Collision-Induced Dissociation and Ion Mobility Mass Spectrometry of Au30(S-tBu)18 Nanoclusters

Author

Christopher HoodFollow

Date of Award

Spring 4-26-2022

Document Type

Undergraduate Thesis

Department

Chemistry and Biochemistry

First Advisor

Amala Dass

Second Advisor

Saumen Chakraborty

Third Advisor

Daniell Mattern

Relational Format

Dissertation/Thesis

Abstract

Collision Induced Dissociation (CID) and Ion Mobility Mass Spectrometry (IM-MS) are methods used to understand the structural arrangement and stability of large molecules. In this study, the gold nanocluster Au₃₀(S-tBu)₁₈ was dissociated at varying Trap collision energies, and drift time vs mass spectrometry data was plotted to determine the order of cluster fragmentation. Comparing Au₃₀(S-tBu)₁₈ data to that of Au₂₅(SCH₂CH₂Ph)₁₈, the only current nanocluster published with IM-MS data, two distinctly different dissociation patterns were seen. Unlike the linear CID fragmentation of Au₂₅(SCH₂CH₂Ph)₁₈ from the parent ion to the resulting Au₁₃ core, Au₃₀(S-tBu)₁₈ fragments into two species regions: Au₃₀(X)_11-18 and Au₂₆(X)_9-14, where x is the total number of ligands, S and S-tBu. These two regions remained present in ionization even at the highest Trap collision energy (200 V). The presence of the two Au₃₀(S-tBu)₁₈ species regions can be seen in both CID mass spec and IM-MS drift time bands. IM-MS m/z vs drift time plots of Au₃₀(S-tBu)₁₈ show two broad positively sloped fragment bands with no viewable fragmentation below Au₂₆S₉. Identification of Au₃₀(S-tBu)₁₈ fragment peaks shows a systematic loss of -S-tBu, -tBu, and -S groups in the protecting thiolate ligand monolayer to the gold core with minimal to no loss of Au atoms. The ability of Au₃₀(S-tBu)₁₈ to lose almost all the protecting carbon chains without loss of Au from the core may be a result of the stability of the Au core structure. Additionally, the high loss of tert-butyl groups in Au₃₀(S-tBu)₁₈ collision, unseen in Au₂₅(SCH₂CH₂Ph)₁₈, may be due to the inherent stability of the tertiary carbocation of tert-butyl after cleavage from the S atom.

Recommended Citation

Hood, Christopher, "Collision-Induced Dissociation and Ion Mobility Mass Spectrometry of Au30(S-tBu)18 Nanoclusters" (2022). Honors Theses. 2546.
https://egrove.olemiss.edu/hon_thesis/2546

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