Synthesis, characterization and thermal properties of small R2R2NX-type quaternary ammonium halides

Twenty-one R₂R^′₂N⁺X⁻ -type (R=methyl or ethyl, R^′=alkyl, X=Br or I) quaternary ammonium (QA) halides have been prepared by using a novel one-pot synthetic route in which a formamide (dimethyl-, diethylformamide, etc.) is treated with alkyl halide in the presence of sodium or potassium carbonate. The formation of QA halides was verified with ¹H-NMR, ¹³C-NMR, MS and elemental analysis. The crystal structures of four QA halides (two bromide and two iodide) were determined using X-ray single crystal diffraction, and the powder diffraction method was used to study the structural similarities between the single crystal and microcrystalline bulk material. The thermal properties of all compounds were studied using TG/DTA and DSC methods. The smallest compounds decomposed during or before melting. The decreasing trend of melting points was observed when the alkyl chain length was increased. The liquid ranges of 120-180 °C were observed for compounds with 5-6 carbon atoms in the alkyl chain. The low melting points and wide liquid ranges suggest potential applicability of these compounds for example as ionic liquids precursors.     

A hybrid material based on [Mo6Br14] inorganic cluster units and [BEDO-TTF] organic monocationic radicals: Synthesis, structure and properties of (BEDO-TTF)2Mo6Br14(PhCN)4

The first charge transfer salt based on non- dimerized [BEDO-TTF]⁺ monocationic radical (BEDO-TTF=bis(ethylenedioxy)tetrathiafulvalene) associated with [Mo₆Br₁₄]²⁻ cluster anions has been synthesized by conventional electro-oxidation and characterized by single crystal X-ray diffraction, UV-VIS-NIR absorption and magnetic susceptibility measurements. (BEDO-TTF)₂Mo₆Br₁₄(PhCN)₄ crystallizes in the monoclinic system, space group P2₁/n, a=10.414(4) Å, b=21.711(7) Å, c=15.958(5) Å, β=93.65(3)°, V=3601(2) Å³, Z=2, R₁=0.0578, wR₂=0.0731. The structure of this hybrid compound is built up from a [BEDO-TTF]⁺ and PhCN (benzonitrile) organic framework in which are hosted the [Mo₆Br₁₄]²⁻ inorganic cluster units. It results in non- dimerized [BEDO-TTF]⁺ cations that exhibit a paramagnetic behavior characteristic of one unpaired electron.     

Synthesis and crystal structure of RMgSi2 compounds (R=La, Ce, Pr, Nd), a particular example of linear intergrowth

A new series of rare earth compounds with stoichiometry RMgSi₂ (R=La, Ce, Pr, Nd) is reported. The single crystal X-ray diffraction showed that CeMgSi₂, which melts congruently at 1200 °C, crystallizes in a new tetragonal structure type (I4₁/amd, tI32, a=4.2652(4) Å, c=36.830(4) Å, Z=8; wR₂=0.042 (19 parameters, 393F₀²), R₁=0.018 (297F₀>4σF₀). The crystal structure of CeMgSi₂ can be formally built up by alternating along the z direction four CeMg₂Si₂-type CeMg₂Si₂ slabs with four AlB₂-type CeSi₂ slabs, one after the other. The structural model obtained from a CeMgSi₂ single crystal has been confirmed for the La, Pr and Nd homologous compounds by means of Rietveld refinement. The trend of the unit-cell parameters, plotted versus the R³⁺ ionic radius, shows a linear behaviour, which strongly suggests a trivalent state for the Ce atoms. An analysis of the features of this new structure is reported, in comparison with the other known CeMg₂Si₂/AlB₂-type linear intergrowth compounds.     

Sr4AlNbO8: A new crystal structure type determined from powder X-ray data

Sr₄AlNbO₈ was synthesized at 1500 °C in air. The crystal structure was initially determined from powder X-ray diffraction data, and later refined with combined X-ray and neutron diffraction data (P2₁/c; a=7.17592(2) Å, b=5.80261(2) Å, c=19.7408(1) Å; β=97.5470(1)°, V=814.869(3) Å³, Z=4, R_p/R_wp=10.04%/13.18% for X-ray data, 4.40%/5.67% for neutron data, and 7.71%/10.74% in total with χ² of 3.76, 23 °C). The crystal structure is a new structure type and may be described as a three-dimensional polyhedral network resulting from the corner-sharing of NbO₆ and Sr1O₆ octahedra and AlO₄ tetrahedra. Also, the other strontium atoms (Sr2, Sr3, and Sr4) occupy the larger cavities surrounded by oxygen atoms to form nine, eight, and 11 coordination, respectively. Considering that Sr, Al, and Nb atoms are crystallographically distinct in terms of interatomic distances and polyhedral coordination, Sr₄AlNbO₈ can be regarded as a stoichiometric compound.     

Crystal structure and magnetic properties of Co2TeO3Cl2 and Co2TeO3Br2

The crystal structures of the two new synthetic compounds Co₂TeO₃Cl₂ and Co₂TeO₃Br₂ are described together with their magnetic properties. Co₂TeO₃Cl₂ crystallize in the monoclinic space group P2₁/m with unit cell parameters a=5.0472(6) Å, b=6.6325(9) Å, c=8.3452(10) Å, β=105.43(1)°, Z=2. Co₂TeO₃Br₂ crystallize in the orthorhombic space group Pccn with unit cell parameters a=10.5180(7) Å, b=15.8629(9) Å, c=7.7732(5) Å, Z=8. The crystal structures were solved from single crystal data, R=0.0328 and 0.0412, respectively. Both compounds are layered with only weak interactions in between the layers. The compound Co₂TeO₃Cl₂ has [CoO₄Cl₂] and [CoO₃Cl₃] octahedra while Co₂TeO₃Br₂ has [CoO₂Br₂] tetrahedra and [CoO₄Br₂] octahedra. The Te(IV) atoms are tetrahedrally [TeO₃E] coordinated in both compounds taking the 5s² lone electron pair E into account. The magnetic properties of the compounds are characterized predominantly by long-range antiferromagnetic ordering below 30 K.     

Synthesis, structure determination, and infrared spectroscopy of (NpO2)2(SO4)(H2O)4: Prevalence of cation-cation interactions and cationic nets in neptunyl sulfate compounds

The compound (NpO₂)₂(SO₄)(H₂O)₄ was synthesized by evaporation of a Np⁵⁺ sulfate solution. The crystal structure was determined using single crystal X-ray diffraction and refined to an R₁=0.0310. (NpO₂)₂(SO₄)(H₂O)₄ crystallizes in triclinic space group P-1, a=8.1102(7) Å, b=8.7506(7) Å, c=16.234(1) Å, α=90.242(2)°, β=92.855(2)°, γ=113.067(2)°, V=1058.3(2) Å³, and Z=2. The structure contains neptunyl pentagonal bipyramids that share vertices through cation-cation interactions to form a sheet or cationic net. The sheet is decorated on each side by vertex sharing with sulfate tetrahedra, and adjacent sheets are linked together through hydrogen bonding. A graphical representation of (NpO₂)₂(SO₄)(H₂O)₄ was constructed to facilitate the structural comparison to similar Np⁵⁺ compounds. The prevalence of the cationic nets in neptunyl sulfate compounds related to the overall stability of the structure is also discussed.     

The role of cation-cation interactions in a neptunyl chloride hydrate and topological aspects of neptunyl structural units

The compound K₄(NpO₂)₃Cl₇(H₂O)₄ was synthesized by evaporation of a Np⁵⁺-bearing solution. The crystal structure was determined by single crystal X-ray diffraction and refined to R₁=0.0374. The compound is triclinic, P−1, a=8.882(1) Å, b=12.082(2) Å, c=12.403(2) Å, α=65.855(2)°, β=69.604(2)°, γ=74.432(2)°, V=1126.0(3) Å³, and Z=2. The structure contains dimers of edge sharing Np⁵⁺ pentagonal bipyramids that are linked into infinite chains through cation-cation interactions with an additional Np⁵⁺ pentagonal bipyramid. The structural units are linked through bonds to interstitial K cations and by H bonding. A graphical representation for neptunyl structural units including cation-cation interactions is introduced.     

Mononuclear ruthenium complexes containing chiral aminooxazolines: Syntheses, X-ray studies and catalytic activity

The synthesis and characterisation of three novel mononuclear ruthenium(II) complexes containing one of the following chiral auxiliary ligands: 2-amino-(4R)-phenyl-2-oxazoline (amphox), indanyl-2-amino-(4R,5S)-2-oxazoline (aminox) or indanyl-(2′-anilinyl)-(4R,5S)-2-oxazoline (aninox) is described using [Ru₂Cl₄(η⁶-p-cym)₂] (p-cym = 1-isopropyl-4-methylbenzene) as the Ru starting material. The new complexes have been identified as the neutral derivatives [RuCl₂(η⁶-p-cym)(amphox-κ¹N_ox)] (1), [RuCl₂(η⁶-p-cym)(aminox-κ¹N_ox)] (2) and the salt [RuCl(η⁶-p-cym)(aninox-κ²N,N′)]Cl (3). These materials have been fully characterised (elemental analysis, NMR, IR, conductance, MS, etc.) and, in the case of 2 and 3, structurally elucidated in the solid-state using single crystal X-ray diffraction methods. All three complexes show good catalytic activity (max. conversion >99%, TOF = 424 h⁻¹) but only modest enantio-selectivity (max. ee = 40%) for the transfer hydrogenation reaction of acetophenone with isopropyl alcohol. The complexes were also tested in an asymmetric Diels-Alder reaction involving cyclopentadiene and acrolein (max. conversion >99%, TOF = 42 h⁻¹). In this case, the diastereo-selectivity was good to moderate (max. de = 84%), but the ee values were poor (max. ee = 12%).     

Synthesis, structures, and photoluminescence properties of novel lanthanide tetracyanoplatinates lacking Pt-Pt interactions

The synthesis of a series of lanthanide tetracyanoplatinates all incorporating 2,2′:6′,2″-terpyridine (terpy) have been carried out by reaction of Ln³⁺ nitrate salts with terpy and potassium tetracyanoplatinate. The incorporation of different Ln³⁺ cations results in the isolation of [Ln(DMF)₂(C₁₅H₁₁N₃)(H₂O)₂(NO₃)]Pt(CN)₄ (Ln=La-Nd, Sm-Yb) under otherwise identical reaction conditions. These compounds have been isolated as single crystals and X-ray diffraction has been used to investigate their structural features. All of the reported compounds are isostructural. Crystallographic data for the representative Eu³⁺ compound (EuPt) are (MoKα, λ=0.71073 Å): monoclinic, space group P2₁/c, a=10.1234(4) Å, b=18.7060(7) Å, c=17.1642(5) Å, β=97.249(3)°, V=3224.4(2), Z=4, R(F)=2.78% for 426 parameters with 7724 reflections with I>2σ(I). The structure consists of a zero-dimensional, ionic salt containing complex [Eu(DMF)₂(C₁₅H₁₁N₃)(H₂O)₂(NO₃)]²⁺ cations and anions. The complex cations contain the Eu³⁺ ions in a tri-capped trigonal prismatic coordination environment with one terdentate 2,2′:6′,2″-terpyridine molecule, one bidentate nitrate anion, two O-bound dimethylformamide molecules, and two coordinated water molecules. Photoluminescence data illustrate that EuPt displays intramolecular energy transfer from the coordinated terpy molecule to the Eu³⁺ cation. The uncoordinated tetracyanoplatinate anion also exhibits visible emission.     

The iron potassium diarsenate KFeAs2O7 structural, electric and magnetic behaviors

Crystals of a new potassium iron (III) diarsenate (KFeAs₂O₇) have been grown and characterized by single crystal X-ray diffraction. It crystallizes in the triclinic space group , with a=7.662(1) Å, b=8.402(2) Å, c=10.100(3) Å, α=90.42(3)°, β=89.74(2)°, γ=106.39(2)°, V=623.8(3) Å³ and Z=4. The final agreement factors are R=0.0342, wR=0.0889, S(F²)=1.01; the structural model is validated by bond valence sum (BVS) and charge distribution (CD) methods. The structure consists of corner-sharing FeO₆ octahedra and As₂O₇ diarsenate groups, the three-dimensional framework delimits tunnels running along [0 1 0] direction where the potassium ions reside. The crystal structure of the title compound is different from that of the monoclinic KAlP₂O₇ type but structural relationships exist between the frameworks. Impedance measurements (frequency/temperature ranges: 5-13,000 Hz/526-668 K) show KFeAs₂O₇ an ionic conductor being the conductivity 2.76×10⁻⁷ S cm⁻¹ at 568 K and E_a is 0.47 eV. The BVS model suggests that the most probable potassium conduction pathway is along b-direction. Magnetic measurements reveal the Curie—Weiss type paramagnetic behavior over the range 30-300 K and ferromagnetic below 29.3 K.     

Crystallographic investigation of the Co-B-O system

The crystalline phases within the Co-B-O system have been investigated with a combination of powder and single crystal X-ray diffraction. By varying the synthetic conditions, four pure phases can be made by solid-state reaction: Co₃(BO₃)O₂, a homometallic ludwigite; Co₃(BO₃)₂, an orthoborate with the kotoite structure; Co₂(B₂O₅), a pyroborate; and the tetraborate Co(B₄O₇). Herein, we report the first structural refinement of the latter phase (orthorhombic, space group Pbca, a=8.1189(7) Å, b=8.621(1) Å, c=13.737(1) Å, V=961.5(2) Å³, Z=8, R₁=0.0319, wR₂=0.0693 [I>2σ(I)]). The pyroborate structure was also refined by single crystal methods in order to match the calculated powder diffraction pattern with the observed pattern (triclinic, space group , a=3.1689(3) Å, b=6.1530(5) Å, c=9.2734(7) Å, α=104.253(4)°, β=90.821(4)°, γ=92.098(5)°, V=175.08(3) Å³, Z=2, R₁=0.0159, wR₂=0.0366 [I>2σ(I)]). Flux growth of Co(B₄O₇) also yielded single crystals of the new compound Co₄(BO₂)₆O (cubic, space group , a=7.4825(3) Å, V=418.93(3) Å³, Z=2, R₁=0.0176, wR₂=0.0373 [I>2σ(I)]).     

Synthesis, crystal structure and thermal behavior of Sr3B2SiO8 borosilicate

Single crystals of Sr₃B₂SiO₈ were obtained by solid-state reaction of stoichiometric mixture at 1200 °C. The crystal structure of the compound has been solved by direct methods and refined to R1=0.064 (wR=0.133). It is orthorhombic, Pnma, a=12.361(4), b=3.927(1), c=5.419(1) Å, V=263.05(11) Å³. The structure contains zigzag pseudo-chains running along the b axis and built up from corner sharing (Si,B)−O polyhedra. Boron and silicon are statistically distributed over one site with their coordination strongly disordered. Sr atoms are located between the chains providing three-dimensional linkage of the structure.The formation of Sr₃B₂SiO₈ has been studied using annealing series in air at 900-1200 °C. According powder XRD, the probe contains pure Sr₃B₂SiO₈ over 1100 °C. The compound is not stable below 900 °C. In the pseudobinary Sr₂B₂O₅-Sr₃B₂SiO₈ system a new series of solid solutions Sr_3−xB₂Si_1−xO_8−3x (x=0-0.9) have been crystallized from melt. The thermal behavior of Sr₃B₂SiO₈ was investigated using powder high-temperature X-ray diffraction (HTXRD) in the temperature range 20-900 °C. The anisotropic character of thermal expansion has been observed: α_a= −1.3, α_b=23.5, α_c=13.9, and α_V=36.1×10⁻⁶ °C⁻¹ (25 °C); α_a= −1.3, α_b=23.2, α_c=5.2, and α_V=27.1×10⁻⁶ °C⁻¹ (650 °C). Maximal thermal expansion of the structure along of the chain direction [0 1 0] is caused by the partial straightening of chain zigzag. Hinge mechanism of thermal expansion is discussed.     

Structure, crystal chemistry and thermal evolution of the δ-Bi2O3-related phase Bi9ReO17

The thermal evolution and structural properties of fluorite-related δ-Bi₂O₃-type Bi₉ReO₁₇ were studied with variable temperature neutron powder diffraction, synchrotron X-ray powder diffraction and electron diffraction. The thermodynamically stable room-temperature crystal structure is monoclinic P2₁/c, a=9.89917(5), b=19.70356(10), c=11.61597(6) Å, β=125.302(2)° (R_p=3.51%, wR_p=3.60%) and features clusters of ReO₄ tetrahedra embedded in a distorted Bi-O fluorite-like network. This phase is stable up to 725 °C whereupon it transforms to a disordered δ-Bi₂O₃-like phase, which was modeled with δ-Bi₂O₃ in cubic Fm3¯m with a=5.7809(1) Å (R_p=2.49%, wR_p=2.44%) at 750 °C. Quenching from above 725 °C leads to a different phase, the structure of which has not been solved but appears on the basis of spectroscopic evidence to contain both ReO₄ tetrahedra and ReO₆ octahedra.     

Chelating ionic versus bridged molecular structures of group 13 metal complexes with bidentate ligands

Complexes of aluminum and gallium trihalides with ethylenediamine (en) and N,N,N′,N′-tetramethylethylenediamine (tmen) of 2:1 composition have been synthesized and structurally characterized by single crystal X-ray diffraction analysis. In contrast to known molecular complexes of hydrido and methyl-substituted analogs, these solid complexes adopt ionic structures of the general type [M¹X₂LL]⁺[M²X₄]⁻ (X = Br, I; M¹, M² = Al or Ga; LL = en, tmen).     

Crystal structures and photocatalysis of the triclinic polymorphs of BiNbO4 and BiTaO4

The high-temperature polymorphs of two photocatalytic materials, BiNbO₄ and BiTaO₄ were synthesized by the ceramic method. The crystal structures of these materials were determined by single-crystal X-ray diffraction. BiNbO₄ and BiTaO₄ crystallize into the triclinic system P1¯ (No. 2), with a=5.5376(4) Å, b=7.6184(3) Å, c=7.9324(36) Å, α=102.565(3)°, β=90.143(2)°, γ=92.788 (4)°, V=326.21 (5) Å³, Z=4 and a=5.931 (1) Å, b=7.672 (2) Å, c=7.786 (2) Å, α=102.94 (3)°, β=90.04 (3)° γ=93.53 (3)°, V=344.59 (1) Å³ and Z=4, respectively. The structures along the c-axis, consist of layers of [Bi₂O₂] units separated by puckered sheets of (Nb/Ta)O₆ octahedra. Photocatalytic studies on the degradation of dyes indicate selectivity of BiNbO₄ towards aromatics containing quinonic and azo functional groups.     

Synthetic and X-ray diffraction studies of borosiloxane cages [R′Si(ORBO)3SiR′] and the adducts of [BuSi{O(PhB)O}3SiBu] with pyridine or N,N,N′,N′-tetramethylethylenediamine

Eleven borosiloxane [R′Si(ORBO)₃SiR′] compounds where R′ = Bu^t and R = Ph (1), 4-PhC₆H₄ (2), 4-Bu^tC₆H₄ (3), 3-NO₂C₆H₄ (4), 4-CH(O)C₆H₄ (5), CpFeC₅H₄ (6), 4-C(O)CH₃C₆H₄ (7), 4-ClC₆H₄ (8), 2,4-F₂C₆H₃ (9), and R′ = cyclo-C₆H₁₁ and R = Ph (10), and 4-BrC₆H₄ (11) have been synthesized and characterized by spectroscopic (IR, NMR), mass spectrometric and, for compounds where R′ = Bu^t and R = 4-PhC₆H₄ (2), 4-Bu^tC₆H₄ (3), 3-NO₂C₆H₄ (4), CpFeC₅H₄ (6) and 2,4-F₂C₆H₃ (9), X-ray diffraction studies. These compounds contain trigonal planar RBO₂ and tetrahedral R′SiO₃ units located around 11-atom “spherical” Si₂O₆B₃ cores. The dimensions of the Si₂O₆B₃ cores in compounds 2, 3, 4, 6 and 9 are remarkably similar. The reaction between [Bu^tSi{O(PhB)O}₃SiBu^t] (1), and excess pyridine yields the 1:1 adduct [Bu^tSi{O(PhB)O}SiBu^t]. NC₅H₅ (12) while the reaction between 1 and N,N,N′,N′-tetramethylethylenediamine in equimolar amounts affords a 2:1 borosiloxane:amine adduct [Bu^tSi{O(PhB)O}₃SiBu^t]₂ · Me₂NCH₂CH₂NMe₂ (13). Compounds 12 and 13 were characterised with IR and (¹H, ¹³C and¹¹B) NMR spectroscopies and the structure of the pyridine complex 12 was determined with X-ray techniques.     

Photofunctional supramolecular solution systems of chiral Schiff base nickel(II), copper(II), and zinc(II) complexes and photochromic azobenzenes

Preparations, crystal structures, electronic and CD spectra are reported for new chiral Schiff base complexes, bis(N-R-1-naphthylethyl-3,5-dichlorosalicydenaminato)nickel(II), copper(II), and zinc(II). Nickel(II) and copper(II) complexes adopt a square planar trans-[MN₂O₂] coordination geometry with Δ(R,R) configuration. While zinc(II) complex adopts a compressed tetrahedral trans-[MN₂O₂] one with Δ(R,R) configuration and exhibits an emission band around 21 000 cm⁻¹ (λ_ex = 27 000 cm⁻¹). Absorption and CD spectra were recorded in N,N′-dimethylformamide, acetone, methanol, chloroform, and toluene solutions to discuss relationships between spectral shifts of d–d and π–π^∗ bands by structural changes of the complexes and physical properties of the solvents. Moreover, we have attempted to investigate conformational changes of the complexes induced by photoisomerization of azobenzene, 4-hydroxyazobenzene, or 4-aminoazobenzene, in various solutions under different conditions. Weak intermolecular interactions between complexes and azobenzenes are important for the phenomenon by conformational changes of bulky π-conjugated moieties of the ligands.     

Synthesis, crystal structure and thermoelectric properties of a new carbide Zr2[Al3.56Si0.44]C5

A new quaternary layered carbide, Zr₂[Al_3.56Si_0.44]C₅, has been synthesized and characterized by X-ray powder diffraction, transmission electron microscopy and thermopower and electrical conductivity measurements. The crystal structure was successfully determined using direct methods, and further refined by the Rietveld method. The crystal is trigonal (space group R3m, Z=3) with lattice dimensions of a=0.331059(5), c=4.09450(5) nm and V=0.38864(1) nm³. The final reliability indices calculated from the Rietveld refinement were R_wp=6.24%, R_p=4.21% and R_B=0.82%. The crystal structure is composed of electroconductive NaCl-type ZrC slabs separated by Al₄C₃-type [Al_3.56Si_0.44]C₃ layers. This material had thermoelectric properties superior to those of the ternary layered carbides Zr₂Al₃C₄ and Zr₃Al₃C₅, with the power factor reaching 7.6×10⁻⁵W m⁻¹ K⁻².     

Structure and conformational processes of bis(o-cumyl)sulfide, sulfoxide and sulfone

The NMR solution spectra of the title sulfide and sulfone show decoalescence of the geminal methyl signals of the isopropyl groups at low temperature (−178 °C for the ¹³C signal of sulfide at 150.8 MHz and −147 °C for the ¹H signal of sulfone at 600 MHz). The barriers for the related dynamic processes were measured (4.3 and 7.0 kcal mol⁻¹ for the sulfide and sulfone, respectively). The preferred conformer of sulfide has a propeller shape with a C₁ symmetry, as suggested by Molecular Mechanics (MM) calculations. In the case of sulfone the preferred conformer has a propeller shape with a C₂-anti symmetry, as indicated by calculations and supported by X-ray crystallographic determination. The computed contour map of the potential energy shows that in both cases the dynamic processes take place via correlated rotations (cogwheel mechanism) of the two aromatic substituents about the Ar-S bonds. Dynamic processes could not be observed by NMR in the title sulfoxide, which was also found to adopt a propeller shaped conformation, as indicated by MM calculations and X-ray diffraction.     

X-ray diffraction study on the thermal expansion behavior of cellulose Iβ and its high-temperature phase

Oriented films of cellulose prepared from algal cellulose were hydrothermally treated to convert them into highly crystalline cellulose Iβ. The lateral thermal expansion behavior of the prepared cellulose Iβ films was investigated using X-ray diffraction at temperatures from 20 to 300 °C. Cellulose Iβ was transformed into the high-temperature phase when the temperature was above 230 °C, allowing the lateral thermal expansion coefficient of cellulose Iβ and its high-temperature phase to be measured. For cellulose Iβ, the thermal expansion coefficients (TECs) of the a- and b-axes were α_a = 9.8 × 10⁻⁵ °C⁻¹ and α_b = 1.2 × 10⁻⁵ °C⁻¹, respectively. This anisotropic thermal expansion behavior in the lateral direction is ascribed to the crystal structure and to the hydrogen-bonding system of cellulose Iβ. For the high-temperature phase, the anisotropy was more conspicuous, and the TECs of the a- and b-axes were α_a = 19.8 × 10⁻⁵ °C⁻¹ and α_b = −1.6 × 10⁻⁵ °C⁻¹, respectively. Synchrotron X-ray fiber diffraction diagrams of the high-temperature phase were also recorded at 250 °C. The cellulose high-temperature phase is composed of a two-chain monoclinic unit cell, a = 0.819 nm, b = 0.818 nm, c (fiber repeat) = 1.037 nm, and γ = 96.4°, with space group = P2₁. The volume of this cell is 4.6% larger than that of cellulose Iβ at 30 °C.