Next Issue
Previous Issue

Table of Contents

Crystals, Volume 2, Issue 1 (March 2012), Pages 1-158

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-14
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle Differential Scanning Calorimetry (DSC) and Synchrotron X-ray Diffraction Study of Unmilled and Milled LiBH4: A Partial Release of Hydrogen at Moderate Temperatures
Crystals 2012, 2(1), 1-21; doi:10.3390/cryst2010001
Received: 30 September 2011 / Revised: 9 December 2011 / Accepted: 14 December 2011 / Published: 27 December 2011
Cited by 6 | PDF Full-text (717 KB) | HTML Full-text | XML Full-text
Abstract
A systematic investigation of phase transitions in unmilled and milled LiBH4 has been performed by Pressurized Differential Scanning Calorimetry (PDSC). It was found that a large exotherm is present below the low temperature (LT) → high temperature (HT) phase transition. This [...] Read more.
A systematic investigation of phase transitions in unmilled and milled LiBH4 has been performed by Pressurized Differential Scanning Calorimetry (PDSC). It was found that a large exotherm is present below the low temperature (LT) → high temperature (HT) phase transition. This exotherm is not caused by air contamination but seems to originate from hydrogen release from a solid solution in the matrix of LiBH4 low temperature phase. The exotherm activation energy has been measured to be 100 kJ mol–1. Calorimetric measurements under argon and hydrogen have shown that for the milled sample, the endothermic peak of the LT → HT transition is split in two when the PDSC scan is performed under hydrogen atmosphere. Synchrotron X-ray powder diffraction on the milled LiBH4 sample revealed only a single-step transition from the LT to HT phase, both under vacuum and under 2 and 40 bar of hydrogen pressure. The axial ratios for the LT LiBH4 below 300 K are significantly altered by milling; they are also considerably different under 40 bar of hydrogen, indicating an interaction between the hydrogen gas and the LT LiBH4 solid phase. Full article
(This article belongs to the Special Issue Hydrogen Storage Alloys)
Open AccessArticle Studies of Modified Hydrogen Storage Intermetallic Compounds Used as Fuel Cell Anodes
Crystals 2012, 2(1), 22-33; doi:10.3390/cryst2010022
Received: 6 September 2011 / Revised: 13 December 2011 / Accepted: 22 December 2011 / Published: 28 December 2011
Cited by 1 | PDF Full-text (446 KB) | HTML Full-text | XML Full-text
Abstract
The possibility of substituting Pt/C with the hydrogen storage alloy MlNi3.6Co0.85Al0.3Mn0.3 as the anode active material of a proton exchange membrane fuel cell system has been analyzed. The electrochemical properties indicate that a much more [...] Read more.
The possibility of substituting Pt/C with the hydrogen storage alloy MlNi3.6Co0.85Al0.3Mn0.3 as the anode active material of a proton exchange membrane fuel cell system has been analyzed. The electrochemical properties indicate that a much more electrochemically active anode is obtained by impregnating the active material loaded anode in a Nafion proton conducting polymer. Such performance improvement might result from the increase of three-phase boundary sites or length in the gas diffusion electrode where the electrochemical reaction occurs. The experimental data revealed that the membrane electrode assembly (MEA) shows better results when the anode active material, MlNi3.6Co0.85Al0.3Mn0.3, is treated with a hot alkaline KBH4 solution, and then chemically coated with 3 wt.% Pd. The MEA with the aforesaid modification presents an enhanced surface capability for hydrogen adsorption, and has been studied by molecular beam-thermal desorption spectrometry. Full article
(This article belongs to the Special Issue Hydrogen Storage Alloys)
Figures

Open AccessArticle Molecular and Crystal Structure of a New High Energy Density Material: Aminoguanidinium-styphnate, [H2NNHC(NH2)2]2[C6HO2(NO2)3]
Crystals 2012, 2(1), 34-42; doi:10.3390/cryst2010034
Received: 2 September 2011 / Revised: 20 December 2011 / Accepted: 26 December 2011 / Published: 4 January 2012
Cited by 4 | PDF Full-text (429 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The title compound [H2NNHC(NH2)2]2[C6HO2(NO2)3] (2) was prepared in 85% yield by treatment of sodium styphnate with 2 equivalents of aminoguanidinium nitrate, followed by crystallization [...] Read more.
The title compound [H2NNHC(NH2)2]2[C6HO2(NO2)3] (2) was prepared in 85% yield by treatment of sodium styphnate with 2 equivalents of aminoguanidinium nitrate, followed by crystallization from aqueous solution. Compound 2 crystallizes in the triclinic space group Pī with unit cell dimensions a = 6.7224(3) Å, b = 10.7473(4) Å, c = 11.9604(5) Å, α = 113.212(4)°, β = 90.579(3)°, γ = 99.815(3)°, V = 779.68(6) Å3, Z = 2. In the solid state structure of 2, no water of crystallization is present. Bond angles within the aromatic ring of the styphnate anion indicate a significant distortion with larger angles (122.04(18)–125.96(18) Å) at the carbons bearing the nitro groups, and smaller ones (113.30(17) and 114.07(17) Å) at the C-O carbon atoms. The crystal structure of 2 consists of layers formed by an extensive network of N-H...O hydrogen bonds between NH2 groups of the aminoguanidinium cation and the negatively charged oxygens of the styphnate anion. The layers are again interconnected by N-H...N hydrogen bonds between neighboring aminoguanidinium cations. Full article
Open AccessArticle New Fulvalenium Salts of Cobalt Bis(dicarbollide): Crystal Structures and Electrical Conductivities
Crystals 2012, 2(1), 43-55; doi:10.3390/cryst2010043
Received: 6 December 2011 / Revised: 21 December 2011 / Accepted: 22 December 2011 / Published: 6 January 2012
Cited by 5 | PDF Full-text (452 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
New radical cation salts (BEDT-TTF)[8,8',(7)-Cl2(Cl0.09)-3,3'-Co(1,2-C2B9H9.91)(1',2'-C2B9H10)] (1), (BEDT-TTF)[8,8'-Br0.75Cl1.25-3,3'-Co(1,2-C2B9H10)2] (2), and (BMDT-TTF) [...] Read more.
New radical cation salts (BEDT-TTF)[8,8',(7)-Cl2(Cl0.09)-3,3'-Co(1,2-C2B9H9.91)(1',2'-C2B9H10)] (1), (BEDT-TTF)[8,8'-Br0.75Cl1.25-3,3'-Co(1,2-C2B9H10)2] (2), and (BMDT-TTF)4[8,8'-Br1.16(OH)0.72-3,3'-Co(1,2-C2B9H10.06)2] (3) were synthesized, and their crystal structures and electrical conductivities were determined. All the radical cation salts are semiconductors. Compounds 1 and 2 were found to be isostructural, however their electrical conductivities strongly differ (s293 = 2 Ω1cm−1 and 10−5 Ω−1cm−1, respectively). Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessArticle Influence of Semiconductor Nanocrystal Concentration on Polymer Hole Transport in Hybrid Nanocomposites
Crystals 2012, 2(1), 78-89; doi:10.3390/cryst2010078
Received: 1 November 2011 / Revised: 30 December 2011 / Accepted: 10 January 2012 / Published: 16 January 2012
Cited by 1 | PDF Full-text (575 KB) | HTML Full-text | XML Full-text
Abstract
This article investigates hole transport in poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV)/CdSe colloidal quantum dot (CQD) nanocomposites using a modified time-of-flight photoconductivity technique. The measured hole drift mobilities are analyzed in the context of Bässler’s Gaussian disorder model and the correlated disorder model in order [...] Read more.
This article investigates hole transport in poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV)/CdSe colloidal quantum dot (CQD) nanocomposites using a modified time-of-flight photoconductivity technique. The measured hole drift mobilities are analyzed in the context of Bässler’s Gaussian disorder model and the correlated disorder model in order to determine the polymer internal morphology of hybrid nanocomposite thin films. This work shows that increasing the CdSe CQD concentration decreases the polymer hole mobility from ~5.9 × 106 cm2/Vs in an MEH-PPV film to ~8.1 × 108 cm2/Vs in a 20:80 (wt%) MEH-PPV:CdSe CQD nanocomposite film (measured at 25 °C and ~2 × 105 V/cm). The corresponding disorder parameters indicate increasing disruption of interchain interaction with increasing CQD concentration. This work quantifies polymer chain morphology in hybrid nanocomposite thin films and provides useful information regarding the optimal use of semiconductor nanocrystals in conjugated polymer-based optoelectronics. Full article
(This article belongs to the Special Issue Semiconductor Nanocrystals)
Figures

Open AccessCommunication Synthesis and Molecular Structure of tert-Butyl 4-(2-tert-butoxy-2-oxoethyl)piperazine-1-carboxylate
Crystals 2012, 2(1), 90-95; doi:10.3390/cryst2010090
Received: 20 December 2011 / Revised: 30 January 2012 / Accepted: 31 January 2012 / Published: 6 February 2012
Cited by 1 | PDF Full-text (481 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The crystal and molecular structure of tert-butyl 4-(2-tert-butoxy-2-oxoethyl)-piperazine-1-carboxylate is reported. The title compound crystallizes from a petroleum ether/ethyl acetate mixture in the monoclinic space group P 21/c with four molecules in the unit cell. The unit cell [...] Read more.
The crystal and molecular structure of tert-butyl 4-(2-tert-butoxy-2-oxoethyl)-piperazine-1-carboxylate is reported. The title compound crystallizes from a petroleum ether/ethyl acetate mixture in the monoclinic space group P 21/c with four molecules in the unit cell. The unit cell parameters are: a = 8.4007(2) Å, b = 16.4716(4) Å, c = 12.4876(3) Å; β = 90.948(1)° and V = 1727.71(7) Å3. Bond lengths and angles of this piperazine-carboxylate are typical. Full article
Open AccessArticle 1,4-Diazabicyclo[2.2.2]octane (DABCO) 5-aminotetrazolates
Crystals 2012, 2(1), 96-104; doi:10.3390/cryst2010096
Received: 10 January 2012 / Revised: 18 January 2012 / Accepted: 19 January 2012 / Published: 6 February 2012
Cited by 2 | PDF Full-text (884 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The crystal structures of four salts of 1,4-diazabicyclo[2.2.2]octane (DABCO) and 5-aminotetrazole are described. Anhydrous 1:1 (Pbca, Rgt = 0.041) and 1:2 (P, Rgt = 0.038) salts form hydrogen-bonded layers of anions and cations. The monohydrate of [...] Read more.
The crystal structures of four salts of 1,4-diazabicyclo[2.2.2]octane (DABCO) and 5-aminotetrazole are described. Anhydrous 1:1 (Pbca, Rgt = 0.041) and 1:2 (P, Rgt = 0.038) salts form hydrogen-bonded layers of anions and cations. The monohydrate of the 1:1 compound (P21/c, Rgt = 0.038) shows infinite chains of DABCO cations and an undulated layer of anions and water molecules. The octahydrate of the 3:2 compound (P21/c, Rgt = 0.042) features DABCO triples and clusters of four tetrazolate ions in a network of water molecules. Full article
Open AccessCommunication The Molecular Structure of 1,2:5,6-Di-O-isopropylidene-3-O-toluenesulfonyl-α-D-glucofuranose
Crystals 2012, 2(1), 105-109; doi:10.3390/cryst2010105
Received: 5 December 2011 / Revised: 16 February 2012 / Accepted: 20 February 2012 / Published: 29 February 2012
PDF Full-text (225 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The crystal and molecular structure of 1,2:5,6-di-O-isopropylidene-3-O-toluenesulfonyl-α-D-glucofuranose is reported. This compound crystallizes from a petroleum ether/ethyl acetate mixture with the chiral orthorhombic space group P212121 with four molecules in the unit cell. The [...] Read more.
The crystal and molecular structure of 1,2:5,6-di-O-isopropylidene-3-O-toluenesulfonyl-α-D-glucofuranose is reported. This compound crystallizes from a petroleum ether/ethyl acetate mixture with the chiral orthorhombic space group P212121 with four molecules in the unit cell. The unit cell parameters are: a = 9.7945(7) Å, b = 10.1945(7) Å, c = 21.306(1) Å, and V = 2127.4(2) Å3. No classical hydrogen bonds were found. Bond lengths and angles of this tosylated glucofuranose derivative are typical. Full article
Open AccessArticle Betaine Chloride-Betaine Tetrachloridoferrate(III)—An Ionic Liquid Related Crystal Structure Governed by the Pearson Concept
Crystals 2012, 2(1), 110-117; doi:10.3390/cryst2010110
Received: 16 January 2012 / Revised: 1 February 2012 / Accepted: 3 February 2012 / Published: 12 March 2012
Cited by 2 | PDF Full-text (925 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The first betaine chloride tetrachloroidoferrate(III) double salt, (Hbet)2Cl[FeCl4] = (Hbet)Cl·(Hbet)[FeCl4], was obtained from a solution of betaine hydrochloride (HbetCl) and FeCl3∙6 H2O in water. The crystal structure (orthorhombic, Pbcm, a = [...] Read more.
The first betaine chloride tetrachloroidoferrate(III) double salt, (Hbet)2Cl[FeCl4] = (Hbet)Cl·(Hbet)[FeCl4], was obtained from a solution of betaine hydrochloride (HbetCl) and FeCl3∙6 H2O in water. The crystal structure (orthorhombic, Pbcm, a = 6.2717(13), b = 12.841(3), c = 25.693(5) Å, Z = 4) is characterized by layers of tetrachloridoferrate(III) anions separated by chloride-bridged, H-bond mediated cationic (Hbet) dimers. The hydrogen bonding network in the crystal structure follows the Pearson HSAB (hard acid-soft base) concept: According to the Pearson concept, the chloride anions show high affinity to the carboxyl group (hard acid and base), and the tetrachloroidoferrate(III) anion preferentially interacts with the activated methyl donors (soft acid and base). These interactions between the COOH group, as hard H-bond donor, and chloride as hard acceptor besides those between the soft, activated methyl groups and the soft tetrachloridoferrate(III) anions are the major structure-directing forces in the crystal structure of (Hbet)2Cl[FeCl4]. Full article
Open AccessArticle Crystal Structure of 2-Ethylimidazole-1-sulfonyl Azide: A New Azidation Reagent
Crystals 2012, 2(1), 118-126; doi:10.3390/cryst2010118
Received: 4 January 2012 / Revised: 21 February 2012 / Accepted: 29 February 2012 / Published: 12 March 2012
Cited by 5 | PDF Full-text (395 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Crystalline 2-ethylimidazole-1-sulfonyl azide was designed as a convenient reagent with improved thermal stability for electrophilic azidation of carbanions. The compound crystallized in the monoclinic space group P21/c. The molecules are arranged into chains by short C–H...O contacts [...] Read more.
Crystalline 2-ethylimidazole-1-sulfonyl azide was designed as a convenient reagent with improved thermal stability for electrophilic azidation of carbanions. The compound crystallized in the monoclinic space group P21/c. The molecules are arranged into chains by short C–H...O contacts along a two-fold screw axis. The quaternary 1-azidosulfonyl-2-ethyl-3-methylimidazolium tetrafluoroborate crystallized in Fdd2 with two independent ion pairs which engage in C–H...F interactions. Full article
Open AccessArticle Synthesis and Crystal Structures of New 5,5'-Azotetrazolates
Crystals 2012, 2(1), 127-136; doi:10.3390/cryst2010127
Received: 27 December 2011 / Revised: 21 February 2012 / Accepted: 29 February 2012 / Published: 15 March 2012
Cited by 7 | PDF Full-text (486 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Five new 5,5'-azotetrazolate salts (amminsilver, trimethylsulfonium, tetramethyl-phosphonium, trimethylsulfoxonium, 2-(hydroxyethyl)trimethylammonium) were prepared and characterized. The crystal structures were determined by X-ray diffraction. Interactions between the ions are identified and discussed. The sensitivities of the highly energetic silver salt were measured by BAM (Bundesanstalt [...] Read more.
Five new 5,5'-azotetrazolate salts (amminsilver, trimethylsulfonium, tetramethyl-phosphonium, trimethylsulfoxonium, 2-(hydroxyethyl)trimethylammonium) were prepared and characterized. The crystal structures were determined by X-ray diffraction. Interactions between the ions are identified and discussed. The sensitivities of the highly energetic silver salt were measured by BAM (Bundesanstalt für Materialforschung und-prüfung) methods. Full article
Open AccessCommunication Synthesis and Crystal Structure of 1-Chloro-2-methyl-4-nitrobenzene
Crystals 2012, 2(1), 137-143; doi:10.3390/cryst2010137
Received: 29 December 2011 / Revised: 12 March 2012 / Accepted: 13 March 2012 / Published: 19 March 2012
PDF Full-text (271 KB) | HTML Full-text | XML Full-text
Abstract
The title compound (3) was prepared from 4-chloroaniline in good yield on successive oxidation and methylation and its crystal and molecular structure is reported. The compound crystallizes in the monoclinic space group P 21/n with unit cell dimensions a = [...] Read more.
The title compound (3) was prepared from 4-chloroaniline in good yield on successive oxidation and methylation and its crystal and molecular structure is reported. The compound crystallizes in the monoclinic space group P 21/n with unit cell dimensions a = 13.5698(8), b = 3.7195 (3), c = 13.5967 (8) Å, ß = 91.703(3) °, V = 685.96 (10) Å3. The molecule is essentially planar with a dihedral angle of 6.2(3) ° between the nitro group and the phenyl ring. The crystal structure is stabilised by π...π contacts between adjacent benzene rings together with C–H...O hydrogen bonds and close Cl...O contacts. Full article
Open AccessArticle Theoretical and Experimental Study of LiBH4-LiCl Solid Solution
Crystals 2012, 2(1), 144-158; doi:10.3390/cryst2010144
Received: 16 February 2012 / Revised: 7 March 2012 / Accepted: 13 March 2012 / Published: 21 March 2012
Cited by 8 | PDF Full-text (747 KB) | HTML Full-text | XML Full-text
Abstract
Anion substitution is at present one of the pathways to destabilize metal borohydrides for solid state hydrogen storage. In this work, a solid solution of LiBH4 and LiCl is studied by density functional theory (DFT) calculations, thermodynamic modeling, X-ray diffraction, and [...] Read more.
Anion substitution is at present one of the pathways to destabilize metal borohydrides for solid state hydrogen storage. In this work, a solid solution of LiBH4 and LiCl is studied by density functional theory (DFT) calculations, thermodynamic modeling, X-ray diffraction, and infrared spectroscopy. It is shown that Cl substitution has minor effects on thermodynamic stability of either the orthorhombic or the hexagonal phase of LiBH4. The transformation into the orthorhombic phase in LiBH4 shortly after annealing with LiCl is for the first time followed by infrared measurements. Our findings are in a good agreement with an experimental study of the LiBH4-LiCl solid solution structure and dynamics. This demonstrates the validity of the adopted combined theoretical (DFT calculations) and experimental (vibrational spectroscopy) approach, to investigate the solid solution formation of complex hydrides. Full article
(This article belongs to the Special Issue Hydrogen Storage Alloys)
Figures

Review

Jump to: Research

Open AccessReview Theory of Photoinduced Phase Transitions in Molecular Conductors: Interplay Between Correlated Electrons, Lattice Phonons and Molecular Vibrations
Crystals 2012, 2(1), 56-77; doi:10.3390/cryst2010056
Received: 1 December 2011 / Revised: 26 December 2011 / Accepted: 31 December 2011 / Published: 6 January 2012
Cited by 7 | PDF Full-text (2874 KB) | HTML Full-text | XML Full-text
Abstract
Dynamics of photoinduced phase transitions in molecular conductors are reviewed from the perspective of interplay between correlated electrons and phonons. (1) The charge-transfer complex TTF-CA shows a transition from a neutral paraelectric phase to an ionic ferroelectric phase. Lattice phonons promote this [...] Read more.
Dynamics of photoinduced phase transitions in molecular conductors are reviewed from the perspective of interplay between correlated electrons and phonons. (1) The charge-transfer complex TTF-CA shows a transition from a neutral paraelectric phase to an ionic ferroelectric phase. Lattice phonons promote this photoinduced transition by preparing short-range lattice dimerization as a precursor. Molecular vibrations stabilize the neutral phase so that the ionic phase, when realized, possesses a large ionicity and the Mott character; (2) The organic salts θ-(BEDT-TTF)2RbZn(SCN)4 and α-(BEDT-TTF)2I3 show transitions from a charge-ordered insulator to a metal. Lattice phonons make this photoinduced transition hard for the former salt only. Molecular vibrations interfere with intermolecular transfers of correlated electrons at an early stage; (3) The organic salt κ-(d-BEDT-TTF)2Cu[N(CN)2]Br shows a transition from a Mott insulator to a metal. Lattice phonons modulating intradimer transfer integrals enable photoexcitation-energy-dependent transition pathways through weakening of effective interaction and through introduction of carriers. Full article
(This article belongs to the Special Issue Molecular Conductors)
Figures

Journal Contact

MDPI AG
Crystals Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
crystals@mdpi.com
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Crystals
Back to Top