Competition Between Different Non-Covalent Interactions in Cluster Ions
Vaden, Timothy Daniel
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Permalink
https://hdl.handle.net/2142/84216
Description
Title
Competition Between Different Non-Covalent Interactions in Cluster Ions
Author(s)
Vaden, Timothy Daniel
Issue Date
2005
Doctoral Committee Chair(s)
Lisy, James M.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Physical
Language
eng
Abstract
Non-covalent interactions are important in ionic systems, where ion-molecule interactions must compete with molecule-molecule interactions. This competition between different non-covalent interactions ultimately governs the behavior of many processes. In this Thesis, competing noncovalent interactions were isolated for study in gas-phase cluster ions. Infrared spectroscopy and quantum chemistry calculations were used to characterize the structures and energetics of the cluster ions. Ion-water interactions were investigated in M +(H2O)Ar species generated via argon evaporative cooling. The results highlight the effect of the ion on the H2O. Internal energy simulations and temperatures deduced from the spectra showed that cluster ions with argon are much colder than those without argon. In a similar manner, ion-alkane interactions were investigated in M+(CH4)Ar species. The ion-methane configurations suggest that alkyl groups may be useful for novel ionophore moieties. Competing interactions were investigated in M+(Phenol)2,3 species. Temperature effects were characterized by studying M+(Phenol)2,3 with and without argon. In all cases the relative populations of hydrogen-bonded isomers were much larger in the cold species than in the warmer species. In the cold species, the ion-phenol interaction competes against the intermolecular hydrogen bonding. Competing interactions were further investigated in M+(Phenol)(H 2O)4, species to model ion-phenol interactions in aqueous environments under room temperature conditions. For M+ (Phenol)(H2O)4, differences between the Na + and K+ species indicated that the phenol O-H group interacts with water molecules around K+ but not Na +. Competing ion-local dipole and ion-water interactions were investigated in M+(Acetone)n(H2O)m and M+(Acetonitrile)n(H2O)m species. The effect of ion-dipole interactions on ion-water interactions was monitored by characterizing different [n,m] combinations at constant n+m. Adding local dipoles to the system decreased the strength of the ion-water interactions as well as the strength of the nearby hydrogen bonds. The role of competing interactions in the size-selective extraction of ions from solution was investigated in M+(12C4)(H2O)n species where 12C4 represents 12-crown-4 ether. The results indicate that the hydrogen bonds around the Li+(12C4) complex are significantly stronger than those around the other M+(12C4) species. This suggests that ion-water interactions are not as important in the Li+ species as they are in other species, presumably because Li+ is extracted from solution.
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