CONICET | Buscador de Institutos y Recursos Humanos

Chlronicotinyl insecticides are a new class of pesticides used worldwide for insect pest management during the last decades. Despite their extensive use, only scarce information on the nature of the degradation products and toxicity of neonicotinoid pesticide residues is found in the literature.Imidacloprid(IMD), Thiacloprid(THIA) and Acetamiprid(ACT) were chosen as probes because their chemical structure show a common chloropyridine group and markedly differ on the chemical group responsible for the insecticide toxicity. Singlet oxygen, O2 (1∆g), is an important reactive oxidant present in natural aquatic reservoirs. Its generation implies the excitation of a photosensitizer whose lowest energy state (a spin-triplet state) may efficiently transfer their energy to the ground triplet state of oxygen molecules. This higher state of the sensitizer may also initiate the degradation of the insecticides through an initial charge transfer mechanism. The Rose Bengal triplet quenching by chloronicotinyl insecticides, and the kinetics and mechanisms of singlet oxygen reaction with insecticides are reported herein. Figure depicts the semilogarithmic plots of the insecticides consumption against photolysis time for experiments in the presence and absence of RB. Singlet oxygen reaction with the insecticides may be explained by a charge transfer pathway leading to the formation of superoxide radical anions, O2.-, and the radical cation of the insecticide in agreement with the reported mechanism for the reaction of 1O2 with substituted amines, involving an a-aminoalkyl radical and its further reaction with molecular oxygen to yield the observed products.