Conformational isomerization dynamics of flexible molecules and their water containing complexes
Abstract
Molecules with several flexible coordinates have potential energy surfaces with a large number of minima and many transition states separating them. A general experimental protocol, based on conformation-specific ultraviolet and infrared spectroscopy, has been developed and described which is capable of studying conformational isomerization in such circumstances, measuring energy thresholds for isomerization of specific X→Y reactant-product isomer pairs following excitation via stimulated emission pumping (SEP). Specific examples involving flexible molecules include 3-indole-propionic acid (IPA), tryptamine (TRA), trans-formanilide (TFA), and their water containing complexes. The studies of isomerization in the water containing complexes, or solute-solvent complexes, are also described, including a measurement of the barrier to isomerization in IPA-H2O complex and a unique isomerization reaction in which a single water molecule is shuttled between H-bonding sites on the trans-formanilide (TFA) molecule. In addition, infrared-ultraviolet population transfer spectroscopy was employed to study a unique system, namely TRA-H2O complex, and provided measurements of (i) the dissociation energy threshold for the tryptamine-H 2O complex, (ii) tryptamine monomer product conformational distributions as a function of energy above this threshold, and (iii) the dissociation rates for levels near threshold, using the techniques of infrared-ultraviolet holeburning and infrared-induced population transfer spectroscopy. In all these circumstances, comparisons with theory are made to extract the maximum physical insight to the dynamics of isomerization in flexible biomolecules and molecular clusters.
Degree
Ph.D.
Advisors
Zwier, Purdue University.
Subject Area
Chemistry
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