Special Issue "Structure, Properties and Behavior of Solid Materials Explored by In-Silico and Experimental Methods"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Organic Crystalline Materials".

Deadline for manuscript submissions: closed (30 June 2020).

Special Issue Editor

Prof. Dr. Paola Paoli
E-Mail Website
Guest Editor
Department of Industrial Engineering, University of Florence, via S. Marta 3, 50139 Florence, Italy
Interests: single crystal and microcrystalline powder X-ray diffraction; computational chemistry; molecular and crystal structures of organic compounds, API and metal complexes; structure-property relationships; supramolecular chemistry; phase transitions; polymorphism

Special Issue Information

Dear Colleagues,

It is well known that the structure and properties of a given substance are closely related to each other, therefore the knowledge of the molecular and crystal arrangement is often a fundamental prerequisite to account for its properties and behavior, be it a metal complex, an active pharmaceutical ingredient (including its solvates, co-crystals, salts and formulations) or, more in general, the fundamental constituent of a material with given chemical–physical properties and functions. Then this knowledge can be exploited for purpose-driven (selective recognition, catalysis, transport, chemosensing, gas-storage, etc.) design and synthesis of new chemical species. In this context, diffraction, microscopic, thermal and spectroscopic techniques, just to name a few, are very popular and largely used for the investigation of solid forms and, when used jointly, they provide an almost complete picture of a solid. On the other hand, in-silico studies (including crystal structure prediction methods, Monte Carlo and molecular dynamics simulations, and quantum chemical calculations, to name but a few) are a source of additional information (e.g. energy landscape, dynamic behavior, electronic features, etc.) that often complement and supplement experimental data allowing for new insights.

This Special Issue aims at gathering research articles in which experiments and modeling are used as a synergistic complementary approach to assessing the structure, properties and behavior of solid materials. Contributions should focus on the strength of a tandem approach (experimental and theoretical) in addressing the large variety of issues and problems related to solid forms.

Prof. Dr. Paola Paoli
Guest Editor

Manuscript Submission Information

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Keywords

  • Molecular and crystal structure of materials
  • Computational methods
  • Structure-property relationships

Published Papers (6 papers)

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Research

Open AccessArticle
A Combined Crystallographic and Computational Study on Dexketoprofen Trometamol Dihydrate Salt
Crystals 2020, 10(8), 659; https://doi.org/10.3390/cryst10080659 - 31 Jul 2020
Cited by 1 | Viewed by 592
Abstract
Dexketoprofen trometamol is the tromethamine salt of dexketoprofen [(2S)-2-(3-benzoylphenyl)propanoic acid-2-amino-2-(hydroxymethyl)propane-1,3-diol], a nonsteroidal anti-inflammatory drug (NSAID) used for the treatment of moderate- to strong-intensity acute pain. The crystal structure of the hitherto sole known hydrate phase of dexketoprofen trometamol (DK-T_2H2O), [...] Read more.
Dexketoprofen trometamol is the tromethamine salt of dexketoprofen [(2S)-2-(3-benzoylphenyl)propanoic acid-2-amino-2-(hydroxymethyl)propane-1,3-diol], a nonsteroidal anti-inflammatory drug (NSAID) used for the treatment of moderate- to strong-intensity acute pain. The crystal structure of the hitherto sole known hydrate phase of dexketoprofen trometamol (DK-T_2H2O), as determined by single-crystal X-ray diffraction, is presented. The water molecules are arranged in dimers included in isolated sites and sandwiched between piles of trometamol cations. The molecular and crystal structures of DK-T_2H2O are analyzed and compared to those of the parent anhydrous crystal form DK-T_A. In both the crystal structures, all the potential H-bond donors and acceptor of the dexketoprofen and trometamol ions are engaged, and both the species crystallize in the P21 space group. However, during the DK-T_ADK-T_2H2O hydration process, the unique symmetry axis is not conserved, i.e., the ions are arranged in a different way with respect to the screw axis, even if the two crystal structures maintain structural blocks of DK anions and T cations. Quantum mechanical solid-state calculations provide some hints for the possible intermediate structure during the crystalline–crystalline hydration/dehydration process. Full article
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Open AccessArticle
Magnetic and Luminescent Properties of Isostructural 2D Coordination Polymers Based on 2-Pyrimidinecarboxylate and Lanthanide Ions
Crystals 2020, 10(7), 571; https://doi.org/10.3390/cryst10070571 - 02 Jul 2020
Cited by 1 | Viewed by 614
Abstract
A couple of isostructural coordination polymers with the general formula [Ln4(pymca)4(AcO)8]n have been obtained from reactions between pyrimidine-2-carboxylate (pymca) ligand and rare-earth ions (Ln = Dy (1), Nd (2)). These two-dimensional compounds [...] Read more.
A couple of isostructural coordination polymers with the general formula [Ln4(pymca)4(AcO)8]n have been obtained from reactions between pyrimidine-2-carboxylate (pymca) ligand and rare-earth ions (Ln = Dy (1), Nd (2)). These two-dimensional compounds have been characterized and the crystal structures have been solved by single-crystal X-ray diffraction technique, resulting in layers along the bc plane based on pymca and acetate anions that act as bridging ligands between metal atoms. Given that pymca and acetate anions possess carboxylate and hetero-nitrogen groups, it is possible to build a coordination polymer whose metal centers have a nine coordination. Furthermore, static and dynamic magnetic measurements of compound 1 reveal the lack of single molecule-magnet (SMM) behavior in this system due to the following two effects: (i) the ligand field does not stabilize magnetic ground states well separated from excited states, and (ii) anisotropy axes are not collinear, according to results with Magellan software. On another level, luminescent properties of compounds 1 and 2 are attributed to singlet π-π* transitions centered on pymca ligand as corroborated by time-dependent density functional theory (TD-DFT) calculations. Full article
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Open AccessArticle
Unravelling the Chemistry of the [Cu(4,7-Dichloroquinoline)2Br2]2 Dimeric Complex through Structural Analysis: A Borderline Ligand Field Case
Crystals 2020, 10(6), 477; https://doi.org/10.3390/cryst10060477 - 04 Jun 2020
Cited by 2 | Viewed by 719
Abstract
Large dark prismatic crystals (P 1 ¯ ) consisting of closely packed centrosymmetric [Cu(4,7-dichloroquinoline)2]2Br4 binuclear units are formed when 4,7-dichloroquinoline (DCQ, C9H5NCl2) binds copper(II). Cu2+ adopts a strongly distorted square pyramidal coordination geometry, perturbed by electrostatic interactions with two axial μ–Br ligands acting as highly asymmetric bridges. It is shown that, as electronic states of ligands are higher in energy than the metal ones, antibonding orbitals bear significant ligand-like character and electronic charge is partially transferred from inner-sphere coordinated halogen atoms to copper. Overall, the title compound sits on the Hoffman’s border between main group and transition chemistry, with non-negligible contributions of the ligands to the frontier orbitals. The relative energy placement of metal and ligand states determines an internal redox process, where the metal is slightly reduced at the expense of partial oxidation of the bromide ligands. In fact, the crystal structure is partially disordered due to the substitution of some penta-coordinated Cu(II) centers with tetra-coordinated Cu(I) ions. The geometry of the complex is rationalized in terms of electrostatic-driven distortions from an ideal octahedral prototype. Implications on the reactivity of Cu(II)–quinoline complexes are discussed. Full article
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Open AccessArticle
Rationalization of Lattice Thermal Expansion for Beta-Blocker Organic Crystals
Crystals 2020, 10(5), 350; https://doi.org/10.3390/cryst10050350 - 29 Apr 2020
Cited by 2 | Viewed by 615
Abstract
Anisotropic lattice expansion could be a source of misunderstanding in powder pattern recognitions, especially in the case of organic crystals where for the interpretation of room temperature patterns single crystal data at low temperature are usually used. Trying to rationalize the thermal lattice [...] Read more.
Anisotropic lattice expansion could be a source of misunderstanding in powder pattern recognitions, especially in the case of organic crystals where for the interpretation of room temperature patterns single crystal data at low temperature are usually used. Trying to rationalize the thermal lattice expansion, we studied two close related β-blocker molecules with similar packing in the solid state but with different thermal behavior. Solid state calculations, using the fast and accurate HF-3c method and the quasi harmonic approximation for the simulation of the lattice expansion, were able to reproduce the experimental trends with good accuracy. The complete analysis of the calculated thermal expansion of the two structures, as well as of other structures with similar packing found in a database survey, revealed the primary role of the hydrogen bonds. Secondary non-covalent interactions in the plane perpendicular to the hydrogen bond system could also play a role. Full article
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Open AccessArticle
Investigating Differences and Similarities between Betaxolol Polymorphs
Crystals 2019, 9(10), 509; https://doi.org/10.3390/cryst9100509 - 29 Sep 2019
Cited by 3 | Viewed by 1345
Abstract
Betaxolol belongs to the class of β1-adrenergic blocking agent. Several polymorphs of racemic betaxolol have been reported in the literature, but only one of them (BE_I) had the crystal structure determined from single-crystal X-ray diffraction. Here, we present a new crystalline [...] Read more.
Betaxolol belongs to the class of β1-adrenergic blocking agent. Several polymorphs of racemic betaxolol have been reported in the literature, but only one of them (BE_I) had the crystal structure determined from single-crystal X-ray diffraction. Here, we present a new crystalline phase of betaxolol (BE_IV). Its solid-state structure has been obtained from single-crystal X-ray diffraction data. The molecular and crystal arrangements of betaxolol in BE_IV have been further investigated by molecular modelling, by Cambridge Structural Database (CSD) surveys and by Hirshfeld surface analysis. A comparison with the solid-state structure of BE_I have been carried out. In the two polymorphs the 2-hydroxy-3-(isopropylamino)-propoxy chain, which is common to other β-blocker drugs, adopts a different conformation. In addition, the rotational isomer found in BE_IV is different with respect to the four already observed in the solid-state structure of analogous compounds. In both the polymorphs, the most significant interaction is due to the H-bonds involving the OH group as donor and the NH as acceptor, while the interaction where OH works as acceptor (NH acts as donor) is definitely less important. The resulting H-bond patterns are however different: Alternate R2,2(10) a > a (OH donors) and R2,2(10) b > b (OH acceptors) in BE_I vs. alternate R4,4 (8) a > b > a > b (OH donors) and R2,2 (10) b > b (OH acceptor) in BE_IV. Full article
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Open AccessArticle
Crystal Structure and Mechanical Properties of ThBC2
Crystals 2019, 9(8), 389; https://doi.org/10.3390/cryst9080389 - 29 Jul 2019
Viewed by 1414
Abstract
Thorium borocarbide compounds have fascinating physical properties and diverse structures, and hence have stimulated great interest. In this work, we determine the ground state structure of ThBC2 by the unbiased structure prediction method based on first-principles calculations. The dynamical and elastic stabilities [...] Read more.
Thorium borocarbide compounds have fascinating physical properties and diverse structures, and hence have stimulated great interest. In this work, we determine the ground state structure of ThBC2 by the unbiased structure prediction method based on first-principles calculations. The dynamical and elastic stabilities of our proposed ThBC2 are verified by the calculations of phonon spectrum and elastic constants. To study the mechanical properties fundamentally, we estimated the elastic anisotropy of ThBC2. The results show that the Young’s and shear moduli possess high degree of anisotropy. The ideal strength calculations reveal that ThBC2 readily collapses upon applied stress due to small ideal strengths. The cleavage fracture probably occurs along the [111] direction while slip may easily appear along the [ 1 ¯ 10 ] direction on the (111) plane for ThBC2. In addition, we provide an atomic explanation for the different characteristics of the strain–stress curves under different strains. Full article
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