a. Department of Physical Chemistry, University of Latvia, Jelgavas 1, Riga 1004, Latvia

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.

a. Department of Physical Chemistry, University of Latvia, Jelgavas 1, Riga 1004, Latvia

b. Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga 1006, Latvia

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.

a. Department of Physical Chemistry, University of Latvia, Jelgavas 1, Riga 1004, Latvia

Already validated methodology for self-association in solutions were used to evaluate if this method could also be used in other studies regarding association in solution. Three isomeric dihydroxybenzoic acids were used to calculate Gibbs free energies of association for homodimers, heterotetramers and associates with solvent molecules by using DFT calculations in multiple environments and having different conformations.

a. Department of Physical Chemistry, University of Latvia, Jelgavas 1, Riga 1004, Latvia

Several 2-substituted 4-nitrobenzoic acid (NBA) derivatives such as 2-chloro-4-nitrobenzoic acid (2C4NBA), 2-methyl-4-nitrobenzoic acid (2CH34NBA) and 2-hydroxy-4-nitrobenzoic acid (2OH4NBA) were selected as model compounds because of their availability and chemically similar structures, in which the different group/atom (R) does not significantly affect the dominant intermolecular interactions – hydrogen bonds formed by the carboxylic group [1]. Quantum chemical calculations of lattice and intermolecular interaction energy were carried out to identify possible factors, which could be, used in prediction of the formation of solid solutions (SS) in binary systems of chemically similar molecules, in this case - various nitrobenzoic acid derivatives. Meanwhile, crystallization experiments were used to determine the experimental information about formation of solid solutions. The obtained crystalline phases were characterized by combined use of powder X-ray diffraction (XRPD) and differential scanning calorimetry/thermogravimetry (DSC/TG) [2].

a. Department of Physical Chemistry, University of Latvia, Jelgavas 1, Riga 1004, Latvia

A detailed study on chiral compound structures found in the Cambridge Structural Database (CSD) is presented. Solvates, salts and co-crystals have intentionally been excluded, in order to focus on the most basic structures of single enantiomers, scalemates and racemates. Similarity between the latter and structures of achiral monomolecular compounds has been established and utilized to arrive at important conclusions about crystallization of chiral compounds. For example, the fundamental phenomenon of conglomerate formation and, in particular, their frequency of occurrence is addressed. In addition, rarely occurring kryptoracemates and scalemic compounds (anomalous racemates) are discussed. Finally, an extended search of enantiomer solid solutions in the CSD is performed to show that there are up to 1800 instances most probably hiding among the deposited crystal structures, while only a couple of dozen have been previously known and studied.