Possible coordination modes of copper(II) atom in model silsesquioxanes complexes at various pH conditions: DFT study

Highlights: • 4 conformers of POSS-1 model ligand were evaluated to check potential binding sites. • Coordination model of copper(II) cation depends on the pH of the solution. • Two oxygen and two nitrogen atoms are responsible for coordination at the pH > 7. • At the pH < 7 participation of ethanol molecules in coordination of Cu²⁺ is predicted. • CSD survey reveals possibility of EtOH contribution in coordination of metal center. The functionalized cage-like silsesquioxanes (POSSs) have enticed scientific community's continuous interest. In this work, we try to supplement empirical expertises and answer questions concerning the coordination modes of copper(II) cation in the POSS-1 ligand neighborhood through the DFT calculations. It is postulated that ethanol solvent molecules take an active part in the coordination to the metallic center in the acidic environment. At the alkaline solution, the square planar shape of two POSS-1 ligands surrounded the copper(II) cation, including two oxygen and two nitrogen atoms in the first coordination sphere of copper, is recommended.