Spectroscopic and inclusion properties of G-series chemical warfare agents and their simulants: a DFT study

Supramolecular Detection of a Sub-ppm Nerve Agent Simulant by a Smartphone Tool

The widespread use of smartphones and related tools is extending their applications in several fields. Herein, we report a reusable smartphone coupled portable detection system for the sensing of sub-ppm level of a nerve agent mimic (dimethylmethylphosphonate) in the gas phase. The detection system is based on multiple hydrogen-bond interactions of the vapor analyte with an ad-hoc functionalized Bodipy chromophore scaffold. The multitopic approach used for the molecular recognition of DMMP leads to the highest binding constant values, high selectivity, and low limits of detection.

Closer Look at Adsorption of Sarin and Simulants on Metal-Organic Frameworks

The development of effective protection against exposure to chemical warfare agents (CWAs), such as sarin, relies on studies of its adsorption on the capturing materials and seeking candidates capable of adsorbing large amounts of sarin gas. Many metal-organic frameworks (MOFs) are promising materials for the effective capture and degradation of sarin and simulant substances. Among the simulants capable of mimicking thermodynamic properties of the agent, not all of them have been investigated on the ability to act similarly in the adsorption process, in particular, whether the agent and a simulant have similar mechanisms of binding to the MOF surface. Molecular simulation studies not only provide a safe way to investigate the aforementioned processes but can also help reveal the mechanisms of interactions between the adsorbents and the adsorbing compounds at the molecular level. We performed Monte Carlo simulations of the adsorption of sarin and three simulants, dimethyl methylphosphonate (DMMP), diisopropyl methylphosphonate (DIMP), and diisopropyl fluorophosphate (DIFP), on selected MOFs that have previously shown strong capabilities to adsorb sarin. On the basis of the calculated adsorption isotherms, enthalpy of adsorption, and radial distribution functions, we revealed common mechanisms among the particularly efficient adsorbents as well as the ability of simulants to mimic them. The findings can help in selecting a suitable simulant compound to study CWA adsorption on MOFs and guide further synthesis of efficient MOFs for the capture of organophosphorus compounds.

Current Status of Quantum Chemical Studies of Cyclodextrin Host-Guest Complexes

This article aims to review the application of various quantum chemical methods (semi-empirical, density functional theory (DFT), second order Møller-Plesset perturbation theory (MP2)) in the studies of cyclodextrin host-guest complexes. The details of applied approaches such as functionals, basis sets, dispersion corrections or solvent treatment methods are analyzed, pointing to the best possible options for such theoretical studies. Apart from reviewing the ways that the computations are usually performed, the reasons for such studies are presented and discussed. The successful applications of theoretical calculations are not limited to the determination of stable conformations but also include the prediction of thermodynamic properties as well as UV-Vis, IR, and NMR spectra. It has been shown that quantum chemical calculations, when applied to the studies of CD complexes, can provide results unobtainable by any other methods, both experimental and computational.

[1]Rotaxanes based on phosphorylated pillar[5]arenes

[1]Rotaxanes based on monosubstituted phosphorus-containing pillar[5]arenes have been synthesized by the Kabachnik–Fields reaction for the first time in good yields.

Supramolecular Sensing of Chemical Warfare Agents

Chemical warfare agents are a class of organic molecules used as chemical weapons due to their high toxicity and lethal effects. For this reason, the fast detection of these compounds in the environment is crucial. Traditional detection methods are based on instrumental techniques, such as mass spectrometry or HPLC, however the use of molecular sensors able to change a detectable property (e. g., luminescence, color, electrical resistance) can be cheaper and faster. Today, molecular sensing of chemical warfare agents is mainly based on the "covalent approach", in which the sensor reacts with the analyte, or on the "supramolecular approach", which involves the formation of non-covalent interactions between the sensor and the analyte. This Review is focused on the recent developments of supramolecular sensors of organophosphorus chemical warfare agents (from 2013). In particular, supramolecular sensors are classified by function of the sensing mechanism: i) Lewis Acids, ii) hydrogen bonds, iii) macrocyclic hosts, iv) multi-topic sensors, v) nanosensors. It is shown how the supramolecular non-covalent approach leads to a reversible sensing and higher selectivity towards the selected analyte respect to other interfering molecules.

Identification of organophosphorus simulants for the development of next-generation detection technologies

Organophosphorus (OP) chemical warfare agents (CWAs) represent an ongoing threat but the understandable widespread prohibition of their use places limitations on the development of technologies to counter the effects of any OP CWA release. Herein, we describe new, accessible methods for the identification of appropriate molecular simulants to mimic the hydrogen bond accepting capacity of the P[double bond, length as m-dash]O moiety, common to every member of this class of CWAs. Using the predictive methodologies developed herein, we have identified OP CWA hydrogen bond acceptor simulants for soman and sarin. It is hoped that the effective use of these physical property specific simulants will aid future countermeasure developments.

Spectroscopically Resolved Binding Sites for the Adsorption of Sarin Gas in a Metal-Organic Framework: Insights beyond Lewis Acidity

Here we report molecular level details regarding the adsorption of sarin (GB) gas in a prototypical zirconium-based metal-organic framework (MOF, UiO-66). By combining predictive modeling and experimental spectroscopic techniques, we unambiguously identify several unique bindings sites within the MOF, using the P═O stretch frequency of GB as a probe. Remarkable agreement between predicted and experimental IR spectrum is demonstrated. As previously hypothesized, the undercoordinated Lewis acid metal site is the most favorable binding site. Yet multiple sites participate in the adsorption process; specifically, the Zr-chelated hydroxyl groups form hydrogen bonds with the GB molecule, and GB weakly interacts with fully coordinated metals. Importantly, this work highlights that subtle orientational effects of bound GB are observable via shifts in characteristic vibrational modes; this finding has large implications for degradation rates and opens a new route for future materials design.

Theoretical study of the molecular aspect of the suspected novichok agent A234 of the Skripal poisoning

Novichoks are the suspected nerve agents in the March 2018 Skripal poisoning. In this context, the novichok agent A234 (chemical structure proposed by Mirzayanov) was studied using computational methods to shed light on its molecular, electronic, spectroscopic, thermodynamic and toxicity parameters as well as on potential thermal and hydrolysis degradation pathways. The poisoning action and antidote of A234 were also investigated. Some of these parameters were compared to three common G- and V-series nerve agents, namely GB, VR and VX. The research findings should be useful towards the detection, development of antidotes and destruction of A234.

Comparison of Binding Affinities of Water-Soluble Calixarenes with the Organophosphorus Nerve Agent Soman (GD) and Commonly-Used Nerve Agent Simulants

The formation of inclusion complexes of the water-soluble p-sulfonatocalix[n]arenes, where n = 4 or 6, with the Chemical Warfare Agent (CWA) GD, or Soman, and commonly used dialkyl methylphosphonate simulants has been studied by experimental solution NMR methods and by Molecular Mechanics (MMFF) and semi-empirical (PM6) calculations. Complex formation in non-buffered and buffered solutions is driven by the hydrophobic effect, and complex stoichiometry determined as 1:1 for all host:guest pairs. Low affinity complexes (K_assoc < 100 M⁻¹) are observed for all guests, attributed to poor host–guest complementarity and the role of buffer cation species accounts for the low affinity of the complexes. Comparison of CWA and simulant behavior adds to understanding of CWA–simulant correlations and the challenges of simulant selection.