Mebendazolium mesylate anhydride salt: rational design based on supramolecular assembly, synthesis, and solid-state characterization

The design mebendazole (MBZ) multicomponent systems is important to obtain new materials that incorporate the API (active pharmaceutical ingredient) with better thermal stability, avoiding the interconversion of desmotropes. Interestingly, the presence of water molecules in the mebendazolium mesylate monohydrate prevents the formation of the R22(8) supramolecular synthon, found in all mebendazolium salts with polyatomic counterions. Here, we designed a new mebendazolium mesylate anhydrous salt based on statistical scrutiny of all mebendazole crystal structures identified in the literature and an exhaustive analysis of the conformational and geometrical requirements for the supramolecular assembly. The synthesis of this new salt and its solid-state characterization through single-crystal X-ray diffraction and complementary techniques are presented. As expected, mebendazole recrystallization in methanol with methanesulfonic acid - a Food and Drug Administration accepted coformer - in the absence of water yields a mesylate anhydrous salt with 1 : 1 stoichiometry. This new salt crystallizes in the P212121 (19) space group. The main intermolecular interactions found in the crystal structure are the hydrogen bonds that form a R22(8) supramolecular motif that assembles the ionic pairs. Additional non-classical H-bond, as well as π⋯π and carbonyl⋯cation interactions, contribute to the final stabilization of the crystal packing. This new salt is stable up to 205 °C when it undergoes the endothermic loss of the ester moiety to yield 2-amino-5-benzoylbenzimidazole. Moreover, preliminary dissolution experiments in aqueous 0.1 mol L-1 HCl suggest an apparent solubility of mebendazolium mesylate anhydride 2.67 times higher than that of the preferred for pharmaceutical formulations MBZ form C.

Combined X-ray Crystallographic, IR/Raman Spectroscopic, and Periodic DFT Investigations of New Multicomponent Crystalline Forms of Anthelmintic Drugs: A Case Study of Carbendazim Maleate

Synthesis of multicomponent solid forms is an important method of modifying and fine-tuning the most critical physicochemical properties of drug compounds. The design of new multicomponent pharmaceutical materials requires reliable information about the supramolecular arrangement of molecules and detailed description of the intermolecular interactions in the crystal structure. It implies the use of a combination of different experimental and theoretical investigation methods. Organic salts present new challenges for those who develop theoretical approaches describing the structure, spectral properties, and lattice energy Elatt. These crystals consist of closed-shell organic ions interacting through relatively strong hydrogen bonds, which leads to Elatt > 200 kJ/mol. Some technical problems that a user of periodic (solid-state) density functional theory (DFT) programs encounters when calculating the properties of these crystals still remain unsolved, for example, the influence of cell parameter optimization on the Elatt value, wave numbers, relative intensity of Raman-active vibrations in the low-frequency region, etc. In this work, various properties of a new two-component carbendazim maleate crystal were experimentally investigated, and the applicability of different DFT functionals and empirical Grimme corrections to the description of the obtained structural and spectroscopic properties was tested. Based on this, practical recommendations were developed for further theoretical studies of multicomponent organic pharmaceutical crystals.

Rational design, supramolecular synthesis and solid state characterization of two bicomponent solid forms of mebendazole

MBZ methyl sulfate and perchlorate were designed based on the statistical probability of the formation of an R22(8) supramolecular heterosynthon.