Electron Spectroscopy and Computational Studies of Dimethyl Methylphosphonate

Abstract

Dimethyl methylphosphonate (DMMP) is one of the most widely used molecules to simulate chemical warfare agents in adsorption experiments. However, the details of the electronic structure of the isolated molecule have not yet been reported. We have directly probed the occupied valence and core levels using gas phase photoelectron spectroscopy and the unoccupied states using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Density functional theory (DFT) calculations were used to study the electronic structure, assign the spectral features, and visualize the molecular orbitals. Comparison with parent molecules shows that valence and core-level binding energies of DMMP follow trends of functional group substitution on the P center. The photoelectron and NEXAFS spectra of the isolated molecule will serve as a reference in studies of DMMP adsorbed on surfaces.

Dimethyl methylphosphonate adsorption and decomposition on MoO2 as studied by ambient pressure x-ray photoelectron spectroscopy and DFT calculations

“…Surfacefacilitated decomposition of DMMP begins with rotation of one of the -OCH 3 groups about a P-OCH 3 bond (path I 1 -I 2 ). The calculated activation barrier of such an internal rotation is low and requires only 5.6 kJ mol -1 , which is ~15 kJ mol -1 lower than in the gas phase [16]. The bond distances P-O3 (1.633 Å) and O3-C3 (1.472 Å) in the structure I 2 (Figure 8b) are elongated by 0.056 Å and 0.01 Å, respectively, as compared to the structure I 1 (Figure 8a), suggesting that further decomposition of DMMP will proceed through the cleavage of one of these bonds.…”

Thermal desorption of dimethyl methylphosphonate from MoO3

“…Gas phase components were constrained to asymmetric Gaussian functions from fits of the gas phase molecule. The P 2p spin-orbit components were constrained to a binding energy splitting of 0.85 eV, the same full widths at half maximum, and an area ratio of 2:1 for the 2p 3/2 and 2p 1/2 components [16].…”

Degradation of Fatal Toxic Nerve Agents on Dry TiO2

“…Therefore, metal oxides are usually used as components of filter materials. Over the last three decades, numerous experimental and theoretical studies were carried out to study atomistic interactions of organophosphorus CWAs and their model compounds with metal oxides. − These studies show that the interaction of simulant compounds with metal oxide surfaces depends on many factors, including a chemical composition, oxidation state of metal atoms, surface structure, and the presence of surface defects, water, and contaminants. Some metal oxides readily adsorb and decompose toxic agents, , whereas other oxides can effectively interact with toxins only in the presence of surface defects or surface hydroxyls. , Metal–organic frameworks − were proposed as potential filter materials because of their catalytic properties.…”