Influence of Weak Interactions on Supramolecular Binding: Characterization of Cucurbituril Complexes with Alkylmonoammonium Ions Using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

• Main Author: Shi, Ruijan
• Format: Others
• Published: BYU ScholarsArchive 2011
• Subjects: cucurbituril complexes; SORI; equilibrium; FT ICR MS; Biochemistry; Chemistry
• Online Access: https://scholarsarchive.byu.edu/etd/2898; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=3897&context=etd

This thesis focuses on using mass spectrometry-based techniques for characterizing the structure and behavior of cucurbituril complexes in the gas phase. Both solvent and counter ion effects can be completely eliminated in the gas phase and the intrinsic interactions in the system are directly shown in the experimental results. Chapter 1 introduces the structures, properties and host-guest chemistry of cucurbituril, and FTICR mass spectrometry including instrumentation, performance and working principles. Two mass spectrometry-based methods for supramolecular characterization, sustained off-resonance irradiation collision induced dissociation (SORI CID) and ion molecule equilibrium measurements, are also discussed in this chapter. Chapter 2 characterizes the dissociation and reaction behaviors of the complexes formed by cucurbit[5]uril (CB5) and primary monoamines [CH3(CH2)nNH2, n = 0-7] as well as similar studies of decamethylcucurbit[5]uril (mc5) in the gas phase. This study probes host-guest interactions between the neutral cucurbituril host and alkyl chains of varying length. All the cucurbit[5]uril and decamethylcucurbit[5]uril complexes have external binding. The dissociation thresholds of the complexes suggest that the optimum monoammonium chain length for binding CB5 in the gas phase occurs for n = 2, whereas for mc5 the optimum is n = 0. Reactivity studies of CB5 and mc5 complexes indicate the highest binding affinity appears at n = 6 for CB5 and n = 5 for mc5. Chapter 3 investigates the complexes formed by cucurbit[6]uril and primary monoamines using energy resolved SORI CID methods and ion molecule equilibrium measurements. The fragmentation data, branching ratios for the various channels, and the reactivities of the complexes suggest the complexes have the monoammonium threaded through the cavity of CB6 forming a pseudorotaxane architecture. Reactivity studies of complexes of cucurbit[7]uril reveal behaviors distinctive from CB5, mc5 or CB6, which suggests both internally-bound and externally-bound structures are present in CB7 complexes.