Chiral Ligand-Protected Bimetallic Nanoclusters: How does the Metal Core Configuration Influence the Nanocluster's Chiroptical Responses?

摘要

We here present electronic structures and chiroptical responses of gold-based bimetallic nanoclusters protected by chiral thiolate ligand, glutathione (GSH), and compare them with those of monometallic counterparts. The nanoclusters examined are AuPd and AuAg bimetallic systems. The effect of Pd or Ag doping on the chiroptical responses of optically active Au nanoclusters as well as the importance of the bimetallic core configurations are discussed. Briefly, we find that GS-protected AuPd or AuAg nanoclusters exhibit quite different Cotton effects from those of the monometallic nanoclusters in metal-based electronic transition regions. In the AuPd system, all bimetallic nanoclusters exhibit featureless absorption profiles, but their circular dichroism (CD) signals are structured, offering a greater advantage in detecting a foreign atom doping in the nanocluster system. In the AuAg system, the nanocluster compounds exhibit relatively weaker CD responses than those of the corresponding Au compounds. This CD decrease can be explained in terms of the increased geometrical isomers that are formed by statistical distribution of Ag heteroatoms in the nanocluster, since an increased number of possible configurations gives an average in the CD response with positive and negative bands of different optical isomers.