Crystal structure and pseudosymmetry analysis of the triclinic prodrug cloxazolam (Z′ = 4)

The prodrug cloxazolam [systematic name: 13‐chloro‐2‐(2‐chlorophenyl)‐3‐oxa‐6,9‐diazatricyclo[8.4.0.0^2,6]tetradeca‐1(10),11,13‐trien‐8‐one], C₁₇H₁₄Cl₂N₂O₂, crystallizes in the triclinic space group P, with four chemically identical independent molecules in the asymmetric unit. However, in order to facilitate the analysis of the striking pseudosymmetry relating the four independent molecules, the structure has been analysed and reported in the nonconventional centred B space‐group setting. Pseudosymmetry is an eminently local property, valid only in the realm of the unit‐cell boundary and not propagating to the whole crystal structure. It has been analyzed using the MP procedure described in the preceding article [Baggio (2019). Acta Cryst. C 75 , 837–850]. The molecules consist of a rigid core made up of three rings (five‐, six‐ and seven‐membered) and an extra six‐membered ring joined to the latter group by a single C—C bond, together with a clamping intramolecular C—H…O interaction preventing free rotation and providing additional rigidity. The four molecules in the asymmetric unit pair into dimers with almost exact twofold pseudosymmetry, further linked into (001) slabs as the building bricks of the structure. Interpenetration of slabs finally leads to a three‐dimensional structure of unusual compactness for an organic structure, with a Kitaigorodskii packing index of ca 0.71.     

The crystal structure of triclinic β-BiNbO4

The crystal structure of β-BiNbO₄ has been determined from three-dimensional X-ray data. The crystals are triclinic with a = 7.61₁ Å, b = 5.53₆ Å, c= 7.91₉ Å, α = 89.88°, β = 77.43°, γ = 87.15°, Z = 4, space group $\text{P}\text{1}$. Full-matrix least-squares refinement using isotropic temperature factors has reached R = 0.122 for 642 visually estimated reflections.The structure contains unusual sheets of formula [NbO₄]_∞ in which the NbO octahedra are joined at four vertices such that the two free ones are cis. NbO distances range from 1.80 to 2.31 Å. The bismuth atoms hold these sheets together and are coordinated to eight oxygens in the form of a very distorted square antiprism.Structurally, β-BiNbO may be considered an antiferroelectric, ferroelastic member of the BaMF₄ prototype family.     

A new triclinic modification of the pyrochlore-type KOs2O6 superconductor

A new modification of KOs₂O₆, the representative of a new structural type (Pearson symbol aP18, a=5.5668(1) Å, b=6.4519(2) Å, c=7.2356(2) Å, α=65.377(3)°, β=70.572(3)°, γ=75.613(2)° space group P−1, no. 2 was synthesized employing high pressure technique. Its structure was determined by single-crystal X-ray diffraction. The structure can be described as two OsO₆ octahedral chains relating to each other through inversion and forming big voids with K atoms inside. Quantum chemical calculations were performed on the novel compound and structurally related cubic compound. High-pressure X-ray study showed that cubic KOs₂O₆ phase was stable up to 32.5(2) GPa at room temperature.     

A pseudosymmetric triclinic modification of tri­phenyl­tin iso­propyl­xanthate

All three independent mol­ecules in the triclinic modification of (O‐iso­propyl di­thio­carbonato‐S)­tri­phenyl­tin, [Sn(C₆H₅)₃(C₄H₇OS₂)], show tetrahedral coordination at their Sn atoms. Bond dimensions involving the Sn atoms are similar to those found in the monoclinic modification of the same compound. Two of the independent mol­ecules are related by a pseudo‐translation allowing a stacking fault that reduces the intensities of h + k odd reflections.     

Crystal structure and physical properties of a new CuTi2S4 modification in comparison to the thiospinel

A new modification of CuTi(2)S(4) was prepared from the elements at 425 degrees C. It crystallizes in the rhombohedral space group Rm, with lattice parameters of a = 7.0242(4) A, c = 34.834(4) A, and V = 1488.4(2) A(3) (Z = 12). Two topologically different interlayer regions exist between the close-packed S layers that alternate along the c axis: one comprises both Cu (in tetrahedral voids) and Ti atoms (in octahedral voids), and the second exclusively Ti atoms (again in octahedral voids). In contrast to the known modification, the spinel, Cu-Ti interactions of 2.88 A occur that have bonding character according to the electronic structure calculations. Both CuTi(2)S(4) modifications are metallic Pauli paramagnets due to Ti d contributions. The Pauli susceptibility of the Rm form is larger than that of the thiospinel in quantitative agreement with the LMTO-ASA band structure calculations. The irreversible transformation to the spinel takes place at temperatures above 450 degrees C.     

Crystal structure of the phenylacetylene-choleic acid

Deoxycholic acid (C₂₄H₄₀O₄, M _r =392.58) and phenylacetylene (C₈H₆, M _r =102.14) form a 2:1 inclusion compound which crystallizes in space groupP2₁2₁2₁ witha=25.542(6),b=13.662(5),c=7.227(2) Å,Z=4. The finalR is 0.07₁ for 2168 observed reflections withI>1.5(I). The crystal packing is characterized by an assembly of antiparallel pleated bilayers of deoxycholic acid molecules which leave empty channels running alongc. Phenylacetylene molecules are accommodated within the cavities in an ordered fashion and are very probably arranged in only one orientation, which was determined by means of Van der Waals energy calculations. Atoms of deoxycholic acid belonging to ring A and to the side-chain are engaged in binding interactions with the guest molecule. The arrangement of the guest molecules supports the experimental results of irradiation, which show a failure of the phenylacetylene molecules to undergo inclusion polymerization. Supplementary Data relevant to this paper have been deposited with the British Library Lending Division under SUP No. 82024 (13 pages).     

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.     

Crystal structure of acrylamide

The crystal structure of acrylamide is re-determined by single crystal X-ray diffraction (133(1) K, BRUKER SMART 1000 CCD, a = 8.228(1) Å, b = 5.759(1) Å, c = 9.760(1) Å, β = 120.04(1)°, V = 400.3(1) Å,³, space group P2₁/c, Z = 4, R = 0.0543 for 867 reflections). In the structure strong hydrogen bonds N-H...O join the molecules of C₃H₅NO into bi-molecular layers that make C...C molecular contacts. It is demonstrated that the process of solid phase polymerization of acrylamide should proceed through the cleavage of double bonds C(1)=C(2) in the monomers and formation of bonds C(1)-C(1) and C(2)-C(2) between the closest carbon atoms of different layers.