(501f) Theoretical Investigation of the Binding of 1-Hexyl-3-Methylimidazolium Based Ionic Liquids with Iron Porphyrin

Ionic liquids are substances composed entirely of cations and anions and can remain liquid under a wide range of temperatures. They have drawn considerable attention of the scientific community for replacing volatile organic solvents in the process industries due to properties such as low vapor pressure, high thermal stability, and design flexibility. As the use of ionic liquids in industry surges, it is critical to examine processes that lead to biodegradation of ionic liquids, so that the effluent discharges of ionic liquids can be properly handled. Experimentally, cytochrome P450, a superfamily of heme-containing enzymes, has been hypothesized as a potential enzyme for ionic liquid biodegradation. Biodegradation of ionic liquid reveals that the long alkyl chain length of the cations are more easily biodegradable. However, recent studies also suggest that organic anions could play a role in the biodegradation process. In this presentation, we will investigate the binding of 1-hexyl-3-methylimidazolium as a cation and five different types of anions namely, chloride, methyl acetate, methane sulfonate, ethyl sulfate, and butyl sulfate with iron porphyrin. We will present frontier molecular orbitals (FMO) such as highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) to show the relation of binding position and these electronic properties. We will also discuss results from conceptual density functional theory (CDFT) to identify the global electrophilicity index and site selectivity of the overall complexation. In addition, we will also elucidate the role of weak interactions using the non-covalent interaction (NCI) analysis. Our decomposition of the overall binding energy into electrostatic energy, repulsion energy, and dispersion energy to identify the dominant energy for the overall binding process.