Thermochemical properties of aromatic radicals determined by Fourier -transform ion cyclotron resonance and flowing afterglow quadrupole -octopole -quadrupole mass spectrometry
Abstract
Flowing Afterglow Guided-Ion Beam (FA-GIB) mass spectrometry allows the determination of a variety of thermochemical values for ionic and neutral molecules, including proton affinities, electron affinities, halide affinities, bond dissociation energies, and reaction threshold energies for endoergic ion-molecule reactions. Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry is another powerful mass spectrometry technique, one uniquely suited to kinetics studies of ion-molecule reactions occurring in the "clean" environment of a high vacuum. The goal of one part of this work was to expand the body of knowledge pertaining to several aromatic monoradicals by the use of these two techniques. Bracketing experiments of proton affinity in FT-ICR were combined with energy-resolved collision-induced dissociation studies in FA-GIB to determine the heats of formation for charged radicals in the gas phase. Another goal of this work was to adapt a new desorption technique, Laser-induced Acoustic Desorption (LIAD), for use in the FA-GIB. The LIAD method uses a laser pulse striking the back of a foil upon which sample has been deposited to mechanically eject neutral molecules into the gas phase, making it useful in the study of non-volatile and thermally unstable compounds. This technique was demonstrated successfully in the FA-GIB. A further goal was the exploration of benzopolysulfane species via FT-ICR. Some of these compounds are known to have antitumor, antimicrobial, and antifungal biological activity. The first benzopolysulfanes possessing a meta-relationship between the bridging points of the sulfur ring were formed. An example was discovered in which the sulfur chain bridges the two radical sites of 4,6-didehydryoquinolinium.
Degree
Ph.D.
Advisors
Kenttamaa, Purdue University.
Subject Area
Chemistry
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