RADIOSENSITISING NITROIMIDAZOLE DRUGS: TRIPLET STATE ENERGY AND REACTIVITY |
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| Authors: | Terence J Kemp Anthony W Parker Peter Wardman |
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| Institution: | Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK;Cancer Research Campaign, Gray Laboratory, Mount Vernon Hospital, Northwood, Middlesex HA6 2RN, UK |
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| Abstract: | Abstract— Although the radiosensitising drugs metronidazole 1 and misonidazole 2 neither phosphoresce nor yield triplet-triplet absorption in the region 350–700 nm, it is, nevertheless, possible to determine their triplet state energies ET by kinetic quenching methods using laser flash photolysis, and also by a steady-state method due to Ullman depending on sensitisation of a colour reaction. Both approaches give acceptable concordance, with figures of 244±4 kJ mol-1 for both 1 and 2. These lead to estimates of triplet excited state one-electron reduction potentials for 1 and 2 in water of 2.04 and 2.14 V vs NHE, enabling an assessment of the possible role of excited 1 and 2 in radiosensitisation. |
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