Sublimation thermodynamics of nucleobases derived from fast scanning calorimetry

Fast scanning calorimetry was utilized to measure the sublimation thermodynamics of nucleobases. The results were rationalized at the molecular level.

Interrelation of thermodynamic sublimation characteristics with crystal structure: adamantane and memantine derivatives of sulfonamide molecular crystals

A number of sulfonamide compounds with adamantane (tricyclo[3.3.1.13,7]decane) and memantine (3,5-dimethyladamantan-1-amine) fragments have been synthesized and characterized.

The influence of solid state information and descriptor selection on statistical models of temperature dependent aqueous solubility

Predicting the equilibrium solubility of organic, crystalline materials at all relevant temperatures is crucial to the digital design of manufacturing unit operations in the chemical industries. The work reported in our current publication builds upon the limited number of recently published quantitative structure-property relationship studies which modelled the temperature dependence of aqueous solubility. One set of models was built to directly predict temperature dependent solubility, including for materials with no solubility data at any temperature. We propose that a modified cross-validation protocol is required to evaluate these models. Another set of models was built to predict the related enthalpy of solution term, which can be used to estimate solubility at one temperature based upon solubility data for the same material at another temperature. We investigated whether various kinds of solid state descriptors improved the models obtained with a variety of molecular descriptor combinations: lattice energies or 3D descriptors calculated from crystal structures or melting point data. We found that none of these greatly improved the best direct predictions of temperature dependent solubility or the related enthalpy of solution endpoint. This finding is surprising because the importance of the solid state contribution to both endpoints is clear. We suggest our findings may, in part, reflect limitations in the descriptors calculated from crystal structures and, more generally, the limited availability of polymorph specific data. We present curated temperature dependent solubility and enthalpy of solution datasets, integrated with molecular and crystal structures, for future investigations.

Improving Dissolution Properties by Polymers and Surfactants: A Case Study of Celastrol

Two polymorphs of celastrol were discovered and fully characterized by X-ray powder diffraction, thermogravimetry analysis, and differential scanning calorimetry. The single-crystal structures of form I and the isostructural solvate of form II were disclosed by single-crystal X-ray diffraction. The apparent solubility and wettability of both the crystalline forms were determined. It was found that surfactant can significantly improve the solubility of celastrol up to more than 10⁴ times. Tween 80 and sodium dodecyl sulfate largely improved the wettability of the 2 crystals. Form I shows better wettability than form II in all the buffer solutions with polymers and surfactants. Compared with form II, form I exhibits higher solubility in carboxymethylcellulose and polyvinylpyrrolidone media but much lower solubility in tween 80 and sodium dodecyl sulfate solutions. An investigation of wettability and solubility mechanisms was fully explored, and a hypothesis was proposed to understand the abnormal solubility differences.

Sublimation thermodynamics aspects of adamantane and memantine derivatives of sulfonamide molecular crystals

The sublimation thermodynamics and thermophysical properties of crystals based on adamantane and memantine structural moieties were studied and the relationship between the noted parameters and the crystal structure descriptors was found.