Polymorphism of Mechanochemically Synthesized Cocrystals

A special issue of Crystals (ISSN 2073-4352).

Deadline for manuscript submissions: closed (25 March 2018)

Special Issue Editor


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Guest Editor
Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, 12489 Berlin, Germany
Interests: co-crystallisation; synchrotron; X-ray powder diffraction; nanomaterials; solid-state; polymorphism; mechanochemistry
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Special Issue Information

Dear Colleagues,

During the last few years, mechanochemistry has emerged as a powerful method to form new structures by application of mechanical energy. In the simplest approach, a mortar and pestle are used to introduce solid transformations. Using automated milling devices, mechanochemical syntheses have become faster and more reliable. Mechanochemistry can produce solid forms, which are different to solution methods, without the need for miscible reactants. Therefore, the mechanochemical approach is now established as a green and efficient route for the formation of cocrystals and their polymorphs. Cocrystals are defined as multicomponent crystalline materials consisting of neutral molecules stabilized by non-covalent interactions, such as hydrogen bonds, π-π stacking, or halogen bonds. The cocrystallization of a compound with a suitable coformer can improve its physiochemical properties, such as solubility or stability, making it attractive for the development of new materials in pharmacy, agriculture, and explosives. The phenomenon of polymorphism is of great interest in academic and industrial research. Although polymorphs usually only differ slightly in energy, properties can change dramatically. Therefore, the control of polymorphism is of huge importance. The addition of liquids and polymers during grinding can influence the outcome of mechanochemical reactions. Mechanistic information is still sparse, making further research in the mechanochemical preparation of polymorphic cocrystals necessary.

Contributions in this Special issue cover, but are not limited to:

  • Mechanochemical syntheses and characterization of cocrystals
  • Transformation and stability of polymorphs
  • Structure/property relationships of cocrystals
  • Control of polymorphism during grinding: the role of solvent/additives in mechanochemical cocrystal formation
  • Prediction and mechanism of cocrystal formations

Dr. Franziska Emmerling
Guest Editor

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Keywords

  • Mechanochemistry
  • Polymorphism
  • Cocrystal

Published Papers (3 papers)

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Research

9 pages, 2985 KiB  
Article
Mechanochemical Synthesis and Crystal Structure of the Lidocaine-Phloroglucinol Hydrate 1:1:1 Complex
by Nancy Evelyn Magaña-Vergara, Porfirio De la Cruz-Cruz, Ana Lilia Peraza-Campos, Francisco Javier Martínez-Martínez and Juan Saulo González-González
Crystals 2018, 8(3), 130; https://doi.org/10.3390/cryst8030130 - 09 Mar 2018
Cited by 8 | Viewed by 5910
Abstract
Molecular complexation is a strategy used to modify the physicochemical or biopharmaceutical properties of an active pharmaceutical ingredient. Solvent assisted grinding is a common method used to obtain solid complexes in the form of cocrystals. Lidocaine is a drug used as an anesthetic [...] Read more.
Molecular complexation is a strategy used to modify the physicochemical or biopharmaceutical properties of an active pharmaceutical ingredient. Solvent assisted grinding is a common method used to obtain solid complexes in the form of cocrystals. Lidocaine is a drug used as an anesthetic and for the treatment of chronic pain, which bears in its chemical structure an amide functional group able to form hydrogen bonds. Polyphenols are used as cocrystal coformers due to their ability to form O–H···X (X = O, N) hydrogen bond interactions. The objective of this study was to exploit the ability of phloroglucinol to form molecular complexes with lidocaine by liquid assisted grinding. The formation of the complex was confirmed by the shift of the O–H and C=O stretching bands in the IR spectra of the polycrystalline ground powders, suggesting the formation of O–H···O=C hydrogen bonds. Hydration of the complexes also was confirmed by IR spectroscopy and by powder X-ray diffraction. The molecular structure was determined by single crystal X-ray diffraction. Full article
(This article belongs to the Special Issue Polymorphism of Mechanochemically Synthesized Cocrystals)
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2575 KiB  
Article
Chalcogenide Quaternary Cu2FeSnS4 Nanocrystals for Solar Cells: Explosive Character of Mechanochemical Synthesis and Environmental Challenge
by Peter Baláž, Matej Baláž, María J. Sayagués, Alexander Eliyas, Nina G. Kostova, Mária Kaňuchová, Erika Dutková and Anna Zorkovská
Crystals 2017, 7(12), 367; https://doi.org/10.3390/cryst7120367 - 09 Dec 2017
Cited by 16 | Viewed by 4563
Abstract
In this study we demonstrate the synthesis of quaternary semiconductor nanocrystals of stannite Cu2FeSnS4/rhodostannite Cu2FeSn3S8 (CFTS) via mechanochemical route using Cu, Fe, Sn and S elements as precursors in one-pot experiments. Methods of X-ray [...] Read more.
In this study we demonstrate the synthesis of quaternary semiconductor nanocrystals of stannite Cu2FeSnS4/rhodostannite Cu2FeSn3S8 (CFTS) via mechanochemical route using Cu, Fe, Sn and S elements as precursors in one-pot experiments. Methods of X-ray diffraction (XRD), nitrogen adsorption, high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) were applied to characterize properties of the unique nanostructures. Mechanochemical route of synthesis induced new phenomena like explosive character of reaction, where three stages could be identified and the formation of nanostructures 5–10 nm in size. By using XPS method, Cu(I), Fe(II), Sn(IV) and S(-II) species were identified on the surface of CFTS. The value of optical band gap 1.27 eV is optimal for semiconductors applicable as absorbers in solar cells. The significant photocatalytic activity of the CFTS nanocrystals was also evidenced. The obtained results confirm the excellent properties of the quaternary semiconductor nanocrystals synthesized from earth-abundant elements. Full article
(This article belongs to the Special Issue Polymorphism of Mechanochemically Synthesized Cocrystals)
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2327 KiB  
Article
The Influence of Liquid on the Outcome of Halogen-Bonded Metal–Organic Materials Synthesis by Liquid Assisted Grinding
by Katarina Lisac and Dominik Cinčić
Crystals 2017, 7(12), 363; https://doi.org/10.3390/cryst7120363 - 07 Dec 2017
Cited by 12 | Viewed by 5424
Abstract
In this work, we describe novel multi-component halogen bonded solids of Co(ii) complexes and 1,4-diiodotetrafluorobenzene, 14tfib. We present the important influence of liquid on the outcome of liquid assisted grinding of dichlorobis(1,10-phenantroline)cobalt(ii), CoCl2(phen)2 [...] Read more.
In this work, we describe novel multi-component halogen bonded solids of Co(ii) complexes and 1,4-diiodotetrafluorobenzene, 14tfib. We present the important influence of liquid on the outcome of liquid assisted grinding of dichlorobis(1,10-phenantroline)cobalt(ii), CoCl2(phen)2 and 14tfib. Grinding of solid reactants with a small amount of water gives the cocrystal product [CoCl2(phen)2](14tfib) (1) while grinding with a small amount of methanol gives an ionic structure, the four-component solid [CoCl(MeOH)(phen)2]Cl(14tfib)(MeOH) (2). Both solid products were also obtained by crystallization from the solution. Single crystal X-ray diffraction reveals that the dominant supramolecular interaction in 1 is the I···Cl halogen bond between 14tfib and CoCl2(phen)2 building blocks. On the other hand, the dominant supramolecular interactions in 2 are I···Cl charge-assisted halogen bonds between the halogen bond donor and the chloride anion as well as hydrogen bonds between the chloride anion and OH groups of coordinated and solvated methanol molecules. Full article
(This article belongs to the Special Issue Polymorphism of Mechanochemically Synthesized Cocrystals)
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