Advances in QSPR/QSTR models of ionic liquids for the design of greener solvents of the future

Abstract

In order to protect the life of all creatures living in the environment, the toxicity arising from various hazardous chemicals must be controlled. This imposes a serious responsibility on different chemical, pharmaceutical, and other biological industries to produce less harmful chemicals. Among various international initiatives on harmful aspects of chemicals, the 'Green Chemistry' ideology appears to be one of the most highlighted concepts that focus on the use of eco-friendly chemicals. Ionic liquids are a comparatively new addition to the huge garrison of chemical compounds released from the industry. Extensive research on ionic liquids in the past decade has shown them to be highly useful chemicals with a good degree of thermal and chemical stability, appreciable task specificity and minimal environmental release resulting in a notion of 'green chemical'. However, studies have also shown that ionic liquids are not intrinsically non-toxic agents and can pose severe degree of toxicity as well as the risk of bioaccumulation depending upon their structural components. Moreover, ionic liquids possess issues of waste generation during synthesis as well as separation problems. Predictive quantitative structure-activity relationship (QSAR) models constitute a rational opportunity to explore the structural attributes of ionic liquids towards various physicochemical and toxicological endpoints and thereby leading to the design of environmentally more benevolent analogues with higher process selectivity. Such studies on ionic liquids have been less extensive compared to other industrial chemicals. The present review attempts to summarize different QSAR studies performed on these chemicals and also highlights the safety, health and environmental issues along with the application specificity on the dogma of 'green chemistry'.

Development of predictive QSAR models for Vibrio fischeri toxicity of ionic liquids and their true external and experimental validation tests

“…Although ILs were originally promoted as green solvents, studies have also shown that ionic liquids, as any organic solvent, may have some degree of toxicity to the various organisms of the ecosystem. 10,11 Predictive QSAR models can explore the structural attributes of ILs towards various physicochemical and toxicological endpoints, thereby leading to the design of "greener" analogues with higher process selectivity. This approach can lead to filling large data gaps, since the toxicity data are only available for a limited number of ILs against different indicator organisms of the ecosystem.…”

Exploring simple, transparent, interpretable and predictive QSAR models for classification and quantitative prediction of rat toxicity of ionic liquids using OECD recommended guidelines

“…Ionic liquids (ILs) are 'neoteric solvents' (new type of solvents or solvents having new properties), characterized by the co-existence of two oppositely charged domains together in the form of ions (Das and Roy, 2013a). They are salts with a low melting point, having interesting and useful properties such as low vapor pressure, high thermal and chemical stabilities, non-flammability and high solvent capacity (Torrecilla et al, 2010).…”

“…ILs were originally promoted as ''green solvents'' but now it is understood that they are not intrinsically devoid of toxicities (Das and Roy, 2013a). Despite recent reports on the toxicities of a number of ILs towards various aquatic organisms and rodents, the experimental investigations to establish these toxicities are time-consuming and require significant physical and chemical resources.…”

“…We have recently reviewed the QSAR studies on various toxicity endpoints of ILs (Das and Roy, 2013a). Several studies indicate that the toxicity of ILs increases with lipophilicity of the cations, while functionalized side chains tend to lower toxicity.…”

Toxicity mechanisms of ionic liquids

“…According to the Green Chemistry concept, an ideal solvent should be of low volatility, chemically and physically stable, recyclable and reusable, and easy to use (1). Due to low volatility, non-flammability, high thermal, chemical and electrochemical stability, and in particular their capability of being recycled, ionic liquids gained considerable attention as potential green replacements for conventional organic solvents in different processes and technologies (1,2). Great interest these solvents have aroused is reflected also in a considerable number of publications (> 50.000) developed over the last 15 years.…”