Solvent effects on the reactivity of fluorenyl nitrenium ion with DNA-like probes

Abstract

Laser Flash Photolysis (LFP) experiments carried out on 2-azidofluorene in aqueous systems generate 2-fluorenyl nitrenium ion (λmax = 450 nm) which decays with first order rate constant and is quenched with 2′-deoxyguanosine originating an intermediate, namely the C8 adduct of 2-fluorenyl nitrenium ion, with bimolecular rate constant in the order of 1.3 × 109 M− 1 s− 1 in pure water. This intermediate very likely mimics the intermediate formed from carcinogens (i.e.: arylnitrenium ions formed through metabolic activation pathways from aminoaromatic substrates) and DNA rests in vivo. Solvent effects demonstrate and support the further stabilization of this intermediate (with respect to fluorenyl nitrenium ion) through hydrogen bonding as compared to other probe systems, and accounts for the enhanced metabolic carcinogenecity observed for this type of compounds. Diverse solvent systems, such as mixtures of water with acetonitrile, 1,1,1-trifluoroethanol, and 1,1,1,3,3,3-hexafluoroisopropanol, are used to interpret solvent–complex interactions.