Preparation and crystal structure of tetraoctylphosphonium tetrakis(pentafluorophenyl)borate ionic liquid for electrochemistry at its interface with water

Abstract

With ongoing and expending global energy needs, nuclear power is likely to be a key energy source for many more generations. A key question is still the fate of spent nuclear fuel (SNF). SNF contains a great deal of valuable material. In order to improve safety and handling, herein is proposed relatively high melting point ionic liquid (IL) or organic ionic plastic crystals (OIPCs) for biphasic water|IL metal ion extraction. The proposed IL, tetraoctylphosphonium tetrakis(pentafluorophenyl)borate, P8888(C6F5)4, was discovered to have a melting point of ~55ºC and a high degree of order by differential scanning calorimetry and X-ray diffraction, respectively. In this way, the IL/OIPC could be used in ligand assisted metal ion extraction from water solutions at elevated temperatures and then 'frozen' at ambient conditions for facile manipulation and transport of the SNF. To test the feasibility of this, electrochemistry such as cyclic voltammetry at a water|IL micro-interface (25 µm in diameter) was employed to assess the thermodynamics of K + ligand assisted transfer. It was revealed that the TRUEX (Transuranium Extraction) ligand octyl(phenyl)-N,N'diisobutylcarbamoylphosphine oxide (CMPO) has a high to moderate coordination to K + at the w| P8888(C6F5)4, micro-interface. Two ligand to K + stoichiometries were determined to be 3:1 and 2:1, respectively.

Single LiBH4 nanocrystal stochastic impacts at a micro water|ionic liquid interface

“…1A). The PPW is 400mV wide and in good agreement with previous results [60][61][62], but is small compared to ILs incorporating fluorinated phenyl borate anions [18,56,58,63,64]. The lower viscosity of P66614NTf2, however, makes it easier to manipulate at ambient temperature (~330mPa s, [65,66]) versus more hydrophobic ILs [18,54,56,58,63,64].…”

“…It is then suggested that solutions of LiBH4 in P66614NTf2 can be used to deliver H2 at reasonable rates; similar results are expected for LiBH4 in P8888Br, an organic ionic plastic crystal (OIPC) [18]. In a typical GC column experiment, 0.…”

“…P66614NTf2 was prepared by metathesis of P66614Br and LiNTf2 in CH2Cl2; the resultant IL was washed several times with water. Tetraoctylphosphonium bromide (P8888Br) was prepared as detailed elsewhere through reaction of trioctylphosphine and 1-bromooctane [18]. During the preparation of tetraalkylphosphonium halides, side reactions often produce the acid halide and acid salt (e.g.…”

“…The former is an IL, while the latter is an organic ionic plastic crystal (OIPC), i.e. is plastic at room temperature [18]. This IL and OIPC were chosen for several reasons.…”

Ionic Liquid Films at the Water–Air Interface: Langmuir Isotherms of Tetra-alkylphosphonium-Based Ionic Liquids

“…For example, ionic-liquid membranes have been suggested as effective media for the separation of volatile organic compounds at the air-liquid interface. Other recent work in this area also explore the possibility of using hydrophobic ILs in electrochemical applications and metal ion extractions [10,11] The knowledge of the structure and packing of ionic liquids at an interface is therefore of utmost importance for the rational design of such media. A key aspect in the design and preparation of functional materials is the control of intermolecular interactions and molecular packing in the first few monolayers at the surface [7].…”