Detection of Chemical Weapon Agents Using Spectroscopic Probes: A Computational Study

Abstract

Organophosphorus compounds are organic compounds widely employed in agriculture as well as in chemical weapons. The use in agriculture is due to their insecticidal properties. However, in chemical warfare, the use of organophosphorus is associated with acetylcholinesterase inhibition, which promotes the cholinergic syndromes. In this line, the fast detection of this class of compound is crucial for the determination of environmental exposure. This improved detection will naturally allow for more prompt courses of treatment depending on the contaminant findings. In this perspective, the dipyrrinone oxime (1) was employed for the detection of organophosphorus compounds that are employed as nerve agents, such as cyclosarin, sarin, soman, diethyl chlorophosphate, diisopropylfluorophosphate, 2-(dimethylamino)ethyl N,N-dimethylphosphoramidofluoridate, O-ethyl-S-[2-(diethylamino)ethyl]methylphosphonothioate, O-ethyl-S-[2(diisopropylamino)ethyl] methylphosphonothioate, and O,O-diethyl-S-[2-(diethylamino)ethyl] phosphorothioate, through fluorescent emission. The thermodynamics and kinetic parameters as well as spectroscopic properties of the complexes formed for 1 and all organophosphorus compounds previously cited were investigated by means of theoretical calculations. From our findings, only the diethyl chlorophosphate, 2-(dimethylamino)ethyl N,N-dimethylphosphoramidofluoridate, and O,O-diethyl-S-[2-(diethylamino)ethyl] phosphorothioate emitted fluorescence in the hexane, toluene, chloroform, dichloromethane, methanol, acetonitrile, water, and dimethyl sulfoxide solvents. The study of the absorption wavelength with the most polar solvent showed higher values compared to apolar solvents. In the same solvent, for instance, soman in hexane showed the lowest absorption wavelength value, 324.5 nm, and DCP the highest value, 330.8 nm. This behavior was observed in other tested solvents. The thermodynamic parameters indicate negative Gibbs free energy (ΔG) values for the O-ethyl-S-[2(diisopropylamino)ethyl] methylphosphonothioate with 1 reaction. On the other hand, the sarin and cyclosarin revealed the lowest Gibbs free energy (ΔG‡) values, being kinetically favorable and presenting more reactivity.

Exploring EPR Parameters of 187Re Complexes for Designing new MRI Probes: from the gas phase to solution and a model protein environment

“…2.a and Eq. ( 2)), allowing us to understand if the Rhenium core is strongly bonded in the complex [29]. The molecular docking of the complex was performed at the active site of the PI3K enzyme to obtain Aiso values for the compound [7,17].…”

Exploring EPR Parameters of 187Re Complexes for Designing New MRI Probes: From the Gas Phase to Solution and a Model Protein Environment

“…To understand whether the complex is thermodynamically stable, a frequency calculation was performed, using the M06L functional, SARC-ZORA-TZVP basis set for rhenium and TZVP for all other atoms and relativistic efects in the Hamiltonian with ZORA, in the ReABT complex, in the Re(CO) 3 + core (Figure 2(c)), and in the tridentate ligand, (NNO) ABT (Figure 2(b)), both in the gas phase, to obtain the ΔG g , and in solution, to obtain ΔG solv (ReABT), ΔG solv (Re(CO) 3 ), and ΔG solv ((NNO) ABT) values. Tis analysis will provide the free energy of complexation of the complex (Figure 2(a) and equation ( 2)), allowing us to understand if the rhenium core is strongly bonded in the complex [29]:…”