Parity-forbidden superatomic molecular orbital interaction and aurophilicity induced H─Au bonding in H@Au 20

Understanding H─Au interaction is essential for elucidating the stereochemistry and reactivity of gold hydrides. By embedding a hydrogen atom in the central tetrahedral cavity of Au 20 , we identify a distinct form of hydrogen-mediated bonding in a gold cluster. Our results show that the H─Au bonding can be described as a process wherein H─Au interactions compensate for relatively weaker Au─Au bonding driven by intrinsic aurophilic interactions. This phenomenon originates from parity-forbidden coupling of superatomic molecular orbitals under a noncentrosymmetric field, giving rise to the atypical H─Au bonding and a formally neutral interstitial H atom. A detailed analysis of optical properties reveals partial suppression of visible-light absorption and emergence of a more favorable phosphorescent channel, a manifestation of the complex nature of this H─Au bonding. These findings suggest a versatile platform for tuning electronic and optical properties of gold cluster systems through subtle atomic-level manipulation.