Conformational Polymorphism

Cruz‐Cabeza, Aurora J.; Bernstein, Joel

doi:10.1021/cr400249d

Cited by 640 publications

(729 citation statements)

References 133 publications

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“…Subsequently, a polymorphic form, 2, was isolated from a failed co-crystallisation experiment in ethanol/chloroform (1/1 v/v) solution between the diamide and 2-(4-hydroxyphenylazo)benzoic acid, which has been employed recently in co-crystallisation experiments, with some measure of success, including with a related diamide [15][16][17]. Remarkably, two quite distinct conformations of the diamide were observed in the polymorphs and hence, are described as conformational polymorphs [18]. Herein, the results of a crystallographic and theoretical investigation of polymorphs 1 and 2 are described.…”

Section: Introductionmentioning

confidence: 99%

Structural, Hirshfeld surface and theoretical analysis of two conformational polymorphs of N,N′-bis(pyridin-3-ylmethyl)oxalamide

Jotani¹,

Zukerman-Schpector

Madureira

et al. 2016

Zeitschrift Für Kristallographie - Crystalline Materials

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Section: Introductionmentioning

confidence: 99%

Structural, Hirshfeld surface and theoretical analysis of two conformational polymorphs of N,N′-bis(pyridin-3-ylmethyl)oxalamide

Jotani¹,

Zukerman-Schpector

Madureira

et al. 2016

Zeitschrift Für Kristallographie - Crystalline Materials

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“…The occurrence of polymorphic modifications in molecular compounds is manifested not only as a consequence of the minimum free energy in the crystalline phase, but also by the kinetics of the crystal nucleation and growth. Conformational polymorphs [73,74] are generated if the molecular conformation is different from one polymorph to the other; packing polymorphs [75] are those in which the molecules of a similar conformation pack into different crystal lattices and solvatomorphs (pseudopolymorphs) [76] that crystallize, including the solvents in the crystal lattice.…”

Section: Crystal Packing Forces and Hydrogen-bonded Networkmentioning

confidence: 99%

Terahertz Vibrations and Hydrogen-Bonded Networks in Crystals

Takahashi

2014

Crystals

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Abstract:The development of terahertz technology in the last few decades has made it possible to obtain a clear terahertz (THz) spectrum. THz vibrations clearly show the formation of weak bonds in crystals. The simultaneous progress in the code of first-principles calculations treating noncovalent interactions has established the position of THz spectroscopy as a powerful tool for detecting the weak bonding in crystals. In this review, we are going to introduce, briefly, the contribution of weak bonds in the construction of molecular crystals first, and then, we will review THz spectroscopy as a powerful tool for detecting the formation of weak bonds and will show the significant contribution of advanced computational codes in treating noncovalent interactions. From the second section, following the Introduction, to the seventh section, before the conclusions, we describe: (1) the crystal packing forces, the hydrogen-bonded networks and their contribution to the construction of organic crystals; (2) the THz vibrations observed in hydrogen-bonded molecules; (3) the computational methods for analyzing the THz vibrations of hydrogen-bonded molecules; (4) the dispersion correction and anharmonicity incorporated into the first-principles calculations and their effect on the peak assignment of the THz spectrum (5) the temperature dependence; and (6) the polarization dependence of the THz spectrum.

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“…[32][33][34][35][36][37][38][39][40][41] Although the α-form is thermodynamically stable under ambient conditions, other forms can be obtained, often concomitantly, as dominant phases or as impurities. [35][36][37][38][39] These metastable phases persist in mixtures under ambient conditions, recrystallising only slowly to the stable form, hastened by humid atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Polymorphism of chlorpropamide on liquid-assisted mechanical treatment: choice of liquid and type of mechanical treatment matter

et al. 2018

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Different types of mechanical treatment (tableting, grinding, milling, etc.) are important technological operations in the pharmaceutical industry. Solid materials are not merely comminuted during such treatment, but can undergo polymorphic transitions and amorphisation. A liquid is often added to the solid sample on purpose, e.g. in order to facilitate comminution. In many cases, liquid is present inadvertently, either as a result of trace solvent following up-stream operations, or sorbed from the atmosphere. This work explores the liquid-assisted mechanical treatment of two metastable forms of a model pharmaceutical compound chlorpropamide (CPA), namely the β-and ε-forms. We investigate the stability of these polymorphs to mechanical treatment in the presence of a series of fluids that have affinity for different fragments of the CPA molecule. In addition to variation in fluids, the effect of different mechanical treatment is explored, employing model shear and restricted impact devices, alongside grinding in a mortar. CPA offers a clear example of the drastically different results of shear and impact on mechanochemical polymorphism, on the importance of the careful selection of solvent for liquid-assisted treatment, and on the possible role of even trace quantities of solvent. Further, this work demonstrates the importance of the starting polymorph in determining the outcome of a mechanochemical process. All of these factors can have notable consequence on the outcome of technological operations that include mechanical treatment.

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Conformational Polymorphism

Cited by 640 publications

References 133 publications

Structural, Hirshfeld surface and theoretical analysis of two conformational polymorphs of N,N′-bis(pyridin-3-ylmethyl)oxalamide

Structural, Hirshfeld surface and theoretical analysis of two conformational polymorphs of N,N′-bis(pyridin-3-ylmethyl)oxalamide

Terahertz Vibrations and Hydrogen-Bonded Networks in Crystals

Polymorphism of chlorpropamide on liquid-assisted mechanical treatment: choice of liquid and type of mechanical treatment matter

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