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

The vibrationally resolved à 2 Σ + ←X ∼ 2 ${\tilde{\rm{X}}}^{2} $ Σ + transitions ofAu 2 + N 2 ${\rm{Au}_{2}^{+}} {\rm{N}_{2}} $ andAu 2 +N 2 O ${\rm{Au}_{2}^{+}} {\rm{N}_{2}{\rm{O}}} $ 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 theAu 2 + ${\mathrm{Au}}_{2}^{+}$ entity in theX ∼ 2 ${\tilde{\rm{X}}}^{2} $ Σ + state by donating electron density into the half‐filled bonding orbital leading to the strengthening of the Au-Au $\text{Au-Au}$ , N-N $\text{N-N}$ , and N-O $\text{N-O}$ bonds. This effect is reversed in the à 2 Σ + state, where the Au-Au $\text{Au-Au}$ bonding orbital is already filled and the ligand destabilizes the Au-Au $\text{Au-Au}$ bond by donating into the antibonding orbitals ofAu 2 + ${\mathrm{Au}}_{2}^{+}$ . 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 ofAu 2 + L ${\mathrm{Au}}_{2}^{+}\text{L}$ 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 ofAu 2 + ${\mathrm{Au}}_{2}^{+}$ in ground and excited electronic state