Microscopic Studies of 2H-NbSe2 Probed by Positive Muon

Abstract

The microscopic state of the positively charged light particle in the transition metal dichalcogenide 2H-NbSe₂ was studied using the muon spin relaxation method (μ⁺SR) and muon level crossing resonance method (μ-LCR). Muons are expected to stay at interlayer position and behaves as a hydrogen like intercalant. We discuss the relation between conduction electron properties and the muon's behavior.     

Crystal Structure of a Non-Conductive Non-Stoichiometric Tetrathiafulvalenium Salt: (TTF)3(BF4)2

Abstract

(TTF)₃(BF₄)₂ crystallizes in the triclinic system, space group P1, a = 8.017(3), b = 8.601(1), c = 11.635(2) Å, α = 108.79(1), β = 100.96(2), γ = 99.09(2)°, Z = 1. The TTF entities are stacked in parallel columns arranged into parallel layers alternating with layers of BF₄ ^? anions. A TTF stack is constituted of (TTF⁺)₂ diads interspersed with TTF° monads; the TTF⁺-TTF⁺ overlap is of the ring-over-ring type while the TTF⁺-TTF⁺ overlap is of the bond-over-ring type. These features explain the low conductivity ([sgrave]_powdcr = 2 × 10^?5 Ω^?l cm^?1) of this apparently non-stoichiometric TTF salt.     

Crystal structures of polymeric complexes of zinc(II) bromide and perchlorate with 1,4-diazoniabicyclo [2.2.2]octane-1,4-diacetate

Two zinc(II) complexes containing a flexible double betaine, namely [{Zn(L)Br₂}_n]·nH₂O (1) and [{Zn(L)₂(H₂O)₂}_n](ClO₄)_2n·4nH₂O (2) [L=1,4-diazoniabicyclo [2.2.2]octane-1,4-diacetate,⁻O₂CCH₂N⁺(CH₂CH₂)₃N⁺CH₂CO₂ ⁻], have been prepared and shown to have polymeric structures by single-crystal X-ray analysis. Complex (1) exhibits an infinite zigzag chain in which each zinc(II) atom is coordinated by two unidentate carboxylate oxygen atoms and two bromide ligands in a distorted tetrahedral geometry. Complex (2) consists of an assembly of catonic Zn(L)₂(H₂O)₂ ²⁺ moieties and discrete perchlorate anions as well as lattice water molecules. In (2) each zinc(II) atom is coordinated by two pairs of unidentate carboxylate oxygen atoms and two aqua ligands in a distorted octahedral geometry and cross-linked by skeletons of double betaine ligands to form a corrugated layer structure corresponding to the plane (100).     

Paramagnetic defects in the mineral hauyne

In blue crystals of hauyne from two localities two broad signals due to Fe³⁺, a hole center of tetragonal site symmetry and an isotropic signal from an electron center were detected by electron paramagnetic resonance (EPR). According to its site symmetry the hole center is tentatively assigned to a [MgO_4/2]⁰ species on an Al site with the unpaired electron delocalized over the oxygens. The site symmetry does not change with cooling to 20 K. The large linewidths of the signals from Fe³⁺ are interpreted as a result of the non-stoichiometry and high static disorder and some dipolar broadening. The linewidths of the other EPR signals are also larger than for corresponding centers in the isotypic sodalite. The cause of the blue colour is briefly discussed.     

Isomorphism of inclusion compounds built with composite host lattices of thiadiazole and V-shaped molecules with the existence of tetrabutylammonium guest template

By using 4,4′-dihydroxydiphenylsulfone (BPS) and 4,4′-dihydroxydiphenylsulfide (BTS) react with amidinethiourea and tetrabutylammonium respectively, two isomorphs of inclusion compounds of (n-C₄H₉)₄N⁺·C₁₂H₉O₄S^?·C₂H₄N₄S (1) and (n-C₄H₉)₄N⁺·C₁₂H₉O₂S^?·C₂H₄N₄S (2) were prepared and characterized by Single crystal X-ray diffraction. Although two varied types of V-shaped molecules were selected to react in the actual experimental process, two isomorphs with similar packing modes were finally obtained. Interestingly, amidinothiourea molecule occurred in situ oxidation reaction to generate a new compound of 3,5-dimido-1,2,4,-thiadiazole during the experiments, and these two inclusion compounds here are the pioneer examples of thiadiazole and tetraalkylammonium and can be regarded as two isomorphs due to their similar crystallization modes. In these two isomorphs, thiadiazole molecules derived from amidinothiourea link with various V-type molecules to develop the similar dumbbell-type hydrogen-bonded ribbons by the alike hydrogen bonding modes, then the ribbons interpenetrate with tetrabutylammonium to result in two stable isomorphism structures.     

Explanations of the optical absorption and ESR spectrum for tetragonal Ni+ centers in CuAlS2:Ni+ crystals

In this paper, the optical absorption and electron spin resonance (ESR) spectrum of Ni⁺‐doped CuAlS₂ crystals have been studied by using a double spin‐orbit (SO) coupling approximation model, where the effects due to the SO coupling of the central metal 3d¹ ion and those of ligands are included. From this model, the formulas of the ESR g factors g_‖, g_⊥ and hyperfine structure constants A_‖, A_⊥ for 3d¹ ions in the tetragonal MX₄ clusters are constructed. The optical absorption and ESR parameters for Cu⁺ sites of CuAlS₂ have been calculated. The results obtained show that Ni⁺ ions substitute for Cu⁺ ions sites. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Two New Salts Based on Bis(1,2,5-thiadiazole-3,4-dithiolate)nickelate Anion with Substituted Benzyl 4-ethylpyridinium: Syntheses,Crystal Structures and Properties

Abstract  

Two new salts based on [Ni(tdas)₂]²⁻ (tdas²⁻ = 1,2,5-thiadiazole-3,4-dithiolate) anion, [Bz4EtPy]₂[Ni(tdas)₂] (1) and [4ClBz4EtPy]₂[Ni(tdas)₂] (2), have been prepared by reaction of Na₂tdas, NiCl₂·6H₂O, and [Bz4EtPy]Br ([Bz4EtPy]⁺ = 1-benzyl-4-ethylpyridinium) or [4ClBz4EtPy]Br ([4ClBz4EtPy]⁺ = 1-(4′-chlorobenzyl)-4-ethylpyridinium), and characterized by elemental analyses, UV, IR, MS spectrum, molar conductivity and single crystal X-ray diffraction. Single-crystal X-ray diffraction analyses indicate that the two salts crystallize in a triclinic system with space group P−1. The unit cell contains two [Bz4EtPy]⁺/[4ClBz4EtPy]⁺ and one [Ni(tdas)₂]²⁻ anion in which the anion exhibits a quasi-planar structure. The crystals of 1 and 2 are stabilized through C–H···S and C–H···Ni hydrogen bonds, π···π stacking interactions and S···Cl short interactions.     

Electron trap centers in Ag-borate glasses

The center created by silver trapping an electron in borate glasses are considered. It is shown by ESR techniques that on trapping an electron, silver ions may form four types of centers: the single Ag⁰ or (Ag⁺ + e) centers, and, at higher Ag contents, the Ag⁰(Ag⁺) or (Ag⁺ + e) (Ag⁺) centers in which a second silver is involved. The formation and stability of these centers is critically dependent on the silver content, the concentration of alkali and the temperature of irradiation and measurement. The Ag⁰(Ag⁺) center is generally enhanced by increasing silver and decreasing alkali content and does not show separate signals for the two isotopes ¹⁰⁷Ag, ¹⁰⁹Ag because the two silvers in proximity occur in three different isotope combinations which are superimposed.Above 20% alkali the hyperfine splitting constant for the silver—electron trap center was found to decrease with increasing alkali content, probably in connection with the increasing appearances of non-bridging oxygens and the trapping of the electron in an oxygen vacancy in the vicinity of Ag⁺, i.e. a change from Ag⁰ to (Ag⁺ + e) center. A similar decrease was observed in high alkali (30% R₂O) glasses with changes of alkali from Li⁺ to K⁺.     

1.48 μm emission properties and the cross-relaxation mechanism in chalcohalide glass doped with Tm

1.48 μm emission properties and the cross-relaxation mechanism of Tm³⁺ ions in 0.7(Ge_0.25As_0.10S_0.65) + 0.15GaS_3/2 + 0.15CsBr glass were investigated. Both the relative intensity ratio of the 1.48 μm emission to 1.82 μm and the measured lifetime of the ³H₄ level decreased with increasing Tm³⁺ concentration. When temperature decreased from room temperature to 20 K, lifetimes of the ³H₄ level increased from 670 to 970 μs. At the same time, the critical distance for cross-relaxation decreased from 1.11 to 0.93 nm. These results indicate that cross-relaxation (³H₄, ³H₆ → ³F₄, ³F₄) became less effective as temperature decreased. Analysis of the temperature dependence of cross-relaxation rates showed that cross-relaxation in Tm³⁺ is a phonon-assisted energy transfer process. The major phonon contributing to the process is from the Ga-Br vibration in [GaS_3/2Br]⁻ units.     

A new class of flexible energetic salts, part 6: the structures of the hydrazinium and hydroxylammonium salts of dinitramide

The crystal structures of two amine base salts, the hydrazinium, 1, and the hydroxylammonium, 2, of dinitramide have been determined. 1 crystallizes in the monoclinic space group P 2₁/c with cell dimensions a = 8.312(3), b = 5.654(1), c = 10.659(3) Å, = 93.73(3)°, while 2 crystallizes in the orthorhombic space group Pcab (nonstandard setting of Pbca) with cell dimensions a = 6.439(2), b = 12.470(4), c = 30.816(14) Å. The structures of 1 and 2 contain protonated amine cations and dinitramide anions linked by hydrogen bonding. In addition, in 2 there are both neutral and zwitterionic hydroxylamine moieties involved in the hydrogen bonding scheme. Thus in 2 the complete formula unit is (NH₃ ⁺OH)₂[N₃O₄ ^–]₂ · (NH₂OH) middot; (NH₃ ⁺O^–), and in this structure the hydroxylamine exists in its three possible forms: protonated, neutral, and zwitterionic. In both structures the conformations adopted by the dinitramine anions can be related to the types of hydrogen bonds it forms with the surrounding amine cations.     

Wide band-gap organic molecules containing benzodithiophene and difluoroquinoxaline derivatives for solar cell applications

Abstract

Two new semiconducting organic small molecules, namely BDTQ-BDT(EH) and BDTQ-BDT(OC), were prepared by attaching electron accepting 2,3-didodecyl-6,7-difluoro-5,8-di(thiophen-2-yl)quinoxaline (DTQ) unit on 2,6-position of electron donating 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene (BDT(EH)) and 4,8-bis(octyloxy)benzo[1,2-b:4,5-b']dithiophene (BDT(OC)) units. Molecule BDTQ-BDT(EH) showed higher thermal stability (5% weight loss temperature, T_d “349 ^оC), slightly lower band-gap (E_g “2.10?eV) and deeper highest occupied molecular orbital energy level (HOMO “–5.36?eV) level compared to those (T_d “336 ^оC, E_g “2.11?eV, and HOMO “–5.30?eV, respectively.) of the molecule BDTQ-BDT(OC). The organic solar cells (OSCs) made with the synthesized molecules as an electron donor and [6,6]-phenyl C₇₁ butyric acid methyl ester (PC₇₀BM) as an electron acceptor gave a maximum power conversion efficiency (PCE) of 1.20% and 0.83%, respectively, for BDTQ-BDT(EH) and BDTQ-BDT(OC). This study confirmed that the substituents attached on the 4,8-position of BDT unit greatly alter the properties of the resulting molecules.     

Charge Transfer in Misfit Layer Chalcogenides, [(MX)n]1+x(TX2)m: a Key for Understanding their Stability and Properties

Abstract

Stability of misfit layer chalcogenides (M.L.C.) is always governed by a charge transfer (C.T.) mechanism. A comparison between M.L.C. and parent intercalated layered binary systems shows comparable characteristics, which illustrate the role of electron donor for the MX part (or its corresponding A-intercalant species) towards the TX² acceptor part. In that way, intercalation chemistry within the vdW gap of multilayered TX² misfit derivatives is also considered. The donor character of the MX part, easy to understand when trivalent M cations are present, can be also assumed if a divalent M cation is partly substituted for a trivalent one, as revealed from precise electron microprobe analysis. Examples of M.L.C. with enlarged MX part (with mixed M^+II, M^+III) emphasize the reality of the C.T. This M-to-T donor effect necessarily controls the transport and intercalation properties.     

Hydrogen Bonding Patterns of Coordinated Ligands in Hybrid Materials: Crystal Structures of Hydronium Tetra(Thiocyanato-κN)-Zinc(II): Tris(2-Amino-4,6-Dimethylpyrimidinium) (2-amino-4,6-dimethylpyrimidine) Dinitrate and Bis(2-Amino-4,6-Dimethylpyrimidinium) Tetrachlorocobaltate(II) Monohydrate

Abstract  

Hydronium tetra(thiocyanato-κN)-zinc (II) tri (2-amino-4,6-dimethylpyrimidinium) 2-amino-4,6-dimethylpyrimidine dinitrate [H₃O⁺ Zn(NCS)₄ 3(C₆H₁₀N₃ ⁺) C₆H₉N₃ 2(NO₃)⁻] and bis(2-amino-4,6-dimethylpyrimidinium) tetrachlorocobaltate(II) monohydrate [2(C₆H₁₀N₃ ⁺)] CoCl₄ H₂O have been synthesized and characterized by X-ray diffraction analysis and spectroscopic studies. In compound 1, the coordination geometry around zinc is distorted tetrahedral, Zn being bonded to four N atoms from the thiocyanate anions. In compound 2, the anion [CoCl₄]²⁻ displays distortion from ideal tetrahedral geometry. The 2-amino-4,6-dimethylpyrimidine cations are not directly coordinated to zinc/cobalt, but are hydrogen bonded to the thiocyanate/chloride ions. In both the compounds the protonated nitrogen N1 and the 2-amino group are hydrogen bonded to the nitro group/chloride ions/water molecule through N–H···O and N–H···Cl hydrogen bonds to form R₂²(8) motifs. In both the compounds, the pyrimidine cations also form base pairs via a pair of N–H···N hydrogen bonds involving the amino group and the unprotonated ring N atom. The crystal structures are further stabilized by N–H···S, O–H···O, C–H···O and C–H···Cl hydrogen bonds.     

Supramolecular Organization in Tetra Aqua (μ-8-Hydroxyquinoline-5-sulfonate) Barium (II) and Ag···I Interactions in a Pseudopolymorphic Form of (7-Iodo-8-hydroxyquinoline-5-sulfonate) Silver (I) Monohydrate

Abstract  

The complexes, Ba (HQS) (H₂O)₄ (HQS = 8-hydroxyquinoline-5-sulfonic acid) (1) and Ag (HIQS) (H₂O) (Ferron = 7-iodo-8-hydroxyquinoline-5-sulfonic acid) (2) have been synthesized and characterized by X-ray diffraction analysis and spectroscopic studies. In compound 1, Ba²⁺ ion has a nine-coordinate monocapped antiprismatic geometry. In compound 2, Ag⁺ has distorted tetrahedral coordination and Ag···I interactions generate the supramolecular architectures. The complexes have been characterized by FT-IR and UV–Visible measurements. In both the structures, the inversion-related organic ligands are stacked over one another leading to three-dimensional networks.     

Crystal structures of four inclusion compounds of 2,2′-dithiosalicylic acid and tetraalkylammonium

Herein four inclusion compounds of 2,2′-dithiosalicylic acid and tetraalkylammonium, 2(CH₃)₄N⁺·C₁₄H₈O₄S₂^2?·H₂O (1), (C₂H₅)₄N⁺·C₁₄H₉O₄S₂^?·0.25H₂O(2), (n-C₃H₇)₄N⁺·C₁₄H₉O₄S₂^? (3) and (n-C₄H₉)₄N⁺·C₁₄H₉O₄S₂^?(4) are prepared and characterized by X-ray single crystal diffraction. As shown in the results, compounds 1 and 3 belong to orthorhombic crystal system with different space groups of P2₁2₁2₁ and Pca2₁, and 2 and 4 are monoclinic system with similar groups of P2₁/n and P2₁/c. The crystallography data are displayed below: 1: a = 10.5903(7) Å, b = 10.6651(7) Å, c = 21.9476(13) Å, V = 2478.9(3) ų, Z = 4, R₁ = 0.0359; 2: a = 8.13340(1) Å, b = 22.0741(3)Å, c = 13.2143(2)Å, β = 101.6360(1) °, V = 2323.70(6) ų, Z = 1, R₁ = 0.0385; 3: a = 15.7857(2) Å, b = 8.24830(1) Å, c = 20.2599(2) Å, V = 2637.94(5) ų, Z = 4, R₁ = 0.0308_degree4: a = 11.7476(2) Å, b = 17.1346(1) Å, c = 16.3583(3)Å, β = 109.4560(1) °, V = 3104.74(9)ų, Z = 4, R₁ = 0.0562. Interestingly, although the carbon chains of the guest templates vary from methyl group to butyl group, the host molecules of 2,2′-dithiosalicylic acid all construct the similar 2D hydrogen-bonded host layers with or without the existence of water molecules to contain the guest templates to yield analogous sandwich-like inclusion compounds. Obviously, although the guest templates will have certain effects on the ultimate formation of these crystal structures, the host molecule of 2,2′-dithiosalicylic acid is a controlling factor to form these four inclusion compounds.     

Paramagnetic defects induced by ion implantation in oxide glasses

Radiation defects induced by ion bombardment of multicomponent oxide glasses of five compositions (phosphates and borosilicates) were investigated by means of electron paramagnetic resonance (EPR). The samples were implanted with N⁺, O⁺, Ar⁺, Mn⁺, Cu⁺ and Pb⁺ ions at energy E=150 keV at three different doses between 3×10¹⁵ and 10¹⁷ ions/cm². The broad anisotropic EPR spectra with principal g-values answering the relationship g_z>g_y>g_x˜g_e (g_e is g-factor of free electron) were observed for the samples of all five compositions. The g-values depend on glass composition. For example, g_z ranges from 2.016 to 2.057. Computer simulation shows that the spectra of many samples are superpositions of two spectra with g-values answering the mentioned relationship. These spectra are attributed to molecular O₂⁻ ions weakly coupled with glass network. In some samples narrow almost symmetric lines with g=2.0025±0.0005 were observed. The possible radiation defects responsible for this signal are discussed.     

Synthesis, Structural Characterization and Crystal Structure of Selenium Bearing 3-(Phenylseleno) Propylammonium Acetate Salt and its Cleavage on Reaction with Mercury(II) and Tin(IV) Salts

Abstract  

3-(Phenylseleno) propylammonium acetate, C₉H₁₄NSe⁺ C₂H₃O₂ ^–, L ¹ , the first example of a selenium bearing acetate salt has been synthesized and characterized by spectroscopic, NMR, DSC and single crystal X-ray crystallographic techniques. L ¹ crystallizes with one cation–anion pair in the asymmetric unit. Reactions of L ¹ with four different metal salts revealed four new selenium bearing compounds (1–4) whose identities are characterized by spectroscopic and NMR techniques. The crystal structure of Compound 1, [C₉H₁₄NSe]₂⁺ [ClO₄]₂^–, whose crystal structure has been confirmed. It crystallizes with two independent cation–anion pairs in the asymmetric unit. Both L ¹ and Compound 1 display strong N–H···O hydrogen bond intermolecular interactions which help stabilize crystal packing in the unit cell.     

Spectroscopy of Molecualr Crystals: A Bibliography for 1975

Abstract

Our previous thermodynamical approach was reexamined to study phase transition of anion radical salts, [(C₆H₅)₃PCH₃]⁺ _{1 ? x}[(C₆H₅)₃AsCH₃]⁺ _x(TCNQ)^? ₂,(0≤x≤1). The mechanism of the phase transition of the solid solution at 1 atm pressure was confirmed to be αy [(C₆H₅)₃PCH₃]⁺ _{1 ? x}[(C₆H₅)₃AsCH₃]⁺ _x(TCNQ)^? ₂,(0≤x≤1) βy, and the volume change assoiated with the phase transition was estimated to be ΔV =-1.3 (1-x) cm³/mol.     

Structural and conductivity study of Y and Rb co-doped TiO2 synthesized by the sol–gel method

Nanoparticles of titanium dioxide co-doped with Y³⁺ and Rb⁺ were prepared using the sol–gel method and were characterized by thermogravimetric-differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. Y³⁺ and Rb⁺ co-doped TiO₂ powder calcined at 800 °C shows a synergistic effect, which shifted the transformation anatase–rutile to higher temperature. X-ray diffraction and XPS analysis revealed that Y³⁺ and Rb⁺ did not enter into the crystal lattices of TiO₂ and are uniformly dispersed onto TiO₂ particles. In this study, the conductivity measurements were performed under ambient atmosphere on undoped and co-doped TiO₂ in order to investigate the defect chemistry by identifying the predominant charge carriers. An increase in the conductivity σ of nano-TiO₂ is shown when the samples were co-doped with Y³⁺ and Rb⁺.     

Very strong hydrogen bonds in hydrated 1:1 adducts of an olefinic double betaine with perchloric and nitric acids: L·HClO4·H2O and L·HNO3·H2O [L=cis-(p-Me2N+C5H4N)2C2(COO−)2]

The hydrated 1:1 adducts of an olefinic double betaine with perchloric and nitric acids, L·HClO₄·H₂O I and L·HNO₃·N₂O2 [L=cis-(p-Me₂N⁺C₅H₄N)₂C₂(COO^–)₂], have been shown to be nearly isostructural by X-ray crystallography and infrared spectroscopy. The common cationic unit HL⁺ of both compounds exhibits significant semi-quinonoid character and possesses symmetrym, ist two coplanar carboxylate groups being linked by a very strong, nearly linear intramolecular O–H–O hydrogen bond [O...O 2.397(9)Å and O–H–O 167.1° for1; 2.388(7)Å and 167.4° for2]. The HL⁺ units are further connected by intermolecular O–H...O hydrogen bonds between the exocyclic carboxyl oxygen atoms and the water molecules to generate polymeric zigzag chains running parallel to thec axis, and the disordered ClO₄ or NO ₃ ^– anions occupy channels running parallel to thea axis in the resulting host lattice.