Abstract
A range of chloroplumbate(II) organic salts, based on the two cations, 1-ethyl-3-methylimidazolium and trihexyl(tetradecyl)phosphonium, was prepared by ionothermal synthesis. Depending on the structure of the organic cation and on the molar ratio of PbCl2 in the product, χPbCl2, the salts were room-temperature ionic liquids or crystalline organic/inorganic hybrid materials. The solids were studied using Raman spectroscopy; the crystal structure of [C2mim]{PbCl3} was determined and shown to contain 1D infinite chloroplumbate(II) strands formed by edge-sharing tetragonal pyramids of pentacoordinate (PbCl5) units. The liquids were analysed using (207)Pb NMR and Raman spectroscopies, as well as viscometry. Phase diagrams were constructed based on differential scanning calorimetry (DSC) measurements. Discrete anions: [PbCl4](2-) and [PbCl3](-), were detected in the liquid state. The trichloroplumbate(II) anion was shown to have a flexible structure due to the presence of a stereochemically-active lone pair. The relationship between the liquid phase anionic speciation and the structure of the corresponding crystalline products of ionothermal syntheses was discussed, and the data were compared with analogous tin(II) systems.
Highlights
Salts comprising of organic cations and halometallate anions are of interest in several fields of material sciences
Synthesis The [C2mim]Cl–PbCl2 system was chosen to study because the [C2mim]+ cation is a popular motif in design of ionic liquids and, at the same time, the [C2mim]Br–PbBr2 system is known to give organic/inorganic hybrid materials which exhibit nonlinear optical behaviour.[21]
In the course of ionothermal synthesis homogenous melts were obtained for χPbCl2 ≤ 0.45
Summary
Salts comprising of organic cations and halometallate anions are of interest in several fields of material sciences. Crystalline chloroplumbate(II) systems may be considered as organic/inorganic hybrid compounds, with a tendency to form 2D perovskites and low-dimensional crystalline materials with electro-optic characteristics ( photoluminescence, electroluminescence and nonlinear optical properties).[1] Lower melting organic halometallates have been investigated as soft materials (ionic liquid crystals[2] or ionic liquids).[3] Both solids and liquids have been studied quite extensively by solidstate and ionic liquid chemists, but each group adopts their own research methodology and approaches. The focus is on crystal structure and material properties. Chlorometallate ionic liquids, on the other hand, have been used for electrochemistry,[4] catalysis[5] and separations,[6] their anionic speciation has been thoroughly investigated,[7,8,9,10] but they have rarely been used for inorganic syntheses,[11] and never for the
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