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Title: Lithium formate ion clusters formation during electrospray ionization: Evidence of magic number clusters by mass spectrometry and ab initio calculations

Small cationic and anionic clusters of lithium formate were generated by electrospray ionization and their fragmentations were studied by tandem mass spectrometry. Singly as well as multiply charged clusters were formed with the general formulae, (HCOOLi)nLi+, (HCOOLi)nLimm+, (HCOOLi)nHCOO- and (HCOOLi)n(HCOO)mm-. Several magic number cluster ions were observed in both the positive and negative ion modes although more predominant in the positive ion mode with (HCOOLi)3Li+ being the most abundant and stable cluster ions. Fragmentations of singly charged clusters proceed first by the loss of a dimer unit ((HCOOLi)2) followed by sequential loss of monomer units (HCOOLi). In the case of positive cluster ions, all fragmentations lead to the magic cluster (HCOOLi)3Li+ at higher collision energies which later fragments to dimer and monomer ions in lower abundance. Quantum mechanical calculations performed for smaller cluster ions showed that the trimer ion has a closed ring structure similar to the phenalenylium structure with three closed rings connected to the lithium ion. Further additions of monomer units result in similar symmetric structures for hexamer and nonamer cluster ions. Thermochemical calculations show that trimer cluster ion is relatively more stable than neighboring cluster ions, supporting the experimental observation of a magic number cluster with enhancedmore » stability.« less
Authors:
 [1] ;  [2]
  1. Biological Sciences Division, Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354, USA
  2. Perkin Elmer, San Jose Technology Center, San Jose, California 95134, USA
Publication Date:
OSTI Identifier:
1274887
Report Number(s):
PNNL-SA-106023
Journal ID: ISSN 0021-9606; KP1704020
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 6
Publisher:
American Institute of Physics (AIP)
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English