Chiral chemistry in metal nanoclusters : Fundamentals and applications

我们发现在一对青霉胺对映体的保护下，金纳米团簇（<2nm）具有较大的光学活性。观察到的光学活性归因于手性配体诱导的不对称场。我们还成功地合成了一对银纳米团簇的光学异构体。它们的热学响应比具有类似核心尺寸的类似金纳米团簇大几倍。手性配体的不对称场效应应该是其光学活性的普遍来源，但在小尺寸银区域中观察到的其增强可能归因于手性银核的额外贡献。其次，对青霉胺保护银纳米团簇的VCD光谱进行了实验研究，并进行了理论分析。光谱分配表明，溶剂效应是解释实验和理论VCD光谱之间一致的必要条件，导致p_n型构象是最可能的异构体。此外，我们还利用手性相转移或硼酸化学实现了非对称转换或对称破缺。

We found large optical activity in gold nanoclusters (<2nm) protected by a pair of penicillamine enantiomers. The observed optical activity was attributed to a dissymmetric field induced by the chiral ligands. We have also succeeded in synthesizing a pair of optical isomers of silver nanoclusters. Their chiroptical response was several-fold larger than that of the analogous gold nanoclusters with comparable core size. The dissymmetric field effect from chiral ligands should be a universal origin for their optical activity, but its enhancement observed in a small size region of silver might be attributed to additional contributions from a chiral silver core. Next, the VCD spectra of penicillamine-protected silver nanoclusters have been studied experimentally, and analyzed theoretically. The spectral assignment suggested that the solvent effect was necessary to account for an agreement between the experimental and theoretical VCD spectra, resulting in the P_N-type conformation as the most probable isomer. Furthermore, we have achieved asymmetric transformation or symmetry breaking of the optically inactive gold and silver nanoclusters using chiral phase-transfer or boronic-acid chemistry.