We have systematically investigated combinations of anions and cations in a number of protic ionic liquids based on alkylamines and used ab initio methods to gain insight into the parameters determining their liquid range and their conductivity. A simple, almost linear, relation of the experimentally determined melting temperature with the calculated volume of the anion forming the ionic liquid is found, whereas the dependence of the melting temperature with increasing cation volume goes through a minimum for relatively short side chain length. On the basis of the present results, we propose a strategy to predict the nature of protic ionic liquids in terms of low vapor pressure and conductivity. Comparisons with previously reported strategies for prediction of melting temperatures for aprotic ionic liquids are also made.

The effect of lithium ion coordination with the bis(oxalato)borate (BOB -) [B(C 2 O 4 ) 2 ]anion in DMSO, PEG, PPG, and d-PPG has been studied in detail by IR and Raman spectroscopy. Ab initio calculations were performed to allow a consistent analysis of the experimental data. The main features observed in the IR and Raman spectra correspond to the presence of "free", un-coordinated, BOBanions. Only with use of d-PPG as solvent a small amount of Li + ‚‚‚BOBion pairs were detected. The Raman spectra and the calculations together indicate that Li + coordinates bidentately with two end-oxygen atoms of the BOBanion. The identification of ion pairs can be used to reveal limitations of LiBOB based electrolytes. The results for LiBOB are compared with literature on other Li salts.

Negative charge stabilized by ring delocalization on five-membered rings is a practical and theoretically interesting alternative to conventional fluorine-based anions. Coordination of the lithium cation to the pyrazole-3,4,5-tricarbonitrile (PATC) anion was studied using vibrational spectroscopy (Raman and IR) and ab initio SCF-MO Hartree−Fock (HF) calculations. Four 1:1 ion pair geometries were found, one being energetically more stable. By comparing theoretical spectra with both IR and Raman spectra of salt solutions, it was found that the lithium ion favors bidentate coordination to the ring nitrogen atoms, as suggested by the binding energies. Finally, comparisons were made with previously calculated coordination strengths for other similar lithium anion 1:1 systems.