Collision-Induced Dissociation of Monolayer Protected Clusters Au144 and Au130 in an Electrospray Time-of-Flight Mass Spectrometer

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• 作者：David M. Black ; Nabraj Bhattarai ; Robert L. Whetten ; Stephan B. H. Bach
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：November 13, 2014
• 年：2014
• 卷：118
• 期：45
• 页码：10679-10687
• 全文大小：318K
• ISSN：1520-5215

文摘

Gas-phase reactions of larger gold clusters are poorly known because generation of the intact parent species for mass spectrometric analysis remains quite challenging. Herein we report in-source collision-induced dissociation (CID) results for the monolayer protected clusters (MPCs) Au₁₄₄(SR)₆₀ and Au₁₃₀(SR)₅₀, where R- = PhCH₂CH₂-, in a Bruker micrOTOF time-of-flight mass spectrometer. A sample mixture of the two clusters was introduced into the mass spectrometer by positive mode electrospray ionization. Standard source conditions were used to acquire a reference mass spectrum, exhibiting negligible fragmentation, and then the capillary-skimmer potential difference was increased to induce in-source CID within this low-pressure region (鈭? mbar). Remarkably, distinctive fragmentation patterns are observed for each MPC[3+] parent ion. An assignment of all the major dissociation products (ions and neutrals) is deduced and interpreted by using the distinguishing characteristics in the standard structure-models for the respective MPCs. Also, we propose a ring-forming elimination mechanism to explain R-H neutral loss, as separate from the channels leading to RS-SR or (AuSR)₄ neutrals.