Formation of Dimers of [MAu₂₄(SC<i>_n</i>H₂<i>_n</i>₊₁)₁₈]⁻ (M = Au, Pt; <i>n</i> = 6, 8, 10, 12) in Gas Phase by Overcoming Electrostatic Repulsion through Aurophilic and Mul

Intercluster interactions in dimers of [MAu₂₄(SC<i>_n</i>H₂<i>_n</i>₊₁)₁₈]^- (M = Au, Pt; <i>n</i> = 6, 8, 10, 12) were studied by anion photoelectron spectroscopy (PES) and density functional theory (DFT) calculations. PES measurements revealed that the electron binding energies of the dimer dianions were smaller by ∼1.0 and ∼0.9 eV for M = Au and Pt, respectively, than those of the corresponding monomer monoanions [MAu₂₄(SC<i>_n</i>H₂<i>_n</i>₊₁)₁₈]^-, due to electrostatic repulsion. DFT calculations of the model dimers ([MAu₂₄(SCH₃)₁₈]^-)₂ suggested that two clusters are bound by an aurophilic interaction between the Au(I) atoms in the Au₂(SCH₃)₃ staples. The binding energy increased further for the dimer of [Au₂₅(SCH₃)₁₀(SC₄H₉)₈]^-, suggesting that multiple vdW interactions between the alkyl chains contribute to the binding. We thus concluded that ([MAu₂₄(SC<i>_n</i>H₂<i>_n</i>₊₁)₁₈]^-)₂ are formed in the gas phase by overcoming the electrostatic repulsion through aurophilic and multiple vdW attractions. These findings will provide a guide for controlling intercluster reactions and for designing cluster-assembled materials.