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

Abstract

AbstractStructure 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 [Au28(C4B10H11)12(tht)8]3+ (Au28, tht=tetrahydrothiophene) possessing an open‐shell electronic structure with 13 free electrons, which was isolated by a facile self‐reduction method with 9‐HC≡C‐closo‐1,2‐C2B10H11 as the two‐in‐one reducing and protecting agent. Notably, Au28 undergoes a complete transformation in methanol into a stable and smaller‐sized nanocluster [Au23(C4B10H11)9(tht)6]2+ (Au23) 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. Au28 and Au23 both display optical absorption covering the UV/Vis–NIR range and NIR emission, which facilitates their potential application in the biomedical and photocatalytic fields.