Reaction Mechanism Governing Formation of 1,3-Bis(diphenylphosphino)propane-Protected Gold Nanoclusters

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• 作者：Jeffrey W. Hudgens ; John M. Pettibone ; Thomas P. Senftle ; Ryan N. Bratton
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：October 17, 2011
• 年：2011
• 卷：50
• 期：20
• 页码：10178-10189
• 全文大小：1057K
• 年卷期：v.50,no.20(October 17, 2011)
• ISSN：1520-510X

文摘

This report outlines the determination of a reaction mechanism that can be manipulated to develop directed syntheses of gold monolayer-protected clusters (MPCs) prepared by reduction of solutions containing 1,3-bis(diphenylphosphino)propane (Lp>3p>) ligand and Au(PPh₃)Cl. Nanocluster synthesis was initiated by reduction of two-coordinate phosphine-ligated [Aup>Ip>LL鈥瞉p>+p> complexes (L, L鈥?= PPh₃, Lp>3p>), resulting in free radical complexes. The [Aup>0p>LL鈥瞉p>鈥?/sup> free radicals nucleated, forming a broad size distribution of ligated clusters. Timed UV鈥搗is spectroscopy and electrospray ionization mass spectrometry monitored the ligated Au_x, 6 鈮?x 鈮?13, clusters, which comprise reaction intermediates and final products. By employing different solvents and reducing agents, reaction conditions were varied to highlight the largest portion of the reaction mechanism. We identified several solution-phase reaction classes, including dissolution of the gold precursor, reduction, continuous nucleation/core growth, ligand exchange, ion鈥搈olecule reactions, and etching of colloids and larger clusters. Simple theories can account for the reaction intermediates and final products. The initial distribution of the nucleation products contains mainly neutral clusters. However, the rate of reduction controls the amount of reaction overlap occurring in the system, allowing a clear distinction between reduction/nucleation and subsequent solution-phase processing. During solution-phase processing, the complexes undergo core etching and core growth reactions, including reactions that convert neutral clusters to cations, in a cyclic process that promotes formation of stable clusters of specific metal nuclearity. These processes comprise 鈥渟ize-selective鈥?processing that can narrow a broad distribution into specific nuclearities, enabling development of tunable syntheses.