Estimation of Lattice Enthalpies of Ionic Liquids Supported by Hirshfeld Analysis.

New measurements of vaporization enthalpies for 15 1:1 ionic liquids are performed by using a quartz-crystal microbalance. Collection and analysis of 33 available crystal structures of organic salts, which comprise 13 different cations and 12 anions, is performed. Their dissociation lattice enthalpies are calculated by a combination of experimental and quantum chemical quantities and are divided into the relaxation and Coulomb components to give an insight into elusive short-range interaction enthalpies. An empirical equation is developed, based on interaction-specific Hirshfeld surfaces and solvation enthalpies, which enables the estimation of the lattice enthalpy by using only the crystal-structure data.

Is universal, simple melting point prediction possible?

An investigation of the melting points of 520 organic 1:1 salts is presented with the aim of developing a universal, simple, physically well-founded prediction scheme. The general reliability and reproducibility of the recorded experimental data are discussed with respect to purity, phase behavior, disorder and thermal history of a given substance. Additionally, mistakes, systematic errors, or lack of conventions can lead to considerable differences in the experimental measurements. A rough error bar for the reproducibility of the melting points of organic salts of ±5 to ±15 °C can be assigned. With this restraint, we developed two simple, semiempirical, five- and nine-parameter schemes with easy-to-calculate quantities. With these, we could predict the melting temperature of a given organic salt in the temperature range of -25 to +300 °C with an average error of 33.5 °C and a relative error of 9.3%. All calculated quantities are assessed with the help of conventional DFT, COSMO and COSMO-RS calculations, and are currently implemented into the IL-Prop module of the upcoming version of COSMOtherm. These prediction schemes are suitable for high-throughput computational screening of substances in the context of "computer-aided synthesis". Therefore, they are valuable tools to find a compound with a suitable melting point before its first synthesis.

An augmented volume-based model of the glass transition temperature of 209 molecular liquids.

It is well known that the amorphous state can greatly enhance the bioavailability of drugs. However, comparatively few compounds form either liquids at room temperature or glasses above it. We present qualitative insights as to why some molecules would form glasses instead of crystals and a fast, straightforward, physically well founded, and nonproprietary method to calculate the expected glass transition temperature before the synthesis of a new drug. This way, a selection of drug candidates can be screened for one that has a high tendency to vitrify and a preferably low temperature of this transition. The new method works reliably for a great span of possible molecules, encompassing well-known drugs, nutrients, and a multitude of other technically interesting compounds.

Modeling the influence of salts on the critical micelle concentration of ionic surfactants.

We show for the first time that a phenomenological, augmented volume-based thermodynamics (aVBT) model is capable to predict the critical micelle concentrations of ionic surfactants, including ionic liquids, with added salts. The model also adjusts for the type of salt added by including its molecular volume, which might form a connection to the Hofmeister effect. The other physico-chemically relevant quantities included in the model include surface area and solvation enthalpies.