Directional Doping and Cocrystallizing an Open-Shell Ag-39 Superatom via Precursor Engineering

摘要

Metal precursors employed in the bottom-up synthesis of metal nanoclusters (NCs) are of great importance in directing their composition and geometrical structure. In this work, a silver nanocluster co-protected by phosphine and thiolate, namely, [Ag-39(PFBT)(24)(TPP)(8)](2-) (Ag-39, PFBT = pentafluorobenzenethiol, TPP = triphenylphosphine), was isolated and structurally characterized. It adopts a three-layered Ag-13@Ag-18@Ag8S24P8 core-shell structure. The Ag-13@Ag(18 )kernel is unusual in multilayer noble metal NCs. By introducing a copper precursor in the synthesis, a bimetallic nanocluster [Ag37Cu2(PFBT)(24)(TPP)(8)](2-) (Ag37Cu2) with an identical structure to Ag 39 apart from two outer Ag atoms being substituted by Cu atoms was obtained. Astoundingly, the Cu precursor used in the synthesis was found to be critical in determining the final structure. The alteration of the Cu precursor led to the cocrystallization of the above alloy nanocluster with a Ag-14 nanocluster, namely, [Ag37Cu2(PFBT)(24)(TPP)(8)](2-)center dot[Ag-14(PFBT)(6)(TPP)(8)] (Ag37Cu2 center dot Ag-14). The electronic structure analyzed by theoretical calculation reveals that Ag-39 is a 17-electron open-shell superatom. The optical absorption of Ag-39, Ag37Cu2, and Ag37Cu2 center dot Ag-14 was compared and studied in detail. This work not only enriches the family of alloy metallic nanoclusters but also provides a metal NC-based cocrystal platform for in-depth study of its crystal growth and photophysical property.