Crystals

13 pages, 3990 KB

Open AccessReview

Coordination Networks Based on Boronate and Benzoxaborolate Ligands

by Saad Sene¹, Marie Alix Pizzoccaro¹, Joris Vezzani¹, Marc Reinholdt¹, Philippe Gaveau¹, Dorothée Berthomieu¹, Sylvie Bégu¹, Christel Gervais², Christian Bonhomme², Guillaume Renaudin^3,4, Adel Mesbah⁵, Arie Van der Lee⁶, Mark E. Smith^7,8 and Danielle Laurencin^1,*

¹ Institut Charles Gerhardt de Montpellier, UMR 5253, CNRS UM ENSCM, Montpellier 34095, France

² Laboratoire de Chimie de la Matière Condensée de Paris, UMR 7574, Sorbonne Universités, UPMC Univ Paris 06, CNRS, Collège de France, Paris 75252, France

³ Université Clermont Auvergne, SIGMA Clermont, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand, France

⁴ CNRS, UMR 6296, ICCF, F-63178 Aubière, France

⁵ Institut de Chimie Séparative de Marcoule, UMR 5257, CNRS CEA UM ENSCM, Bagnols-sur-Cèze 30207, France

⁶ Institut Européen des Membranes, CNRS-UMR 5635, UM, Montpellier 34095, France

⁷ Vice-Chancellor’s Office, University House, Lancaster University, Lancaster LA1 4YW, UK

⁸ Magnetic Resonance Centre, Department of Physics, University of Warwick, Coventry CV4 7HS, UK

Crystals 2016, 6(5), 48; https://doi.org/10.3390/cryst6050048 - 2 May 2016

Cited by 9 | Viewed by 9522

Abstract

Despite the extensive range of investigations on boronic acids (R-B(OH)₂), some aspects of their reactivity still need to be explored. This is the case for the coordination chemistry of boronate anions (R-B(OH)₃⁻), which has only recently been started [...] Read more.

Despite the extensive range of investigations on boronic acids (R-B(OH)₂), some aspects of their reactivity still need to be explored. This is the case for the coordination chemistry of boronate anions (R-B(OH)₃⁻), which has only recently been started to be studied. The purpose of this review is to summarize some of the key features of boronate ligands (and of their cyclic derivatives, benzoxaborolates) in materials: (i) coordination properties; (ii) spectroscopic signatures; and (iii) emerging applications. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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16 pages, 3129 KB

Open AccessArticle

The Role of Coulomb Interactions for Spin Crossover Behaviors and Crystal Structural Transformation in Novel Anionic Fe(III) Complexes from a π-Extended ONO Ligand

by Suguru Murata¹, Kazuyuki Takahashi^1,*

, Takahiro Sakurai², Hitoshi Ohta³, Takashi Yamamoto⁴, Yasuaki Einaga⁴, Yoshihito Shiota⁵ and Kazunari Yoshizawa⁵

¹ Department of Chemistry, Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, Hyogo 657-8501, Japan

² Center for Support of Education and Research Activities, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, Hyogo 657-8501, Japan

³ Molecular Photoscience Research Center, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, Hyogo 657-8501, Japan

⁴ Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan

⁵ Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan

Crystals 2016, 6(5), 49; https://doi.org/10.3390/cryst6050049 - 3 May 2016

Cited by 18 | Viewed by 7080

Abstract

To investigate the π-extension effect on an unusual negative-charged spin crossover (SCO) Fe^III complex with a weak N₂O₄ first coordination sphere, we designed and synthesized a series of anionic Fe^III complexes from a π-extended naphthalene derivative ligand. Acetonitrile-solvate [...] Read more.

To investigate the π-extension effect on an unusual negative-charged spin crossover (SCO) Fe^III complex with a weak N₂O₄ first coordination sphere, we designed and synthesized a series of anionic Fe^III complexes from a π-extended naphthalene derivative ligand. Acetonitrile-solvate tetramethylammonium (TMA) salt 1 exhibited an SCO conversion, while acetone-solvate TMA salt 2 was in a high-spin state. The crystal structural analysis for 2 revealed that two-leg ladder-like cation-anion arrays derived from π-stacking interactions between π-ligands of the Fe^III complex anion and Coulomb interactions were found and the solvated acetone molecules were in one-dimensional channels between the cation-anion arrays. A desolvation-induced single-crystal-to-single-crystal transformation to desolvate compound 2’ may be driven by Coulomb energy gain. Furthermore, the structural comparison between quasi-polymorphic compounds 1 and 2 revealed that the synergy between Coulomb and π-stacking interactions induces a significant distortion of coordination structure of 2. Full article

(This article belongs to the Special Issue High Spin Molecules)

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21 pages, 8083 KB

Open AccessReview

N,O-Type Carborane-Based Materials

by José Giner Planas^*

, Francesc Teixidor and Clara Viñas

Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus U.A.B., 08193 Bellaterra, Spain

Crystals 2016, 6(5), 50; https://doi.org/10.3390/cryst6050050 - 4 May 2016

Cited by 26 | Viewed by 9447

Abstract

This review summarizes the synthesis and coordination chemistry of a series of carboranyl ligands containing N,O donors. Such carborane-based ligands are scarcely reported in the literature when compared to other heteroatom-containing donors. The synthetic routes for metal complexes of these N,O-type carborane ligands [...] Read more.

This review summarizes the synthesis and coordination chemistry of a series of carboranyl ligands containing N,O donors. Such carborane-based ligands are scarcely reported in the literature when compared to other heteroatom-containing donors. The synthetic routes for metal complexes of these N,O-type carborane ligands are summarized and the properties of such complexes are described in detail. Particular attention is paid to the effect that the incorporation of carboranes has into the coordination chemistry of the otherwise carbon-based ligands and the properties of such materials. The reported complexes show a variety of properties such as those used in magnetic, chiroptical, nonlinear optical, catalytic and biomedical applications. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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12 pages, 824 KB

Open AccessArticle

Broadband Transmission Loss Using the Overlap of Resonances in 3D Sonic Crystals

by Alexandre Lardeau¹, Jean-Philippe Groby² and Vicente Romero-García^2,*

¹ Laboratoire DRIVE-ISAT, 49 rue Mademoiselle Bourgeois, 58027 Nevers Cedex, France

² Laboratoire d’Acoustique de l’Université du Maine, Avenue Olivier Messiaen, Cedex 9, 72085 Le Mans, France

Crystals 2016, 6(5), 51; https://doi.org/10.3390/cryst6050051 - 11 May 2016

Cited by 20 | Viewed by 6533

Abstract

The acoustic properties of a three-dimensional sonic crystal made of square-rod rigid scatterers incorporating a periodic arrangement of quarter wavelength resonators are theoretically and experimentally reported in this work. The periodicity of the system produces Bragg band gaps that can be tuned in [...] Read more.

The acoustic properties of a three-dimensional sonic crystal made of square-rod rigid scatterers incorporating a periodic arrangement of quarter wavelength resonators are theoretically and experimentally reported in this work. The periodicity of the system produces Bragg band gaps that can be tuned in frequency by modifying the orientation of the square-rod scatterers with respect to the incident wave. In addition, the quarter wavelength resonators introduce resonant band gaps that can be tuned by coupling the neighbor resonators. Bragg and resonant band gaps can overlap allowing the wave propagation control inside the periodic resonant medium. In particular, we show theoretically and experimentally that this system can produce a broad frequency band gap exceeding two and a half octaves (from 590 Hz to 3220 Hz) with transmission lower than 3%. Finite element methods were used to calculate the dispersion relation of the locally resonant system. The visco-thermal losses were accounted for in the quarter wavelength resonators to simulate the wave propagation in the semi-infinite structures and to compare the numerical results with the experiments performed in an echo-free chamber. The simulations and the experimental results are in good agreement. This work motivates interesting applications of this system as acoustic audible filters. Full article

(This article belongs to the Special Issue Phononic Crystals)

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12 pages, 3801 KB

Open AccessArticle

Formation of Bragg Band Gaps in Anisotropic Phononic Crystals Analyzed With the Empty Lattice Model

by Yan-Feng Wang¹, Alexei A. Maznev² and Vincent Laude^1,*

¹ Franche-Comté Electronique Mécanique Thermique et Optique, CNRS UMR 6174, Université de Franche-Comté, Besançon F-25030, France

² Department of Chemistry, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA

Crystals 2016, 6(5), 52; https://doi.org/10.3390/cryst6050052 - 11 May 2016

Cited by 24 | Viewed by 10494

Abstract

Bragg band gaps of phononic crystals generally, but not always, open at Brillouin zone boundaries. The commonly accepted explanation stems from the empty lattice model: assuming a small material contrast between the constituents of the unit cell, avoided crossings in the phononic band [...] Read more.

Bragg band gaps of phononic crystals generally, but not always, open at Brillouin zone boundaries. The commonly accepted explanation stems from the empty lattice model: assuming a small material contrast between the constituents of the unit cell, avoided crossings in the phononic band structure appear at frequencies and wavenumbers corresponding to band intersections; for scalar waves the lowest intersections coincide with boundaries of the first Brillouin zone. However, if a phononic crystal contains elastically anisotropic materials, its overall symmetry is not dictated solely by the lattice symmetry. We construct an empty lattice model for phononic crystals made of isotropic and anisotropic materials, based on their slowness curves. We find that, in the anisotropic case, avoided crossings generally do not appear at the boundaries of traditionally defined Brillouin zones. Furthermore, the Bragg “planes” which give rise to phononic band gaps, are generally not flat planes but curved surfaces. The same is found to be the case for avoided crossings between shear (transverse) and longitudinal bands in the isotropic case. Full article

(This article belongs to the Special Issue Phononic Crystals)

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45 pages, 23138 KB

Open AccessReview

Epitaxial Graphene on SiC: A Review of Growth and Characterization

by Gholam Reza Yazdi^*, Tihomir Iakimov and Rositsa Yakimova

Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping, Sweden

Crystals 2016, 6(5), 53; https://doi.org/10.3390/cryst6050053 - 12 May 2016

Cited by 230 | Viewed by 42896

Abstract

This review is devoted to one of the most promising two-dimensional (2D) materials, graphene. Graphene can be prepared by different methods and the one discussed here is fabricated by the thermal decomposition of SiC. The aim of the paper is to overview the [...] Read more.

This review is devoted to one of the most promising two-dimensional (2D) materials, graphene. Graphene can be prepared by different methods and the one discussed here is fabricated by the thermal decomposition of SiC. The aim of the paper is to overview the fabrication aspects, growth mechanisms, and structural and electronic properties of graphene on SiC and the means of their assessment. Starting from historical aspects, it is shown that the most optimal conditions resulting in a large area of one ML graphene comprise high temperature and argon ambience, which allow better controllability and reproducibility of the graphene quality. Elemental intercalation as a means to overcome the problem of substrate influence on graphene carrier mobility has been described. The most common characterization techniques used are low-energy electron microscopy (LEEM), angle-resolved photoelectron spectroscopy (ARPES), Raman spectroscopy, atomic force microscopy (AFM) in different modes, Hall measurements, etc. The main results point to the applicability of graphene on SiC in quantum metrology, and the understanding of new physics and growth phenomena of 2D materials and devices. Full article

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25 pages, 10483 KB

Open AccessReview

Bottom-Up Assembly and Applications of Photonic Materials

by Hanbin Zheng and Serge Ravaine^*

CNRS, University of Bordeaux, CRPP, UPR 8641, F-33600 Pessac, France

Crystals 2016, 6(5), 54; https://doi.org/10.3390/cryst6050054 - 12 May 2016

Cited by 49 | Viewed by 18881

Abstract

The assembly of colloidal building-blocks is an efficient, inexpensive and flexible approach for the fabrication of a wide variety of photonic materials with designed shapes and large areas. In this review, the various assembly routes to the fabrication of colloidal crystals and their [...] Read more.

The assembly of colloidal building-blocks is an efficient, inexpensive and flexible approach for the fabrication of a wide variety of photonic materials with designed shapes and large areas. In this review, the various assembly routes to the fabrication of colloidal crystals and their post-assembly modifications to the production of photonic materials are first described. Then, the emerging applications of the colloidal photonic structures in various fields such as biological and chemical sensing, anti-reflection, photovoltaics, and light extraction are summarized. Full article

(This article belongs to the Special Issue Colloidal Crystals)

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24 pages, 10332 KB

Open AccessReview

How to Increase the h-BN Crystallinity of Microfilms and Self-Standing Nanosheets: A Review of the Different Strategies Using the PDCs Route

by Sheng Yuan^1,2, Catherine Journet¹

, Sébastien Linas¹, Vincent Garnier²

, Philippe Steyer²

, Stéphane Benayoun³, Arnaud Brioude¹ and Bérangère Toury^1,*

¹ Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, Université de Lyon, LYON1, F-69622 Villeurbanne, France

² Matériaux Ingénierie et Science, UMR CNRS 5510, INSA de Lyon, Université de Lyon, F-69621 Villeurbanne, France

³ Laboratoire de Tribologie et Dynamique des Systèmes, Ecole Centrale de Lyon, F-69130 Ecully, France

Crystals 2016, 6(5), 55; https://doi.org/10.3390/cryst6050055 - 13 May 2016

Cited by 25 | Viewed by 11904

Abstract

Hexagonal boron nitride (h-BN) is a well-known material whose use is almost restricted to lubricating applications in domains ranging from metallurgy to cosmetics. Howover, h-BN displays many other interesting properties, opening new perspectives for other engineering applications, such as as a solid lubricant [...] Read more.

Hexagonal boron nitride (h-BN) is a well-known material whose use is almost restricted to lubricating applications in domains ranging from metallurgy to cosmetics. Howover, h-BN displays many other interesting properties, opening new perspectives for other engineering applications, such as as a solid lubricant in aeronautics, as the perfect substrate to graphene for electronic devices, etc. However, all these promising developments require tailored h-BN shapes displaying a high level of crystallization, ensuring its properties for the long term. Here, we developed three strategies, all associated with the Polymer Derived Ceramics (PDCs) route, to prepare highly crystallized supported thick coatings and self-standing nanosheets. The first strategy concerns the innovative implementation of a Rapid Thermal Annealing to prepare micrometric h-BN coatings on thermal sensitive substrates. Compared to conventional treatment the crystallization of h-BN has successfully lowered to about 300 °C. The second strategy consists of an additivation of the used polymer precursor. Effect of lithium nitride as a crystallization promoter was investigated lowering the onset crystallization temperature from 1400 °C (traditionally) to 1000 °C. This novel synthetic route allows preparing self-standing highly crystallized h-BN nanolayers. Finally, the third strategy is based on a unique combination of the PDCs route with Spark Plasma Sintering to profit of both approaches. This original method leads to large and well-crystallized flakes available for a subsequent exfoliation. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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11 pages, 2051 KB

Open AccessArticle

Comparisons between Crystallography Data and Theoretical Parameters and the Formation of Intramolecular Hydrogen Bonds: Benznidazole

by Boaz G. Oliveira^1,*, Edilson B. Alencar Filho²

and Mário L. A. A. Vasconcellos³

¹ Instituto de Ciências Ambientais e Desenvolvimento Sustentável, Universidade Federal da Bahia, Barreiras, Bahia 47808-021, Brazil

² Colegiado de Farmácia, Universidade Federal do Vale do São Francisco, Petrolina, Pernambuco 56304-917, Brazil

³ Departamento de Química, Universidade Federal da Paraíba, João Pessoa, Paraíba 58036-300, Brazil

Crystals 2016, 6(5), 56; https://doi.org/10.3390/cryst6050056 - 12 May 2016

Cited by 6 | Viewed by 5238

Abstract

The conformational preferences of benznidazole were examined through the application of DFT, PCM and QTAIM calculations, whose results were compared with crystallography data. The geometries were fully optimized with minimum potential energy surface by means of the Relaxed Potential Energy Surface Scan (RPESS) [...] Read more.

The conformational preferences of benznidazole were examined through the application of DFT, PCM and QTAIM calculations, whose results were compared with crystallography data. The geometries were fully optimized with minimum potential energy surface by means of the Relaxed Potential Energy Surface Scan (RPESS) at AM1, followed by the B3LYP/6-311++G(d,p) theoretical level. As a result, the s-cis conformation (1C) was shown to be more stable (4.78 kcal∙mol⁻¹) than s-trans (1T). The Quantum Theory Atoms in Molecules (QTAIM) was applied in order to characterize the (N–H∙∙∙O=N) and (C–H∙∙∙=N) intramolecular hydrogen bonds. The simulation of solvent effect performed by means of the implicit Polarized Continuum Model (PCM) revealed great results, such as, for instance, that the conformation 1W is more stable (23.17 kcal∙mol⁻¹) in comparison to 1C. Our main goal was stressed in the topological description of intramolecular hydrogen bonds in light of the QTAIM approach, as well as in the solvent simulation to accurately obtain an important conformation of benznidazole. Full article

(This article belongs to the Special Issue Analysis of Hydrogen Bonds in Crystals)

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7 pages, 1562 KB

Open AccessArticle

The Synthesis and Crystal Structure of Two New Hydrazone Compounds

by Li-Hua Wang¹ and Xi-Shi Tai^2,*

¹ College of Information and Engineering, Weifang University, Weifang 261061, China

² College of Chemistry and Chemical Engineering, Weifang University, Weifang 261061, China

Crystals 2016, 6(5), 57; https://doi.org/10.3390/cryst6050057 - 17 May 2016

Cited by 10 | Viewed by 6455

Abstract

Two new hydrazone compounds, 4-formylimidazole-4-hydroxybenzhydrazone dihydrate (1) and 2-nitrobenzaldehyde-2-furan formylhydrazone (2), were synthesized via the classical synthesis method. Their structure was determined via elemental analysis and X-ray single crystal diffraction analysis. Compound 1 crystallizes in triclinic, space group P-1 with a = [...] Read more.

Two new hydrazone compounds, 4-formylimidazole-4-hydroxybenzhydrazone dihydrate (1) and 2-nitrobenzaldehyde-2-furan formylhydrazone (2), were synthesized via the classical synthesis method. Their structure was determined via elemental analysis and X-ray single crystal diffraction analysis. Compound 1 crystallizes in triclinic, space group P-1 with a = 7.0321(14) Å, b = 7.3723(15) Å, c = 13.008(3) Å, α = 98.66(3)°, β = 101.69(3)°, γ = 92.25(3)°, V = 651.2(2) Å³, Z = 2, Dc = 1.358 g·cm⁻³, μ = 0.106 mm⁻¹, F(000) = 280, and final R₁ = 0.0564, ｗR₂ = 0.1420. Compound 2 crystallizes in monoclinic, space group P2₁/c with a = 17.3618(9) Å, b = 9.1506(4) Å, c = 15.5801(7) Å, β = 104.532(5)°, V = 2396.05(19) Å³, Z = 8, Dc = 1.437 g·cm⁻³, μ = 0.111 mm⁻¹, F(000) = 1072, and final R₁ = 0.0633, wR₂ = 0.1649. Compound 1 forms a 2D-layered structure via the interactions of 1D chains and Compound 2 forms a 3D network structure via the interactions of 1D chains. Full article

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20 pages, 5432 KB

Open AccessReview

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

by Malcolm A. Halcrow

School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK

Crystals 2016, 6(5), 58; https://doi.org/10.3390/cryst6050058 - 18 May 2016

Cited by 122 | Viewed by 22237

Abstract

The relationship between chemical structure and spin state in a transition metal complex has an important bearing on mechanistic bioinorganic chemistry, catalysis by base metals, and the design of spin crossover materials. The latter provide an ideal testbed for this question, since small [...] Read more.

The relationship between chemical structure and spin state in a transition metal complex has an important bearing on mechanistic bioinorganic chemistry, catalysis by base metals, and the design of spin crossover materials. The latter provide an ideal testbed for this question, since small changes in spin state energetics can be easily detected from shifts in the spin crossover equilibrium temperature. Published structure-function relationships relating ligand design and spin state from the spin crossover literature give varied results. A sterically crowded ligand sphere favors the expanded metal–ligand bonds associated with the high-spin state. However, steric clashes at the molecular periphery can stabilize either the high-spin or the low-spin state in a predictable way, depending on their effect on ligand conformation. In the absence of steric influences, the picture is less clear since electron-withdrawing ligand substituents are reported to favor the low-spin or the high-spin state in different series of compounds. A recent study has shed light on this conundrum, showing that the electronic influence of a substituent on a coordinated metal ion depends on its position on the ligand framework. Finally, hydrogen bonding to complexes containing peripheral N‒H groups consistently stabilizes the low-spin state, where this has been quantified. Full article

(This article belongs to the Special Issue High Spin Molecules)

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5 pages, 940 KB

Open AccessEditorial

Analysis of Hydrogen Bonds in Crystals

by Sławomir J. Grabowski^1,2

¹ Kimika Fakultatea, Euskal Herriko Unibertsitatea UPV/EHU, and Donostia International Physics Center (DIPC), P.K. 1072, 20080 San Sebastian, Spain

² IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain

Crystals 2016, 6(5), 59; https://doi.org/10.3390/cryst6050059 - 17 May 2016

Cited by 40 | Viewed by 10684

Abstract

The determination of crystal structures provides important information on the geometry of species constituting crystals and on the symmetry relations between them. Additionally, the analysis of crystal structures is so conclusive that it allows us to understand the nature of various interactions. The [...] Read more.

The determination of crystal structures provides important information on the geometry of species constituting crystals and on the symmetry relations between them. Additionally, the analysis of crystal structures is so conclusive that it allows us to understand the nature of various interactions. The hydrogen bond interaction plays a crucial role in crystal engineering and, in general, its important role in numerous chemical, physical and bio-chemical processes was the subject of various studies. That is why numerous important findings on the nature of hydrogen bonds concern crystal structures. This special issue presents studies on hydrogen bonds in crystals, and specific compounds and specific H-bonded patterns existing in crystals are analyzed. However, the characteristics of the H-bond interactions are not only analyzed theoretically; this interaction is compared with other ones that steer the arrangement of molecules in crystals, for example halogen, tetrel or pnicogen bonds. More general findings concerning the influence of the hydrogen bond on the physicochemical properties of matter are also presented. Full article

(This article belongs to the Special Issue Analysis of Hydrogen Bonds in Crystals)

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85 pages, 36438 KB

Open AccessReview

Silver and Copper Complexes with closo-Polyhedral Borane, Carborane and Metallacarborane Anions: Synthesis and X-ray Structure

by Varvara V. Avdeeva^1,*

, Elena A. Malinina¹, Igor B. Sivaev^2,*

, Vladimir I. Bregadze² and Nikolai T. Kuznetsov¹

¹ N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 31 Leninskii Prospect, Moscow, 119991, Russia

² A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilov Street, Moscow 119991, Russia

Crystals 2016, 6(5), 60; https://doi.org/10.3390/cryst6050060 - 20 May 2016

Cited by 72 | Viewed by 10807

Abstract

Synthesis and structure of silver and copper salts and complexes with polyhedral boron hydride anions, including closo-decaborate [B₁₀H₁₀]²⁻, closo-dodecaborate [B₁₂H₁₂]²⁻, 1-carba-closo- decaborate [1-CB₉H₁₀] [...] Read more.

Synthesis and structure of silver and copper salts and complexes with polyhedral boron hydride anions, including closo-decaborate [B₁₀H₁₀]²⁻, closo-dodecaborate [B₁₂H₁₂]²⁻, 1-carba-closo- decaborate [1-CB₉H₁₀]⁻, carba-closo-dodecaborate [CB₁₁H₁₂]⁻, and cobalt bis(dicarbollide) [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻ anions and their derivatives, are reviewed. The complexes demonstrate a wide variety of structural types, relating to both the metal coordination environment and coordination modes of boron hydride anions. The latter can range from strong coordination via the polyhedron triangular face including formation of 3c-2e MHB bonds in the case of the [B₁₀H₁₀]²⁻ dianion, the structure of which contains two four-coordinated boron atoms, to very weak M…H interactions with the hydride atoms in the case of bulky [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻ monoanion. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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10 pages, 4616 KB

Open AccessArticle

Colloidal Photonic Crystals Containing Silver Nanoparticles with Tunable Structural Colors

by Chun-Feng Lai^* and Yu-Chi Wang

Department of Photonics, Feng Chia University, Seatwen, Taichung 40724, Taiwan

Crystals 2016, 6(5), 61; https://doi.org/10.3390/cryst6050061 - 19 May 2016

Cited by 29 | Viewed by 13002

Abstract

Polystyrene (PS) colloidal photonic crystals (CPhCs) containing silver nanoparticles (AgNPs) present tunable structural colors. PS CPhC color films containing a high concentration of AgNPs were prepared using self-assembly process through gravitational sedimentation method. High-concentration AgNPs were deposited on the bottom of the substrate [...] Read more.

Polystyrene (PS) colloidal photonic crystals (CPhCs) containing silver nanoparticles (AgNPs) present tunable structural colors. PS CPhC color films containing a high concentration of AgNPs were prepared using self-assembly process through gravitational sedimentation method. High-concentration AgNPs were deposited on the bottom of the substrate and acted as black materials to absorb background and scattering light. Brilliant structural colors were enhanced because of the absorption of incoherent scattering light, and color saturation was increased by the distribution AgNPs on the PS CPhC surfaces. The vivid iridescent structural colors of AgNPs/PS hybrid CPhC films were based on Bragg diffraction and backward scattering absorption using AgNPs. The photonic stop band of PS CPhCs and AgNPs/PS hybrid CPhCs were measured by UV–visible reflection spectrometry and calculated based on the Bragg–Snell law. In addition, the tunable structural colors of AgNPs/PS hybrid CPhC films were evaluated using color measurements according to the Commission International d’Eclairage standard colorimetric system. This paper presents a simple and inexpensive method to produce tunable structural colors for numerous applications, such as textile fabrics, bionic colors, catalysis, and paints. Full article

(This article belongs to the Special Issue Colloidal Crystals)

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16 pages, 3127 KB

Open AccessReview

Floating Zone Growth of Bi₂Sr₂Ca₂Cu₃O_y Superconductor

by Andrey Maljuk^1,* and C. T. Lin²

¹ Leibniz Institute for Solid State and Materials Research Dresden, D-01171 Dresden, Germany

² Max Planck Institute for Solid State Research, D-70569 Stuttgart, Germany

Crystals 2016, 6(5), 62; https://doi.org/10.3390/cryst6050062 - 20 May 2016

Cited by 13 | Viewed by 10896

Abstract

The crystal growth of high-temperature oxide superconductors has been hampered by the complexities of these materials and the lack of knowledge of corresponding phase diagrams. The most common crystal growth technique adopted for these materials is the so-called “Flux” method. This method, however, [...] Read more.

The crystal growth of high-temperature oxide superconductors has been hampered by the complexities of these materials and the lack of knowledge of corresponding phase diagrams. The most common crystal growth technique adopted for these materials is the so-called “Flux” method. This method, however, suffers from several drawbacks: (i) crystals are often crucible and flux contaminated; (ii) crystals are difficult to detach from solidified melt; and (iii) crystals are rather small. In most cases, these drawbacks can be overcome by the crucible-free floating zone method. Moreover, this technique is suitable for crystal growth of incongruently melting compounds, and has been thus successfully used to make large single crystals of Bi₂Sr₂Ca₂Cu₃O_y superconductor. In this review, the authors summarize the published and their own growth efforts as well as detailed characterization of as-grown and post-growth annealed samples. The optimal growth conditions that allowed one to obtain the large-size, almost single phase and homogeneous in composition Bi₂Sr₂Ca₂Cu₃O_y single crystals are presented. The effect of long lasting post-growth heat treatment on both crystal quality and superconducting properties has also been demonstrated. Full article

(This article belongs to the Special Issue Traveling Solvent Floating Zone (TSFZ) Method in Crystal Growth)

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