Molecular characterization of monolayer-protected clusters commonly known as ‘MPCs’ is a challenging task that is often daunting due to strict synthetic procedures, time consumable and the laborious crucial need for purification, and strict solubility parameters required for certain cluster chemistries. Among various available analytical tools for characterization, mass spectrometry has demonstrated great promise as a powerful tool for these synthetic nanostructured molecules. We have determined parameters and conditions for measurement of two ≥50 kDa hydrophilic gold clusters in the gas phase, along with other readily ionizable compounds in the range of 32-35 kDa. We have also demonstrated how the electrospray ionization mass spectrometry (ESI-MS) could be used as a unique source for precise identification and composition assignment of ligand-core stoichiometry for discrete metallurgy research. To prove that we have chosen the ubiquitous ~29 kDa (molecular mass) core Au clusters with versatile capping agents/ligands ranging from simplest alkanethiol (C2-C5), tertiary amine (captamino), benzyl, MPA ester, to more complicated 11-mercaptoundecyl-(tetra) ethylene glycol (TEG-OH) and 11-mercaptoundecyl)-N, N, N- trimethylammonium hexafluorophosphate (udTMA). Furthermore, the isotopic resolution confirms the charge (z) assignment for alkanthiolated Au clusters.

Electrospray gold standards {32 - 52 kDa} virus-like clusters of metal atoms: LC-ESI-MS identification & determination of diverse forms of the {144/145A, 60X} compounds

ACS Spring 2022

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