LE3 .A278 2009

2009

McFarland, Sherri

Acadia University

Bachelor of Science

Honours

Chemistry

Chemistry

Artificial nucleases based on ruthenium (II) coordination complexes show promise as agents in photodynamic therapy (PDT). Advantages of PDT are two.fold: (a) toxicity of the agent is localized, and (b) there is essentially no peripheral thermal damage. The optimal PDT agent elicits direct double-strand scission when excited in the phototherapeutic window [2]. To date, no satisfactory pre.clinical or clinical agent has been reported. To identify and understand possible DNA cleavage pathways of the agents, photophysical and photochemical parameters are critical. Using absorbance, steady.state luminescence, and time.resolved luminescence spectroscopies, photophysical parameters, specifically the quantum yield, and the luminescent lifetime, of ruthenium (II) based complexes are established under three conditions: (a) room temperature in air, (b) thirty.minute argon.purge at room temperature, and (c) 50:50 (v:v) methanol:ethanol glass at 77 K. Energy transfer to oxygen from a molecule.s triplet excited state(s) is measured as emission from cytotoxic singlet oxygen. Complexes 6 . 10 demonstrated high singlet oxygen quantum yields, up to 94%. Malignant and drug.resistant tumours often incorporate hypoxic tissue [1], rendering damage by singlet oxygen an ineffective treatment. Emission from two states, ligand.centered (LC) and metal.to.ligand charge transfer (MLCT), was measured for complexes 6 . 10. Emission structure and energy indicated the LC emission emanated from a pyrene moiety. Non.radiative processes dominate the photophysics of Ru (II) complexes 1 . 10, illustrating that fast and efficient coupling to the ground state controls excited state dynamics of these molecules.

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