Comment on 'Solution growth and thermal treatment of crystals lead to two new forms of 2-((2,6-dimethylphenyl)amino)benzoic acid' by R. Hu, Y. Zhoujin, M. Liu, M. Zhang, S. Parkin, P. Zhou, J. Wang, F. Yu and S. Long, , 2018, , 15459.

The study mentioned in the title of this comment article reports on two new polymorphic forms of 2-((2,6-dimethylphenyl)amino)benzoic acid, one with new X-ray diffraction data showing its crystal structure, and the other without. However, our investigation suggests that the newly reported crystal structure (Form II) is in fact the same structure previously reported (Form I), differing in how the structure refinement was performed. Herein, we demonstrated from the raw crystallographic data of Form I that both structures are the same, which invalidates the discovery of the new polymorph.

Supramolecular Similarity in Polymorphs: Use of Similarity Indices (I).

A systematic investigation to assess the degree of similarity between polymorphs was carried out. A similarity indices (I) approach was applied in ten series of polymorphs with different characteristics and number of molecules in the asymmetric unit. Geometric (I), contact area (I), and stabilization energy (I) parameters were used.

Supramolecular Packing of a Series of -Phenylamides and the Role of NH···O=C Interactions.

A series of seven -phenylamides [R-C(O)NHPh, in which R: CH, C(CH), Ph, CF, CCl, CBr, and H] were used as models in this study. Molecular packing and intermolecular interactions were evaluated by theoretical calculations, solution NMR, and quantum theory of atoms in molecules analyses. Crystallization mechanisms were proposed based on the energetic and topological parameters using the supramolecular cluster as demarcation.

Impact of Anions on the Partition Constant, Self-Diffusion, Thermal Stability, and Toxicity of Dicationic Ionic Liquids.

Partition constants (), molecular dynamics (, , and DOSY measurements), thermal stability, and toxicity of dicationic ionic liquids (ILs) were determined. The dicationic ILs derived from 1,-bis(3-methylimidazolim-1-yl)octane, [BisOct(MIM)][2X] (in which X = Cl, Br, NO, SCN, BF, and NTf), were evaluated to verify the influence of anion structure on the IL properties. A monocationic IL [Oct(MIM)][Br] was also monitored for comparison.

Insights on the Similarity of Supramolecular Structures in Organic Crystals Using Quantitative Indexes.

The quest for concepts of isostructurality in organic crystals has been long and mostly based on geometric data, even with the development of modern software. This field of study is of great interest to the pharmaceutical industry and for the prediction of crystal structures. Despite this, there is still no methodology that provides broad quantitative and comparable similarity data between two complete crystalline structures.

Heteroassembly Ability of Dicationic Ionic Liquids and Neutral Active Pharmaceutical Ingredients.

Extensive investigation of interactions and aggregation properties of IL + API systems is necessary to apply ionic liquids (ILs) with different hydrophobic characteristics to drug delivery or in active pharmaceutical ingredient (API) formulations. Therefore, this study aims to investigate the heteroassembly between dicationic ILs ([BisOct(MIM)][2X], in which X is Br or BF, and [BisOct(BnIM)][2Br]), both in the absence and the presence of neutral APIs (salicylic acid, ibuprofen, and paracetamol) with different functional groups. Isothermal titration calorimetry results demonstrate that IL-API associations occur at very low concentrations of IL.

Synthesis, Crystal Structure, and Supramolecular Understanding of 1,3,5-Tris(1-phenyl-1H-pyrazol-5-yl)benzenes.

Understanding the supramolecular environment of crystal structures is necessary to facilitate designing molecules with desirable properties. A series of 12 novel 1,3,5-(1-phenyl-1-pyrazol-5-yl)benzenes was used to assess the existence of planar stacking columns in supramolecular structures of pyrazoles. This class of molecules with different substituents may assist in understanding how small structural changes affect the supramolecular environment.

Synthesis, effect of substituents on the regiochemistry and equilibrium studies of tetrazolo[1,5-]pyrimidine/2-azidopyrimidines.

An efficient synthesis methodology for a series of tetrazolo[1,5-]pyrimidines substituted at the 5- and 7-positions from the cyclocondensation reaction [CCC + NCN] was developed. The NCN corresponds to 5-aminotetrazole and CCC to β-enaminone. Two distinct products were observed in accordance with the β-enaminone substituent.