Host-guest chemistry in the gas phase: Complex formation of cucurbit[6]uril with proton-bound water dimer

Dong Hun Noh, Shin Jung C Lee, Jong Wha Lee, Hugh I. Kim

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

The hydration of cucurbit[6]uril (CB[6]) in the gas phase is investigated using electrospray ionization traveling wave ion mobility mass spectrometry (ESI-TWIM-MS). Highly abundant dihydrated and tetrahydrated species of diprotonated CB[6] are found in the ESI-TWIM-MS spectrum. The hydration patterns of the CB[6] ion and the dissociation patterns of the hydrated CB[6] ion indicate that two water molecules are bound to each other, forming a water dimer in the CB[6] complex. Ion mobility studies combined with the structures calculated by density functional theory suggest that the proton-bound water dimer is present as a Zundel-like structure in the CB[6] portal, forming a hydrogen bond network with carbonyl groups of the CB[6]. When a large guest molecule is bound to a CB[6] portal, water molecules cannot bind to the portal. In addition, the strong binding energy of the water dimer blocks the portal, hindering the insertion of the long alkyl chain of the guest molecule into the CB[6] cavity. With small alkali metal cations, such as Li+ and Na+, a single water molecule interacts with the CB[6] portal, forming hydrogen bonds with the carbonyl groups of CB[6]. A highly stable Zundel-like structure of the proton-bound water dimer or a metal-bound water molecule at the CB[6] portal is suggested as an initial hydration process for CB[6], which is only dissolved in aqueous solution with acid or alkali metal ions. [Figure not available: see fulltext.]

Original languageEnglish
Pages (from-to)410-421
Number of pages12
JournalJournal of the American Society for Mass Spectrometry
Volume25
Issue number3
DOIs
Publication statusPublished - 2014 Mar 1
Externally publishedYes

Keywords

  • Cucurbit[6]uril
  • Host-guest chemistry
  • Hydration
  • Ion mobility mass spectrometry
  • Zundel structure

ASJC Scopus subject areas

  • Structural Biology
  • Spectroscopy

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