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Crystals, Volume 2, Issue 2 (June 2012), Pages 159-729

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Open AccessArticle Mechanical and Thermal Dehydrogenation of Lithium Alanate (LiAlH4) and Lithium Amide (LiNH2) Hydride Composites
Crystals 2012, 2(2), 159-175; doi:10.3390/cryst2020159
Received: 13 January 2012 / Revised: 21 February 2012 / Accepted: 22 March 2012 / Published: 2 April 2012
Cited by 7 | PDF Full-text (532 KB) | HTML Full-text | XML Full-text
Abstract
Hydrogen storage properties of the (nLiAlH4+ LiNH2) hydride composite where n = 1, 3, 11.5 and 30, synthesized by high energy ball milling have been investigated. The composite with the molar ratio n = 1 releases large quantities of
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Hydrogen storage properties of the (nLiAlH4 + LiNH2) hydride composite where n = 1, 3, 11.5 and 30, synthesized by high energy ball milling have been investigated. The composite with the molar ratio n = 1 releases large quantities of H2 (up to ~5 wt.%) during ball milling up to 100–150 min. The quantity of released H2 rapidly decreases for the molar ratio n = 3 and is not observed for n = 11.5 and 30. The XRD studies indicate that the H2 release is a result of a solid state decomposition of LiAlH4 into (1/3)Li3AlH6 + (2/3)Al + H2 and subsequently decomposition of (1/3)Li3AlH6 into LiH + (1/3)Al + 0.5H2. Apparently, LiAlH4 is profoundly destabilized during ball milling by the presence of a large quantity of LiNH2 (37.7 wt.%) in the n = 1 composite. The rate of dehydrogenation at 100–170 °C (at 1 bar H2) is adversely affected by insufficient microstructural refinement, as observed for the n = 1 composite, which was milled for only 2 min to avoid H2 discharge during milling. XRD studies show that isothermal dehydrogenation of (nLiAlH4 + LiNH2) occurs by the same LiAlH4 decomposition reactions as those found during ball milling. The ball milled n = 1 composite stored under Ar at 80 °C slowly discharges large quantities of H2 approaching 3.5 wt.% after 8 days of storage. Full article
(This article belongs to the Special Issue Hydrogen Storage Alloys)
Open AccessCommunication The Synthesis and Molecular Structure of 2-(4-Methoxybenzyl)-4-nitro-2H-indazole
Crystals 2012, 2(2), 176-181; doi:10.3390/cryst2020176
Received: 23 December 2011 / Revised: 21 February 2012 / Accepted: 23 March 2012 / Published: 10 April 2012
Cited by 1 | PDF Full-text (821 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Two novel indazole derivatives protected with p-methoxybenzyl group were synthesized and characterized. The crystal and molecular structure of 2-(4-methoxybenzyl)-4-nitro-2H-indazole as one out of the two regioisomers is reported. The compound was obtained from a saturated petroleum ether/ethyl acetate mixture and
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Two novel indazole derivatives protected with p-methoxybenzyl group were synthesized and characterized. The crystal and molecular structure of 2-(4-methoxybenzyl)-4-nitro-2H-indazole as one out of the two regioisomers is reported. The compound was obtained from a saturated petroleum ether/ethyl acetate mixture and crystallizes in the triclinic space group P`1. The unit cell parameters are: a = 6.8994(1) Å, b = 9.8052(2) Å, c = 11.1525(2) Å; α = 71.729(1)°, β = 79.436(1)°, γ = 74.349(1)° and V = 685.83(2) Å3. There are two independent molecules found in the asymmetric unit. Full article
Open AccessCommunication A New BEDT-TTF-Based Organic Charge Transfer Salt with a New Anionic Strong Acceptor, N,N'-Disulfo-1,4-benzoquinonediimine
Crystals 2012, 2(2), 182-192; doi:10.3390/cryst2020182
Received: 21 February 2012 / Revised: 27 March 2012 / Accepted: 28 March 2012 / Published: 10 April 2012
Cited by 2 | PDF Full-text (757 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A novel organic dianion, N,N'-Disulfo-1,4-benzoquinonediimine (1) has been prepared, which is a strong electron acceptor. The reduction potential of the PPh4 salt indicates that 1 is a stronger acceptor than DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone). The dianionic acceptor provided a
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A novel organic dianion, N,N'-Disulfo-1,4-benzoquinonediimine (1) has been prepared, which is a strong electron acceptor. The reduction potential of the PPh4 salt indicates that 1 is a stronger acceptor than DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone). The dianionic acceptor provided a BEDT-TTF salt, (BEDT-TTF)41·3H2O, the structures and physical properties of which are reported. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessArticle Ammonia Uptake and Release in the MnX2–NH3 (X = Cl, Br) Systems and Structure of the Mn(NH3)nX2 (n = 6, 2) Ammines
Crystals 2012, 2(2), 193-212; doi:10.3390/cryst2020193
Received: 21 February 2012 / Revised: 18 March 2012 / Accepted: 30 March 2012 / Published: 10 April 2012
Cited by 11 | PDF Full-text (556 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Hexa-ammine complexes, Mn(NH3)6X2 (X = Cl, Br), have been synthesized by ammoniation of the corresponding transition metal halide and characterized by Powder X-ray diffraction (PXRD) and Raman spectroscopy. The hexa-ammine complexes are isostructural (Cubic, Fm-3m
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Hexa-ammine complexes, Mn(NH3)6X2 (X = Cl, Br), have been synthesized by ammoniation of the corresponding transition metal halide and characterized by Powder X-ray diffraction (PXRD) and Raman spectroscopy. The hexa-ammine complexes are isostructural (Cubic, Fm-3m, Z = 4; a = 10.2742(6) Å and 10.527(1) Å for X = Cl, Br respectively). Temperature programmed desorption (TPD) demonstrated that ammonia release from Mn(NH3)6X2 complexes occurred in three stages corresponding to the release of 4, 1 and 1 NH3 equivalents respectively. The chloride and bromide both exhibit a deammoniation onset temperature below 323 K. The di-ammoniates from the first desorption step were isolated during TPD measurements and their crystal structures determined by Rietveld refinement against PXRD data (X = Cl: orthorhombic Cmmm, a = 8.1991(9) Å, b = 8.2498(7) Å, c = 3.8212(4) Å, Z = 2; X = Br: orthorhombic Pbam, a = 6.0109(5) Å, b = 12.022(1) Å, c = 4.0230(2) Å, Z = 2). Full article
(This article belongs to the Special Issue Hydrogen Storage Alloys)
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Open AccessArticle Synthesis and Crystal Structures of the Quaternary Zintl Phases RbNa8Ga3Pn6 (Pn = P, As) and Na10NbGaAs6
Crystals 2012, 2(2), 213-223; doi:10.3390/cryst2020213
Received: 21 December 2011 / Revised: 27 March 2012 / Accepted: 31 March 2012 / Published: 11 April 2012
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Abstract
The new Zintl compounds RbNa8Ga3Pn6 (Pn = P, As) and Na10NbGaAs6 have been synthesized from the corresponding elements at high temperatures. RbNa8Ga3P6 and RbNa8Ga3As6
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The new Zintl compounds RbNa8Ga3Pn6 (Pn = P, As) and Na10NbGaAs6 have been synthesized from the corresponding elements at high temperatures. RbNa8Ga3P6 and RbNa8Ga3As6 crystallize with a novel structure type that features trigonal planar [Ga3P6]9 and [Ga3As6]9 motifs, which are isosteric with the 1,3,5-trioxanetrione (a cyclic trimer of carbon dioxide). Na10NbGaAs6, an unforeseen side product of the same reactions boasts a structure, which is based on NbAs4 and GaAs4 tetrahedra, condensed by sharing common edges into [NbGaAs6]10– dimers. The bonding characteristics of both structures are discussed. All three compounds reported herein represent the first compounds found in the respective quaternary systems. Full article
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Open AccessArticle Properties of Mn2+ and Π-Electron Spin Systems Probed by 1H and 13C NMR in the Organic Conductor κ-(BETS)2Mn[N(CN)2]3
Crystals 2012, 2(2), 224-235; doi:10.3390/cryst2020224
Received: 7 March 2012 / Revised: 30 March 2012 / Accepted: 31 March 2012 / Published: 12 April 2012
Cited by 1 | PDF Full-text (942 KB) | HTML Full-text | XML Full-text
Abstract
Properties of the spin systems of the localized 3d Mn2+ ions and the conduction π electrons in quasi-two-dimensional organic conductor κ-(BETS)2Mn[N(CN)2]3 were accessed using 1H and 13C NMR in order to find their
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Properties of the spin systems of the localized 3d Mn2+ ions and the conduction π electrons in quasi-two-dimensional organic conductor κ-(BETS)2Mn[N(CN)2]3 were accessed using 1H and 13C NMR in order to find their relation to the metal-insulator transition which occurs at ∼23 K. The transition of the system into the insulating state is shown to be followed by localization of the π spins into a long-range ordered staggered structure of AF type. In contrast, the 3d Mn2+ electron spin moments form a disordered tilted structure, which may signify their trend to AF order, frustrated geometrically by the triangular arrangement of Mn in the anion layer. This result suggests that the MI transition in κ-(BETS)2Mn[N(CN)2]3 is not the consequence of the interactions within the Mn2+ spins but due to the interactions within the π-electron system itself. Vice versa, it is more likelythat the disordered tilted structure of the Mn2+ spins is induced by the ordered π-spins via the π-d interaction. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessArticle Equivalence of Electron-Vibration Interaction and Charge-Induced Force Variations: A New O(1) Approach to an Old Problem
Crystals 2012, 2(2), 236-247; doi:10.3390/cryst2020236
Received: 8 March 2012 / Revised: 2 April 2012 / Accepted: 9 April 2012 / Published: 18 April 2012
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Abstract
Calculating electron-vibration (vibronic) interaction constants is computationally expensive. For molecules containing N nuclei it involves solving the Schrödinger equation for Ο(3N) nuclear configurations in addition to the cost of determining the vibrational modes. We show that quantum vibronic interactions are proportional to
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Calculating electron-vibration (vibronic) interaction constants is computationally expensive. For molecules containing N nuclei it involves solving the Schrödinger equation for Ο(3N) nuclear configurations in addition to the cost of determining the vibrational modes. We show that quantum vibronic interactions are proportional to the classical atomic forces induced when the total charge of the system is varied. This enables the calculation of vibronic interaction constants from O(1) solutions of the Schrödinger equation. We demonstrate that the O(1) approach produces numerically accurate results by calculating the vibronic interaction constants for several molecules. We investigate the role of molecular vibrations in the Mott transition in κ-(BEDT-TTF)2Cu[N(CN)2]Br. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessArticle New BEDT-TTF Radical Cation Salt with Mixed Anions: α'-[BEDT-TTF]2[CuBr2]0.4[CuCl2]0.6
Crystals 2012, 2(2), 284-293; doi:10.3390/cryst2020284
Received: 8 March 2012 / Revised: 13 April 2012 / Accepted: 13 April 2012 / Published: 23 April 2012
Cited by 2 | PDF Full-text (1098 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A new mixed-anion crystal composed of BEDT-TTF radical cation salt [BEDT-TTF]2(CuBr2)0.4(CuCl2)0.6 with an α'-type donor arrangement with a formal charge of +0.5 per BEDT-TTF was prepared by using a chemical oxidation method and
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A new mixed-anion crystal composed of BEDT-TTF radical cation salt [BEDT-TTF]2(CuBr2)0.4(CuCl2)0.6 with an α'-type donor arrangement with a formal charge of +0.5 per BEDT-TTF was prepared by using a chemical oxidation method and characterized by using X-ray diffraction, four-probe electrical resistivity measurements (semiconductor: ρrt = 2 × 102 Ω cm, Ea = 0.2 eV), and energy band calculations. The results showed that this system had a quasi-one dimensional Fermi surface. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessArticle Preparation and Crystal Structure of 5-Azido-3-nitro-1H-1,2,4-triazole, Its Methyl Derivative and Potassium Salt
Crystals 2012, 2(2), 294-305; doi:10.3390/cryst2020294
Received: 22 March 2012 / Revised: 11 April 2012 / Accepted: 16 April 2012 / Published: 23 April 2012
Cited by 7 | PDF Full-text (2052 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
5-Azido-3-nitro-1H-1,2,4-triazole, its methyl derivative and potassium salt were synthesized and characterized by various spectroscopic methods. The crystal structures were determined by low temperature single crystal X-ray diffraction. The interactions between the molecules or ions were analyzed and discussed. Furthermore, all compounds
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5-Azido-3-nitro-1H-1,2,4-triazole, its methyl derivative and potassium salt were synthesized and characterized by various spectroscopic methods. The crystal structures were determined by low temperature single crystal X-ray diffraction. The interactions between the molecules or ions were analyzed and discussed. Furthermore, all compounds were tested according to BAM (Bundesanstalt für Materialforschung und -prüfung) methods. Full article
Open AccessArticle Polymorphism and Metallic Behavior in BEDT-TTF Radical Salts with Polycyano Anions
Crystals 2012, 2(2), 306-326; doi:10.3390/cryst2020306
Received: 27 March 2012 / Revised: 12 April 2012 / Accepted: 13 April 2012 / Published: 23 April 2012
Cited by 3 | PDF Full-text (1788 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Up to five different crystalline radical salts have been prepared with the organic donor BEDT-TTF and three different polynitrile anions. With the polynitrile dianion tcpd2− (=C[C(CN)2]32−), two closely related radical salts: α'-(ET)4tcpd·THF (1)
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Up to five different crystalline radical salts have been prepared with the organic donor BEDT-TTF and three different polynitrile anions. With the polynitrile dianion tcpd2− (=C[C(CN)2]32−), two closely related radical salts: α'-(ET)4tcpd·THF (1) (THF = tetrahydrofurane) and α'-(ET)4tcpd·H2O (2) have been prepared, depending on the solvent used in the synthesis. With the mono-anion tcnoetOH (=[(NC)2CC(OCH2CH2OH)C(CN)2]) two polymorphs with similar physical properties but different crystal packings have been synthesized: θ-(ET)2(tcnoetOH) (3) and β''-(ET)2(tcnoetOH) (4). Finally, with the mono-anion tcnoprOH (=[(NC)2CC(OCH2CH2CH2OH)C(CN)2]) we have prepared a metallic radical salt: β''-(ET)2(tcnoprOH)(CH2Cl2CH3Cl)0.5 (5). Salts 14 are semiconductors with high room temperature conductivities and activation energies in the range 0.1–0.5 eV, whereas salt 5 is metallic down to 0.4 K although it does not show any superconducting transition above this temperature. Full article
(This article belongs to the Special Issue Molecular Conductors)
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Open AccessArticle Halogen Bonding Interactions in DDQ Charge Transfer Salts with Iodinated TTFs
Crystals 2012, 2(2), 327-337; doi:10.3390/cryst2020327
Received: 22 March 2012 / Revised: 11 April 2012 / Accepted: 11 April 2012 / Published: 24 April 2012
Cited by 7 | PDF Full-text (1234 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Oxidation of 3,4-ethylenedithio-3'-iodo-tetrathiafulvalene (EDT-TTF-I) and 3,4-ethylenedithio-3',4'-diiodo-tetrathiafulvalene (EDT-TTF-I2) with DDQ afforded two different salts formulated as (EDT-TTF-I)(DDQ) and (EDT-TTF-I2)2(DDQ)·(CH3CN), both characterized with a full charge transfer to the DDQ acceptor moiety and by short and linear
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Oxidation of 3,4-ethylenedithio-3'-iodo-tetrathiafulvalene (EDT-TTF-I) and 3,4-ethylenedithio-3',4'-diiodo-tetrathiafulvalene (EDT-TTF-I2) with DDQ afforded two different salts formulated as (EDT-TTF-I)(DDQ) and (EDT-TTF-I2)2(DDQ)·(CH3CN), both characterized with a full charge transfer to the DDQ acceptor moiety and by short and linear halogen bonding interactions between the iodine atom as halogen bond donor, and the carbonyl oxygen or the nitrile nitrogen atoms of reduced DDQ. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessArticle Electroactive Bisiminopyridine Ligands: Synthesis and Complexation Studies
Crystals 2012, 2(2), 338-348; doi:10.3390/cryst2020338
Received: 22 March 2012 / Revised: 6 April 2012 / Accepted: 9 April 2012 / Published: 24 April 2012
Cited by 10 | PDF Full-text (639 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The condensation reaction of (4-(6,7-dimethyldithio-tetrathiafulvalene)-aniline) with 2,6-diformylpyridine afforded an electroactive Schiff base (N,N,N) pincer (3). This pincer was reacted with Zn(II) cation to yield the corresponding Zinc chloride complex (4). The crystal structure of the newly prepared electroactive zinc
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The condensation reaction of (4-(6,7-dimethyldithio-tetrathiafulvalene)-aniline) with 2,6-diformylpyridine afforded an electroactive Schiff base (N,N,N) pincer (3). This pincer was reacted with Zn(II) cation to yield the corresponding Zinc chloride complex (4). The crystal structure of the newly prepared electroactive zinc complex reveals that the tetrathiafulvalene (TTF) is neutral and the zinc cation is pentacoordinated. The two chlorines are involved in a set of hydrogen bonds giving rise to a 2D supramolecular grid arrangement. The electronic absorption properties and the electrochemical behavior have been elucidated. These two compounds are promising for the construction of crystalline radical cation salts. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessArticle Crystal Structure of the 5-Chloro Salicylamides: Three Different Types of the H-bonding Influenced Linear Chain Formation in the Solid State
Crystals 2012, 2(2), 349-361; doi:10.3390/cryst2020349
Received: 18 January 2012 / Revised: 16 April 2012 / Accepted: 17 April 2012 / Published: 3 May 2012
Cited by 1 | PDF Full-text (556 KB) | HTML Full-text | XML Full-text
Abstract
Three N-substituted 5-chlorosalicylamides (4-chlorophenyl, 2a; benzyl, 2b; phenethyl 2c) differing in the length of the 'linker' between the benzene ring and the amide moiety were prepared in order to compare their supramolecular architecture. The intramolecular NH···O(H) hydrogen bond and
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Three N-substituted 5-chlorosalicylamides (4-chlorophenyl, 2a; benzyl, 2b; phenethyl 2c) differing in the length of the 'linker' between the benzene ring and the amide moiety were prepared in order to compare their supramolecular architecture. The intramolecular NH···O(H) hydrogen bond and the intermolecular C=O···H–O hydrogen bond were found in the crystal structure of 2a and 2c thus forming an infinite linear chain. Compound 2b had a different arrangement with the intramolecular C=O···H–O hydrogen bond and another intermolecular NH···O(H) hydrogen forming a linear infinite chain. Full article
Open AccessArticle Polyoxotungstate-Surfactant Layered Crystal toward Conductive Inorganic-Organic Hybrid
Crystals 2012, 2(2), 362-373; doi:10.3390/cryst2020362
Received: 12 February 2012 / Revised: 17 April 2012 / Accepted: 27 April 2012 / Published: 3 May 2012
Cited by 9 | PDF Full-text (391 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A polyoxotungstate-surfactant hybrid layered compound was synthesized as a single phase by using decatungstate ([W10O32]4−, W10) and hexadecylpyridinium (C16py). The X-ray structure analysis combined with infrared spectroscopy and elemental analysis revealed the formula
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A polyoxotungstate-surfactant hybrid layered compound was synthesized as a single phase by using decatungstate ([W10O32]4−, W10) and hexadecylpyridinium (C16py). The X-ray structure analysis combined with infrared spectroscopy and elemental analysis revealed the formula to be (C16py)4[W10O32] (C16py-W10). The layered structure consisted of alternative stacking of W10 inorganic monolayers and interdigitated C16py bilayers with layered periodicity of 23.3 Å. Each W10 anion in the W10 inorganic monolayers was isolated by the hydrophilic heads of C16py. The hybrid crystals of C16py-W10 decomposed at around 500 K. The conductivity of the hybrid layered crystal was estimated to be 4.8 × 10−6 S cm−1 at 423 K by alternating current (AC) impedance spectroscopy. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessArticle Synthesis and Properties of 2-Alkylidene-1,3-dithiolo[4,5-d]-4,5-ethylenediselenotetrathiafulvalene Derivatives and Crystal Structures of Their Cation Radical Salts
Crystals 2012, 2(2), 393-412; doi:10.3390/cryst2020393
Received: 23 March 2012 / Revised: 24 April 2012 / Accepted: 24 April 2012 / Published: 9 May 2012
Cited by 1 | PDF Full-text (2775 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Tetrathiafulvalene derivatives condensed with 2-alkylidene-1,3-dithiole moiety, MeDTES (2-isopropylidene-1,3-dithiolo[4,5-d]-4,5-ethylenediselenotetrathiafulvalene), EtDTES (2-(pentan-3-ylidene)-1,3-dithiolo[4,5-d]-4,5-ethylenediselenotetrathiafulvalene), and CPDTES (2-cyclopentanylidene-1,3-dithiolo[4,5-d]-4,5-ethylenediselenotetrathiafulvalene) have been synthesized. Crystal structure analysis of MeDTES salts with Au(CN)4, ReO4, and I3 and a
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Tetrathiafulvalene derivatives condensed with 2-alkylidene-1,3-dithiole moiety, MeDTES (2-isopropylidene-1,3-dithiolo[4,5-d]-4,5-ethylenediselenotetrathiafulvalene), EtDTES (2-(pentan-3-ylidene)-1,3-dithiolo[4,5-d]-4,5-ethylenediselenotetrathiafulvalene), and CPDTES (2-cyclopentanylidene-1,3-dithiolo[4,5-d]-4,5-ethylenediselenotetrathiafulvalene) have been synthesized. Crystal structure analysis of MeDTES salts with Au(CN)4, ReO4, and I3 and a CPDTES salt with I3 reveals that the donor−anion ratios of all salts are 1:1. Band calculation of (MeDTES)[Au(CN)4] suggests a quasi-one-dimensional Fermi surface that could be the result of the uniform stack of donor molecules. In spite of this stacking, the salt is a Mott insulator because of a large on-site Coulomb interaction U. (MeDTES)(ReO4)(H2O)0.5 possesses Fermi points and exhibits semiconducting behavior with small activation energy (Ea = 0.058 eV). I3 ions form disordered infinite chain in (MeDTES)(I3)(DCE)0.25, but those in (CPDTES)(I3) exist as discrete ions. They show low conductivity (10−4−10−2 S cm−1) at room temperature and the band calculation suggests that they are band insulator. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessArticle Synthesis, Structure and Solid State Properties of Cyclohexanemethylamine Substituted Phenalenyl Based Molecular Conductor
Crystals 2012, 2(2), 446-465; doi:10.3390/cryst2020446
Received: 30 March 2012 / Revised: 20 April 2012 / Accepted: 2 May 2012 / Published: 14 May 2012
Cited by 2 | PDF Full-text (1001 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We report the preparation, crystallization and solid state characterization of a cyclohexanemethylamine substituted spirobiphenalenyl radical; in the solid state the compound is iso-structural with its dehydro-analog (benzylamine-substitued compound), and the molecules packed in a one-dimensional fashion that we refer to as a π-step
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We report the preparation, crystallization and solid state characterization of a cyclohexanemethylamine substituted spirobiphenalenyl radical; in the solid state the compound is iso-structural with its dehydro-analog (benzylamine-substitued compound), and the molecules packed in a one-dimensional fashion that we refer to as a π-step stack. Neighboring molecules in the stack interact via the overlap of one pair of active (spin bearing) carbon atoms per phenalenyl unit. The magnetic susceptibility measurement indicates that in the solid state the radical remains paramagnetic and the fraction of Curie spins is 0.75 per molecule. We use the analytical form of the Bonner-Fisher model for the S = 1/2 antiferromagnetic Heisenberg chain of isotropically interacting spins with intrachain spin coupling constant J = 6.3 cm−1, to fit the experimentally observed paramagnetism [χp (T)] in the temperature range 4–330 K. The measured room temperature conductivity (σRT = 2.4 × 10–3 S/cm) is comparable with that of the iso-structural benzyl radical, even though the calculated band dispersions are smaller than that of the unsaturated analog. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessCommunication Ethyl 2,6-Dimethoxybenzoate: Synthesis, Spectroscopic and X-ray Crystallographic Analysis
Crystals 2012, 2(2), 521-527; doi:10.3390/cryst2020521
Received: 19 March 2012 / Revised: 4 May 2012 / Accepted: 9 May 2012 / Published: 22 May 2012
Cited by 2 | PDF Full-text (230 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The acid catalyzed esterification of 2,6-dimethoxybenzoic acid (1) in the presence of absolute ethanol afforded ethyl 2, 6-dimethoxybenzoate (2). The structure of the resulting compound was supported by spectroscopic data and unambiguously confirmed by single crystal X-ray diffraction studies.
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The acid catalyzed esterification of 2,6-dimethoxybenzoic acid (1) in the presence of absolute ethanol afforded ethyl 2, 6-dimethoxybenzoate (2). The structure of the resulting compound was supported by spectroscopic data and unambiguously confirmed by single crystal X-ray diffraction studies. The title compound crystallized in the triclinic space group P ī with unit cell parameters a = 8.5518(3) Å, b = 10.8826(8) Å, c = 11.9939(6) Å, α = 101.273(5)°, β = 98.287(3)°, γ = 94.092(4)°, V = 1077.54(10) Å3, Z = 4, Dc = 1.296 Mg/m3, F(000) = 448 and μ = 0.098 mm−1. Compound (2) crystallizes with two molecules in the asymmetric unit with similar conformations. Full article
Open AccessArticle Comprehensive Optical Investigations of Charge Order in Organic Chain Compounds (TMTTF)2X
Crystals 2012, 2(2), 528-578; doi:10.3390/cryst2020528
Received: 2 March 2012 / Revised: 30 April 2012 / Accepted: 1 May 2012 / Published: 23 May 2012
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Abstract
Charge ordering in the (TMTTF)2X salts with centrosymmetric anions (X = PF‾6 , AsF‾6 , SbF‾6 ) leads to a ferroelectric state around 100 K. For the first time and in great completeness, the intra- and intermolecular vibrational
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Charge ordering in the (TMTTF)2X salts with centrosymmetric anions (X = PF‾6 , AsF‾6 , SbF‾6 ) leads to a ferroelectric state around 100 K. For the first time and in great completeness, the intra- and intermolecular vibrational modes of (TMTTF)2X have been investigated by infrared and Raman spectroscopy as a function of temperature and pressure for different polarizations. In this original paper, we explore the development and amount of charge disproportionation and the coupling of the electronic degrees of freedom to the counterions and the underlying lattice. The methyl groups undergo changes with temperature that are crucial for the anion cage formed by them. We find that the coupling of the TMTTF molecules to the hexafluorine anions changes upon cooling and especially at the charge-order transition, indicating a distortion of the anion. Additional features are identified that are caused by the anharmonic potential. The spin-Peierls transition entails additional modifications in the charge distribution. To complete the discussion, we also add the vibrational frequencies and eigenvectors based on ab-initio quantum-chemical calculations. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessArticle Spin and Charge Transport in the X-ray Irradiated Quasi-2D Layered Compound: κ-(BEDT-TTF)2Cu[N(CN)2]Cl
Crystals 2012, 2(2), 579-589; doi:10.3390/cryst2020579
Received: 23 March 2012 / Revised: 25 April 2012 / Accepted: 11 May 2012 / Published: 24 May 2012
Cited by 1 | PDF Full-text (863 KB) | HTML Full-text | XML Full-text
Abstract
The interplane spin cross relaxation time Tx measured by high frequency ESR in X-ray irradiated κ-(BEDT-TTF)2Cu[N(CN)2]Cl is compared to the interplane resisitivity ρ⊥and the in-plane resistivity ρII between 50 K and 250 K. The irradiation
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The interplane spin cross relaxation time Tx measured by high frequency ESR in X-ray irradiated κ-(BEDT-TTF)2Cu[N(CN)2]Cl is compared to the interplane resisitivity ρ⊥and the in-plane resistivity ρII between 50 K and 250 K. The irradiation transforms the semiconductor behavior of the non-irradiated crystal into metallic. Irradiation decreases Tx, ρ⊥ and ρII but the ratio Tx/ρ⊥ and ρ⊥/ρII remain unchanged between 50 and 250 K. Models describing the unusual defect concentration dependence in κ-(BEDT-TTF)2Cu[N(CN)2]Cl are discussed. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessArticle Growth Mechanisms of CdS Nanocrystals in Aqueous Media
Crystals 2012, 2(2), 618-626; doi:10.3390/cryst2020618
Received: 7 December 2011 / Revised: 16 May 2012 / Accepted: 23 May 2012 / Published: 6 June 2012
Cited by 1 | PDF Full-text (789 KB) | HTML Full-text | XML Full-text
Abstract
CdS nanocrystals were prepared in water-in-oil microemulsions. The nanocrystal properties, absorption and luminescence spectra and size distributions, were monitored at different times after mixing the microemulsions of the two precursors to obtain information on their growth mechanism. In particular, CdS nanocrystals were prepared
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CdS nanocrystals were prepared in water-in-oil microemulsions. The nanocrystal properties, absorption and luminescence spectra and size distributions, were monitored at different times after mixing the microemulsions of the two precursors to obtain information on their growth mechanism. In particular, CdS nanocrystals were prepared using water-in-heptane or water-in-nonane microemulsions. The results obtained from the investigation of nanocrystals prepared using heptane as the organic phase, confirmed that nanocrystal nucleation is fast while their growth is determined by droplet exchange content rate. Size distribution histograms obtained from the sample at early time points after mixing presented a bimodal population having average sizes of 3.0 ± 0.1 and 5.8 ± 0.1 nm, thus indicating that surface process controls the nanocrystal growth. With longer reaction times the occurrence of water droplet coalescence is likely responsible for the formation of nanocrystal agglomerates. Using a water-in-nonane microemulsion, the droplet exchange rate can be modified, thus leading to smaller CdS nanocrystals. However, the development of structural defects cannot be excluded, as evidenced by the luminescence spectra of the suspension. In general, aging of the nanocrystal in the pristine microemulsion resulted in the development of cubic semiconductor nanostructures. Full article
(This article belongs to the Special Issue Semiconductor Nanocrystals)
Open AccessArticle Single-Crystal-to-Single-Crystal Transformation from δ-(BEDT-TTF)4[OsNOCl5]1.33(C6H5NO2)0.67 to β"-(BEDT-TTF)3[OsNOCl5]
Crystals 2012, 2(2), 627-642; doi:10.3390/cryst2020627
Received: 16 March 2012 / Revised: 15 May 2012 / Accepted: 15 May 2012 / Published: 7 June 2012
Cited by 1 | PDF Full-text (1345 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We report on the single-crystal-to-single-crystal transformation occurring over time in a layered organic molecular conductor based on BEDT-TTF. The process is connected with removal of solvent molecules from the complex anion layer resulting in concomitant partial irreversible conversion of the δ-(BEDT-TTF)4[OsNOCl
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We report on the single-crystal-to-single-crystal transformation occurring over time in a layered organic molecular conductor based on BEDT-TTF. The process is connected with removal of solvent molecules from the complex anion layer resulting in concomitant partial irreversible conversion of the δ-(BEDT-TTF)4[OsNOCl5]1.33(C6H5NO2)0.67 structure to the β"-(BEDT-TTF)3[OsNOCl5] structure. Along with symmetry lowering from I2/a to Р, huge, drastic changes in the conducting BEDT-TTF layer as well as in the anion arrangement are observed, meanwhile crystallinity of the sample is retained. Coexistence of two phases, parent δ and daughter β" in the same crystal helps in the study of their mutual orientation as well as to formulate a mechanism for the structural transformation. Full article
(This article belongs to the Special Issue Molecular Conductors)
Figures

Open AccessArticle Single-Component Charge-Transfer Crystals Based on Spin-Carrying TCNQ (7,7,8,8-Tetracyanoquinodimethane) Derivatives
Crystals 2012, 2(2), 662-668; doi:10.3390/cryst2020662
Received: 16 March 2012 / Revised: 1 June 2012 / Accepted: 5 June 2012 / Published: 12 June 2012
Cited by 2 | PDF Full-text (329 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Three TCNQ derivatives carrying nitroxide radicals (3a3c) were prepared and were found to form single-component charge-transfer (CT) complexes by self-assembly, in which outer nitroxide groups of a couple of different molecules work as donors and the inner TCNQ unit
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Three TCNQ derivatives carrying nitroxide radicals (3a3c) were prepared and were found to form single-component charge-transfer (CT) complexes by self-assembly, in which outer nitroxide groups of a couple of different molecules work as donors and the inner TCNQ unit of another molecule as an acceptor. While the CT interactions found for the TEMPO (2,2,6,6-tetramethylpiperidin-1-oxy) derivative 3a and the PROXYL (2,2,5,5-tetramethylpirrolidin-1-oxy) derivative 3b are point-to-face fashion between the oxygen atom of each nitroxide group and the six-membered ring of inner TCNQ unit, the CT interactions found for the PO (2,2,5,5-tetramethyl-3-pyrrolin-1-oxy) derivative 3c are point-to-point contacts between the oxygen atoms of outer nitroxide groups and the carbon atoms of a couple of cyano groups. Full article
(This article belongs to the Special Issue Molecular Conductors)
Figures

Open AccessCommunication Non-Covalent Interactions in the Crystal Structure of Methyl 4-Hydroxy-3-Nitrobenzoate
Crystals 2012, 2(2), 669-674; doi:10.3390/cryst2020669
Received: 18 April 2012 / Revised: 22 May 2012 / Accepted: 1 June 2012 / Published: 12 June 2012
Cited by 1 | PDF Full-text (338 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Methyl 4-hydroxy-3-nitrobenzoate, (I), C8H7NO5, crystallizes with two unique molecules, A and B, in the asymmetric unit of the triclinic unit cell. The space group was assigned as P-1, with lattice parameters a = 0.72831(15), b = 1.0522(2),
[...] Read more.
Methyl 4-hydroxy-3-nitrobenzoate, (I), C8H7NO5, crystallizes with two unique molecules, A and B, in the asymmetric unit of the triclinic unit cell. The space group was assigned as P-1, with lattice parameters a = 0.72831(15), b = 1.0522(2), c = 1.1410(2) nm, α = 83.38(3), β = 80.83(3), γ = 82.02(3)°, Z = 4, V = 0.8510(3) nm3, Mr = 197.15, Dc = 1.539 g/m3, µ= 0.131 mm−1, F(000) = 408, R = 0.1002 and wR = 0.2519. In the crystal structure, 12 hydrogen bonding and two p-stacking interactions link the molecules into infinite stacked sheets parallel to (101). Full article
Open AccessArticle Inorganic Amino-Nitro-Guanidinium Derivatives
Crystals 2012, 2(2), 675-689; doi:10.3390/cryst2020675
Received: 2 May 2012 / Revised: 6 June 2012 / Accepted: 7 June 2012 / Published: 18 June 2012
Cited by 3 | PDF Full-text (889 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
1-Amino-3-nitroguanidine (ANQ, 1) was synthesized by hydrazinolysis of nitroguanidine (NQ) with hydrazine hydrate. Four different amino-nitroguanidinium salts (chloride (2), bromide (3), iodide (4) and sulfate (5)) were synthesized and structurally characterized by low-temperature X-ray
[...] Read more.
1-Amino-3-nitroguanidine (ANQ, 1) was synthesized by hydrazinolysis of nitroguanidine (NQ) with hydrazine hydrate. Four different amino-nitroguanidinium salts (chloride (2), bromide (3), iodide (4) and sulfate (5)) were synthesized and structurally characterized by low-temperature X-ray diffraction. The halides 24 could only be obtained crystalline as monohydrates. In addition, they were characterized by NMR and vibrational spectroscopy, elemental analysis and the sensitivities towards impact, friction and electrostatic discharge were determined. The compounds can be used in silver (AgX, X = Cl, Br, I) and barium (BaSO4) based metathesis reactions in order to form more complex salts of 1-amino-nitroguanidine. Full article
Open AccessArticle Silica-Metal Composite for Hydrogen Storage Applications
Crystals 2012, 2(2), 690-703; doi:10.3390/cryst2020690
Received: 2 February 2012 / Revised: 23 May 2012 / Accepted: 6 June 2012 / Published: 18 June 2012
Cited by 1 | PDF Full-text (1679 KB) | HTML Full-text | XML Full-text
Abstract
In spite of their favourable chemical characteristics, using AB5 alloys as fixed bed for hydrogen storage devices requires proper management of a number of technological aspects. Among these, the mechanical stability of metal particle grains under hydrogen cycling and the overall thermal conductivity
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In spite of their favourable chemical characteristics, using AB5 alloys as fixed bed for hydrogen storage devices requires proper management of a number of technological aspects. Among these, the mechanical stability of metal particle grains under hydrogen cycling and the overall thermal conductivity of the material bed constitute crucial features. We developed by High Energy Ball Milling HEBM a mechanically stable silica-based AB5 composite with enhanced thermal conductivity. Here, focusing on the material’s physical-chemical properties, we report on the silica-AB5 composite development and characterization. Particularly, we studied the material consolidation process, the resulting composite morphology and the system behaviour under hydrogen loading/unloading cycling. Full article
(This article belongs to the Special Issue Hydrogen Storage Alloys)
Open AccessArticle Ru11Lu20, a New Intermetallic Compound with Eight- to Ten-Coordinate Ruthenium Atoms
Crystals 2012, 2(2), 704-709; doi:10.3390/cryst2020704
Received: 14 May 2012 / Revised: 11 June 2012 / Accepted: 12 June 2012 / Published: 20 June 2012
Cited by 3 | PDF Full-text (807 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The new intermetallic compound Ru11Lu20 was obtained as black single crystals during an attempted comproportionation reaction of lutetium(III) chloride, LuCl3, with metallic lutetium in the presence of ruthenium metal at 950 °C. Ru11Lu20 crystallizes with
[...] Read more.
The new intermetallic compound Ru11Lu20 was obtained as black single crystals during an attempted comproportionation reaction of lutetium(III) chloride, LuCl3, with metallic lutetium in the presence of ruthenium metal at 950 °C. Ru11Lu20 crystallizes with the trigonal space group R-3, Z = 6, a = 1255.1(1), c = 2973.0(4) pm, R1 for all data: 0.0380. Ruthenium atoms center eight-, nine- and ten-vertex polyhedra of lutetium atoms which are connected in a complicated manner to a three-dimensional network. Full article
Open AccessArticle Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range
Crystals 2012, 2(2), 710-729; doi:10.3390/cryst2020710
Received: 7 February 2012 / Revised: 14 June 2012 / Accepted: 14 June 2012 / Published: 20 June 2012
Cited by 4 | PDF Full-text (1170 KB) | HTML Full-text | XML Full-text
Abstract
Using hydrogenography, we investigate the thermodynamic parameters and hysteresis behavior in Mg thin films capped by Ta/Pd, in a temperature range from 333 K to 545 K. The enthalpy and entropy of hydride decomposition, ∆Hdes = −78.3 kJ/molH2,S
[...] Read more.
Using hydrogenography, we investigate the thermodynamic parameters and hysteresis behavior in Mg thin films capped by Ta/Pd, in a temperature range from 333 K to 545 K. The enthalpy and entropy of hydride decomposition, ∆Hdes = −78.3 kJ/molH2, Sdes = −136.1 J/K molH2, estimated from the Van't Hoff analysis, are in good agreement with bulk results, while the absorption thermodynamics, ∆Habs = −61.6 kJ/molH2, ∆Sabs = −110.9 J/K molH2, appear to be substantially affected by the clamping of the film to the substrate. The clamping is negligible at high temperatures, T > 523 K, while at lower temperatures, T < 393 K, it is considerable. The hysteresis at room temperature in Mg/Ta/Pd films increases by a factor of 16 as compared to MgH2 bulk. The hysteresis increases even further in Mg/Pd films, most likely due to the formation of a Mg-Pd alloy at the Mg/Pd interface. The stress–strain analysis of the Mg/Ta/Pd films at 300–333 K proves that the increase of the hysteresis occurs due to additional mechanical work during the (de-)hydrogenation cycle. With a proper temperature correction, our stress–strain analysis quantitatively and qualitatively explains the hysteresis behavior in thin films, as compared to bulk, over the whole temperature range. Full article
(This article belongs to the Special Issue Hydrogen Storage Alloys)

Review

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Open AccessReview Superconductivity in Layered Organic Metals
Crystals 2012, 2(2), 248-265; doi:10.3390/cryst2020248
Received: 6 March 2012 / Revised: 14 April 2012 / Accepted: 16 April 2012 / Published: 19 April 2012
Cited by 5 | PDF Full-text (949 KB) | HTML Full-text | XML Full-text
Abstract
In this short review, I will give an overview on the current understanding of the superconductivity in quasi-two-dimensional organic metals. Thereby, I will focus on charge-transfer salts based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET for short). In these materials, strong electronic correlations are clearly
[...] Read more.
In this short review, I will give an overview on the current understanding of the superconductivity in quasi-two-dimensional organic metals. Thereby, I will focus on charge-transfer salts based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET for short). In these materials, strong electronic correlations are clearly evident, resulting in unique phase diagrams. The layered crystallographic structure leads to highly anisotropic electronic as well as superconducting properties. The corresponding very high orbital critical field for in-plane magnetic-field alignment allows for the occurrence of the Fulde–Ferrell– Larkin–Ovchinnikov state as evidenced by thermodynamic measurements. The experimental picture on the nature of the superconducting state is still controversial with evidence both for unconventional as well as for BCS-like superconductivity. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessReview Theory of Dirac Electrons in Organic Conductors
Crystals 2012, 2(2), 266-283; doi:10.3390/cryst2020266
Received: 26 March 2012 / Revised: 10 April 2012 / Accepted: 10 April 2012 / Published: 20 April 2012
Cited by 2 | PDF Full-text (705 KB) | HTML Full-text | XML Full-text
Abstract
The dynamical property of electrons with the tilted Dirac cone was examined using the tilted Weyl equation. The polarization function exhibits cusps and nonmonotonic structures by varying both the frequency and the momentum. A pair of tilted Dirac cones exhibits a new plasmon
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The dynamical property of electrons with the tilted Dirac cone was examined using the tilted Weyl equation. The polarization function exhibits cusps and nonmonotonic structures by varying both the frequency and the momentum. A pair of tilted Dirac cones exhibits a new plasmon for the intermediate magnitude of momentum owing to the combined effects of two tilted cones. Dirac electrons with the zero-gap state (ZGS) in organic conductor α-(BEDT-TTF)2I3 are examined by calculating the Berry curvature, which displays the peak structure for a pair of Dirac particles between the conduction band and the valence band. The ZGS is theoretically predicted for α-(BEDT-TTF)2NH4Hg(SCN)4 under uniaxial pressure. Examining the band structure of the stripe charge ordered state of α-(BEDT-TTF)2I3 under pressure, we have found a topological transition from a conventional insulator to a new phase of a pair of Dirac electrons with a finite mass. Further, investigating the zero-energy (N = 0) Landau level under a strong magnetic field, we propose ferromagnetism breaking the SU(2) valley-pseudo-spin symmetry, and the phase fluctuations of the order parameters leading to Kosterlitz-Thouless transition at lower temperatures. Full article
(This article belongs to the Special Issue Molecular Conductors)
Figures

Open AccessReview Mott-Anderson Transition in Molecular Conductors: Influence of Randomness on Strongly Correlated Electrons in the κ-(BEDT-TTF)2X System
Crystals 2012, 2(2), 374-392; doi:10.3390/cryst2020374
Received: 12 March 2012 / Revised: 18 April 2012 / Accepted: 20 April 2012 / Published: 8 May 2012
Cited by 9 | PDF Full-text (867 KB) | HTML Full-text | XML Full-text
Abstract
The Mott-Anderson transition has been known as a metal-insulator (MI) transition due to both strong electron-electron interaction and randomness of the electrons. For example, the MI transition in doped semiconductors and transition metal oxides has been investigated up to now as a typical
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The Mott-Anderson transition has been known as a metal-insulator (MI) transition due to both strong electron-electron interaction and randomness of the electrons. For example, the MI transition in doped semiconductors and transition metal oxides has been investigated up to now as a typical example of the Mott-Anderson transition for changing electron correlations by carrier number control in concurrence with inevitable randomness. On the other hand, molecular conductors have been known as typical strongly correlated electron systems with bandwidth controlled Mott transition. In this paper, we demonstrate our recent studies on the randomness effect of the strongly correlated electrons of the BEDT-TTF molecule based organic conductors. X-ray irradiation on the crystals introduces molecular defects in the insulating anion layer, which cause random potential modulation of the correlated electrons in the conductive BEDT-TTF layer. In combination with hydrostatic pressure, we are able to control the parameters for randomness and correlations for electrons approaching the Mott-Anderson transition. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessReview Moderate Temperature Dense Phase Hydrogen Storage Materials within the US Department of Energy (DOE) H2 Storage Program: Trends toward Future Development
Crystals 2012, 2(2), 413-445; doi:10.3390/cryst2020413
Received: 20 March 2012 / Revised: 20 April 2012 / Accepted: 23 April 2012 / Published: 10 May 2012
Cited by 3 | PDF Full-text (1437 KB) | HTML Full-text | XML Full-text
Abstract
Hydrogen has many positive attributes that make it a viable choice to augment the current portfolio of combustion-based fuels, especially when considering reducing pollution and greenhouse gas (GHG) emissions. However, conventional methods of storing H2 via high-pressure or liquid H2 do
[...] Read more.
Hydrogen has many positive attributes that make it a viable choice to augment the current portfolio of combustion-based fuels, especially when considering reducing pollution and greenhouse gas (GHG) emissions. However, conventional methods of storing H2 via high-pressure or liquid H2 do not provide long-term economic solutions for many applications, especially emerging applications such as man-portable or stationary power. Hydrogen storage in materials has the potential to meet the performance and cost demands, however, further developments are needed to address the thermodynamics and kinetics of H2 uptake and release. Therefore, the US Department of Energy (DOE) initiated three Centers of Excellence focused on developing H2 storage materials that could meet the stringent performance requirements for on-board vehicular applications. In this review, we have summarized the developments that occurred as a result of the efforts of the Metal Hydride and Chemical Hydrogen Storage Centers of Excellence on materials that bind hydrogen through ionic and covalent linkages and thus could provide moderate temperature, dense phase H2 storage options for a wide range of emerging Proton Exchange Membrane Fuel Cell (PEM FC) applications. Full article
(This article belongs to the Special Issue Hydrogen Storage Alloys)
Open AccessReview Structural Aspects of the Bechgaard and Fabre Salts: An Update
Crystals 2012, 2(2), 466-520; doi:10.3390/cryst2020466
Received: 20 March 2012 / Revised: 19 April 2012 / Accepted: 20 April 2012 / Published: 21 May 2012
Cited by 21 | PDF Full-text (973 KB) | HTML Full-text | XML Full-text
Abstract
We review structural aspects of the Bechgaard and Fabre salts in relationship with their electronic, magnetic and superconducting properties. We emphasize the role of bond and charge modulations of the quarter filled organic stack in the various instabilities and ground states exhibited by
[...] Read more.
We review structural aspects of the Bechgaard and Fabre salts in relationship with their electronic, magnetic and superconducting properties. We emphasize the role of bond and charge modulations of the quarter filled organic stack in the various instabilities and ground states exhibited by these salts. A special consideration is also devoted to the influence of anions and methyl groups in these processes. In particular we point out the importance of the anions in achieving the inter-stack coupling by either direct or indirect (via the polarization of the methyl group cavities) interactions with the donors. In this framework we discuss the role of anions and methyl group disorders in the inhibition of the divergence of the high temperature bond order wave instability of the Bechgaard salts. We analyze the modulation in the magnetic ground states by considering explicitly the coupling of the magnetization with structural degrees of freedom. We consider the role of the anions and methyl groups in stabilizing the charge ordering pattern in the Fabre salts. We also discuss the spin-Peierls transition of the Fabre salts in relation with the charge ordering transition and the adiabaticity of the phonon field. We review the anion ordering transitions by considering more particularly the influence of the ordering process on the electronic structure and on the ground states which results. In this framework we show that the texture of the anion ordered structure has direct consequences on the superconducting properties of (TMTSF)2ClO4. Finally we conclude on the essential implication of the structural degrees of freedom on the generic phase diagram of the Bechgaard and Fabre salts. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessReview Photoinduced Phase Transitions in α-, θ-, and κ-type ET Salts: Ultrafast Melting of the Electronic Ordering
Crystals 2012, 2(2), 590-617; doi:10.3390/cryst2020590
Received: 14 March 2012 / Revised: 23 April 2012 / Accepted: 24 April 2012 / Published: 30 May 2012
Cited by 5 | PDF Full-text (2202 KB) | HTML Full-text | XML Full-text
Abstract
Photoinduced phase transitions in organic compounds with strong electron correlation ET [bis(ethylenedithio)-tetrathiafulvalene)-based salts α-(ET)2I3, θ-(ET)2RbZn(SCN)4, κ-(d-ET)2Cu[N(CN)2Br] were discussed based, on time resolved optical pump-probe spectroscopy using ~150 fs mid-infrared
[...] Read more.
Photoinduced phase transitions in organic compounds with strong electron correlation ET [bis(ethylenedithio)-tetrathiafulvalene)-based salts α-(ET)2I3, θ-(ET)2RbZn(SCN)4, κ-(d-ET)2Cu[N(CN)2Br] were discussed based, on time resolved optical pump-probe spectroscopy using ~150 fs mid-infrared pulse, 12 fs near infrared pulse, and sub-picosecond terahertz pulse. (i) In charge-ordered insulators α-(ET)2I3 and θ-(ET)2RbZn(SCN)4, we captured ultrafast snapshots of charge dynamics i.e., immediate (ca. 15 fs) generation of a microscopic metallic state (or equivalently the microscopic melting of the charge order) which is driven by the coherent oscillation (period; 18 fs) of correlated electrons. Subsequently, condensation of the microscopic metallic state to the macroscopic scale occurs in α-(ET)2I3. However, in θ-(ET)2RbZn(SCN)4, such condensation is prevented by the large potential barrier reflecting the structural difference between the insulator and metal; (ii) In a Dimer–Mott insulator κ-(d-ET)2Cu[N(CN)2Br], photogeneration of the metallic state rises during ca. 1 ps that is much slower than the melting of charge order, because the photoinduced insulator to metal transition is driven by the intradimer molecular displacement in the dimer Mott insulator. The ultrafast dynamics of photoinduced insulator–metal transitions depend strongly on the molecular arrangement, reflecting various competing phases in the ET sheets. Full article
(This article belongs to the Special Issue Molecular Conductors)
Open AccessReview Transport Phenomena in Multilayered Massless Dirac Fermion System α-(BEDT-TTF)2I3
Crystals 2012, 2(2), 643-661; doi:10.3390/cryst2020643
Received: 14 March 2012 / Revised: 28 May 2012 / Accepted: 29 May 2012 / Published: 11 June 2012
Cited by 2 | PDF Full-text (3580 KB) | HTML Full-text | XML Full-text
Abstract
A zero-gap state with a Dirac cone type energy dispersion was discovered in an organic conductor α-(BEDT-TTF)2I3 under high hydrostatic pressures. This is the first two-dimensional (2D) zero-gap state discovered in bulk crystals with a layered structure. In contrast to
[...] Read more.
A zero-gap state with a Dirac cone type energy dispersion was discovered in an organic conductor α-(BEDT-TTF)2I3 under high hydrostatic pressures. This is the first two-dimensional (2D) zero-gap state discovered in bulk crystals with a layered structure. In contrast to the case of graphene, the Dirac cone in this system is highly anisotropic. The present system, therefore, provides a new type of massless Dirac fermion system with anisotropic Fermi velocity. This system exhibits remarkable transport phenomena characteristic to electrons on the Dirac cone type energy structure. Full article
(This article belongs to the Special Issue Molecular Conductors)

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