Submit to Special Issue Submit Abstract to Special Issue Review for Crystals Propose a Special Issue

Journal Browser

► Journal Browser

Crystalline Materials: Polymorphism

Special Issue Editors
Special Issue Information
Keywords
Published Papers

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystal Engineering".

Deadline for manuscript submissions: 12 August 2024 | Viewed by 7209

Share This Special Issue

Special Issue Editor

Prof. Dr. Edward R.T. Tiekink

E-Mail Website
Guest Editor

Distinguished Professor and Head, Research Centre for Crystalline Materials, School of Science and Technology, Sunway University, No 5 Jalan Universiti, 47500 Bandar Sunway, Selangor Darul Ehsan, Malaysia
Interests: molecular crystallography; crystal engineering; intermolecular interactions; metal-organic materials; coordination polymers; co-crystals; metal-based drugs

Special Issue Information

Dear Colleagues,

Polymorphism impacts upon society in many different ways (e.g., in agrochemicals, dyes, pharmaceuticals, etc.) as the arrangement of molecules in a crystal dictates many of the crucial physiochemical properties of these materials (e.g., solubility, bioavailability, etc.). Accordingly, the study of polymorphism transcends pure academic pursuits and opens a conduit between academia and industry. The aim of this Special Issue of Crystals is to gather impactful papers in the broad field of polymorphism. Topics included in this SI should relate to the study of polymorphs, their formation, characterisation, transformation, etc., and the impact this phenomenon has upon materials science, in its broadest sense. Thus, contributions, primary papers, and authoritative reviews in all aspects of polymorphism/pseudo-polymorphism are welcome.

Please consider contributing to this project!

Prof. Dr. Edward R.T. Tiekink
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

polymorphism
pharmaceuticals
crystallisation
structure–property relationships
phase transformations
supramolecular chemistry
crystallography

Published Papers (6 papers)

Download All Papers

Research

16 pages, 8235 KiB

Open AccessArticle

Enumeration of Self-Avoiding Random Walks on Lattices as Model Chains in Polymer Crystals

by Javier Benito, Unai Urrutia, Nikos Ch. Karayiannis and Manuel Laso

Crystals 2023, 13(9), 1316; https://doi.org/10.3390/cryst13091316 - 29 Aug 2023

Viewed by 770

Abstract

Recent simulation studies have revealed a wealth of distinct crystal polymorphs encountered in the self-organization of polymer systems driven by entropy or free energy. The present analysis, based on the concept of self-avoiding random walks (SAWs) on crystal lattices, is useful to calculate upper bounds for the entropy difference of the crystals that are formed during polymer crystallization and thus to predict the thermodynamic stability of distinct polymorphs. Here, we compare two pairs of crystals sharing the same coordination number, n_coord: hexagonal close-packed (HCP) and face centered cubic (FCC), both having n_coord = 12 and the same packing density, and the less dense simple hexagonal (HEX) and body centered cubic (BCC) lattices, with n_coord = 8. In both cases, once a critical number of steps is reached, one of the crystals shows a higher number of SAWs compatible with its geometry. We explain the observed trends in terms of the bending and torsion angles as imposed by the geometric constraints of the crystal lattice. Full article

(This article belongs to the Special Issue Crystalline Materials: Polymorphism)

► Show Figures

Figure 1

12 pages, 2811 KiB

Open AccessCommunication

Structural Investigation of Tetra-n-Butylammonium Perchlorate

by Irene Ling, Alexandre N. Sobolev, Chang Hoong Chek and Jack M. Harrowfield

Crystals 2023, 13(8), 1255; https://doi.org/10.3390/cryst13081255 - 14 Aug 2023

Viewed by 784

Abstract

The crystal structure of tetra-n-butylammonium perchlorate has been successfully elucidated using single-crystal X-ray diffraction. The compound crystallizes in the triclinic space group P

\bar{1}

with unit cell of dimensions a = 14.2706(7) Å, b = 20.6904(9) Å, c = 39.970(2) Å, α [...] Read more.

The crystal structure of tetra-n-butylammonium perchlorate has been successfully elucidated using single-crystal X-ray diffraction. The compound crystallizes in the triclinic space group P

\bar{1}

with unit cell of dimensions a = 14.2706(7) Å, b = 20.6904(9) Å, c = 39.970(2) Å, α = 89.316(4)°, β = 88.638(4)°, and γ = 87.801(4)°. Although complicated by partial disorder, the structure has remarkable features where columns of some of the perchlorate anions running down [100] lie within what can be regarded as nanotubular entities formed by some of the tetrabutylammonium cations, while the remaining tetrabutylammonium cations lie in parallel columns surrounded by the remaining perchlorate anions, one entity being essentially the inverse of the other. Interactions within the structure have been characterized using Hirshfeld surface analysis and comparisons drawn with other unsolvated salts of the cation. Full article

(This article belongs to the Special Issue Crystalline Materials: Polymorphism)

► Show Figures

Figure 1

16 pages, 5607 KiB

Open AccessArticle

Two Conformational Polymorphs of a Bioactive Pyrazolo[3,4-d]pyrimidine

by Sang Loon Tan, Yee Seng Tan, Jia Hui Ng, Anton V. Dolzhenko and Edward R. T. Tiekink

Crystals 2023, 13(6), 974; https://doi.org/10.3390/cryst13060974 - 19 Jun 2023

Viewed by 918

Abstract

Two monoclinic (P2₁/c; Z′ = 1) polymorphs, α (from methanol) and β (from ethanol, n-propanol and iso-propanol), of a bioactive pyrazolo[3,4-d]pyrimidine derivative have been isolated and characterised by X-ray crystallography as well as by a range of computational chemistry techniques. The different conformations observed for the molecules in the crystals are due to the dictates of molecular packing as revealed by geometry-optimisation calculations. The crucial difference in the molecular packing pertains to the formation of phenylamino-N–H···N(pyrazolyl) hydrogen bonding within supramolecular chains with either helical (α-form; 2₁-screw symmetry) or zigzag (β-form; glide symmetry). As a consequence, the molecular packing is quite distinct in the polymorphs. Lattice energy calculations indicate the β-form is more stable by 11 kJ/mol than the α-form. Full article

(This article belongs to the Special Issue Crystalline Materials: Polymorphism)

► Show Figures

Figure 1

12 pages, 5572 KiB

Open AccessArticle

Additive-Assisted Crystallization of 9,10-Diphenylanthracene

by Alina A. Sonina, Darya S. Cheshkina and Maxim S. Kazantsev

Crystals 2023, 13(6), 861; https://doi.org/10.3390/cryst13060861 - 24 May 2023

Viewed by 1121

Abstract

Crystallization control of organic conjugated small molecules is in high demand for the engineering of functional materials in organic optoelectronics. Here, we report solution additive-assisted crystallization of a model non-planar aromatic hydrocarbon derivative 9,10-diphenylanthracene. Among the studied series of related aromatic hydrocarbons comprising pyrene, perylene, anthracene, tetracene, and rubrene, only tetracene revealed clear reproducible effects allowing one to perform selective crystallization of metastable 9,10-diphenylanthracene polymorphs. Additionally, crystallization of 9,10-diphenylanthracene and pyrene produced a stoichiometric co-crystal (PYR–DPA) having a segregated layered molecular packing with alternating 9,10-diphenylanthracene and pyrene layers. Remarkably, the molecular packing of pyrene within the co-crystal is unique and represented by the herringbone motif, whereas the molecular packing in known pyrene polymorphs is represented by π-stacked molecules. The co-crystal also demonstrated a bright photoluminescence with a photoluminescence quantum yield of 51%. Considering the morphology of 9,10-diphenylanthracene crystals obtained and crystal structures of PYR–DPA co-crystal and tetracene, we have proposed the mechanism of additive-assisted polymorphism based on the inhibition of (111) facet of α-DPA and promoting of the layered structure crystallization corresponding to metastable polymorphs (β- and γ-DPA). We highlight the additive-assisted crystallization approach as a powerful tool for the crystal engineering of functional materials for organic optoelectronics. Full article

(This article belongs to the Special Issue Crystalline Materials: Polymorphism)

► Show Figures

Figure 1

11 pages, 2342 KiB

Open AccessArticle

Relative Stability of Pyrazinamide Polymorphs Revisited: A Computational Study of Bending and Brittle Forms Phase Transitions in a Broad Temperature Range

by Aleksandr S. Dubok and Denis A. Rychkov

Crystals 2023, 13(4), 617; https://doi.org/10.3390/cryst13040617 - 04 Apr 2023

Cited by 2 | Viewed by 1670

Abstract

Pyrazinamide may exist in at least four known polymorphic forms, which were obtained experimentally. One of these polymorphs, (α), shows outstanding mechanical properties, demonstrating a significant anisotropic plasticity in a three-point bending test, while the δ form was brittle. Despite a δ → α transition as well as β and γ behavior being experimentally studied, the relative stability of pyrazinamide polymorphs remains unclear and even controversial. In this work we provide a pure computational study of the thermodynamic relationships between all four polymorphs as a function of temperature using periodic DFT calculations. It was shown that the β but not the δ form is the most stable at low temperatures. Moreover, the relative stability of the δ form in comparison to α is questioned, showing that the “brittle to bending” δ → α transition was kinetically hindered in the experiments. We show that α and γ polymorphs were stabilized at higher temperatures due to an entropy term. Finally, the calculated stability of the bending α form of pyrazinamide at room temperature was in perfect agreement with previous experiments, which showed a transformation of all other forms to α during six month storage or grinding. Full article

(This article belongs to the Special Issue Crystalline Materials: Polymorphism)

► Show Figures

Figure 1

12 pages, 1702 KiB

Open AccessArticle

Two Crystal Forms of 4′-Methyl-2,4-dinitrodiphenylamine: Polymorphism Governed by Conformational Flexibility of a Supramolecular Synthon

by Ivan V. Fedyanin and Aida I. Samigullina

Crystals 2023, 13(2), 296; https://doi.org/10.3390/cryst13020296 - 10 Feb 2023

Viewed by 1241

Abstract

Single crystals of two polymorphic forms of 4′-methyl-2,4-dinitrodiphenylamine were obtained by crystallization and characterized by X-ray diffraction analysis. One of the forms is non-centrosymmetric (space group P2₁2₁2), while the second is centrosymmetric (space group P¯1) and contains two crystallographically independent molecules in the asymmetric unit. In both forms, the same supramolecular synthon, a dimer linked by bonding N-H···O, O···O, and C-H···O interactions were found. Despite nearly the same connectivity of the bonding interactions, the conformation of the supramolecular synthon is different, including its unavoidably different symmetry in two polymorphs. The comparison of the crystal packing of the orthorhombic polymorph with that of the related 2,4-dinitrodiphenylamine (space group P2₁/n) shows the quasi-isostructurality of the fragments, infinite π-stacks joined by weak non-directional intermolecular interactions. However, the fragments are linked by the supramolecular synthons via either a two-fold axis or an inversion center, which lead to only the partial isostructurality of the crystals. Full article

(This article belongs to the Special Issue Crystalline Materials: Polymorphism)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Crystalline Materials: Polymorphism

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (6 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI