Hadden, David J. (2013) Exploring the role of σ* driven photochemistry in heteroaromatic molecules. PhD thesis, University of Warwick.

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Abstract

1πσ* or 1nσ* mediated dissociation of X-H and X-CH3 bonds (where X = N,
O or S) has been studied herein, progressing previous work into the role of 1πσ* and
1nσ* states as mediators for excited state relaxation. By investigating the role of
these states in excited state dynamics of sub-units and analogues of biomolecular
systems, spectroscopic signatures can be observed with greater ease. These
signatures may then be extended to elucidate the role of these dissociative states in
excited state relaxation processes of more realistic systems, namely DNA bases and
amino acids.
The work undertaken in this thesis specifically focuses on 1πσ* mediated
hydrogen elimination from imidazole and mequinol, as well as 1πσ* or 1nσ*
mediated CH3 elimination in anisole, thioanisole and mequinol. Through the use of
time resolved velocity map imaging, the timescale for these dissociation processes
can be determined by independently measuring the radicals produced with a
characteristic kinetic energy. From these timescales, information about the rate of
coupling to these 1πσ* and 1nσ* states can be inferred. The results obtained show
that population of these states can occur via several different mechanisms including:
direct excitation; coupling through conical intersections; and tunnelling. The results
also project the importance of 1πσ* or 1nσ* mediated processes in much larger
biological systems, strongly suggesting the need to extend these measurements and
begin to bridge the gap between the microscopic, such as DNA bases and amino
acids, and the macroscopic, such as oligonucleotides and polypeptides.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Photochemistry, Excited state chemistry, Dissociation, Elimination reactions
Official Date:	January 2013
Dates:	Date Event January 2013 Submitted
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Stavros, Vasilios
Extent:	232 leaves : illustrations.
Language:	eng

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