Enhancement of metal-binding affinity for Cu+/Cu2+ complexes by hydrogen bond network

Using density functional theory, polyols were used as model ligands for Cu⁺/Cu²⁺ complexes to study the role of the hydrogen bond network on the metal binding affinity. In addition to the gas phase studies, the calculations were performed in 1-decanol and DMSO solvents. The Cu²⁺ complexes were the most stable complexes with the highest bond dissociation energies (BDE). The presence of three H-bonds in the first shell increased BDE values up to 17.99 and 57.07 kcal/mol for Cu⁺ and Cu²⁺ complexes in the gas phase, respectively, whereas the presence of another three H-bonds in the second shell increased BDE values up to 7.27 and 24.35 kcal/mol for Cu⁺ and Cu²⁺ complexes in the gas phase, respectively. Therefore, this H-bond network caused, for example, a more stable Cu⁺ complex with a formation constant of 1.4 × 10¹⁷ times. The natural bond orbital (NBO), atoms in molecules (AIM), and reduced density gradient (RDG) analyses showed that the intramolecular hydrogen bond network led to the enhancement of metal-binding affinity.