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

An elegant statistical mechanics approach has been exploited in combination with accurate quantum chemical calculations to justify the disorder in two previously reported racemic solids. Generated canonical ensembles and performed lattice energy calculations show that the disorder in the studied systems of small organic enantiomer molecules can be modelled with great accuracy. Ensemble averages fully correspond to the disordered structure models repeatedly obtained in X-ray diffraction studies. The present work not only demonstrates that disorder and its extent in molecular crystals can be theoretically calculated, but also explains from a thermodynamic point of view the origins of the rarely encountered phenomenon of enantiomer solid solutions. Such phases are promising in materials science as their properties can be finely tuned depending on the composition. The lack of complete enantiomer discrimination in the studied examples is evident and it is related to the absence of any donor–acceptor groups providing highly directional interactions, as well as to conformational flexibility in one case and a specific inner symmetry of the molecule in the other one.

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

Nitrofurantoin was crystallized from multiple mixtures of water and organic solvents with and without additives to try to find and identify factors affecting phase obtained in crystallization and provide possible information on crystallization control. Obtained crystals were identified with powder X-ray diffractometry. Crystallization control possibilities were evaluated by using polymer additives and crystallization additives, by also using quantum chemical calculations to investigate the association of nitrofurantoin and additive molecules and calculate Gibbs energy of association.

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

b. Laboratory of Crystallography, University of Bayreuth, Universitaetsstrasse 30, Bayreuth 95440, Germany

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

In a study of the solid form landscape of R-encenicline hydrochloride (Enc-HCl), it was found that this compound is dodecamorphic and presents the first published example of polymorphism with a record-breaking 10 solved crystal structures. In addition to the four known polymorphs, eighth new polymorphs and their precursor solvates as well as several new hydrates have been characterized. The polymorph formation behavior is investigated by analyzing crystal structures of polymorphs and solvates used in their preparation. Molecular packing in crystal structures of the polymorphs is highly similar to that in the precursor solvates, whereas conformations in all structures are nearly identical and correspond to the same energy minimum.