Modeling Nmr Parameters of Oximes in Water and Ionic Liquids – Implications of Solvation Shell Structure

Organophosphophorus compounds (OP) has been widely used as pesticides and as warfare nerve agents. They act by phosphorylating the hydroxyl group of the Ser 203 residue of the Acetylcholinesterase (AChE) active site, inhibiting its catalytic activity, causing the cholinergic Syndrome [1]. Currently, the OP poisoning treatment consists in the use of reactivators, for example oximes, a class of compounds that is able to reactivate the inhibited enzyme [2]. Typically, expensive techniques are employed for the detection of OPs, such as GC and HPLC, but new techniques have been developed for this purpose using sensors, biosensors and electrolytes [3]. Currently, the use of ionic liquids (IL) as reactional medium for these sensors is little explored, but very promising [4]. In this sense, modern spectroscopic techniques, such as NMR Spectroscopy seems to be adequate for the characterization of this system [5]. In line with that, this work aims to investigate the solvent and thermal effects on NMR parameters of oximes in two different solvents, water and 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4). By using the OPLS force field in the GROMACS 4.6.510 program, 10 ns of classical molecular dynamics simulations were performed for the oxime 3-fluoro-4[(hydroxyimino)methyl]-1-methyl-pyridinium (3-Fluoro-4-PAM) (Figure 1) in water and ionic liquid.