An Rh–Au nanocluster protected by an N-heterocyclic carbene: synthesis, structure, and single-molecule conductance properties

Atomically precise metal nanoclusters protected by N-heterocyclic carbenes (NHCs) constitute an emerging frontier in nanoscience, yet alloy cluster systems remain underexplored. In this work, we report the synthesis of an atomically defined gold-rhodium (Au-Rh) alloy nanocluster stabilized by NHC ligands. Its composition and structure were unambiguously determined through single-crystal X-ray diffraction, high-resolution mass spectrometry, and X-ray photoelectron spectroscopy. Systematic characterization revealed its ultraviolet-visible absorption and photoluminescence properties. Leveraging these optical characteristics, we investigated photo-modulation of electrical conductivity at the single-cluster level. Notably, 290 nm illumination induced a 338% increase in conductivity in the single-cluster junction compared to the dark state. Variable light-power experiments attributed this phenomenon mechanistically to light-induced localized surface plasmon resonance. This study proposes a design strategy for photo-responsive heterometallic cluster materials in optoelectronic applications.