Abstract:
In recent years, transition metal complexes have been
developed for catalytical degradation of a phosphate ester bond, particularly
in RNA and DNA; however, less consideration has been given for
development of complexes for the degradation of a phosphorothioate bond,
as they are the foremost used pesticides in the environment and are toxic to
human beings. In this context, we have developed copper complexes of
benzimidazolium based ligands for catalytical degradation of a series of
organophosphates (parathion, paraoxon, methyl-parathion) at ambient
conditions. The copper complexes (assigned as N1−N3) were characterized
using single X-ray crystallography which revealed that all three complexes
are mononuclear and distorted square planner in geometry. Further, the
solution state studies of the prepared complexes were carried out using UV−
visible absorption, fluorescence spectroscopy, and cyclic voltametry. The
complexes N1 and N2 have benzimidazolium ionic liquid as base attached
with two 2-mercapto-benzimidazole pods, whereas complex N3 contains a nonionic ligand. The synthesized copper complexes
were evaluated for their catalytic activity for degradation of organophosphates. It is interesting that the complex containing the
ionic ligand efficiently degrades phosphorothioate pesticides, whereas complex N3 was not found to be appropriate for
degradation due to a weaker conversion rate. The organophosphate degradation studies were monitored by recording
absorbance spectra of parathion in the presence of catalyst, i.e., copper complexes with respect to time. The parathion was
hydrolyzed into para-nitrophenol and diethyl thiophosphate. Moreover, to analyze the inhibition activity of the pesticides
toward acetylcholine esterase enzyme in the presence of prepared metal complexes, Ellman’s assay was performed and revealed
that, within 20 min, the inhibition of acetylcholine esterase enzyme decreases by up to 13%.
