Cu(I) COORDINATION COMPOUNDS WITH PROMISING ANTIVIRAL ACTIVITY: ASSESSMENT OF THE MOLECULAR AND ELECTRONIC STRUCTURE BY XPS AND XAS

In the framework of the design, synthesis and testing of a library of copper-based complexes and nanostructured assemblies potentially endowed with antiviral activity and useful for several applications, from drugs and related delivery systems to the development of biocidal nanomaterials, here we present the detailed spectroscopic investigation of the molecular and electronic structure of new copper(I) coordination compounds. Recently, new chelating ligands (as such or functionalized with selected biomolecules) showing potential activity against SARS-CoV-2 and other viral agents have been prepared by our research group, and the coordination geometry and molecular structure of their Cu(I) complexes have been assessed by X-ray Absorption Spectroscopy (XAS) and X-ray Photoemission Spectroscopy (XPS). The spectroscopic investigation allowed to investigate in detail the electronic structure of the Cu(I) coordination compounds, as well as the electronic interaction arising between the metal ion and the ligands. In particular, XPS enabled us to specifically probe the ligand-metal interaction and to evaluate the coordination compounds molecular stability, providing an accurate description of their molecular and electronic structures, in comparison with the pristine ligands. XAS measurements performed at the Cu K-edge allowed to ascertain the coordination geometry at the copper ion site. It is noteworthy that biological studies suggest a key role of the copper ion in the antiviral activity; this observation makes the assessment of the electronic interaction between the metal ion and the ligands and the investigation of the copper ion oxidation state stability of primary importance for a better comprehension of the biological activity.