Analysis of crystal structures, molecular properties, interaction strength in solution, and computationally generated nonsolvated form crystal structure landscapes of five chloronitrobenzoic acid isomers and two additional 2-substituted 4-nitrobenzoic acids were used to rationalize the obtained solvate landscape of these compounds. Screening of the solid forms was performed for each of the compounds, and crystal structures of the obtained nonsolvated forms and selected solvates were determined. Molecular conformation, intermolecular interactions, and packing efficiency of nonsolvated forms and solvates were analyzed to understand factors contributing to structure stabilization and determining the formation of the observed crystal structures. Computationally generated crystal structure landscapes of nonsolvated forms were tested for the possibility to predict the propensity to form solvates and identify polymorphic compounds. It was observed that most of the solvates were obtained with solvents acting as strong hydrogen bond acceptors and/or able to form aromatic interactions. Solute–solvent association Gibbs energy representing interaction strength was found to be the most apparent identifiable factor explaining the solvate formation of the studied compounds, and using this tool, the existence of 3 new multicomponent phases was successfully predicted.

The binary system of xanthone−thioxanthone has been explored, showing that two solid solutions (formed based on xanthone and thioxanthone parent structures, respectively) exist for this system. One of the solid solutions shows miscibility of both molecules in a large composition range (>0−80 mol % of xanthone). The structure of thioxanthone has been redetermined to reveal a special case of nonmerohedral twinning in the crystals. Such a twinning feature has apparently been the reason for incorrect crystal structure determination previously. A structure of thioxanthone:xanthone (75:25 mol %) solid solution is also presented. Several similar molecules to the title compounds have been found in the Cambridge Structural Database and shown to crystallize in structures isostructural to that of thioxanthone. The different packing of pure xanthone is thus an exception among the explored compounds.

Solid solutions with fine-tunable photoluminescence have been obtained in a 4-iodothioxanthone−4-chlorothioxanthone system. Both pure components are room-temperature luminophors demonstrating different luminescence properties. It was discovered that in the 4-chlorothioxanthone structure, up to half of the molecules can be replaced by the iodo analogue obtaining solid solutions in the respective composition range. Despite this solid solution existing in such a large composition range, the variation of the luminescence spectra is not substantial. In the 4-iodothioxanthone structure, only up to ∼20% of the molecules can be replaced by the chloro analogue before the composition limit of this solid solution is reached. In contrast, there is a strong composition-dependent response of the luminescence. A considerable change in luminescence spectra is observed even if only a few mol % of the opposite component is added. The spectra of mechanical mixtures of pure components are different from those of the solid solutions, which demonstrates the unique behavior of the newly obtained solid phases. This study shows great potential to use solid solution engineering in the organic solid state to tune material properties in a continuum as opposed to other crystal engineering approaches, leading to property tunability in a stepwise fashion.

We present an experimental and computational study of solid solution formation between structurally highly similar active pharmaceutical ingredients droperidol and benperidol in nonsolvates, dihydrates, and several solvates formed by these compounds. We demonstrate that the formation of solid solutions strongly depends on the crystal structure of the phase. In some of the structures, almost complete replacement of benperidol with droperidol can be achieved, whereas in other structures, the replacement is possible only up to a limited molar ratio. However, only limited replacement of droperidol with benperidol can be achieved and only in some of the structures. The solid solution formation is primarily determined by the change in intermolecular interaction energy resulting from the molecule replacement. Only structures where molecule replacement allows the formation of efficient intermolecular interactions can be obtained experimentally. The results indicate that the energy requirements of intermolecular interaction changes to obtain solid solutions in the nonsolvated phase are less strict than those for solvates.

In this study, new composite materials of montmorillonite, biochar, or aerosil, containing metal–organic frameworks (MOF) were synthesized in situ. Overall, three different MOFs—CuBTC, UTSA-16, and UiO-66-BTEC—were used. Obtained adsorbents were characterized using powder X-ray diffraction, thermogravimetric analysis, nitrogen adsorption porosimetry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectrophotometry. Additionally, the content of metallic and nonmetallic elements was determined to investigate the crystalline structure, surface morphology, thermal stability of the obtained MOF-composites, etc. Cyclic CO2 adsorption analysis was performed using the thermogravimetric approach, modeling adsorption from flue gasses. In our study, the addition of aerosil to CuBTC (CuBTC-A-15) enhanced the sorbed CO2 amount by 90.2% and the addition of biochar (CuBTC-BC-5) increased adsorbed the CO2 amount by 75.5% in comparison to pristine CuBTC obtained in this study. Moreover, the addition of montmorillonite (CuBTC-Mt-15) increased the adsorbed amount of CO2 by 27%. CuBTC-A-15 and CuBTC-BC-5 are considered to be the most perspective adsorbents, capturing 3.7 mmol/g CO2 and showing good stability after 20 adsorption-desorption cycles.