| 研究実績の概要 |
In FY 2022, we successfully synthesized gold nanoclusters stabilized by N-heterocyclic carbene (NHC) ligands in collaboration with the Tsukuda and Hakkinen group. We demonstrated that the use of chiral, BIANP-inspired NHCs to prepare chiral Au10 nanoclusters with a unique elongated central Au10 core. ESI-MS and single-crystal X-ray crystallography confirmed the molecular formula to be [Au10(bisNHC)4Br2]2+. The chiral Au10 nanocluster adopts a linear edge-shared tetrahedral geometry with a prolate shape. The UV-vis spectrum this cluster in CH2Cl2 displayed four prominent absorption bands at 291, 325, and 546 nm, which is a significant departure from the spectra of bis-NHC dinuclear Au(I) complexes. CD spectra demonstrate chirality transfer from the chiral bisNHC ligand to the inner Au10 nanocluster core. The reaction monitoring by ESI-MS and UV-vis spectroscopy indicated the formation of [Au9(bisNHC)4Br]2+ as a key intermediate.
In addition, we achieved the synthesis of a toroidal Au10 cluster stabilized by NHC bearing bulky 2,4,6-trimethylbenzyl units. The [Au10(NHC)6Br3]Br cluster readily undergoes conversion to form a biicosahedral Au25 cluster, while the corresponding Cl cluster showed no conversion. This facyt may be explained both by the steric environment imposed by the bulky mesityl-substituted NHC ligand, as well as steric and electronic factors introduced by the smaller chloride ligands.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
We have been able to make new examples of gold nanoclusters containing NHC ligands. These nanoclusters are the first example of isolable Au10-NHC clusters with chirality, which promise to be an important starting point for the development of new types of ligands for magic number clusters. In addition, we have clarified for the first time that the Au10 nanocluster is an important intermediate of Au25 nanocluster. This is a very important finding for understanding the formation process of gold clusters.
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| 今後の研究の推進方策 |
Future work will entail the synthesis of new series of gold nanoclusters by using designed NHC ligands to control size and shape of gold core. Focusing on the bulkiness of ligands, we aim to control the size of stable nanoclusters. Additionally, building on our synthetic method, the synthesis of new heterobimetallic clusters stabilized by NHC ligands will be examined. For application to catalysis, homogeneous electrochemical investigation of NHC-gold nanoclusters will be established.
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