Size Effect on Aurophilic Interaction in Gold-Chloride Cluster Anions of Au Cl ^- (2 ≤ n ≤ 7)

Aurophilic interaction plays a very important role in gold-related clusters. Here, we investigate the Au Cl ^- (n = 1-7) cluster ions using Fourier transform ion cyclotron resonance mass spectrometry in combination with theoretical calculations. Three cluster ions of Au₂Cl₃ ^-, Au₃Cl₄ ^-, and Au₄Cl₅ ^- show their remarkable intensities in the mass spectrum. Geometric structure optimizations for Au Cl ^- (n = 1-7) were performed on the MP2 level. The results show that the most stable structures of Au Cl ^- (n = 2-7) are all characterized by a zigzag structure. Furthermore, it can be found that the aurophilic interactions containing terminal gold atoms strengthen with the increase of total gold atoms and progressively stabilize for large clusters of Au₆Cl₇ ^- and Au₇Cl₈ ^-, whereas the aurophilic interactions between nonterminal adjacent gold atoms stabilize at n = 5.