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Here we focus on the thermal and variable temperature electrochemical stabilities of two ionic liquids (ILs) having a common tributyloctyl phosphonium cation [P 4,4,4,8 ] + and two different orthoborate anions: bis(mandelato)borate [BMB] - and bis(salicylato)borate [BScB] - . The thermo-gravimetric analysis data suggest that [P 4,4,4,8 ][BScB] is thermally more stable than [P 4,4,4,8 ][BMB] in both nitrogen atmosphere and air, while the impedance spectroscopy reveals that [P 4,4,4,8 ][BScB] has higher ionic conductivity than [P 4,4,4,8 ][BMB] over the whole studied temperature range. In contrast, the electrochemical studies confirm that [P 4,4,4,8 ][BMB] is more stable and exhibits a wider electrochemical stability window (ESW) on a glassy carbon electrode surface as compared to [P 4,4,4,8 ][BScB]. A continuous decrease in the ESWs of both ILs is observed as a function of operation temperature.

Five new n‐tetrabutylphosphonium (P4444)+ cation‐based ionic liquids (ILs) with oligoether substituted aromatic carboxylate anions have been synthesized. The nature and position of the oligoether chain affect thermal stability (up to 330 °C), phase behaviour (Tg<−55 °C) and ion transport. Furthermore, with the aim of application in lithium batteries, electrolytes were created for two of the ILs by 10 mol% doping using the corresponding Li‐salts. This affects the ion diffusion negatively, from being higher and equal for cations and anions to lower for all ions and unequal. This is due to the stronger ionic interactions and formation of aggregates, primarily between the Li+ ions and the carboxylate group of the anions. Electrochemically, the electrolytes have electrochemical stability windows up to 3.5 V, giving some promise for battery application. [ABSTRACT FROM AUTHOR]

Phosphonium ionic liquids with orthoborate anions have been studied in terms of their interfacial film formation, both physisorbed and sacrificial from chemical breakdown, in sheared contacts of varying harshness. The halogen-free anion architecture was varied through (i) the heteronuclear ring size, (ii) the hybridisation of the constituent atoms, and (iii) the addition of aryl functionalities. Time of Flight-Secondary Ion Mass Spectrometry analysis revealed the extent of sacrificial tribofilm formation allowing the relative stability of the ionic liquids under tribological conditions to be determined and their breakdown mechanisms to be compared to simple thermal decomposition. Overall, ionic liquids outperformed reference oils as lubricants; in some cases, sacrificial films were formed (with anion breakdown a necessary precursor to phosphonium cation decomposition) while in other cases, a protective, self-assembly lubricant layer or hybrid film was formed. The salicylate-based anion was the most chemically stable and decomposed only slightly even under the harshest conditions. It was further found that surface topography influenced the degree of breakdown through enhanced material transport and replenishment. This work thus unveils the relationship between ionic liquid composition and structure, and the ensuing inter- and intra-molecular interactions and chemical stability, and demonstrates the intrinsic tuneability of an ionic liquid lubrication technology. [ABSTRACT FROM AUTHOR]

The main purpose of this work was to investigate the potential of ionic liquids (ILs) in crystal engineering. We have employed ILs with different combinations of cations and anions to study their role in directing crystal structure formation of a nicotinamide (NIC) and oxalic acid (OXA) system. A new crystal form of NIC-OXA salt (2:1) was identified and characterized using standard solid state tools such as powder X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and Raman and infrared spectroscopy. The crystal structure of the 2:1 salt was elucidated using single-crystal X-ray diffraction. The NIC-OXA 2:1 salt form revealed a two-dimensional layered structure, while the known 1:1 salt had a perpendicular "tape-like" structure. The 2:1 salt form could only be crystallized from the ILs possessing hydrogen bond acceptor functionality. We demonstrated that specific ILs could be selected as solvents for altering the solid-state structure of organic and inorganic materials. [ABSTRACT FROM AUTHOR]