The impact of optical excitation on the binding in complexes of the cationic gold dimer: Au2+N2${\rm{Au}_{2}^{+}} {\rm{N}_{2}} $ and Au2+N2O${\rm{Au}_{2}^{+}} {\rm{N}_{2}{\rm{O}}} $

Abstract The vibrationally resolved à 2 Σ + ← Σ + transitions of and are reported together with a detailed characterization of important geometric and electronic properties, enabling a deep understanding of the bonding mechanism at the molecular level. Comparison with time‐dependent density functional theory calculations reveals that the ligand stabilizes the entity in the Σ + state by donating electron density into the half‐filled bonding orbital leading to the strengthening of the , , and bonds. This effect is reversed in the à 2 Σ + state, where the bonding orbital is already filled and the ligand destabilizes the bond by donating into the antibonding orbitals of . The spectral detail obtained provides a deep understanding of the interplay of multiple electronic states in gas‐phase metal‐complex cations, opening the door for a systematic approach in the study of excited state reactivity in organometallic chemistry. Key points High‐resolution spectroscopic characterization of complexes by photodissociation of mass‐selected ions in the optical range and determination of fundamental molecular constants and ligand binding energies Detailed insight into geometric and electronic structure of ground and excited state of catalytically relevant gold cluster cations Effect of ligands on chemical bonding and reactivity of in ground and excited electronic state