Exploration of the potential energy surfaces of the Cu2+(MeOH)n=9,10 clusters: Solvent phase vs gas phase

Abstract

In the present work, we investigated the potential energy surfaces (PESs) of the structures of the ${\mathrm{Cu}}^{2+}$ ion in methanol clusters in two different media: gas and solvent phases. The effects of medium polarization by the integral equation formalism polarized continuum model (IEF-PCM) on structural and energetic parameters were examined on the conformers of the ${\mathrm{Cu}}^{2+}{\left(\mathrm{MeOH}\right)}_{n=9,10}$ clusters using the M06-2X/6-31++G(d,p) level of theory. Thus, in the solvent phase, the cluster structures are hexa-coordinated in the global minimum isomer. The study of the temperature dependency shows that the hexa-, and penta-coordinated structures compete with a large predominance of the hexa-coordinate structures with two solvation shells in the solvent phase. The Wiberg bond indices (WBI) analysis of the ionic bond confirms the structural study. In the IEF-PCM solvent compared to the gas medium, Wiberg bond indices of the tetra-, and penta-coordinate conformers are weaker, and the hexa-coordinate conformers in both media are nearly identical. This proves that compared to the solvent phase, the dative bond is stronger in the gas phase. This is supported by the significant difference in the electronic binding energies at saturation found with a single fitting function which are -88.6 and -146.6 $\text{kJ}\text{mol}{}^{\mathrm{-1}}$ in the solvent and gas phases, respectively.