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Crystals, Volume 5, Issue 3 (September 2015), Pages 275-417

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Research

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Open AccessArticle The First Chelate-Free Crystal Structure of a Silicide Transition Metal Complex [K0.28Rb7.72Si9Ni(CO)2]2·16NH3
Crystals 2015, 5(3), 275-282; doi:10.3390/cryst5030275
Received: 10 April 2015 / Revised: 3 June 2015 / Accepted: 5 June 2015 / Published: 24 June 2015
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Abstract
Single-crystals X-ray structure analysis of very thermally labile and moisture sensitive ammoniate crystals of [K0.28Rb7.72Si9Ni(CO)2]2·16NH3 show the presence of the very rarely observed nickel-silicide complex [{Ni(CO)2}2(µ-Si9)
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Single-crystals X-ray structure analysis of very thermally labile and moisture sensitive ammoniate crystals of [K0.28Rb7.72Si9Ni(CO)2]2·16NH3 show the presence of the very rarely observed nickel-silicide complex [{Ni(CO)2}2(µ-Si9)2]8−, which was up to now only known in the 18-crown-6 involving solid [Rb@18-crown-6)]2[K@18-crown-6)]2Rb4[{Ni(CO)2}2(µ-Si9)2]·22NH3. This shows that, like already known for the heavier homologues, the presence of 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) is no precondition for the stabilization of the silicide cluster anion in solid state and the absence of the alkali metal ligand even allows for the crystallization in the higher symmetric monoclinic space group C2/c compared to the triclinic space group P-1 when 18-crown-6 is present. Full article
Figures

Open AccessArticle Two Closely Related Organic Charge-Transfer Complexes Based on Tetrathiafulvalene and 9H-fluorenone Derivatives. Competition between Hydrogen Bonding and Stacking Interactions
Crystals 2015, 5(3), 283-293; doi:10.3390/cryst5030283
Received: 6 March 2015 / Revised: 4 June 2015 / Accepted: 12 June 2015 / Published: 25 June 2015
Cited by 1 | PDF Full-text (897 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Two 1:1 charge-transfer organic complexes were formed using tetrathiafulvalene as a donor and a 9H-fluorenone derivative as acceptor: 4,5,7-trinitro-9H-fluoren-9-one-2-carboxylic acid (complex 1) or 4,5,7-trinitro-9H-fluoren-9-one-2-carboxylic acid methyl ester (complex 2). Both systems crystallize with alternated donor
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Two 1:1 charge-transfer organic complexes were formed using tetrathiafulvalene as a donor and a 9H-fluorenone derivative as acceptor: 4,5,7-trinitro-9H-fluoren-9-one-2-carboxylic acid (complex 1) or 4,5,7-trinitro-9H-fluoren-9-one-2-carboxylic acid methyl ester (complex 2). Both systems crystallize with alternated donor and acceptor stacks. However, the crystal structure of 1 is influenced by classical hydrogen bonds involving carboxylic acid groups, which force to arrange acceptors as centrosymmetric dimers in the crystal, via R2 2(8) ring motifs, while such a restriction is no longer present in the case of 2, affording thus a different crystal structure. This main difference is reflected in stacking interactions, and, in turn, in the degree of charge transfer observed in the complexes. The degree of charge transfer, estimated using Raman spectroscopy, is δ1 = 0.07 for 1 and δ2 = 0.14 for 2. It thus seems that, at least for the studied complexes, hydrogen bonding is an unfavorable factor for charge transfer. Full article
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Open AccessArticle Synthesis, Crystal Structure and Antibacterial Activity of Mg(II) Complex [Mg(H2O)6]·(4-amino-3-methylbenzenesulfonate)2
Crystals 2015, 5(3), 294-301; doi:10.3390/cryst5030294
Received: 22 July 2015 / Revised: 6 August 2015 / Accepted: 7 August 2015 / Published: 19 August 2015
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Abstract
A Mg(II) complex, [Mg(H2O)6]·L2 (H2L = 4-amino-3-methylbenzenesulfonate), has been synthesized and characterized by elemental analysis, Infrared (IR) and single-crystal X-ray diffraction. The results indicated that the Mg(II) complex was monoclinic with P21/n
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A Mg(II) complex, [Mg(H2O)6]·L2 (H2L = 4-amino-3-methylbenzenesulfonate), has been synthesized and characterized by elemental analysis, Infrared (IR) and single-crystal X-ray diffraction. The results indicated that the Mg(II) complex was monoclinic with P21/n, a = 6.3184(16) Å, b = 7.0522(18) Å, c = 24.434(6) Å, β = 93.946(3)°, V = 1086.2(5) Å3, Z = 2, Mr = 504.81, Dc = 1.544 g/cm3, T = 296(2) K, F(000) = 532, μ(MoKa) = 0.338 mm−1, R = 0.0339 and wR =0.1194. The Mg(II) ion lies in a distorted octahedral geometry. The hydrogen bonds and π-π stacking interaction play an important role in the forming of one dimensional chain structure. The antibacterial activity against Escherichia coli, Bacillus subtilis and Staphylococcus white of the Mg(II) complex has also been investigated. Full article
Open AccessArticle Pitch-Length Independent Threshold Voltage of Polymer/Cholesteric Liquid Crystal Nano-Composites
Crystals 2015, 5(3), 302-311; doi:10.3390/cryst5030302
Received: 3 July 2015 / Revised: 7 August 2015 / Accepted: 13 August 2015 / Published: 19 August 2015
Cited by 4 | PDF Full-text (3721 KB) | HTML Full-text | XML Full-text
Abstract
Polymer/cholesteric liquid crystal (ChLC) nano-composites consisting of mesogenic monomers and LCs have nano-sized LC domains dispersed in an anisotropic polymer matrix. They exhibit characteristics not observed in conventional ChLCs, such as sub-millisecond and “deformation-free” electro-optic tuning of the selective reflection band; however, their
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Polymer/cholesteric liquid crystal (ChLC) nano-composites consisting of mesogenic monomers and LCs have nano-sized LC domains dispersed in an anisotropic polymer matrix. They exhibit characteristics not observed in conventional ChLCs, such as sub-millisecond and “deformation-free” electro-optic tuning of the selective reflection band; however, their driving voltage is high compared to conventional ChLCs, and is an issue that needs to be solved for the practical use. Here, we investigate the helical pitch dependence of threshold voltage in polymer/ChLC nano-composites. Five samples with different helical pitches were prepared and their electro-optic characteristics were compared before and after photopolymerization. Although the threshold voltage of the unpolymerized samples were inversely proportional to its helical pitch, the threshold voltage of the polymerized samples showed no dependence on the helical pitch. These results are explained to be a consequence of the driving mechanism of the polymer/ChLC nano-composite, in which electro-optic switching is achieved as a consequence of the nano-confined LC molecules reorienting along the electric field, instead of the helical structure becoming unwound. The threshold voltage is independent of pitch length because the pore sizes are similar in all samples. Full article
(This article belongs to the Special Issue Liquid Crystal Films)
Open AccessArticle Nickel-Doped Ceria Nanoparticles: The Effect of Annealing on Room Temperature Ferromagnetism
Crystals 2015, 5(3), 312-326; doi:10.3390/cryst5030312
Received: 30 June 2015 / Revised: 21 July 2015 / Accepted: 17 August 2015 / Published: 21 August 2015
Cited by 5 | PDF Full-text (1775 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Nickel-doped cerium dioxide nanoparticles exhibit room temperature ferromagnetism due to high oxygen mobility within the doped CeO2 lattice. CeO2 is an excellent doping matrix as it can lose oxygen whilst retaining its structure. This leads to increased oxygen mobility within the
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Nickel-doped cerium dioxide nanoparticles exhibit room temperature ferromagnetism due to high oxygen mobility within the doped CeO2 lattice. CeO2 is an excellent doping matrix as it can lose oxygen whilst retaining its structure. This leads to increased oxygen mobility within the fluorite CeO2 lattice, leading to the formation of Ce3+ and Ce4+ species and hence doped ceria shows a high propensity for numerous catalytic processes. Magnetic ceria are important in several applications from magnetic data storage devices to magnetically recoverable catalysts. We investigate the effect doping nickel into a CeO2 lattice has on the room temperature ferromagnetism in monodisperse cerium dioxide nanoparticles synthesised by the thermal decomposition of cerium(III) and nickel(II) oleate metal organic precursors before and after annealing. The composition of nanoparticles pre- and post-anneal were analysed using: TEM (transmission electron microscopy), XPS (X-ray photoelectron spectroscopy), EDS (energy-dispersive X-ray spectroscopy) and XRD (X-ray diffraction). Optical and magnetic properties were also studied using UV/Visible spectroscopy and SQUID (superconducting interference device) magnetometry respectively. Full article
(This article belongs to the Special Issue Nanostructured Oxide Crystals)
Open AccessArticle Dissection of the Factors Affecting Formation of a CH∙∙∙O H-Bond. A Case Study
Crystals 2015, 5(3), 327-345; doi:10.3390/cryst5030327
Received: 24 July 2015 / Revised: 14 August 2015 / Accepted: 19 August 2015 / Published: 25 August 2015
Cited by 8 | PDF Full-text (853 KB) | HTML Full-text | XML Full-text
Abstract
Quantum calculations are used to examine how various constituent components of a large molecule contribute to the formation of an internal CH∙∙∙O H-bond. Such a bond is present in the interaction between two amide units, connected together by a series of functional groups.
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Quantum calculations are used to examine how various constituent components of a large molecule contribute to the formation of an internal CH∙∙∙O H-bond. Such a bond is present in the interaction between two amide units, connected together by a series of functional groups. Each group is removed one at a time, so as to monitor the effect of each upon the H-bond, and thereby learn the bare essentials that are necessary for its formation, as well as how its presence affects the overall molecular structure. Also studied is the perturbation caused by change in the length of the aliphatic chain connecting the two amide groups. The energy of the CH∙∙∙O H-bond is calculated directly, as is the rigidity of the entire molecular framework. Full article
(This article belongs to the Special Issue Analysis of Hydrogen Bonds in Crystals) Printed Edition available
Open AccessArticle A Comparative Theoretical Study of Picric Acid and Its Cocrystals
Crystals 2015, 5(3), 346-354; doi:10.3390/cryst5030346
Received: 15 July 2015 / Revised: 14 August 2015 / Accepted: 20 August 2015 / Published: 1 September 2015
Cited by 5 | PDF Full-text (1015 KB) | HTML Full-text | XML Full-text
Abstract
A novel cocrystal of picric acid/acetophenone was prepared by solvent evaporation method and the crystal structure was characterized by single crystal X-ray diffraction. Analysis of the crystal structure shows that the hydrogen bonding, van der Waals and π-π stacking are the main driving
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A novel cocrystal of picric acid/acetophenone was prepared by solvent evaporation method and the crystal structure was characterized by single crystal X-ray diffraction. Analysis of the crystal structure shows that the hydrogen bonding, van der Waals and π-π stacking are the main driving forces for the cocrystal formation. Density functional theory (DFT) calculation was performed to better understand the formation mechanism and properties of the cocrystal. The results suggest that π-π stacking is more important than hydrogen bonding considering their interaction energies. Furthermore, Mulliken charge analysis shows picric acid becomes less sensitive after cocrystallization with other compounds because of the electron transfer. Full article
(This article belongs to the Special Issue Energetic Materials)
Open AccessArticle Synthesis, Crystal Structures, and DFT Calculations of Three New Cyano(phenylsulfonyl)indoles and a Key Synthetic Precursor Compound
Crystals 2015, 5(3), 376-393; doi:10.3390/cryst5030376
Received: 14 July 2015 / Revised: 22 August 2015 / Accepted: 31 August 2015 / Published: 10 September 2015
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Abstract
Three cyano-1-(phenylsulfonyl)indole derivatives, 3-cyano-1-(phenylsulfonyl) indole, (I), 2-cyano-1-(phenylsulfonyl)indole, (II), and 2,3-dicyano-1-(phenylsulfonyl) indole, (III), and a key synthetic precursor 1-(phenylsulfonyl)-1-(1,1-dimethylethyl) indole-3-carboxamide, (IV), have been synthesized and their structures determined by single crystal X-ray crystallography. (I),
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Three cyano-1-(phenylsulfonyl)indole derivatives, 3-cyano-1-(phenylsulfonyl) indole, (I), 2-cyano-1-(phenylsulfonyl)indole, (II), and 2,3-dicyano-1-(phenylsulfonyl) indole, (III), and a key synthetic precursor 1-(phenylsulfonyl)-1-(1,1-dimethylethyl) indole-3-carboxamide, (IV), have been synthesized and their structures determined by single crystal X-ray crystallography. (I), C15H10N2O2S, is orthorhombic with space group P 212121 and cell constants: a = 4.9459(3) Å, b = 10.5401(7) Å, c = 25.0813(14) Å, V = 1307.50(14) Å3 and Z = 4. (II), C15H10N2O2S, is monoclinic with space group C 2/c and cell constants: a = 18.062(2) Å, b = 11.293(2) Å, c = 15.922(3) Å, α = 90°, β = 124.49(2)°, g = 90°, V = 2676.7 Å3 and Z = 8. (III), C16H9N3O2S, is triclinic with space group P-1 and cell constants: a = 8.1986(8) Å, b = 9.6381(11) Å, c = 9.8113(5) Å, α = 95.053(6)°, β = 101.441(6)°, g = 108.071(9)°, V = 713.02(11) Å3 and Z = 2. (IV), C19H20N2O3S, is orthorhombic with space group P ccn and cell constants: a = 13.7605(8) Å, b = 27.3177(14) Å, c = 9.7584(6) Å, α = 90°, β = 90°, g =90°, V = 3668.2(4) Å3 and Z = 8. All four compounds have the same indole nitrogen phenylsulfonyl substituent and (I), (II), and (III) are nitrile derivatives. (IV) is a tert-butylamide. In the crystals, the dihedral angle between the mean planes of the indole and phenylsulfonyl groups are 85.4(2)° (I), 87.2(7)° (II), 75.1(7)° (III), and 88.6(2)° (IV), respectively. Additionally, DFT geometry-optimized molecular orbital calculations were performed and frontier molecular orbitals of each compound are displayed. Correlation between the calculated molecular orbital energies (eV) for the surfaces of the frontier molecular orbitals to the electronic excitation transitions from the absorption spectra of each compound has been proposed. Full article
Open AccessArticle Electrically Rotatable Polarizer Using One-Dimensional Photonic Crystal with a Nematic Liquid Crystal Defect Layer
Crystals 2015, 5(3), 394-404; doi:10.3390/cryst5030394
Received: 31 July 2015 / Revised: 4 September 2015 / Accepted: 10 September 2015 / Published: 14 September 2015
Cited by 1 | PDF Full-text (1514 KB) | HTML Full-text | XML Full-text
Abstract
Polarization characteristics of defect mode peaks in a one-dimensional (1D) photonic crystal (PC) with a nematic liquid crystal (NLC) defect layer have been investigated. Two different polarized defect modes are observed in a stop band. One group of defect modes is polarized along
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Polarization characteristics of defect mode peaks in a one-dimensional (1D) photonic crystal (PC) with a nematic liquid crystal (NLC) defect layer have been investigated. Two different polarized defect modes are observed in a stop band. One group of defect modes is polarized along the long molecular axis of the NLC, whereas another group is polarized along its short axis. Polarizations of the defect modes can be tuned by field-induced in-plane reorientation of the NLC in the defect layer. The polarization properties of the 1D PC with the NLC defect layer is also investigated by the finite difference time domain (FDTD) simulation. Full article
(This article belongs to the Special Issue Liquid Crystal Films)
Open AccessArticle Structures and Energetic Properties of Two New Salts Comprising the 5,5'-Azotetrazolate Dianion
Crystals 2015, 5(3), 405-417; doi:10.3390/cryst5030405
Received: 31 July 2015 / Revised: 27 August 2015 / Accepted: 8 September 2015 / Published: 18 September 2015
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Abstract
Two new potentially energetic salts comprising the 5,5'-azotetrazolate dianion have been prepared and structurally characterized. The new azotetrazolates are tetraphenylphosphonium-5,5'-azotetrazolate (1) and 1H-1,2,4-triazole-1-carboxamidine-5,5'-azotetrazolate (2). The crystal structures of both compounds have been determined by single-crystal X-ray diffraction
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Two new potentially energetic salts comprising the 5,5'-azotetrazolate dianion have been prepared and structurally characterized. The new azotetrazolates are tetraphenylphosphonium-5,5'-azotetrazolate (1) and 1H-1,2,4-triazole-1-carboxamidine-5,5'-azotetrazolate (2). The crystal structures of both compounds have been determined by single-crystal X-ray diffraction and their energetic properties have been tested. Due to its high nitrogen-content of 73.14%, compound 2 was found to be significantly impact-sensitive. Full article
(This article belongs to the Special Issue Energetic Materials)

Review

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Open AccessReview Dendrite Growth Kinetics in Undercooled Melts of Intermetallic Compounds
Crystals 2015, 5(3), 355-375; doi:10.3390/cryst5030355
Received: 2 June 2015 / Revised: 6 August 2015 / Accepted: 27 August 2015 / Published: 7 September 2015
Cited by 9 | PDF Full-text (3485 KB) | HTML Full-text | XML Full-text
Abstract
Solidification needs an undercooling to drive the solidification front. If large undercoolings are achieved, metastable solid materials are solidified from the undercooled melt. Containerless processing provides the conditions to achieve large undercoolings since heterogeneous nucleation on container walls is completely avoided. In the
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Solidification needs an undercooling to drive the solidification front. If large undercoolings are achieved, metastable solid materials are solidified from the undercooled melt. Containerless processing provides the conditions to achieve large undercoolings since heterogeneous nucleation on container walls is completely avoided. In the present contribution both electromagnetic and electrostatic levitation are applied. The velocity of rapidly advancing dendrites is measured as a function of undercooling by a High-Speed-Camera. The dendrite growth dynamics is investigated in undercooled melts of intermetallic compounds. The Al50Ni50 alloy is studied with respect to disorder trapping that leads to a disordered superlattice structure if the melt is undercooled beyond a critical undercooling. Disorder trapping is evidenced by in situ energy dispersive diffraction using synchrotron radiation of high intensity to record full diffraction pattern on levitated samples within a short time interval. Experiments on Ni2B using different processing techniques of varying the level of convection reveal convection-induced faceting of rapidly growing dendrites. Eventually, the growth velocity is measured in an undercooled melt of glass forming Cu50Zr50 alloy. A maximum in the growth velocity–undercooling relation is proved. This is understood by the fact that the temperature dependent diffusion coefficient counteracts the thermodynamic driving force for rapid growth if the temperature of the undercooled melt is approaching the temperature regime above the glass transition temperature. The analysis of this result allows for determining the activation energy of atomic attachment kinetics at the solid–liquid interface that is comparable to the activation energy of atomic diffusion as determined by independent measurements of the atomic diffusion in undercooled Cu50Zr50 alloy melt. Full article
(This article belongs to the Special Issue Intermetallics)

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