Graduate School of Material Science, University of Hyogo, 3-2-1 Koto, Ako-gun, Hyogo 678-1297, Japan.
Nanoscale. 2012 Feb 7;4(3):955-63. doi: 10.1039/c2nr11544a. Epub 2012 Jan 5.
Versatile functionalization of metal clusters is a key step in understanding the reactivity of protective monolayers. We here demonstrate that reaction of the outermost amino groups on (S)-/(R)-penicillamine-protected gold clusters with ethyl isocyanate readily modifies the chiral surface structure through carbamoylation. Interestingly, the clusters are electrophoretically separated by the size of the surface ligand, not by the size of the gold core, which is revealed by UV-vis, IR, and energy dispersive X-ray (EDX) spectroscopy as well as SAXS measurements. The ligand size (or length) is extended through additional reactions of the carbamoylated amino groups with isocyanate, while the chemical similarity in ligand structures is realized by their IR spectral similarity. Optical and chiroptical responses of the separated cluster compounds are thus overall similar to each other, but a close inspection reveals that the ligand size has a small but distinct influence on the chiroptical response of the gold clusters.
多功能官能化金属簇是理解保护单层反应性的关键步骤。我们在这里证明，（S）/（R）-青霉素胺保护的金簇最外层氨基与异氰酸乙酯的反应可以通过氨甲酰化轻易地修饰手性表面结构。有趣的是，通过电泳分离出表面配体的大小，而不是通过金核的大小，这通过紫外可见光谱、红外光谱和能量色散 X 射线（EDX）光谱以及小角 X 射线散射（SAXS）测量得到证实。通过与异氰酸酯进一步反应，使氨甲酰化氨基延长配体的长度，同时通过红外光谱的相似性实现配体结构的化学相似性。因此，分离出的簇化合物的光学和手性响应总体上彼此相似，但仔细观察发现，配体的大小对手性金簇的光学响应有微小但明显的影响。
