Crystal Structure and Energetics of Arsenic(III)-Oxide Intercalates with Rubidium Chloride and Their Comparison with Isostructural Intercalates of Potassium Halides

Abstract

Two intercalation compounds of arsenic(III) oxide and rubidium chloride have been crystallized and characterized. The first, anhydrous RbCl·2As2O3 (PRbCl), crystallizes in space group P6/mmm with cell parameters a = 5.23520(16) Å and c = 9.0495(4) Å, and it is isostructural with anhydrous intercalates of arsenic(III) oxide with potassium halides. The second one, RbCl·As2O3·1/2H2O (Y′RbCl), crystallizes in space group P6/mmm with a = 5.25072(17) Å and c = 12.6472(5) Å, and its crystal structure is very similar to that of KCl·As2O3·1/2H2O. In the case of a large single crystal of compound Y′RbCl, weak satellite reflections were observed. The commensurate superstructure that gives rise to them has been described using the supercell approach (a = 9.019(4) Å, c = 12.6433(7) Å) and briefly discussed. The structures of intercalates PRbCl and Y′RbCl have been studied by 87Rb solid-state magic-angle spinning nuclear magnetic resonance (ssNMR) spectroscopy which has indicated the presence of one and two rubidium cations with distinct chemical environments, respectively. The comparison of these spectra allowed for the assignment of peaks to rubidium cations occupying particular sites. Infrared (IR) spectra and 1H ssNMR spectra of intercalate Y′RbCl have revealed dynamic disorder of water molecules occurring on the time scale of the IR experiment. Last but not least, interlayer interaction energies as well as thermodynamic stability of intercalate PRbCl and isostructural arsenic(III)-oxide intercalates with potassium halides have been studied computationally in the framework of density functional theory. Results of the calculations indicate that an increase in the size of anions or cations leads to an increase in the stability of the obtained intercalates.