ESI-MS of Cucurbituril Complexes Under Negative Polarity

Journal Article · Wed Nov 15 00:00:00 EST 2017 · Journal of the American Society for Mass Spectrometry

DOI:https://doi.org/10.1007/S13361-017-1758-0· OSTI ID:22776850

Rodrigues, Maria A. A.; Mendes, Débora C. ^[1]; Ramamurthy, Vaidhyanathan ^[2]; Silva, José P. Da, ^[1]

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1. Meditbio, University of Algarve (Portugal)
2. University of Miami, Department of Chemistry (United States)

Electrospray ionization mass spectrometry (ESI-MS) is a powerful tool to study host–guest supramolecular interactions. ESI-MS can be used for detailed gas-phase reactivity studies, to clarify the structure, or simply to verify the formation of complexes. Depending on the structure of the host and of the guest, negative and/or positive ESI are used. Here we report the unexpected formation of host–guest complexes between cucurbit[n]urils (n = 7, 8, CB[n]) and amine, styryl pyridine, and styryl pyridine dimer cations, under negative ESI. Non-complexed CB[n] form double charged halide (Br{sup -}, Cl{sup -}, F{sup -}) adducts. Under negative ESI, halide ions interact with CB[n] outer surface hydrogen atoms. One to one host–guest complexes (1:1) of CB[n] with positive charged guests were also observed as single and double charged ions under negative ESI. The positive charge of guests is neutralized by ion-pairing with halide anions. Depending on the number of positive charges guests retain in the gas phase, one or two additional halide ions are required for neutralization. Complexes 1:2 of CB[8] with styryl pyridines retain two halide ions in the gas phase, one per guest. Styryl pyridine dimers form 1:1 complexes possessing a single extra halide ion and therefore a single positive charge. Negative ESI is sensitive to small structural differences between complexes, distinguishing between 1:2 complexes of styryl pyridine-CB[8] and corresponding 1:1 complexes with the dimer. Negative ESI gives simpler spectra than positive ESI and allows the determination of guest charge state of CB[n] complexes in the gas phase. .

• OSTI ID: 22776850
• Journal Information: Journal of the American Society for Mass Spectrometry, Vol. 28, Issue 11; Other Information: Copyright (c) 2017 American Society for Mass Spectrometry; http://www.springer-ny.com; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-0305
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
CHARGE STATES
INTERACTIONS
IONIZATION
MASS SPECTROSCOPY
PYRIDINE
REACTIVITY
SPECTRA
TOOLS