Sustainable solvents are a topic of growing interest in both the research community and the chemical industry due to a growing awareness of the impact of solvents on pollution, energy usage, and contributions to air quality and climate change. Solvent losses represent a major portion of organic pollution, and solvent removal represents a large proportion of process energy consumption. To counter these issues, a range of greener or more sustainable solvents have been proposed and developed over the past three decades. Much of the focus has been on the environmental credentials of the solvent itself, although how a substance is deployed is as important to sustainability as what it is made from. In this Review, we consider several aspects of the most prominent sustainable organic solvents in use today, ionic liquids, deep eutectic solvents, supercritical fluids, switchable solvents, liquid polymers, and renewable solvents. We examine not only the performance of each class of solvent within the context of the reactions or extractions for which it is employed, but also give consideration to the wider context of the process and system within which the solvent is deployed. A wide range of technical, economic, and environmental factors are considered, giving a more complete picture of the current status of sustainable solvent research and development.

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In this work we experimentally investigate solvent and temperature induced conformational transitions of proteins and examine the role of ion-protein interactions in determining the conformational preferences of avidin, a homotetrameric...

Ionic liquids offer exciting possibilities for biocatalysis as solvent properties provide rare opportunities for customizable, energy-efficient bioprocessing. Unfortunately, proteins and enzymes are generally unstable in ionic liquids and several attempts have been made to explain why; however, a comprehensive understanding of the ionic liquid–protein interactions remains elusive. Here, we present an analytical framework (circular dichroism (CD), fluorescence, ultraviolet-visible (UV/Vis) and nuclear magnetic resonance (NMR) spectroscopies, and small-angle X-ray scattering (SAXS)) to probe the interactions, structure, and stability of a model protein (green fluorescent protein (GFP)) in a range (acetate, chloride, triflate) of pyrrolidinium and imidazolium salts. We demonstrate that measuring protein stability requires a similar holistic analytical framework, as opposed to single-technique assessments that provide misleading conclusions. We reveal information on site-specific ionic liquid–protein interactions, revealing that triflate (the least interacting anion) induces a contraction in the protein size that reduces the barrier to unfolding. Robust frameworks such as this are critical to advancing non-aqueous biocatalysis and avoiding pitfalls associated with single-technique investigations.

Difference spectroscopy of functionalised ionic liquids can help resolve photoemission signals beyond that previously thought possible.

Thermal decomposition (TD) products of the ionic liquids (ILs) [CnC1Im][BF4] and [CnC1Im][PF6] ([CnC1Im]+ = 1-alkyl-3-methylimidazolium, [BF4]- = tetrafluoroborate, and [PF6]- = hexafluorophosphate) were prepared, ex situ, by bulk heating experiments in a bespoke setup. The respective products, CnC1(C3N2H2)BF3 and CnC1(C3N2H2)PF5 (1-alkyl-3-methylimidazolium-2-trifluoroborate and 1-alkyl-3-methylimidazolium-2-pentafluorophosphate), were then vaporized and analyzed by direct insertion mass spectrometry (DIMS) in order to identify their characteristic MS signals. During IL DIMS experiments we were subsequently able, in situ, to identify and monitor signals due to both IL vaporization and IL thermal decomposition. These decomposition products have not been observed in situ during previous analytical vaporization studies of similar ILs. The ex situ preparation of TD products is therefore perfectly complimentary to in situ thermal stability measurements. Experimental parameters such as sample surface area to volume ratios are consequently very important for ILs that show competitive vaporization and thermal decomposition. We have explained these experimental factors in terms of Langmuir evaporation and Knudsen effusion-like conditions, allowing us to draw together observations from previous studies to make sense of the literature on IL thermal stability. Hence, the design of experimental setups are crucial and previously overlooked experimental factors.

Thermally-stable ionic liquids (ILs) have limited structural possibilities and lack coordinating anions or functional groups. Thermal stability effectively incurs a tunability penalty, limiting ionic liquid function to render them as simple heat-stable fluids. In this work, a series of new thermally-stable dicationic ionic liquids with pyridine functional groups, abbreviated [(C8ImC1)2Py]­[A]2, are presented and compared to nonfunctional geminal dicationic ILs. All ILs have been thermally characterized to understand their elevated temperature stabilities and the processes that lead to their decomposition. Importantly, functional [(C8ImC1)2Py]­[A]2 with noncoordinating anions (i.e., [NTf2]−) have thermal stabilities comparable to those of geminal dicationic ILs, with the added advantage of a functional pyridine moiety. Dissolution of Zn­[NTf2]2 in [(C8ImC1)2Py]­[NTf2]2 is demonstrated, and the resulting solutions are characterized to show their liquid properties, high thermal stabilities, and the coordination of the metal center to the functional group. This is the first example of a thermally-stable functional IL with the potential to reclaim the tunable, task-specific nature of ILs at elevated temperatures. Importantly, these properties open new avenues for high-temperature applications of IL by extending their operational ranges; catalysis, metal remediation, and separation-based applications are potential key areas of improvement.

This is a repository copy of Zinc 1s Valence-to-Core X-ray Emission Spectroscopy of Halozincate Complexes.