Characterization of Cucurbituril Complex Ions in the Gas Phase Using Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Characterization of Cucurbituril Complex Ions in the Gas Phase Using Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

by Zhang, Haizhen 1976-

Host-guest interactions have been well studied in the new century to obtain fundamental insights into supramolecular chemistry. Most of the pioneering works have been done using techniques such as NMR, X-ray crystallography, IR spectroscopy and so on. However, none of these techniques is universal for the investigation of all types of supramolecules, and usually they have one or more limiting factors such as relatively large sample consumption, matrix effects from solvents, etc.

Electrospray mass spectrometry has been widely used to investigate host-guest interactions in the gas phase. A particular advantage of gas phase host-guest research is that the experimental results can be directly compared to computational results because complicating interferences from solvents are not present. Thus electrospray mass spectrometry coupled with high-level computational methods becomes a powerful tool to elucidate binding behavior in host-guest complexes.

With rigid, symmetric structures available in a range of sizes, cucurbiturils have been ideal prototypical host molecules in host-guest chemistry since they were characterized in 1980s. Recent research in my group has shown cucurbiturils can form various complexes with positive ions in the gas phase, such as molecular containers trapping small neutral guest molecules inside or wheel-and-axle architectures with linear molecules threaded through.

Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) is an ideal technique for investigation of host-guest supramolecular complexes due to its ultra-high mass resolving power, ultra-high mass accuracy, and high sensitivity. Moreover it has the capability of trapping ions for ion chemistry, and versatile tandem mass spectrometry capabilities.

This dissertation focuses on the characterization of cucurbituril complexes in the gas phase using electrospray ionization FT-ICR mass spectrometry. Chapter 1 describes FTICR mass spectrometry techniques including principles, performance, instrumentation and applications. Electrospray ionization methods are also discussed in this chapter. Chapter 2 introduces structures, properties, synthesis and host-guest chemistry of the cucurbituril family. Chapters 3 investigate cucurbituril complexation behavior with amino acids and peptides. Chapter 4 investigates the alkali metal ions “lids removal†from cucurbit[5]uril molecular box. Chapter 5 characterizes the cucurbit[6]uril pseudorotaxanes in the gas phase. Chapter 6 characterizes the complexes formed by cucurbit[6]uril and alkyldiammonium cations in the gas phase, using energy-resolved SORI-CID method. High-level computational methods were also performed to explain the experimental results.