ESI-MS of Cucurbituril Complexes Under Negative Polarity

Maria A.A. Rodrigues, Débora C. Mendes, Vaidhyanathan Ramamurthy, José P. Da Silva

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


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 - , Cl - , F - ) 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. [Figure not available: see fulltext.].

Original languageEnglish (US)
Pages (from-to)2508-2514
Number of pages7
JournalJournal of the American Society for Mass Spectrometry
Issue number11
StatePublished - Nov 1 2017


  • Amines
  • Halide adducts
  • Host–guest complexes
  • Ion-pairing
  • Photodimers
  • Styryl pyridines

ASJC Scopus subject areas

  • Structural Biology
  • Spectroscopy


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