Details of Grant 

EPSRC Reference:	GR/S97972/02
Title:	Investigation of Photoinitiated Bergman Cyclization Reactions using High Resolution Laser Spectroscopy
Principal Investigator:	Smith, Professor DM
Other Investigators:	Wood, Dr M
Researcher Co-Investigators:
Project Partners:
Department:	Chemistry
Organisation:	University of Bristol
Scheme:	Standard Research (Pre-FEC)
Starts:	01 October 2005	Ends:	31 August 2008	Value (£):	130,210
EPSRC Research Topic Classifications:	Gas & Solution Phase Reactions
EPSRC Industrial Sector Classifications:	No relevance to Underpinning Sectors
Related Grants:
Panel History:
Summary on Grant Application Form
Bergman cyclization reactions are of considerable interest to chemists. Under certain conditions, the structure of organic molecules which contain double and triple bonds may change from a linear to cyclic form. The products of these internal Bergman cyclizations are very reactive because they contain two unpaired electrons. This reactivity means that the parent molecules have many applications, in fields as diverse as biomedicinal, astrophysical and materials chemistry. For example, the products react easily with DNA and the potent toxicity of many naturally occurring antibiotics is thought to result from an initial Bergman cyclization step. Indeed, a new anti-leukaemia drug, Mylotarg, whose activity results from a Bergman cyclization process has recently been released to the market.These cyclization reactions only occur, however, if excess energy is provided, either as heat or as light. Most investigations to date have concentrated upon thermally activated processes. Unfortunately, the application of antibiotics based on thermal Bergman cyclization steps appears to be limited by either the very high toxicity or the extreme temperatures required for thermal activation. In contrast, the mechanism for the photochemical reactions is very poorly understood. Very few experimental investigations into photochemically excited states have been performed. Furthermore, theoretical calculations on molecules in excited states are extremely difficult to perform and the results are often unreliable. This limitation currently restricts the possible applications of photoinitiated Bergman cyclization steps. The development of an antibiotic whose activity could be initiated by light would offer the possibility of targeted treatment through photodynamic therapy.We propose to build and use a laser spectrometer to enable us to study Bergman cyclization reactions. One of the strengths of the proposal lies in the use of the established experimental techniques of resonance-enhanced multiphoton-ionization and laser-induced-fluorescence spectroscopies to study a chemical system with direct applications. These techniques are both more reliable and cost effective than alternative methods. From our research we will be able to deduce how the structures of the reactant molecules change upon photoexcitation. These experimental observations will allow the results of theoretical calculations to be tested and more reliable models for the cyclization mechanisms developed. We also intend to monitor the formation of product molecules and characterize the structures of these species. We will determine the propensity for reaction at different excitation wavelengths. By relating our observations to our understanding of the excited states of the reactants, we will be able to learn more about how and why photoinitiated Bergman reactions occur.
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