Ionic liquids are considered as “designer solvents” because the physical, chemical and biological properties of ionic liquids can be tuned by altering the combination of their ionic constituents. However, finding the proper combination of anions and cations and their mixtures among 1018 possibilities to yield required properties is a major challenge. Many attempts have been tried to design and synthesize “task-specific” ionic liquids in the last decade. For example, Abe et al. [122] based on their experimental observations that hydrophilic imidazolium ionic liquids having alkyl ether functionalizing sulfate salts were appropriate for lipase-catalyzed reaction have anticipated that phosphonium

salt which alkyl ether group might also be appropriate for lipase. Their anticipation relied on the fact that phosphonium salt commonly exists in living creatures. Several types of phosphonium ionic liquids have been prepared and tested for the activity of ionic liquid coating lipase. A novel ionic liquids, 2-methoxyethoxymethyl (tri-n-butyl)-phosphonium bis (trifluoromethanesulfonyl) amide ([P444MEM][Tf2N]) was successfully found to enhance the activity two times while perfectly maintaining enantioselectivity of ionic liquid — coated lipase. However, this approach is mainly based on the experimental trial-error means. More recently, many methods including ab initio calculation, molecular simulation, quantum chemistry, and correlation have been successfully applied to calculate and/or predict the physical properties of ionic liquids [123, 124]. Not only physical, but also chemical and biological properties of ionic liquids can be predicted by these methods. This opens a new path for designing task specific ionic liquids which depends less on the experimental trial-and-errors. For instance, in our studies, quantitative structure-activity relationship (QSAR) model based on the information from the structure of ionic liquids (structural molecular

descriptors derived from CODESSA program) were used to predict the activity of Candida antarctica lipase B (CALB) in the kinetic resolution of sec-phenylethanol in ionic liquids. An optimal QSAR model with 5 structural molecular descriptors was established with the correlation efficient (R2) of 0.9481 and 0.9208 for 18 training and 5 testing ionic liquids set, respectively. This indicates that the performance of enzy­matic reaction in new ionic liquids could be predicted by QSAR model based on the structural molecular descriptors of ionic liquids.