Kinetic analysis of the complete mechanochemical synthesis of a palladium(II) carbene complex

Mechanochemical Transformations of Pharmaceutical Cocrystals: Polymorphs and Coformer Exchange

Transformations of solid samples under solvent-free or minimal solvent conditions set the future trend and define a modern strategy for the production of new materials. Of the various technologies tested in recent years, the mechanochemical approach seems to be the most promising for economic and ecological reasons. The aim of this review article is to present the current state of art in solid state research on binary systems, which have found numerous applications in the pharmaceutical and materials science industries. This article is divided into three sections. In the first part, we describe the new equipment improvements, which include the innovative application of thermo-mechanochemistry, sono-mechanochemistry, photo-mechanochemistry, electro-mechanochemistry, as well as resonant acoustic mixing (RAM), and transformation under high-speed sample spinning ("SpeedMixing"). A brief description of techniques dedicated to ex-situ and in-situ studies of progress and the mechanism of solid matter transformation (PXRD, FTIR, Raman and NMR spectroscopy) is presented. In the second section, we discuss the problem of cocrystal polymorphism highlighting the issue related with correlation between mechanochemical parameters (time, temperature, energy, molar ratio, solvent used as a liquid assistant, surface energy, crystal size, crystal shape) and preference for the formation of requested polymorph. The last part is devoted to the description of the processes of coformer exchange in binary systems forced by mechanical and/or thermal stimuli. The influence of the thermodynamic factor on the selection of the best-suited partner for the formation of a two-component stable structure is presented.

Mechanochemistry: A Green Approach in the Preparation of Pharmaceutical Cocrystals

Mechanochemistry is considered an alternative attractive greener approach to prepare diverse molecular compounds and has become an important synthetic tool in different fields (e.g., physics, chemistry, and material science) since is considered an ecofriendly procedure that can be carried out under solvent free conditions or in the presence of minimal quantities of solvent (catalytic amounts). Being able to substitute, in many cases, classical solution reactions often requiring significant amounts of solvents. These sustainable methods have had an enormous impact on a great variety of chemistry fields, including catalysis, organic synthesis, metal complexes formation, preparation of multicomponent pharmaceutical solid forms, etc. In this sense, we are interested in highlighting the advantages of mechanochemical methods on the obtaining of pharmaceutical cocrystals. Hence, in this review, we describe and discuss the relevance of mechanochemical procedures in the formation of multicomponent solid forms focusing on pharmaceutical cocrystals. Additionally, at the end of this paper, we collect a chronological survey of the most representative scientific papers reporting the mechanochemical synthesis of cocrystals.