Electronic Stability of Phosphine-Protected Au20 Nanocluster: Superatomic Bonding

• Published in: Journal of physical chemistry. C Vol. 117; no. 25; pp. 13276 - 13282
• Main Authors: Yuan, Yuan, Cheng, Longjiu, Yang, Jinlong
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 27.06.2013
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron states; Exact sciences and technology; Methods of electronic structure calculations; Physics; Molecular orbital; Nanocluster; Valence; Theoretical study; Density functional method; Carrier density; Pyridyl radicals
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp402816b

A recent experiment reported that a newly crystallized phosphine-protected Au20 nanocluster [Au20(PPhy2)10Cl4]Cl2 [PPhpy2 = bis(2-pyridyl)phenylphosphine] owns a very stable Au20 core, but the number of valence electrons of the Au20 core is 14e, which is not predicted by the superatom model. So we apply the density functional theory to further study this cluster from its molecular orbital and chemical bonding. The results suggest that the Au20 (+6) core is an analogue of the F2 molecule based on the super valence bond model, and the 20-center–14-electron Au20 (+6) core can be taken as a superatomic molecule bonded by two 11-center–7-electron superatoms, where the two 11c superatoms share two Au atoms and two electrons to meet an 8-electron closed shell for each. The electronic shell closure enhances the stability of the Au20 core, besides the PN bridges. Exceptionally, the theoretical HOMO–LUMO gap (1.03 eV) disagrees with the experimental value (2.24 eV), and some possible reasons for this big difference are analyzed in this paper.