(657c) Automatic Generation of Ionic Liquid Libraries for High Throughput Screening

Ionic liquids are a class of solvents comprised entirely of bulky cations and anions. The asymmetry in the ionic structures often prevents organized packing, which results in these solvents existing as liquids at or below room temperatures. Manipulation of the cation, anion, and the substituents on the ions is the primary strategy aimed at designing a large number of ionic liquids possessing desired physicochemical, electrical, or biological properties. Probably one of the most studied substituents is the alkyl chain, especially attached to the cation. For the most part, the focus in the literature has been predominantly on the n-alkyl group; the isomerism embedded in the alkyl chain has been examined to a significantly lesser extent. As the number of isomers grows dramatically with the carbon chain length, there is a great potential for exploiting the isomerism to expand the number of ionic liquids.

In this presentation, we will describe an algorithm for enumerating the structural isomers of alkyl groups up to hexadecyl and the corresponding SMILES strings. We will then elaborate on our protocol for eliminating SMILES strings producing identical isomers, so that the computational effort is concentrated only on unique isomers. Next, we will describe methods for attaching the isomers to various functional groups and generating three-dimensional starting structures from SMILES strings by taking the 1-alkyl-3-methylimidazolium family of cations as an example. Results of the frontier energy orbitals obtained from electronic structure calculations will be presented and analyzed for patterns based on the respective Tanimoto similarity index.