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Themed collection Editor’s Collection: Polymorphism in Molecular Crystals

24 items
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Polymorphism in p-aminobenzoic acid

We review the polymorphism of p-aminobenzoic acid (pABA), a model drug compound whose crystallisation and polymorphic behaviour has been extensively studied in recent years.

Graphical abstract: Polymorphism in p-aminobenzoic acid
From the themed collection: 2019 Highlight article collection
Communication

Thermosalient effect of two polymorphs of a diketopyrrolopyrrole dye with different crystal systems and molecular arrangements

Two polymorphs of a diketopyrrolopyrrole dye, one yellow and the other orange, were obtained.

Graphical abstract: Thermosalient effect of two polymorphs of a diketopyrrolopyrrole dye with different crystal systems and molecular arrangements
Open Access Communication

SURMOF induced polymorphism and crystal morphological engineering of acetaminophen polymorphs: advantage of heterogeneous nucleation

Surface metal organic framework substrates were engineered as heterogeneous surfaces and the importance of these designed surfaces towards polymorphs and morphological engineering was discussed for the first time.

Graphical abstract: SURMOF induced polymorphism and crystal morphological engineering of acetaminophen polymorphs: advantage of heterogeneous nucleation
Open Access Communication

Unusual seeding effect in the liquid-assisted high-pressure polymorphism of chlorpropamide

When crystals of four polymorphs – a stable α-form and three metastable ones (β-, γ-, δ-forms) – are simultaneously present in a pressure cell, immersed in a 1 : 1 pentane–isopentane mixture, the least stable β-form recrystallises exclusively into the γ-form (if no δ-form seed is present) or concomitantly into the γ- and δ-forms (if a seed of the δ-form is present).

Graphical abstract: Unusual seeding effect in the liquid-assisted high-pressure polymorphism of chlorpropamide
Communication

An unprecedented case of dodecamorphism: the twelfth polymorph of aripiprazole formed by seeding with its active metabolite

Twelfth polymorph of the anti-psychotic drug aripiprazole was discovered where its active metabolite acted as a template during recrystallization.

Graphical abstract: An unprecedented case of dodecamorphism: the twelfth polymorph of aripiprazole formed by seeding with its active metabolite
Communication

Ostwald's rule and enantiotropy: polymorph appearance in the crystallisation of p-aminobenzoic acid

The development of rational crystallisation strategies in polymorphic systems requires the experimental manipulation of both kinetics and thermodynamics.

Graphical abstract: Ostwald's rule and enantiotropy: polymorph appearance in the crystallisation of p-aminobenzoic acid
Open Access Paper

High-pressure polymorphism in L-threonine between ambient pressure and 22 GPa

The amino acid L-threonine undergoes three phase transitions between ambient pressure and 22.3 GPa which modify both hydrogen bonding and the molecular conformation.

Graphical abstract: High-pressure polymorphism in l-threonine between ambient pressure and 22 GPa
Open Access Paper

Crystallisation in printed droplets: understanding crystallisation of D-mannitol polymorphs

Crystallising D-mannitol in printed droplets provides new insights into understanding the effect of foreign surfaces on the formation of its polymorphs.

Graphical abstract: Crystallisation in printed droplets: understanding crystallisation of d-mannitol polymorphs
Paper

On the prevalence of smooth polymorphs at the nanoscale: implications for pharmaceuticals

Ball mill neat grinding leads to smoother whereas liquid assisted grinding leads to rougher pharmaceutical forms.

Graphical abstract: On the prevalence of smooth polymorphs at the nanoscale: implications for pharmaceuticals
Open Access Paper

Polymorph control in batch seeded crystallizers. A case study with paracetamol

We show that seeding is not always sufficient to control cystal polymorphism and illustrate how kinetic modeling can help controlling polymorphism.

Graphical abstract: Polymorph control in batch seeded crystallizers. A case study with paracetamol
Paper

Robust bulk preparation and characterization of sulfamethazine and saccharine salt and cocrystal polymorphs

The complex between sulfamethazine and saccharine (SMT–SAC) can exist in two polymorphs, one is a cocrystal and the other is a salt.

Graphical abstract: Robust bulk preparation and characterization of sulfamethazine and saccharine salt and cocrystal polymorphs
Paper

A new polymorph of the common coformer isonicotinamide

A polymorph of the widely employed coformer isonicotinamide crystallizing in the space group Pca21 is described for the first time.

Graphical abstract: A new polymorph of the common coformer isonicotinamide
Paper

Solid state photodimerization of 9-tert-butyl anthracene ester produces an exceptionally metastable polymorph according to first-principles calculations

Molecular crystal engineering seeks to tune the material properties by controlling the crystal packing.

Graphical abstract: Solid state photodimerization of 9-tert-butyl anthracene ester produces an exceptionally metastable polymorph according to first-principles calculations
Paper

Exploring polymorphism and stoichiometric diversity in naproxen/proline cocrystals

This work studies a multitude of cocrystals obtained by combining chiral and/or racemic naproxen and proline, 17 in total.

Graphical abstract: Exploring polymorphism and stoichiometric diversity in naproxen/proline cocrystals
Paper

Serendipitous isolation of a disappearing conformational polymorph of succinic acid challenges computational polymorph prediction

A new polymorph of succinic acid is an unusually challenging test for metastable polymorph prediction.

Graphical abstract: Serendipitous isolation of a disappearing conformational polymorph of succinic acid challenges computational polymorph prediction
Open Access Paper

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

Different types of mechanical treatment (tableting, grinding, milling, etc.) are important technological operations in the pharmaceutical industry.

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

L-Malic acid crystallization: polymorphism, semi-spherulites, twisting, and polarity

A new polymorph and twisted semi-spherulites of L-malic acid are described and discussed in this work.

Graphical abstract: l-Malic acid crystallization: polymorphism, semi-spherulites, twisting, and polarity
Paper

Polymorphism in secondary squaramides: on the importance of π-interactions involving the four membered ring

We report the crystal structures of four new squaric acid derivatives, i.e. three polymorphs of 3,4-bis((2-(dimethylamino)ethyl)amino)cyclobut-3-ene-1,2-dione (1a–c) and a cocrystal with resorcinol. A DFT study has been also carried out to investigate the supramolecular assemblies.

Graphical abstract: Polymorphism in secondary squaramides: on the importance of π-interactions involving the four membered ring
Open Access Paper

Effect of pressure on two polymorphs of tolazamide: why no interconversion?

Pressure-resistant transformation between two polymorphs of tolazamide was monitored by X-ray diffraction and rationalized by DFT calculations.

Graphical abstract: Effect of pressure on two polymorphs of tolazamide: why no interconversion?
Paper

Polymorphism, isostructurality and physicochemical properties of glibenclamide salts

Glibenclamide sodium salt polymorphs namely forms I and II showed differences in geometry of the central metal atom and ligand orientation. The solubility and stability of glibenclamide of GBA-K form I are superior for pharmaceutical development.

Graphical abstract: Polymorphism, isostructurality and physicochemical properties of glibenclamide salts
Paper

4-Aminoquinaldine monohydrate polymorphism: prediction and impurity aided discovery of a difficult to access stable form

Crystal structure prediction studies of 4-aminoquinaldine monohydrate led, 80 years after its first synthesis, to the thermodynamically most stable form under conditions relevant for production and storage.

Graphical abstract: 4-Aminoquinaldine monohydrate polymorphism: prediction and impurity aided discovery of a difficult to access stable form
Paper

Polymorphism of vanillin revisited: the discovery and selective crystallization of a rare crystal structure

65 years ago McCrone postulated vanillin to be trimorphic but only one polymorph has been structurally characterized since. Herein, a new and rare crystal structure is reported. Selective crystallization of this polymorph was achieved using polymer induced heterogeneous nucleation.

Graphical abstract: Polymorphism of vanillin revisited: the discovery and selective crystallization of a rare crystal structure
Open Access Paper

Static and lattice vibrational energy differences between polymorphs

Lattice energy, entropy and free energy differences for over 500 pairs of known polymorphs are computed and discussed.

Graphical abstract: Static and lattice vibrational energy differences between polymorphs
Paper

Concerning the crystal morphologies of the α and β polymorphs of p-aminobenzoic acid

A detailed morphological study on an organic polymorphic system highlighting the influence of desolvation on crystal habit.

Graphical abstract: Concerning the crystal morphologies of the α and β polymorphs of p-aminobenzoic acid
24 items

About this collection

This Editor’s collection, guest edited by Editorial Board member Aurora Cruz-Cabeza, highlights a number of recent articles in the field of Polymorphism in Molecular Crystals. Contributions include the discovery of new elusive polymorphs, the development of new strategies for polymorph control or the study of crystallisation and milling processes and their impact on polymorphism.

We dedicate this collection to the late Professor Joel Bernstein who endeavoured much of his work to the study of polymorphism and inspired many of us.

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