Single-molecule manipulation of copper nanoclusters for modulating nonlinear optics
Xuekun Gong, Zhuang‐Hua Liu, Qing‐Hua Xu, Lin Wang, Qingxiang Guo, Jian Xin Zhang, Qiaohong Li, Wei-Hui Fang, Hui Shen
Abstract
The molecular-level elucidation of structure-property relationships of metal nanoclusters is quite valuable for further structure design and performance optimization. Nevertheless, the single-molecule manipulation of metal nanoclusters for controlling their physic-chemical properties remains a grand challenge. Herein, we demonstrate that the third-order nonlinear optical (NLO) performance of structurally precise copper nanoclusters can be efficiently modulated by single-molecule chemistry. Two analogous clusters, [Cu<sub>25</sub>(RS)<sub>18</sub>H<sub>10</sub>]<sup>3-</sup> (Cu<sub>25</sub>) and [Cu<sub>26</sub>(RS)<sub>18</sub>H<sub>10</sub>(PPh<sub>3</sub>)]<sup>2-</sup> (Cu<sub>26</sub>, RSH is 2-fluorobenzenethiol), have been attained and structure determined in the work. Both clusters feature a centered cuboctahedron Cu<sub>13</sub> core with a similar shell structure, save for the addition of one more PPh<sub>3</sub>Cu<sup>+ </sup>unit on the Cu<sub>26</sub> cluster. Remarkably, the single molecule difference in the structure has essentially altered their properties including optical characteristics and stability. In comparison to Cu<sub>25</sub>, Cu<sub>26</sub> displays better optical limiting activity. Theoretical calculations suggest that the substantial electron transfer from the PPh<sub>3</sub> ligand to the metal core boosts the NLO performance of Cu<sub>26</sub>. This work not only showcases that structurally precise copper nanoclusters are a promising class of optical limiting (OL) materials but also deepens the understanding of fabricating nanoparticulate materials via the single molecule strategy.