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Molecular Crystals: Structures, Physicalities, and Behaviors (or Dynamics)

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Chemistry".

Deadline for manuscript submissions: closed (30 June 2020) | Viewed by 15066

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Special Issue Editor

Prof. Dr. Hyuma Masu

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Guest Editor

Chemical Analysis Center, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
Interests: organic crystal; chirality; molecular network; phase transition

Special Issue Information

Dear Colleagues,

Molecular crystals from organic or organometallic compounds are important targets of research and development in material science and pharmaceutical science, because they provide extremely various structures and properties from simple components with multimodal inter- or intramolecular interactions.
Therefore, this Special Issue aims to illustrate the most recent and distinct studies of molecular crystals as viewed from organic chemistry, physicochemistry, and structural analysis.

Articles and reviews on the abovementioned topics are particularly welcome.

Prof. Dr. Hyuma Masu
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. Molecules is an international peer-reviewed open access semimonthly 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 2700 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

Organic or organometallic crystals
Distinctive structures
Polymorphism or pseudopolymorphism
Physicochemical properties
Dynamics of crystal

Published Papers (4 papers)

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Research

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12 pages, 9809 KiB

Open AccessFeature PaperArticle

Improved Water-Tree Resistances of SEBS/PP Semi-Crystalline Composites under Crystallization Modifications

by Jun-Qi Chen, Xuan Wang, Wei-Feng Sun and Hong Zhao

Molecules 2020, 25(16), 3669; https://doi.org/10.3390/molecules25163669 - 12 Aug 2020

Cited by 5 | Viewed by 2408

Abstract

Water-tree resistances of styrene block copolymer/polypropylene (SEBS/PP) composites are investigated by characterizing crystallization structures in correlation with the dynamic mechanical properties to elucidate the micro-structure mechanism of improving insulation performances, in which the accelerated aging experiments of water trees are performed with water-knife electrodes. The water-tree morphology in spherulites, melt-crystallization characteristics and lamella structures of the composite materials are observed and analyzed by polarizing microscopy (PLM), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. Dynamic relaxation and stress-strain characteristics are specifically studied by means of a dynamic thermomechanical analyzer (DMA) and electronic tension machine, respectively. No water-tree aging occurs in both the highly crystalline PP and the noncrystalline SEBS elastomer, while the water trees arising in SEBS/PP composites still has a significantly lower size than that in low-density polyethylene (LDPE). Compared with LDPE, the PP matrix of the SEBS/PP composite represent a higher crystallinity with a larger crystallization size in consistence with its higher mechanical strength and lower dynamic relaxation loss. SEBS molecules agglomerate as a “island” phase, and PP molecules crystallize into thin and short lamellae in composites, leading to the blurred spherulite boundary and the appreciable slips between lamellae under external force. The high crystallinity of the PP matrix and the strong resistance to slips between lamellae in the SEBS/PP composite essentially account for the remarkable inhibition on water-tree growth. Full article

(This article belongs to the Special Issue Molecular Crystals: Structures, Physicalities, and Behaviors (or Dynamics))

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12 pages, 1609 KiB

Open AccessArticle

Structural Basis for Broad Substrate Selectivity of Alcohol Dehydrogenase YjgB from Escherichia coli

by Giang Thu Nguyen, Yeon-Gil Kim, Jae-Woo Ahn and Jeong Ho Chang

Molecules 2020, 25(10), 2404; https://doi.org/10.3390/molecules25102404 - 21 May 2020

Cited by 3 | Viewed by 3447

Abstract

In metabolic engineering and synthetic biology fields, there have been efforts to produce variable bioalcohol fuels, such as isobutanol and 2-phenylethanol, in order to meet industrial demands. YjgB is an aldehyde dehydrogenase from Escherichia coli that shows nicotinamide adenine dinucleotide phosphate (NADP)-dependent broad selectivity for aldehyde derivatives with an aromatic ring or small aliphatic chain. This could contribute to the design of industrial synthetic pathways. We determined the crystal structures of YjgB for both its apo-form and NADP-complexed form at resolutions of 1.55 and 2.00 Å, respectively, in order to understand the mechanism of broad substrate selectivity. The hydrophobic pocket of the active site and the nicotinamide ring of NADP(H) are both involved in conferring its broad specificity toward aldehyde substrates. In addition, based on docking-simulation data, we inferred that π–π stacking between substrates and aromatic side chains might play a crucial role in recognizing substrates. Our structural analysis of YjgB might provide insights into establishing frameworks to understand its broad substrate specificity and develop engineered enzymes for industrial biofuel synthesis. Full article

(This article belongs to the Special Issue Molecular Crystals: Structures, Physicalities, and Behaviors (or Dynamics))

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Graphical abstract

13 pages, 1494 KiB

Open AccessArticle

Can We Predict the Pressure Induced Phase Transition of Urea? Application of Quantum Molecular Dynamics

by Anna Mazurek, Łukasz Szeleszczuk and Dariusz Maciej Pisklak

Molecules 2020, 25(7), 1584; https://doi.org/10.3390/molecules25071584 - 30 Mar 2020

Cited by 13 | Viewed by 3247

Abstract

Crystalline urea undergoes polymorphic phase transition induced by high pressure. Form I, which is the most stable form at normal conditions and Form IV, which is the most stable form at 3.10 GPa, not only crystallize in various crystal systems but also differ significantly in the unit cell dimensions. The aim of this study was to determine if it is possible to predict polymorphic phase transitions by optimizing Form I at high pressure and Form IV at low pressure. To achieve this aim, a large number of periodic density functional theory (DFT) calculations were performed using CASTEP. After geometry optimization of Form IV at 0 GPa Form I was obtained, performing energy minimization of Form I at high pressure did not result in Form IV. However, employing quantum molecular isothermal–isobaric (NPT) dynamics calculations enabled to accurately predict this high-pressure transformation. This study shows the potential of different approaches in predicting the polymorphic phase transition and points to the key factors that are necessary to achieve the success. Full article

(This article belongs to the Special Issue Molecular Crystals: Structures, Physicalities, and Behaviors (or Dynamics))

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Review

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19 pages, 7507 KiB

Open AccessReview

Advances in the Synthesis of Ferrierite Zeolite

by Hao Xu, Jie Zhu, Longfeng Zhu, Enmu Zhou and Chao Shen

Molecules 2020, 25(16), 3722; https://doi.org/10.3390/molecules25163722 - 14 Aug 2020

Cited by 15 | Viewed by 5313

Abstract

As one of the most important porous materials, zeolites with intricate micropores have been widely employed as catalysts for decades due to their large pore volume, high surface area, and good thermal and hydrothermal stabilities. Among them, ferrierite (FER) zeolite with a two-dimensional micropore structure is an excellent heterogeneous catalyst for isomerization, carbonylation, cracking, and so on. In the past years, considering the important industrial application of FER zeolite, great efforts have been made to improve the synthesis of FER zeolite and thus decrease the synthesis cost and enhance catalytic performance. In this review, we briefly summarize the advances in the synthesis of FER zeolite including the development of synthesis routes, the use of organic templates, organotemplate-free synthesis, the strategies of morphology control, and the creation of intra-crystalline mesopores. Furthermore, the synthesis of hetero-atomic FER zeolites such as Fe-FER and Ti-FER has been discussed. Full article

(This article belongs to the Special Issue Molecular Crystals: Structures, Physicalities, and Behaviors (or Dynamics))

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