Counter-Anions Rendered Weak-Interactions Perturb the Stability of Tyrosinase-Mimicked Peroxo-Dicopper(II) Active Site: Unraveling Computational Indicators

It has been observed in literature that the stability of tyrosinase-mimicked μ-η²:η²-peroxo-dicopper(II) (P) can be perturbed in presence of counter-anions (CAs) such as PhCO₂⁻, CF₃SO₃⁻, TsO⁻ and SbF₆⁻. In this work, we unravel computational indicators using density functional theory to screen and study the stability of P in experimentally-reported cases. These indicators are Gibbs energies, geometrical parameters such as distances and angles, independent gradient model based on Hirshfeld partition (IGMH) generated data, orbitals’ overlap, and distortion-interaction (DI) energies. Our DFT computed Gibbs energies indicate that P is stable in case of PhCO₂⁻ and TsO⁻. CF₃SO₃⁻ allows P and its isoelectronic species bis-μ-oxo-dicopper (O) to coexist. SbF₆⁻ shows that O is in excess. Our indicators reveal that the stability of P in case of PhCO₂⁻ and TsO⁻ is due to the better placing of P and its CA, thus leading to better interactions and overlap of orbitals. Other indicator displays that the plane of Cu₂O₂ core in P is more bend in PhCO₂⁻ and TsO⁻ cases as compared to the plane in the other two cases. In addition, the IGMH-based indicator displays higher values in the case of PhCO₂⁻ and TsO⁻ than the other CAs.