#### Abstract Title

Quantum Mechanical Calculations of the Interaction Energy in Ionic Liquids

#### Additional Funding Sources

This project was funded by the Critical Materials Institute, BEA/Idaho National Lab, Idaho State University, Contract No. DE-AC07-05ID14517.

#### Abstract

Quantum Mechanical Calculations of the Interaction Energy in Ionic Liquids

Rare earth metals (REMs) are a key material found in microelectronics, advanced batteries, and high-efficiency electric motors. Current methods for producing REMs require high temperatures (i.e. energy intensive) and produce an abundance of hazardous fluoride waste. Unlike molten salts which are currently used as an electrolyte in the electrochemical production process, room temperature ionic liquids (RTILs) are an ideal alternative electrolyte because they allow for a low-temperature, energy-efficient electrochemical process. RTIL properties such as viscosity and conductivity determine how effective they can be in this process. Since both viscosity and conductivity are directly related to both intra and intermolecular forces, this study sets out to investigate these forces in two RTILs-Trihexyltetradecylphosphonium dicyanamide (Cyphos 105) and Trihexyltetradecylphosphonium bistriflimide (Cyphos 109). Results from 2-dimensional nuclear magnetic resonance (2D NMR) spectroscopy suggest that there is an interaction between the tetradecyl tail and the phosphorus atom of the Cyphos ionic liquid. In order to establish whether this is an intra or an inter-molecular interaction, DFT-based computational calculations were performed to determine whether the distance between the tetradecyl tail and the P atom is approximately 5 Å. This distance is necessary to show the Nuclear Overhauser (NOE) effect. Calculations were done both in the gas phase and with propylene carbonate as an augmenting solvent. Here, we report distance and energy calculations for Cyphos 105 monomers and dimers before and after optimization. Results show that there is minimal intramolecular interaction between the tetradecyl tail and the phosphorus atom of the Cyphos 105 RTIL. Rather, the data suggest that the interaction seen in the 2D NMR experiment is likely of an intermolecular nature instead. Calculations for the Cyphos 109 RTIL are not yet available, but once all the calculations for Cyphos 105 are completed, similar methodologies will be applied to Cyphos 109.

Quantum Mechanical Calculations of the Interaction Energy in Ionic Liquids

Quantum Mechanical Calculations of the Interaction Energy in Ionic Liquids

Rare earth metals (REMs) are a key material found in microelectronics, advanced batteries, and high-efficiency electric motors. Current methods for producing REMs require high temperatures (i.e. energy intensive) and produce an abundance of hazardous fluoride waste. Unlike molten salts which are currently used as an electrolyte in the electrochemical production process, room temperature ionic liquids (RTILs) are an ideal alternative electrolyte because they allow for a low-temperature, energy-efficient electrochemical process. RTIL properties such as viscosity and conductivity determine how effective they can be in this process. Since both viscosity and conductivity are directly related to both intra and intermolecular forces, this study sets out to investigate these forces in two RTILs-Trihexyltetradecylphosphonium dicyanamide (Cyphos 105) and Trihexyltetradecylphosphonium bistriflimide (Cyphos 109). Results from 2-dimensional nuclear magnetic resonance (2D NMR) spectroscopy suggest that there is an interaction between the tetradecyl tail and the phosphorus atom of the Cyphos ionic liquid. In order to establish whether this is an intra or an inter-molecular interaction, DFT-based computational calculations were performed to determine whether the distance between the tetradecyl tail and the P atom is approximately 5 Å. This distance is necessary to show the Nuclear Overhauser (NOE) effect. Calculations were done both in the gas phase and with propylene carbonate as an augmenting solvent. Here, we report distance and energy calculations for Cyphos 105 monomers and dimers before and after optimization. Results show that there is minimal intramolecular interaction between the tetradecyl tail and the phosphorus atom of the Cyphos 105 RTIL. Rather, the data suggest that the interaction seen in the 2D NMR experiment is likely of an intermolecular nature instead. Calculations for the Cyphos 109 RTIL are not yet available, but once all the calculations for Cyphos 105 are completed, similar methodologies will be applied to Cyphos 109.