Li Yingwei, Cowan Michael J, Zhou Meng, Taylor Michael G, Wang He, Song Yongbo, Mpourmpakis Giannis, Jin Rongchao
Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States.
ACS Nano. 2020 Jun 23;14(6):6599-6606. doi: 10.1021/acsnano.0c01000. Epub 2020 Apr 21.
Dipole moment (μ) is a critical parameter for molecules and nanomaterials as it affects many properties. In metal-thiolate (SR) nanoclusters (NCs), μ is commonly low (0-5 D) compared to quantum dots. Herein, we report a doping strategy to give giant dipoles (∼18 D) in M (M = Au/Ag/Cd) NCs, falling in the experimental trend for II-VI quantum dots. In M NCs, high μ is caused by the Cd-Br bond and the arrangement of heteroatoms along the axis. Strong dipole-dipole interactions are observed in crystalline state, with energy exceeding 5 kJ/mol, directing a "head-to-tail" alignment of AuAgCd(SR)X (SR = adamantanethiolate) dipoles. The alignment can be controlled by doping. The optical absorption peaks of M show solvent polarity-dependent shifts (∼25 meV) with negative solvatochromism. Detailed electronic structures of M are revealed by density functional theory and time-dependent DFT calculations. Overall, the doping strategy for obtaining large dipole moments demonstrates an atomic-level design of clusters with useful properties.
偶极矩（μ）是分子和纳米材料的一个关键参数，因为它会影响许多性质。在金属硫醇盐（SR）纳米团簇（NCs）中，与量子点相比，μ通常较低（0 - 5 D）。在此，我们报告一种掺杂策略，可在M（M = Au/Ag/Cd）NCs中产生巨大偶极（约18 D），符合II - VI族量子点的实验趋势。在M NCs中，高μ是由Cd - Br键以及杂原子沿轴的排列引起的。在晶体状态下观察到强偶极 - 偶极相互作用，能量超过5 kJ/mol，引导AuAgCd(SR)X（SR = 金刚烷硫醇盐）偶极呈“头对尾”排列。这种排列可以通过掺杂来控制。M的光吸收峰显示出与溶剂极性相关的位移（约25 meV），具有负溶剂化显色现象。通过密度泛函理论和含时密度泛函理论计算揭示了M的详细电子结构。总体而言，获得大偶极矩的掺杂策略展示了具有有用性质的团簇的原子级设计。
