Determination of bond dissociation energies using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry

The objective of this work was to use Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) to determine bond dissociation energies (BDE's) of important species such as solvated anions and host-guest complexes using two different techniques: photodetachment and on-resonance collisionally activated dissociation (CAD).;Photodetachment has been widely used in measuring the electron affinities of various anions. Since the electron affinities of the halides are well known, this part of the work has utilized photodetachment to measure the halides' binding energies with alcohol solvents in the gas phase. An Nd;Collisionally activated dissociation (CAD) processes in mass spectrometry can provide quantitative bond dissociation energy (BDE) estimates if the interaction energy is precisely controlled during collisions. This work has concentrated on improving the accuracy of measuring the thresholds and providing more precise quantitative measurements of host-guest complex interactions in the gas phase by accounting for the effects of multiple ion-molecule collisions, internal energy of precursor ions, thermal spread of energies of the collision gas and the dissociation lifetime of the intermediates. The use of an electrospray ionization (ESI) source for soft ionization that produces intact, multiple charged and solvated gas-phase ions directly from various compounds in solution has been critical for this work. We have measured the binding energies of hydronium and alkali metal ions to the crown ethers (12-crown-4,15-crown-5, and 18-crown-6). The effects of metal size, cavity size and polarizability of different crown ethers are discussed.