Theoretical approach for radiosensitizers. Correlation between calculated electroaffinity and sensitization factors of nitro-compounds.

The electron affinity of eight well-known nitroaromatic and nitroheterocyclic radiosensitizers is computed resorting to a quantum mechanical approach. Four of the compounds studied were nitroimidazoles; but p-nitroacetophenone and some 5-nitrofuran derivatives were also investigated for comparison. A good correlation between the theoretical electroaffinity values and the radiosensitization efficiencies is found in the case of the nitroimidazoles, in which the pi-electron system appears to be limited to the aromatic ring, except for small side groups. In the case of molecules where the pi-electron system spreads out on the side-chain the theoretical procedure seems to fail.