Palladium(ii) in liquid ammonia: an investigation of structural and dynamical properties by applying quantum mechanical charge field molecular dynamics (QMCF-MD)

Abstract

The structural and dynamical properties of Pd in liquid ammonia have been investigated via quantum mechanical charge field molecular dynamics. Similar to the case of aqueous Pd, a six-fold coordination polyhedron in the form of a tetrahedrally elongated octahedron is observed with two ligands in axial positions forming an extended first shell. To highlight the difference in solvation between the aqueous and ammonia case a selection based on the angular-radial distribution with respect to the well-known square planar motif was applied also providing a detailed understanding of ligand exchange between the extended first and second shells. All structural properties resulting from this investigation compare well with the available solid-state data of various N-containing complexes. From the dynamical perspective, Pd in liquid ammonia forms a more flexible complex with a higher rate of ligand exchange than that of its aqueous counterpart.

Toward Advanced QM/MM MD Simulations of Solid–Liquid Interfaces–Adsorption and Proton Transfer of Multilayer Water on R-TiO2(001)

“…Thus, only Coulombic forces contribute to the QM/MM coupling involving the QM solute and MM solvent molecules, which require less effort in the parametrization. In the applications to liquid systems, MD simulations based on the QMCF framework were highly successful when investigating the structural, dynamical, and thermodynamic properties of a broad variety of solvated systems, ranging from solvation complexes in pure and mixed aqueous and ammonia solutions − to complex molecular species in aqueous solutions, , in excellent agreement with data obtained in various experimental investigations. However, when the QM/MM framework is applied to simulations of interfacial solid-state systems (e.g., solid–gas or solid–liquid systems), several challenges are encountered.…”

Conversion of dimethyl ether to liquid hydrocarbons over the nano‐Pd‐ZnHZSM‐5 catalyst obtained by laser electrodispersion of the metal

“…It can be assumed that small palladium particles form Pd(NH 3 ) x 2+ complex ions that are disrupted with increasing temperature. Thus, the number of acid sites can be increased 9,27 . A shift of the maximum of the low‐temperature peak towards higher temperatures, a broadening of the low‐temperature peak, and smoothing of the maximum of the high‐temperature peak were noted.…”

Conversion of Dimethyl Ether to Triptane-Rich Liquid Hydrocarbons on Pd-LaHY with a Hierarchical Porous Structure

“…The high proportion of strong AS on the Pd-0.5LaHY h -catalysts can be explained by taking into account the possibility of nonstoichiometric binding of ammonia molecules with palladium ions. As a result of the formation and destruction of Pd­(NH 3 ) x 2+ complex ions with increasing temperature, the number of strong acid sites and, consequently, their proportion can be overestimated. , Samples molded with γ-Al 2 O 3 are characterized by low values of the total amount of AS and a low proportion of strong AS. The shift of the high-temperature maxima of the thermal desorption peaks to the region of low temperatures upon the introduction of modifiers into the composition of the zeolite indicates a decrease in the strength of the acid sites of both types.…”