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

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 17487

Special Issue Editor


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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

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Keywords

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

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Published Papers (4 papers)

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Research

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12 pages, 9809 KiB  
Article
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 8 | Viewed by 2809
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 [...] Read more.
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
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12 pages, 1609 KiB  
Article
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 7 | Viewed by 4002
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 [...] Read more.
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
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13 pages, 1494 KiB  
Article
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 14 | Viewed by 3716
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 [...] Read more.
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
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Review

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19 pages, 7507 KiB  
Review
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 18 | Viewed by 6159
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 [...] Read more.
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
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