.