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

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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) | Viewed by 18419

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Prof. Dr. Paola Paoli

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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
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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

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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.

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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

14 pages, 3968 KiB

Open AccessArticle

A Combined Crystallographic and Computational Study on Dexketoprofen Trometamol Dihydrate Salt

by Patrizia Rossi, Paola Paoli, Stella Milazzo, Laura Chelazzi, Maria Paola Giovannoni, Gabriella Guerrini, Andrea Ienco, Maurizio Valleri and Luca Conti

Crystals 2020, 10(8), 659; https://doi.org/10.3390/cryst10080659 - 31 Jul 2020

Cited by 6 | Viewed by 2680

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), 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_A➔DK-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

(This article belongs to the Special Issue Structure, Properties and Behavior of Solid Materials Explored by In-Silico and Experimental Methods)

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12 pages, 3566 KiB

Open AccessArticle

Magnetic and Luminescent Properties of Isostructural 2D Coordination Polymers Based on 2-Pyrimidinecarboxylate and Lanthanide Ions

by Amalia García-García, Andoni Zabala-Lekuona, Ainhoa Goñi-Cárdenas, Javier Cepeda, José M. Seco, Alfonso Salinas-Castillo, Duane Choquesillo-Lazarte and Antonio Rodríguez-Diéguez

Crystals 2020, 10(7), 571; https://doi.org/10.3390/cryst10070571 - 02 Jul 2020

Cited by 5 | Viewed by 2294

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 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

(This article belongs to the Special Issue Structure, Properties and Behavior of Solid Materials Explored by In-Silico and Experimental Methods)

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16 pages, 2945 KiB

Open AccessArticle

Unravelling the Chemistry of the [Cu(4,7-Dichloroquinoline)₂Br₂]₂ Dimeric Complex through Structural Analysis: A Borderline Ligand Field Case

by Giada Finocchio, Silvia Rizzato, Giovanni Macetti, Gers Tusha and Leonardo Lo Presti

Crystals 2020, 10(6), 477; https://doi.org/10.3390/cryst10060477 - 04 Jun 2020

Cited by 3 | Viewed by 3453

Abstract

Large dark prismatic crystals (P

\bar{1}

Large dark prismatic crystals (P

\bar{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

(This article belongs to the Special Issue Structure, Properties and Behavior of Solid Materials Explored by In-Silico and Experimental Methods)

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11 pages, 3250 KiB

Open AccessArticle

Rationalization of Lattice Thermal Expansion for Beta-Blocker Organic Crystals

by Paola Paoli, Stella Milazzo, Patrizia Rossi and Andrea Ienco

Crystals 2020, 10(5), 350; https://doi.org/10.3390/cryst10050350 - 29 Apr 2020

Cited by 6 | Viewed by 2128

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 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

(This article belongs to the Special Issue Structure, Properties and Behavior of Solid Materials Explored by In-Silico and Experimental Methods)

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13 pages, 2711 KiB

Open AccessArticle

Investigating Differences and Similarities between Betaxolol Polymorphs

by Patrizia Rossi, Paola Paoli, Stella Milazzo, Laura Chelazzi, Andrea Ienco and Luca Conti

Crystals 2019, 9(10), 509; https://doi.org/10.3390/cryst9100509 - 29 Sep 2019

Cited by 7 | Viewed by 3296

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 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

(This article belongs to the Special Issue Structure, Properties and Behavior of Solid Materials Explored by In-Silico and Experimental Methods)

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10 pages, 2200 KiB

Open AccessArticle

Crystal Structure and Mechanical Properties of ThBC₂

by Xinchun Zhou and Baobing Zheng

Crystals 2019, 9(8), 389; https://doi.org/10.3390/cryst9080389 - 29 Jul 2019

Cited by 2 | Viewed by 3996

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 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 [

\bar{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

(This article belongs to the Special Issue Structure, Properties and Behavior of Solid Materials Explored by In-Silico and Experimental Methods)

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