Special Issue "Polymorphism in Crystals"

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

Deadline for manuscript submissions: 31 December 2019.

Special Issue Editors

Guest Editor
Prof. Dr. Mirta Rubčić Website E-Mail
Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia
Interests: supramolecular chemistry; tautomerism; chemical crystallography; coordination chemistry; mechanochemistry; polyoxometalates
Guest Editor
Prof. Dr. Ivica Đilović Website E-Mail
Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia
Interests: anion receptors; supramolecular chemistry; chemical crystallography; coordination chemistry

Special Issue Information

Dear Colleagues,

Polymorphism, as a ubiquitous phenomenon where the same chemical entities comprise different solid-state architectures by virtue of their different spatial arrangement and intermolecular connectivity, has been intriguing scientists for more than a century. It is always fascinating to observe how the same building blocks, whether they are single constituents, ionic pairs or multicomponent systems like cocrystals or solvates, can produce a variety of solid phases with unique properties. Therefore, it is not surprising that this phenomenon, and its various aspects, have received considerable attention both in the academic community and industry. Despite recent advances in methodology and technology, with the experience accumulated over the past decades, some features of polymorphism remain puzzling even today. We strongly believe that the combination of traditional (diffraction and thermodynamics) and cutting-edge methods (quantum mechanical modelling and NMR crystallography) will undoubtedly open new venues in the structural landscape of polymorphs, providing completely new perspectives and rationales regarding structure–property relationships. Even though we are still not able to predict the exact number of polymorphs for a particular system, every comprehensively investigated example brings us one step closer to this goal. With that in mind, with the armoury of developed methods and techniques, we are certainly on the right path. Through this issue we would like to highlight the importance of polymorphism in everyday life and to address how new approaches can help in the quest of finding new polymorphic forms.

Prof. Dr. Mirta Rubčić
Prof. Dr. Ivica Đilović
Guest Editors

Manuscript Submission Information

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Keywords

  • polymorphism
  • supramolecular chemistry
  • computational modelling
  • mechanochemistry
  • physical properties
  • diffraction methods
  • solid-state NMR
  • thermodynamics

Published Papers (3 papers)

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Research

Open AccessArticle
Synthesis, Characterization, and Crystal Structure Determination of a New Lithium Zinc Iodate Polymorph LiZn(IO3)3
Crystals 2019, 9(9), 464; https://doi.org/10.3390/cryst9090464 - 04 Sep 2019
Abstract
Synthesis and characterization of anhydrous LiZn(IO3)3 powders prepared from an aqueous solution are reported. Morphological and compositional analyses were carried out by using scanning electron microscopy and energy-dispersive X-ray measurements. The synthesized powders exhibited a needle-like morphology after annealing at [...] Read more.
Synthesis and characterization of anhydrous LiZn(IO3)3 powders prepared from an aqueous solution are reported. Morphological and compositional analyses were carried out by using scanning electron microscopy and energy-dispersive X-ray measurements. The synthesized powders exhibited a needle-like morphology after annealing at 400 °C. A crystal structure for the synthesized compound was proposed from powder X-ray diffraction and density-functional theory calculations. Rietveld refinements led to a monoclinic structure, which can be described with space group P21, number 4, and unit-cell parameters a = 21.874(9) Å, b = 5.171(2) Å, c = 5.433(2) Å, and  = 120.93(4)°. Density-functional theory calculations supported the same crystal structure. Infrared spectra were also collected, and the vibrations associated with the different modes were discussed. The non-centrosymmetric space group determined for this new polymorph of LiZn(IO3)3, the characteristics of its infrared absorption spectrum, and the observed second-harmonic generation suggest it is a promising infrared non-linear optical material. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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Open AccessArticle
Polymorph Selection of ROY by Flow-Driven Crystallization
Crystals 2019, 9(7), 351; https://doi.org/10.3390/cryst9070351 - 09 Jul 2019
Abstract
The selection of polymorphs of the organic compound 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, ROY, is studied experimentally in the confined space between two horizontal glass plates when an acetone solution of ROY of variable concentration is injected at a variable flow rate into water. Depending on the [...] Read more.
The selection of polymorphs of the organic compound 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, ROY, is studied experimentally in the confined space between two horizontal glass plates when an acetone solution of ROY of variable concentration is injected at a variable flow rate into water. Depending on the local concentration within the radial flow, a polymorph selection is observed such that red prisms are favored close to the injection center while yellow needles are the preferred polymorph close to the edge of the injected ROY domain. At larger flow rates, a buoyancy-driven instability induces stripes at the outer edge of the displacement pattern, in which specific polymorphs are seen to crystallize. Our results evidence the possibility of a selection of ROY polymorph structures in out-of-equilibrium flow conditions. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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Open AccessArticle
Crystal Structure Optimization and Gibbs Free Energy Comparison of Five Sulfathiazole Polymorphs by the Embedded Fragment QM Method at the DFT Level
Crystals 2019, 9(5), 256; https://doi.org/10.3390/cryst9050256 - 17 May 2019
Abstract
Molecular crystal plays an important role in many fields of science and technology, but it often crystallizes in different polymorphs with different physical properties. To guide the experimental synthesis of candidate materials, the atomic-scale model is frequently used to predict the most stable [...] Read more.
Molecular crystal plays an important role in many fields of science and technology, but it often crystallizes in different polymorphs with different physical properties. To guide the experimental synthesis of candidate materials, the atomic-scale model is frequently used to predict the most stable polymorph and its structural properties. Here, we show how an ab initio method can be used to achieve a rapid and accurate prediction of sulfathiazole crystal polymorphs (an antibiotic drug), based on the Gibbs free energy calculation and Raman spectra analysis. At the atmospheric pressure and the temperature of 300 K, we demonstrate that form III (FIII) is the most stable structure of sulfathiazole. The agreement between the predicted and experimental crystal structures corresponds to the order of stability for five sulfathiazole polymorphs as FI < FV < FIV < FII < FIII, which is achieved by employing the density functional theory (DFT) calculations. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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