Experimental Investigation of the Stability of AunCln+m− (n = 1–5; m = 1, 3, 5, 7) Clusters by Laser Desorption/Ionization Mass Spectrometry

The stability of gold chloride clusters is an important topic in catalysis and nanomaterials, but experimental data are missing. Here, fourteen different clusters were obtained simultaneously using laser desorption/ionization mass spectrometry and were identified as Au_nCl_n+m^- (n = 1-5; m = 1, 3, 5, 7) or AuCl_n+1^-, Au₂Cl_2n+1^-, Au₃Cl_2n+2^-, Au₄Cl_2n+1^- and Au₅Cl_2n+2^-. Consequently, the effects of laser intensity on their stability were evaluated, considering differences in the AuCl unit or the number of Cl atoms. For the Au_nCl_n+1^- and Au_nCl_n+3^- groups, the relative intensity of the clusters decreased with each additional AuCl unit as the laser intensity increased. Au_nCl_n+5^- clusters showed a different trend in relative intensities: Au₃Cl₈^- > Au₂Cl₇^- > Au₄Cl₉^- > Au₅Cl₁₀^-. The mononuclear AuCl₄^- showed the highest stability, which is consistent with their "superhalogen" character. In the Au₂Cl_2n+1^- clusters, Au₂Cl₅^- with Au (III)-Au(I) interaction was more stable at lower laser intensities, while Au₂Cl₃ with Au(I)-Au(I) bonds became more dominant at higher intensities. Among the Au₃Cl_2n+2^-, Au₄Cl_2n+1^- clusters, those with purely "aurophilic" interactions became increasingly stable with increasing laser intensity. These results emphasize the importance of bond type and cluster size for the stability of gold chloride clusters at different laser intensities.