Theoretical prediction of superatom molecular orbitals (SAMOs) in the ice-like cluster (H2O)10 and its impact in the supramolecular chemistry and function of nanostructured water

Abstract

Superatom molecular orbitals (SAMOs) are atom-like molecular orbitals that have been observed in the buckminsterfullerene C60 molecule. We studied the ice-like water cluster (H2O)10 that is expected to be ubiquitous in nature in nanoscale microenvironments at ambient temperatures due to the nanoconfinement effect. We report for the first time the theoretical prediction of the existence of SAMOs in the adamantanoid nanostructured water cluster (H2O)10. The geometry of the adamantanoid water cluster (H2O)10 was optimized using the Restricted Hartree-Fock method and the ab-initio second-order Møller-Plesset perturbation theory (MP2) method, as well as the aqueous solvent phase polarizable continuum method (PCM). The optimized (H2O)10 structure is a distorted adamantanoid that closely matches the crystal structure of (H2O)10 that was previously reported. The theoretical studies using Hartree-Fock (HF), MP2, or Density Functional Theory (DFT) predict that the adamantanoid water cluster (H2O)10 exhibits SAMOs in the low-lying LUMOs. The orbital energies calculated with these methods are reported. The lowest-lying SAMOs in the water cluster (H2O)10 is the most intriguing SAMO due to its s-orbital character and potential to delocalize electrons in a large area that surrounds the cluster. The electron affinity of the water cluster (H2O)10 was calculated using HF, MP2, and DFT methods and the values obtained from each method were (kJ/mol) +74.71, -770.58, and -48.57, respectively. The existence of SAMOs in low-lying LUMO levels indicate of possible supramolecular chemistry of the water clusters with interfacial implications in nanoconfined spaces. Overall, these theoretical results predict new fundamental properties of water clusters that may have deep implications and impact in biological and nanotechnology systems that involve nanostructured water in confined spaces.