title: Collision-induced dissociation of monolayer protected clusters Au144 and Au130 in an electrospray time-of-flight mass spectrometer.
abstract: 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 (∼4 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.
authors.affiliation: Department of Chemistry, University of Texas at San Antonio , One UTSA Circle, San Antonio, Texas 78249, United States.
authors.forename: David M
authors.initials: DM
authors.lastname: Black
authors.forename: Nabraj
authors.initials: N
authors.lastname: Bhattarai
authors.forename: Robert L
authors.initials: RL
authors.lastname: Whetten
authors.forename: Stephan B H
authors.initials: SB
authors.lastname: Bach
mesh_terms: D017612:Gold Compounds / Q000737:chemistry*; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D017612:Gold Compounds