Heavier Counterparts for Phosphine-Protected Gold Clusters. Electronic, Bonding, and Optical Properties of Au13Cl2(L5) and Au13(L6) Superatoms.

Ligand-protected clusters with atomically precise structures serve as prototypical models for understanding versatility at the bottom of the nanoscale regime. Here, we set to investigate the impact of ligand identity on the structural, bonding, and optical properties based on Au13Cl2 and Au13 cluster cores coordinated by bidentate ligands from phosphines to heavier pnictogens members, provided by arsine, stibine, and bismuthine, in isostructural prototypical templates. Our results reveal contrasting trends in Au-Au core distances between Au13Cl2 and Au13 clusters upon ligand substitution, with Au-L bond lengths increasing down the group, in addition to a systematic decrease in ligand-core interaction energies driven by reduced electrostatic and orbital contributions, indicating weaker coordination and increased ligand lability for heavier ligands. Optical properties exhibit ligand-dependent UV-vis absorption shifts and phosphorescent emissions, with heavier ligands causing notable red-shifts and altered excited-state geometries. These findings demonstrate the tunability of Au13 cluster properties through ligand modification, providing insights for designing superatomic clusters with tailored photophysical and chemical functionalities for catalysis and optoelectronic applications.