Storage performance of LiFe<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>PO<Subscript>4</Subscript> nanoplates (<Emphasis Type="Italic">x </Emphasis>= 0, 0.5, and 1)

Although LiFePO₄ (LFP) is considered to be a potential cathode material for the lithium-ion batteries, its rate performance is significantly restricted by sluggish kinetics of electrons and lithium ions. Several attempts have been made so far to improve the performance of LiFePO₄ by reducing the grain size, doping with aliovalent atoms, and coating conductive materials such as carbon or RuO₂. We report here synthesis of LFP nanoplates by solvothermal method, tailoring the thickness as well as carbon coverage at surfaces to explore their influence on the storage performance. Due to the fact that Li⁺ ion diffuses along the b-axis, solvothermal method was aimed to control the thickness of nanoplates across the b-axis. We synthesized several nanoplates with various plate thicknesses along b-axis; among those, nanoplates of LFP with ～30-nm-thick b-axis having thin (2–5 nm) and uniform layer of carbon coating exhibits high storage capacity as well as high rate performances. Thus, a favorable morphology for LiFePO₄ has been achieved via solvothermal method for fast insertion/extraction of Li⁺ as compared to spherical nanoparticles of carbon-coated LFP. Galvanostatic cycling shows a capacity of 164?±?5 mAh g^?1 at 0.1 C rate, 100?±?5 mAh g^?1 at 10 C rate, and 46?±?5 mAh g^?1 at 30 C rate, with excellent capacity retention of up to 50 cycles. Further attempts have been made to synthesize LiMnPO₄ (LMP) as well as Li(Fe_1???x Mn _x )PO₄/C (x?=?0.5) nanoplates using solvothermal method. Although LiMnPO₄ does not exhibit high storage behavior comparable with that of LiFePO₄, the mixed systems have shown an impressive storage performance.     

Enhanced lithium-ion intercalation and conduction of transparent tantalum oxide films by lithium addition with an atmospheric pressure plasma jet

An investigation is conducted on enhancing lithium-ion intercalation and conduction performance of transparent organo tantalum oxide (TaO _y C _z ) films, by addition of lithium via a fast co-synthesis onto 40 Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates at the short exposed durations of 33–34 s, using an atmospheric pressure plasma jet (APPJ) at various mixed concentrations of tantalum ethoxide [Ta(OC₂H₅)₅] and lithium tert-butoxide [(CH₃)₃COLi] precursors. Transparent organo-lithiated tantalum oxide (Li _x TaO _y C _z ) films expose noteworthy Li⁺ ion intercalation and conduction performance for 200 cycles of reversible Li⁺ ion intercalation and deintercalation in a 1 M LiClO₄-propylene carbonate electrolyte, by switching measurements with a potential sweep from ?1.25 to 1.25 V at a scan rate of 50 mV/s and a potential step at ?1.25 and 1.25 V, even after being bent 360° around a 2.5-cm diameter rod for 1000 cycles. The Li⁺ ionic diffusion coefficient and conductivity of 6.2?×?10^?10 cm²/s and 6.0?×?10^?11 S/cm for TaO _y C _z films are greatly progressed of up to 9.6?×?10^?10 cm²/s and 7.8?×?10^?9 S/cm for Li _x TaO _y C _z films by co-synthesis with an APPJ.     

Structural improvement of ZnO electrodes through solution-processed routes for enhancing open-circuit voltage in dye-sensitized solar cells

We report herein one of our recent studies on nanostructured ZnO electrodes for application in dye-sensitized solar cells, focusing on achieving a higher open-circuit voltage (V_OC). ZnO films were obtained through solution-processed routes including pyrolytic conversion of layered hydroxide zinc acetate (LHZA) films deposited on a fluorine-doped tin oxide-coated conducting glass substrate by a chemical bath deposition method. The morphology of the initial LHZA and the converted ZnO films was tuned from a thick (approximately 12 μm) flower bed-/lawn-like bilayer structure to a thin (1.2 μm) lawn-like quasi-monolayer structure by decreasing the Zn source concentration in the chemical bath. V_OC was found to be enhanced with this morphological change from 0.692 (the bilayer structure) to 0.735 V (the quasi-monolayer structure). Fine tuning of the quasi-monolayer structure by introducing the grain growth effect led to V_OC of the cell as high as 0.807 V, although a short-circuit photocurrent density (J_SC) remained low. Further attempts were then made to increase J_SC while maintaining the high V_OC. When the thickness of the lawn-like monolayer film was increased up to approximately 5 μm, the resultant cell showed V_OC?=?0.750 V, J_SC?=?6.20 mA cm^?2 and a conversion efficiency (η) of 2.83%. The film with a modified flower bed-/lawn-like bilayer structure approximately 11 μm in thickness finally yielded V_OC?=?0.741 V, J_SC?=?13.6 mA cm^?2, and η?=?5.44%.     

Extensive enhancement in power conversion efficiency of dye-sensitized solar cell by using Al-doped TiO<Subscript>2</Subscript> photoanode

In this work, we have prepared Al-doped TiO₂ nanoparticles via a hydrothermal method and used it for making photoanode in dye-sensitized solar cell (DSSC). Material characterizations were done using XRD, AFM, SEM, TEM and EDAX. XPS results reveal that Al is introduced successfully into the structure of TiO₂ creating new impurity energy levels in the forbidden gap. This resulted in tuning of the conduction band of TiO₂ and reduced charge recombination which led to better current conversion efficiency of DSSC. Greater dye loading and enhanced surface area was obtained for Al-doped TiO₂ compared to un-doped TiO₂. I-V analysis, EIS and Bode plots are employed to evaluate photovoltaic performance. The short-circuit current density (J _sc) and efficiency (η) of cell employing Al-doped TiO₂ photoanode were extensively enhanced compared to the cell using un-doped TiO₂. The optical band gap (E _g) for Al-doped and un-doped TiO₂ was obtained as 2.8 and 3.2 eV, respectively. J _sc and η were 13.39 mAcm^?2 and 4.27%, respectively, under illumination of 100 mWcm^?2 light intensity when thin films of 1% Al-doped TiO₂ was employed as photoanode in DSSC using N719 as the sensitizer dye. With the use of un-doped TiO₂ as photoanode under similar conditions, J _sc 5.12 mAcm^?2 and η 1.06% only could be obtained. The maximum IPCE% obtained with Al-doped TiO₂ and un-doped TiO₂ was 67 and 38% respectively at the characteristic wavelength of dye (λ _max = 540 nm). The EIS analyses revealed resistive and capacitive elements that provided an insight into various interfacial processes in terms of the charge transport. It was observed that Al-doping reduced the interfacial resistance leading to better charge transport which has improved both photocurrent density and conversion efficiency. Higher electron mobility and fast diffusion resulting in greater charge collection efficiency was obtained for Al-doped TiO₂ compared to the un-doped TiO₂. Using the Mott–Schottky plot, the donor density was calculated for un-doped and Al-doped TiO₂. The work demonstrated that the Al-doped TiO₂ is potential photoanode material for low-cost and high-efficiency DSSC.     

The sol–gel chromium-modified V<Subscript>6</Subscript>O<Subscript>13</Subscript> as a cathodic material for lithium batteries

A new V₆O₁₃-based material has been synthesized via the sol–gel route. This sol–gel mixed oxide has been obtained from an appropriate heat treatment of the chromium-exchanged V₂O₅ xerogel performed under reducing atmosphere. This new compound, with the chemical formula Cr_0.36V₆O_13.50, exhibits a monoclinic structure (C2/m) with the following unit cell parameters, a=11.89 Å, b=3.68 Å, c=10.14 Å, β=101.18°. The electrochemical characterization of this compound has been performed using galvanostatic discharge–charge experiments in the potential range 4–1.5 V and completed by ac impedance spectroscopy measurements. It exhibits a specific capacity of about 370 mAh g^?1, which makes the compound Cr_0.36V₆O_13.50 the best one in the V₆O₁₃-based system: 85% of the initial capacity (315 mAh g^?1) after the 35th cycle is still available at C/25 without any polarization. From impedance spectroscopy, a high kinetics of Li transport (D _Li=1.8×10^?9 cm² s^?1) is found at mid-discharge.     

Investigation of the Expansion of an Oxygen Microwave Remote Plasma for the Growth of Functional Oxide Thin Films

The expansion of an oxygen low-pressure microwave plasma was investigated in order to determine the optimal plasma parameters for the growth of functional oxide semiconductors. Langmuir probe measurements show that the electron density (n _e ) increases with the injected power up to a saturation value of 3.0 × 10⁹ cm^?3 determined at 10 mTorr while electron temperature (T _e ) remains constant at a value of 1.5 eV. When pressure is varied, n _e shows a maximum value at a range from 12 to 20 mTorr while T _e decreases monotonously with increasing pressure. In addition, both n _e and T _e decrease with the axial distance from the plasma source. These effects were discussed through the loss mechanisms in the remote plasma. For a pressure of 13 mTorr and at a substrate temperature of 500 °C, plasma enhanced oxidation of pure metallic Ti thin films lead to the formation of a pure TiO₂ anatase phase compared to a mixed phase of TiO₂ and TiO in the absence of plasma activation. For Mn thin films, the exposure to oxygen remote plasma led to the formation of MnO₂ as opposed to obtaining Mn₃O₄ when oxidation is performed in the oxygen gas ambient. Remote plasma processing was thus found to provide selective pathways to control oxidation states, stoichiometry and phase composition of technologically attractive oxide thin films.     

Band-gap energy estimation from diffuse reflectance measurements on sol–gel and commercial TiO<Subscript>2</Subscript>: a comparative study

A comparison of the band gap energy estimated from UV–vis reflectance spectra of TiO₂ powders prepared by sol–gel route versus commercial TiO₂ powders, nanopowder, bulkpowder and P25 is reported. The experimental results obtained from the optical absorption spectra were reported for all the TiO₂ samples. Graphic representations were used to calculate E_g: absorbance versus λ; F(R) versus E; (F(R) hν)ⁿ versus E, with n = ½ for an indirect allowed transition and n = 2 for a direct allowed transition. From the results, it could be seen that E_g strongly varied according to the equation used for the graphic representation. Differences in E_g up to 0.5 eV for the same semiconductor depending on the transition chosen were observed. Accurate E_g estimation in the four semiconductors studied was obtained by using the general equation α (hν) ≈ B (hν ? E_g)ⁿ (where α ~ F(R)) and indirect allowed transition.     

Synthesis of water soluble metalloporphyrin-cored amphiphilic star block copolymer photocatalysts for an environmental application

Two series of water-soluble metalloporphyrin-cored amphiphilic star block copolymers were synthesized by controlled radical polymerizations such as atom transfer radical polymerization (ATRP) and reversible addition fragmentation chain transfer (RAFT), which gave eight amphiphilic block copolymer arm chains consisting of poly(n-butyl acrylate-b-poly(ethylene glycol) methyl ether methacylate) (PnBA-b-PEGMEMA, M_n,GPC = 78,000, M_w/M_n = 1.2, 70 wt% of PPEGMEMA) and poly(styrene-b-2-dimethylamino ethyl acrylate) (PS-b-PDMAEA, M_n,GPC = 83,000, M_w/M_n = 1.2, 67 wt% of PDMAEA), yielding porphyrin(Pd)-(PnBA-b-PPEGMEMA)₈ and porphyrin(Pd)-(PS-b-PDMAEA)₈, respectively. Obtained metalloporphyrin polymer photocatalysts were homogeneously solubilized in water to apply to the removal of chlorophenols in water, and was distinguished from conventional water-insoluble small molecular metalloporphyrin photocatalysts. Notably, we found that the water-soluble star block copolymers with hydrophobic–hydrophilic core–shell structures more effectively decomposed the chlorophenol, 2,4,6-trichlorophenol (2,4,6-TCP), in water under visible light irradiation (k = 1.39 h^?1, t_1/2 = 0.5 h) in comparison to the corresponding water-soluble star homopolymer, because the hydrophobic core near the metalloporphyrin effectively captured and decomposed the hydrophobic chlorophenols in water.     

EPR study of the nature of the impurity centers responsible for the scintillation properties of the Li<Subscript>2</Subscript>Zn<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> crystal

The binary molybdate Li₂Zn₂(MoO₄)₃ of a new crystal type was characterized by EPR, optical spectroscopy, and X-ray diffraction methods. The crystals have the Pnma symmetry group and the lattice parameters a = 5.1139(5) Å, b = 10.4926(13) Å, c = 17.6445(22) Å; Z = 4. The crystals possess scintillation properties; emission is caused by the presence of impurity levels in the forbidden band. The EPR studies of the nature of the impurity centers responsible for the scintillation characteristics of the crystal showed that the centers were Cu²⁺ ions substituted for zinc ions in the oxygen octahedra. The directions of the main values of the g and tensors (g _zz , A _zz ) correspond to the direction of O-Cu-O of the oxygen octahedron distorted along the Z axis. The EPR spectra of the copper ions are described by the spin Hamiltonian with the parameters g _‖ = 2.38, g _⊥ = 2.06; A _‖ = 116 G, A _⊥ = 0 G.     

Synthesis and characterization of half-sandwich ruthenium(II) complexes with N-alkyl pyridyl-imine ligands and their application in transfer hydrogenation of ketones

A series of new arene ruthenium(II) complexes were prepared by reaction of ruthenium(II) precursors of the general formula [(η⁶-arene)Ru(μ-Cl)Cl]₂ with N,N′-bidentate pyridyl-imine ligands to form complexes of the type [(η⁶-arene)RuCl(C₅H₄N-2-CH=N-R)]PF₆, with arene = C₆H₆, R = iso-propyl (1a), tert-butyl (1b), cyclohexyl (1c), cyclopentyl (1d) and n-butyl (1e); arene = p-cymene, R = iso-propyl (2a), tert-butyl (2b). The complexes were fully characterized by ¹H NMR and ¹³C NMR, UV–Vis and IR spectroscopies, elemental analyses, and the single-crystal X-ray structures of 2a and 2b have been determined. The single-crystal molecular structure revealed both compounds with a pseudo-octahedral geometry around the Ru(II) center, normally referred to as a piano stool conformation, with the pyridyl-imine as a bidentate N,N ligand. The activity of all complexes in the transfer hydrogenation of cyclohexanone in the presence of NaOH and iso-propanol is reported, the compounds showing turnover numbers of close to 1990 and high conversions. Complex 2b was also shown to be very effective for a range of aliphatic and cyclic ketones, giving conversions of up to 100 %.     

X-ray diffraction study on phase transition of orthorhombic LiMnO2 in electrochemical conversions

Orthorhombic LiMnO₂ was synthesized by hydrothermal reaction. Phase transition during electrochemical process has been investigated using the high-resolution X-ray diffraction. Contrary to numerous earlier reports, phase analysis of the orthorhombic LiMnO₂ electrode cycled for three times evidences the irreversible structure transition from orthorhombic LiMnO₂ (Pmnm) to spinel LiMn₂O₄ (Fd3m) and rock salt Li_0.5Mn_0.5O (Fm \( \overline{3} \) m). Here, the spinel structure with a cell parameter a?=?8.241 (1) Å has a large cationic disorder on lithium and manganese sites, i.e., about 9% of the Li positions are occupied by Mn and vice versa. For Li_0.5Mn_0.5O, the cell parameter is a?=?4.121 (3) Å, and both Li⁺ and Mn³⁺ cations occupy the octahedral 4a sites with mole ratio 1:1. The quantity of Li_0.5Mn_0.5O phase is greatly dependent on cycling rate, namely, the higher the current density is, the larger the quantity of formed-rock salt structure is.     

Synthesis,crystal structure,and hydrogen-bonded displacive-type structural phase transition of guanidine dichloroacetate

Guanidine dichloroacetate was synthesized and separated as crystals. Differential scanning calorimetry (DSC) measurement shows that this compound undergoes a reversible phase transition at about 275 K with a heat hysteresis of 28 K. Step-like dielectric anomaly observed at 274 K further confirms the phase transition. The single-crystal X-ray diffraction data suggested that these was a transition from a room-temperature phase with the space group of P2₁/n (a = 8.030(5), b = 12.014(9), c = 8.124(6) Å, β = 96.089(1)°, V = 779.3(1) Å³, and Z = 4) to a low-temperature one with the space group of P2₁/c (a = 7.941(2), b = 11.828(3), c = 10.614(2) Å, β = 130.985(1)°, V = 752.6(3) Å³, and Z = 4). The displacements of hydrogen bonds induce the structure phase transition.     

Synthesis and characterization of a new monophosphate (C<Subscript>6</Subscript>H<Subscript>16</Subscript>N<Subscript>2</Subscript>)(H<Subscript>2</Subscript>PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Chemical preparation, crystal structure, and NMR spectroscopy of a new trans-2,5-dimethylpiperazinium monophosphate are given. This new compound crystallizes in the triclinic system, with the space group P-1 and the following parameters: a = 6.5033(3), b = 7.6942(4), c = 8.1473(5) Å, α = 114.997(3), β = 92.341(3), γ = 113.136(3), V = 329.14(3) ų, Z = 1, and D_x = 1.565 g cm^?3. The crystal structure has been determined and refined to R = 0.030 and R _w(F ²) = 0.032 using 1558 independent reflections. The structure can be described as infinite [H₂PO₄] _n ^n? chains with (C₆H₁₆N₂)²⁺ organic cations anchored between adjacent polyanions to form columns of anions and cations running along the b axis. This compound has also been investigated by IR, thermal, and solid-state, ¹³C and ³¹P MAS NMR spectroscopies and Ab initio calculations.     

<Emphasis Type="Italic">cis</Emphasis>-Dioxomolybdenum(VI) complexes of sterically encumbered phenol-based tetradentate N<Subscript>2</Subscript>O<Subscript>2</Subscript> ligands: Structural,spectroscopic, and electrochemical studies

Two cis-dioxomolybdenum(VI) complexes [MoO₂L] (L: L ¹, 2 and L: L ², 3) in a phenol-based sterically encumbered N₂O₂ ligand environment have been synthesized, and their crystallographic characterizations are reported. The orange crystals of 2 are monoclinic, space group P2₁/a with unit cell dimensions as a=16.2407(17) Å, b=7.2857(8) Å, c=18.400(2) Å, β=98.002(9)°, Z=4, and d _cal=1.486 g cm^?3. The light orange crystals of 3, however, are orthorhombic, space group, Pbcn, with unit cell dimensions a=8.3110(12) Å, b=12.637(3) Å, c=34.673(5) Å, Z=4, and d _cal=1.187 g cm^?3. The structures were refined by a full-matrix least-squares procedure on F ² to a final R=0.046 (0.055 for 3) using 4944 (3677) all independent data. In both the cases, the Mo atom exists in a distorted octahedral geometry defined by a N₂O₄ donor set, which features a cis-Mo(–O)₂ and a trans-Mo(OPh)₂ arrangement. Compound 2 undergoes a quasireversible one-electron reduction at ?1.3 V vs Ag/AgCl reference due to Mo^VIO₂/Mo^VO₂ electron transfer and thus providing a rare example of steric solution to the comproportionation–dimerization problem encountered frequently in the development of valid biomimetic models for the active sites of oxomolybdenum enzymes.     

Synthesis,structural, and electrochemical properties of NaCo(PO<Subscript>3</Subscript>)<Subscript>3</Subscript> cathode for sodium-ion batteries

A new Co-base sodium metaphosphate compound, NaCo(PO₃)₃, has been synthesized here by solid-state method. The crystal structure is refined by the Rietveld method, and the results reveal that NaCo(PO₃)₃ has an orthorhombic structure with the space group of P2 ₁ 2 ₁ 2 ₁ and lattice parameters of a = 14.2453(2) Å, b = 14.2306(1) Å, and c = 14.2603(2) Å. Its typical morphology and chemical composition are confirmed by scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). The valence states of all elements and the internal/external vibrational modes of NaCoP₃O₉ compound are measured by X-ray photoelectron and vibrational spectrum, where a typical feature of the (PO₃)^? polyanion group is observed. Meanwhile, the electrochemical properties of NaCo(PO₃)₃ cathode for sodium-ion batteries are also elevated and an initial discharge capacity of 33.8 mAh/g can be obtained at 0.05 C within 1.5–4.2 V. After 20 cycles, a discharge capacity of 26.7 mAh/g can be obtained and a well-kept oxidation–reduction plateau is still observed for NaCo(PO₃)₃ cathode, indicating the good reversibility of this metaphosphate electrode.     

Synthesis,crystal structure and fungicidal activity of 1-(4-chlorophenyl)-2-(5-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-phenyl-4H-1,2,4-triazol-3-ylthio)ethanone

A novel bis-heterocyclic compound was synthesized and characterized. The crystal structure of the title compound (C₂₂H₂₀ClN₅OS, Mr = 437.94) has been determined by single-crystal X-ray diffraction. The crystal is of triclinic, space group P-1 with a = 8.646 (2), b = 9.148 (3), c = 14.540 (4) Å, α = 94.422 (4), β = 98.500 (4), γ = 102.823 (4)°, V = 1101.8 (5) Å³, Z = 2, F(000) = 312, Dc = 1.320 g/cm³, μ = 0.2900 mm^?1, the final R ₁ = 0.041000 and wR ₂ = 0.1160 for 2675 observed reflections with I > 2σ(I). A total of 5623 reflections were collected, of which 3866 were independent (R _int = 0.019000). The fungicidal activity of title compound was determined, the results showed the title compound displayed moderate fungicidal activity against G. zeae Petch, Phytophthora infestans (Mont.) de Bary, Botryosphaeria berengeriana f. sp. piricola (Nose) koganezawa et Sakuma, Fusarium oxysporum f.sp. cucumerinum, and Cercospora arachidicola.     

Molecular mechanism of propane oxidative dehydrogenation on surface oxygen radical sites of VO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/TiO<Subscript>2</Subscript> catalysts

Minimum energy pathways of propane oxidative dehydrogenation to propene and propanol on supported vanadium oxide catalyst VO _x /TiO₂ were studied by periodic discrete Fourier transform (DFT) using a surface oxygen radical as the active site. The propene formation pathway was shown to consist of two consecutive hydrogen abstraction steps. The first step includes C_β–H bond activation of propane followed by the formation of a surface hydroxyl group V–O _t H and a propyl radical n-C₃H₇. This step with the activation energy E* = 0.56 eV (54.1 kJ/mol) appears to be rate-determining. The second step involves the reaction of the bridging O _b oxygen atom with the methylene C–H bond of propyl radical n-C₃H₇ followed by the formation of a hydroxylated surface site HO _t –V⁴⁺–O _b H and propene. The initial steps of the C–H bond activation during propane conversion to propanol and propene by ODH on V⁵⁺–(O _t O _b )^? active sites are identical. The obtained results demonstrate that participation of surface oxygen radicals as the active sites of propane ODH makes it possible to explain relatively low activation energies observed for this reaction on the most active catalysts. The presence of very active radical species in low concentration seems to be the key factor for obtaining high selectivity.     

Enzymatic Hydrolysis of Black Liquor Xylan by a Novel Xylose-Tolerant,Thermostable β-Xylosidase from a Tropical Strain of <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis> CBS 135684

From three cell-associated β-xylosidases produced by Aureobasidium pullulans CBS 135684, the principal enzyme was enriched to apparent homogeneity and found to be active at high temperatures (60–70 °C) over a pH range of 5–9 with a specific activity of 163.3 units (U) mg^?1. The enzyme was thermostable, retaining over 80% of its initial activity after a 12-h incubation at 60 °C, with half-lives of 38, 22, and 10 h at 60, 65, and 70 °C, respectively. Moreover, it was tolerant to xylose inhibition with a K _i value of 18 mM. The K _m and V _max values against p-nitrophenyl-β-d-xylopyranoside were 5.57 ± 0.27 mM and 137.0 ± 4.8 μmol min^?1 mg^?1 protein, respectively. When combining this β-xylosidase with xylanase from the same A. pullulans strain, the rate of black liquor xylan hydrolysis was significantly improved by up to 1.6-fold. The maximum xylose yield (0.812 ± 0.015 g g^?1 dry weight) was obtained from a reaction mixture containing 10% (w/v) black liquor xylan, 6 U g^?1 β-xylosidase and 16 U g^?1 xylanase after incubation for 4 h at 70 °C and pH 6.0.     

Synthesis,structural phase transition,and characterization of potassium hydrogen bis-dichloroacetate

Potassium hydrogen bis-dichloroacetate (1) was synthesized and separated as crystals. Differential scanning calorimetry (DSC) measurement reveals that this compound undergoes a reversible phase transition at about 259 K with a heat hysteresis of 23.5 K. Dielectric anomaly observed at 260 K in the heating process further confirms the phase transition. The room temperature X-ray single-crystal structure determination indicates that 1 crystallizes in the monoclinic crystal system with a centrosymmetric space group P2₁/c, and cell parameters are a =?6.240(1), b =?23.177(4), c =?7.335(1) Å, β =?106.938(1)°, V =?1014.8(3) ų, and Z =?4. In the low temperature phase, 1 also crystallizes in monolinic with space group P2₁/c, and cell parameters are a =?6.180(1), b =?22.988(2), c =?7.200(1) Å, β =?108.098(1)°, V =?972.4(1) ų, and Z =?4. The structural phase transition is dominating caused by the torsion of bond angles.     

Die Kristallstruktur des Lithiumdigermanats Li2Ge2O5

The compound Li₂Ge₂O₅ has been prepared by annealing a glassy melt (500° C). The lattice parameters have been determined from single crystal photographs:a=5,99,b=15,19,c=4,97 Å and β=90,0°, space group C _S ⁴ :?Cc. Li₂Ge₂O₅ has a layer structure and is isostructural with Li₂Si₂O₅.