Carboranealkynyl-Protected Gold Nanoclusters: Size Conversion and UV/Vis-NIR Optical Properties

Structure evolution has become an effective way to assemble novel monolayer-protected metal nanomolecules. However, evolution with alkynyl-stabilized metal clusters still remains rarely explored. Herein, we present a carboranealkynyl-protected gold nanocluster [Au-28(C4B10H11)(12)(tht)(8)](3+) (Au-28, tht=tetrahydrothiophene) possessing an open-shell electronic structure with 13 free electrons, which was isolated by a facile self-reduction method with 9-HC equivalent to C-closo-1,2-C2B10H11 as the two-in-one reducing and protecting agent. Notably, Au-28 undergoes a complete transformation in methanol into a stable and smaller-sized nanocluster [Au-23(C4B10H11)(9)(tht)(6)](2+) (Au-23) bearing 12 valence electrons and crystal-field-like split superatomic 1D orbitals. The transformation process was systematically monitored with ESI-MS and UV/Vis absorption spectra. Au-28 and Au-23 both display optical absorption covering the UV/Vis-NIR range and NIR emission, which facilitates their potential application in the biomedical and photocatalytic fields.

Automated summary

The preparation and transformation process of carboranealkynyl-protected gold nanoclusters were studied, revealing their potential applications in biomedicine and photocatalysis.