Crystals

18 pages, 3517 KB

Open AccessEditor’s ChoiceArticle

Spatio-temporal Investigations of the Incomplete Spin Transition in a Single Crystal of [Fe(2-pytrz)₂{Pt(CN)₄}]·3H₂O: Experiment and Theory

by Houcem Fourati, Guillaume Bouchez, Miguel Paez-Espejo, Smail Triki and Kamel Boukheddaden

Crystals 2019, 9(1), 46; https://doi.org/10.3390/cryst9010046 - 16 Jan 2019

Cited by 15 | Viewed by 4475

Abstract

Optical microscopy technique is used to investigate the thermal and the spatio-temporal properties of the spin-crossover single crystal [Fe(2-pytrz)

_{2}

{Pt(CN)

_{4}

}]·3H

_{2}

O, which exhibits a first-order spin transition from a full high-spin (HS) state at high temperature to an intermediate, [...] Read more.

Optical microscopy technique is used to investigate the thermal and the spatio-temporal properties of the spin-crossover single crystal [Fe(2-pytrz)

_{2}

{Pt(CN)

_{4}

}]·3H

_{2}

O, which exhibits a first-order spin transition from a full high-spin (HS) state at high temperature to an intermediate, high-spin low-spin (HS-LS) state, below 153 K, where only one of the two crystallographic Fe(II) centers switches from the HS to HS-LS state. In comparison with crystals undergoing a complete spin transition, the present transformation involves smaller volume changes at the transition, which helps to preserving the crystal’s integrity. By analyzing the spatio-temporal properties of this spin transition, we evidenced a direct correlation between the orientation and shape of HS/HS-LS domain wall with the crystal’s shape. Thanks to the small volume change accompanying this spin transition, the analysis of the experimental data by an anisotropic reaction-diffusion model becomes very relevant and leads to an excellent agreement with the experimental observations. Full article

(This article belongs to the Special Issue Synthesis and Applications of New Spin Crossover Compounds)

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10 pages, 3859 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Tripling the Optical Efficiency of Color-Converted Micro-LED Displays with Funnel-Tube Array

by Fangwang Gou, En-Lin Hsiang, Guanjun Tan, Yi-Fen Lan, Cheng-Yeh Tsai and Shin-Tson Wu

Crystals 2019, 9(1), 39; https://doi.org/10.3390/cryst9010039 - 14 Jan 2019

Cited by 62 | Viewed by 11744

Abstract

Color-converted micro-LED displays consist of a mono-color micro-LED array and color conversion materials to achieve full color, while relieving the burden of epitaxial growth of three-color micro-LEDs. However, it usually suffers from low efficiency and color crosstalk due to the limited optical density [...] Read more.

Color-converted micro-LED displays consist of a mono-color micro-LED array and color conversion materials to achieve full color, while relieving the burden of epitaxial growth of three-color micro-LEDs. However, it usually suffers from low efficiency and color crosstalk due to the limited optical density of color conversion materials. With funnel-tube array, the optical efficiency of the color-converted micro-LED display can be improved by ~3X, while the crosstalk is eliminated. After optimization of the tapper angle, the ambient contrast ratio is also improved due to higher light intensity. Full article

(This article belongs to the Special Issue Advanced LED Solid-State Lighting Optics)

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16 pages, 667 KB

Open AccessEditor’s ChoiceReview

Peculiarities of Protein Crystal Nucleation and Growth

by Christo N. Nanev

Crystals 2018, 8(11), 422; https://doi.org/10.3390/cryst8110422 - 8 Nov 2018

Cited by 12 | Viewed by 5861

Abstract

This paper reviews investigations on protein crystallization. It aims to present a comprehensive rather than complete account of recent studies and efforts to elucidate the most intimate mechanisms of protein crystal nucleation. It is emphasized that both physical and biochemical factors are at [...] Read more.

This paper reviews investigations on protein crystallization. It aims to present a comprehensive rather than complete account of recent studies and efforts to elucidate the most intimate mechanisms of protein crystal nucleation. It is emphasized that both physical and biochemical factors are at play during this process. Recently-discovered molecular scale pathways for protein crystal nucleation are considered first. The bond selection during protein crystal lattice formation, which is a typical biochemically-conditioned peculiarity of the crystallization process, is revisited. Novel approaches allow us to quantitatively describe some protein crystallization cases. Additional light is shed on the protein crystal nucleation in pores and crevices by employing the so-called EBDE method (equilibration between crystal bond and destructive energies). Also, protein crystal nucleation in solution flow is considered. Full article

(This article belongs to the Special Issue Biological Crystallization)

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14 pages, 2116 KB

Open AccessFeature PaperEditor’s ChoiceArticle

NMR Crystallography of the Polymorphs of Metergoline

by Jiri Czernek, Martina Urbanova and Jiri Brus

Crystals 2018, 8(10), 378; https://doi.org/10.3390/cryst8100378 - 25 Sep 2018

Cited by 17 | Viewed by 5008

Abstract

Two polymorphs of the drug compound metergoline (C₂₅H₂₉N₃O₂) were investigated in detail by solid-state NMR measurements. The results have been analysed by an advanced procedure, which uses experimental input together with the results of quantum [...] Read more.

Two polymorphs of the drug compound metergoline (C₂₅H₂₉N₃O₂) were investigated in detail by solid-state NMR measurements. The results have been analysed by an advanced procedure, which uses experimental input together with the results of quantum chemical calculations that were performed for molecular crystals. In this way, it was possible to assign the total of 40 ¹H–¹³C correlation pairs in a highly complex system, namely, in the dynamically disordered polymorph with two independent molecules in the unit cell of a large volume of 4234 Å³. For the simpler polymorph, which exhibits only small-amplitude motions and has just one molecule in the unit cell with a volume of 529.0 Å³, the values of the principal elements of the ¹³C chemical shift tensors were measured. Additionally, for this polymorph, a set of crystal structure predictions were generated, and the {¹³C, ¹H} isotropic and ¹³C anisotropic chemical shielding data were computed while using the gauge-including projector augmented-wave approach combined with the “revised Perdew-Burke-Ernzerhof“ exchange-correlation functional (GIPAW-RPBE). The experimental and theoretical results were combined in an application of the newly developed strategy to polymorph discrimination. This research thus opens up new routes towards more accurate characterization of the polymorphism of drug formulations. Full article

(This article belongs to the Special Issue NMR Crystallography)

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26 pages, 4591 KB

Open AccessEditor’s ChoiceReview

The Crystal Orbital Hamilton Population (COHP) Method as a Tool to Visualize and Analyze Chemical Bonding in Intermetallic Compounds

by Simon Steinberg and Richard Dronskowski

Crystals 2018, 8(5), 225; https://doi.org/10.3390/cryst8050225 - 18 May 2018

Cited by 284 | Viewed by 22058

Abstract

Recognizing the bonding situations in chemical compounds is of fundamental interest for materials design because this very knowledge allows us to understand the sheer existence of a material and the structural arrangement of its constituting atoms. Since its definition 25 years ago, the [...] Read more.

Recognizing the bonding situations in chemical compounds is of fundamental interest for materials design because this very knowledge allows us to understand the sheer existence of a material and the structural arrangement of its constituting atoms. Since its definition 25 years ago, the Crystal Orbital Hamilton Population (COHP) method has been established as an efficient and reliable tool to extract the chemical-bonding information based on electronic-structure calculations of various quantum-chemical types. In this review, we present a brief introduction into the theoretical background of the COHP method and illustrate the latter by diverse applications, in particular by looking at representatives of the class of (polar) intermetallic compounds, usually considered as “black sheep” in the light of valence-electron counting schemes. Full article

(This article belongs to the Special Issue Compounds with Polar Metallic Bonding)

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19 pages, 44833 KB

Open AccessEditor’s ChoiceArticle

Tuning of Luminescent and Magnetic Properties via Metal Doping of Zn-BTC Systems

by Taoguang Qu, Qiang Wei, Carlos Ordonez, Jennifer Lindline, Michael Petronis, Marina S. Fonari and Tatiana Timofeeva

Crystals 2018, 8(4), 162; https://doi.org/10.3390/cryst8040162 - 8 Apr 2018

Cited by 7 | Viewed by 6664

Abstract

In order to assess how metal doping affects the luminescence and magnetic properties of anionic Metal-Organic Frameworks (MOFs), seven single-metal doped MOFs {M-Zn-BTC}{Me₂NH₂⁺} (M = Co, Cu, Ni, Mn, Ca, Mg, Cd) and three dual-metal doped MOFs {Zn-M [...] Read more.

In order to assess how metal doping affects the luminescence and magnetic properties of anionic Metal-Organic Frameworks (MOFs), seven single-metal doped MOFs {M-Zn-BTC}{Me₂NH₂⁺} (M = Co, Cu, Ni, Mn, Ca, Mg, Cd) and three dual-metal doped MOFs {Zn-M₁-M₂-BTC}{Me₂NH₂⁺} (M₁ = Co, Cu; M₂ = Ni, Co) were synthesized. Trace amounts of different metals were doped via addition of another metal salt during the synthetic process. All compounds retained the same crystal structure as that of the parent {Zn-BTC}{Me₂NH₂⁺} MOF, which was supported by single crystal and powder X-ray diffraction studies. Thermal Gravimetric Analysis (TGA) of these compounds also revealed that all MOFs had similar stability up to ~450 °C. Solid state photoluminescent studies indicated that {Zn-Mn-BTC}{Me₂NH₂⁺}, {Zn-Cd-BTC}{Me₂NH₂⁺}, and {Zn-Ca-BTC}{Me₂NH₂⁺} had a significant red shifting effect compared to the original {Zn-BTC}{Me₂NH₂⁺} MOF. Applications of this doping method to other MOF systems can provide an efficient way to tune the luminescence of such systems, and to obtain a desired wavelength for several applications such as sensors and white light LED materials. Because Zn, Co, Cu, Ni, Mg have magnetic properties, the effect of the doping metal atom on the magnetism of the {Zn-BTC}{Me₂NH₂⁺} networks was also studied. To characterize the magnetic behavior of the synthesized MOFs, we conducted low-temperature (10 K) saturation remanence experiments in a 3 Tesla applied field, with the principal goal of identifying the domain state of the synthesized materials (Zn, Zn-Co, Zn-Cu-Co, Zn-Cu-Ni, Zn-Mg, Zn-Mn, Zn-Ni-Co, Zn-Ni). During room/low temperature saturation magnetization experiments, Zn, Zn-Co, Zn-Cu-Co, and Zn-Cu-Ni systems yielded data indicative of superparamagnetic behavior, yet during zero field and field cooled experiments Zn-Co showed a slight paramagnetic effect, Zn showed no temperature dependence on warming and Zn-Cu-Co and Zn-Cu-Ni demonstrated only a slight temperature dependence on warming. These behaviors are consistent with ferromagnetic ordering. Zero field and field cooled experiments indicate that Zn-Mg and Zn-Ni have a ferromagnetic ordering and Zn-Mn and Zn-Ni-Co show paramagnetic ordering behavior. Full article

(This article belongs to the Special Issue Crystal Structure Analysis of Supramolecular and Porous Solids)

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13 pages, 14797 KB

Open AccessEditor’s ChoiceReview

Radiation Damage in Macromolecular Crystallography—An Experimentalist’s View

by Helena Taberman

Crystals 2018, 8(4), 157; https://doi.org/10.3390/cryst8040157 - 4 Apr 2018

Cited by 18 | Viewed by 9303

Abstract

Radiation damage still remains a major limitation and challenge in macromolecular X-ray crystallography. Some of the high-intensity radiation used for diffraction data collection experiments is absorbed by the crystals, generating free radicals. These give rise to radiation damage even at cryotemperatures (~100 K), [...] Read more.

Radiation damage still remains a major limitation and challenge in macromolecular X-ray crystallography. Some of the high-intensity radiation used for diffraction data collection experiments is absorbed by the crystals, generating free radicals. These give rise to radiation damage even at cryotemperatures (~100 K), which can lead to incorrect biological conclusions being drawn from the resulting structure, or even prevent structure solution entirely. Investigation of mitigation strategies and the effects caused by radiation damage has been extensive over the past fifteen years. Here, recent understanding of the physical and chemical phenomena of radiation damage is described, along with the global effects inflicted on the collected data and the specific effects observed in the solved structure. Furthermore, this review aims to summarise the progress made in radiation damage studies in macromolecular crystallography from the experimentalist’s point of view and to give an introduction to the current literature. Full article

(This article belongs to the Special Issue Recent Advances in Protein Crystallography)

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15 pages, 3401 KB

Open AccessEditor’s ChoiceArticle

Intra-/Intermolecular Bifurcated Chalcogen Bonding in Crystal Structure of Thiazole/Thiadiazole Derived Binuclear (Diaminocarbene)Pd^II Complexes

by Alexander S. Mikherdov, Alexander S. Novikov, Mikhail A. Kinzhalov, Andrey A. Zolotarev and Vadim P. Boyarskiy

Crystals 2018, 8(3), 112; https://doi.org/10.3390/cryst8030112 - 27 Feb 2018

Cited by 53 | Viewed by 6179

Abstract

The coupling of cis-[PdCl2(CNXyl)2] (Xyl = 2,6-Me2C6H3) with 4-phenylthiazol-2-amine in molar ratio 2:3 at RT in CH2Cl2 leads to binuclear (diaminocarbene)PdII complex 3c. The complex was characterized by HRESI+-MS, 1H NMR spectroscopy, and its structure was elucidated by single-crystal XRD. Inspection of [...] Read more.

The coupling of cis-[PdCl2(CNXyl)2] (Xyl = 2,6-Me2C6H3) with 4-phenylthiazol-2-amine in molar ratio 2:3 at RT in CH2Cl2 leads to binuclear (diaminocarbene)PdII complex 3c. The complex was characterized by HRESI+-MS, 1H NMR spectroscopy, and its structure was elucidated by single-crystal XRD. Inspection of the XRD data for 3c and for three relevant earlier obtained thiazole/thiadiazole derived binuclear diaminocarbene complexes (3a EYOVIZ; 3b: EYOWAS; 3d: EYOVOF) suggests that the structures of all these species exhibit intra-/intermolecular bifurcated chalcogen bonding (BCB). The obtained data indicate the presence of intramolecular S•••Cl chalcogen bonds in all of the structures, whereas varying of substituent in the 4th and 5th positions of the thiazaheterocyclic fragment leads to changes of the intermolecular chalcogen bonding type, viz. S•••π in 3a,b, S•••S in 3c, and S•••O in 3d. At the same time, the change of heterocyclic system (from 1,3-thiazole to 1,3,4-thiadiazole) does not affect the pattern of non-covalent interactions. Presence of such intermolecular chalcogen bonding leads to the formation of one-dimensional (1D) polymeric chains (for 3a,b), dimeric associates (for 3c), or the fixation of an acetone molecule in the hollow between two diaminocarbene complexes (for 3d) in the solid state. The Hirshfeld surface analysis for the studied X-ray structures estimated the contributions of intermolecular chalcogen bonds in crystal packing of 3a–d: S•••π (3a: 2.4%; 3b: 2.4%), S•••S (3c: less 1%), S•••O (3d: less 1%). The additionally performed DFT calculations, followed by the topological analysis of the electron density distribution within the framework of Bader’s theory (AIM method), confirm the presence of intra-/intermolecular BCB S•••Cl/S•••S in dimer of 3c taken as a model system (solid state geometry). The AIM analysis demonstrates the presence of appropriate bond critical points for these interactions and defines their strength from 0.9 to 2.8 kcal/mol indicating their attractive nature. Full article

(This article belongs to the Special Issue Chalcogen Bonding in Crystalline and Catalyst Materials)

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16 pages, 9480 KB

Open AccessEditor’s ChoiceReview

Multifunctional Aromatic Carboxylic Acids as Versatile Building Blocks for Hydrothermal Design of Coordination Polymers

by Jinzhong Gu, Min Wen, Xiaoxiao Liang, Zifa Shi, Marina V. Kirillova and Alexander M. Kirillov

Crystals 2018, 8(2), 83; https://doi.org/10.3390/cryst8020083 - 3 Feb 2018

Cited by 113 | Viewed by 9611

Abstract

Selected recent examples of coordination polymers (CPs) or metal-organic frameworks (MOFs) constructed from different multifunctional carboxylic acids with phenyl-pyridine or biphenyl cores have been discussed. Despite being still little explored in crystal engineering research, such types of semi-rigid, thermally stable, multifunctional and versatile [...] Read more.

Selected recent examples of coordination polymers (CPs) or metal-organic frameworks (MOFs) constructed from different multifunctional carboxylic acids with phenyl-pyridine or biphenyl cores have been discussed. Despite being still little explored in crystal engineering research, such types of semi-rigid, thermally stable, multifunctional and versatile carboxylic acid building blocks have become very promising toward the hydrothermal synthesis of metal-organic architectures possessing distinct structural features, topologies, and functional properties. Thus, the main aim of this mini-review has been to motivate further research toward the synthesis and application of coordination polymers assembled from polycarboxylic acids with phenyl-pyridine or biphenyl cores. The importance of different reaction parameters and hydrothermal conditions on the generation and structural types of CPs or MOFs has also been highlighted. The influence of the type of main di- or tricarboxylate ligand, nature of metal node, stoichiometry and molar ratio of reagents, temperature, and presence of auxiliary ligands or templates has been showcased. Selected examples of highly porous or luminescent CPs, compounds with unusual magnetic properties, and frameworks for selective sensing applications have been described. Full article

(This article belongs to the Special Issue Structural Design and Properties of Coordination Polymers)

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12 pages, 3731 KB

Open AccessEditor’s ChoiceArticle

A Graphene-Based Microfluidic Platform for Electrocrystallization and In Situ X-ray Diffraction

by Shuo Sui, Yuxi Wang, Christos Dimitrakopoulos and Sarah L. Perry

Crystals 2018, 8(2), 76; https://doi.org/10.3390/cryst8020076 - 1 Feb 2018

Cited by 17 | Viewed by 7256

Abstract

Here, we describe a novel microfluidic platform for use in electrocrystallization experiments. The device incorporates ultra-thin graphene-based films as electrodes and as X-ray transparent windows to enable in situ X-ray diffraction analysis. Furthermore, large-area graphene films serve as a gas barrier, creating a [...] Read more.

Here, we describe a novel microfluidic platform for use in electrocrystallization experiments. The device incorporates ultra-thin graphene-based films as electrodes and as X-ray transparent windows to enable in situ X-ray diffraction analysis. Furthermore, large-area graphene films serve as a gas barrier, creating a stable sample environment over time. We characterize different methods for fabricating graphene electrodes, and validate the electrical capabilities of our device through the use of methyl viologen, a redox-sensitive dye. Proof-of-concept electrocrystallization experiments using an internal electric field at constant potential were performed using hen egg-white lysozyme (HEWL) as a model system. We observed faster nucleation and crystal growth, as well as a higher signal-to-noise for diffraction data obtained from crystals prepared in the presence of an applied electric field. Although this work is focused on the electrocrystallization of proteins for structural biology, we anticipate that this technology should also find utility in a broad range of both X-ray technologies and other applications of microfluidic technology. Full article

(This article belongs to the Special Issue Protein Crystallization under the Presence of an Electric Field)

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14 pages, 4990 KB

Open AccessEditor’s ChoiceArticle

Prussian Blue Analogue Mesoframes for Enhanced Aqueous Sodium-ion Storage

by Huiyun Sun, Wei Zhang and Ming Hu

Crystals 2018, 8(1), 23; https://doi.org/10.3390/cryst8010023 - 7 Jan 2018

Cited by 19 | Viewed by 9138

Abstract

Mesostructure engineering is a potential avenue towards the property control of coordination polymers in addition to the traditional structure design on an atomic/molecular scale. Mesoframes, as a class of mesostructures, have short diffusion pathways for guest species and thus can be an ideal [...] Read more.

Mesostructure engineering is a potential avenue towards the property control of coordination polymers in addition to the traditional structure design on an atomic/molecular scale. Mesoframes, as a class of mesostructures, have short diffusion pathways for guest species and thus can be an ideal platform for fast storage of guest ions. We report a synthesis of Prussian Blue analogue mesoframes by top-down etching of cubic crystals. Scanning and transmission electron microscopy revealed that the surfaces of the cubic crystals were selectively removed by HCl, leaving the corners, edges, and the cores connected together. The mesoframes were used as a host for the reversible insertion of sodium ions with the help of electrochemistry. The electrochemical intercalation/de-intercalation of Na⁺ ions in the mesoframes was highly reversible even at a high rate (166.7 C), suggesting that the mesoframes could be a promising cathode material for aqueous sodium ion batteries with excellent rate performance and cycling stability. Full article

(This article belongs to the Special Issue Structural Design and Properties of Coordination Polymers)

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