Vol 61, No 7 (2016)

The two-wave dynamical diffraction in the Laue geometry has been theoretically considered for a plane X-ray wave in a crystal with a third-order nonlinear response to the external field. An analytical solution to the problem stated is found for certain diffraction conditions. A nonlinear pendulum effect is analyzed. The nonlinear extinction length is found to depend on the incident-wave intensity. A pendulum effect of a new type is revealed: the intensities of the transmitted and diffracted waves periodically depend on the incidentwave intensity at a fixed crystal thickness. The rocking curves and Borrmann nonlinear effect are numerically calculated.

Ternary compound Cu₄SSe has been first synthesized by alloying the Cu, S, and Se elements taken in stoichiometric ratios. An X-ray diffraction study of polycrystalline samples has revealed the synthesized material to be crystallized into the trigonal system with unit-cell parameters а = 4.021(1) Å, с = 6.838(1) Å, and V = 95.75(4) ų; sp. gr. P\(\bar 3\) m1; Z = 1; D_x = 6.333(3) g/cm³. The crystal structure has been solved and refined to the reliability factor R_Bragg = 0.40%.

The organic carbonitrile namely methyl (6-amino-5-cyano-2-methyl-4-(2-nitrophenyl)-4H-pyran)- 3-carboxylate is synthesized via one-pot multi-component reaction at room temperature using commercially available urea as inexpensive and environmentally benign organo-catalyst and its crystal structure is determined by X-ray technique. The crystals are monoclinic, sp. gr. C2/c, a = 12.3069(8) Å, b = 9.7023(7) Å, c = 24.812(2) Å, β = 94.862(6)°, Z = 8. The dihedral angle between pyran and phenyl rings is 87.8(1)°; the pyran ring is almost planar The dihedral angle between the mean planes of phenyl ring and nitro group is 44.4(2)°. The crystal structure is stabilized by N−H···N and N−H···O hydrogen bonds. In addition, C−H···π interactions are also observed in the crystal structure.

The iridium(I) cyclooctadiene complex with two (3-tert-butylimidazol-2-ylidene) ligands [(H-Im^tBu)₂Ir(COD)]⁺PF₆⁻ (C₂₂H₃₂PF₆IrN₄) has been prepared, and its crystal structure is determined by X-ray diffraction. Complex exhibits slightly distorted square planar configurations around the metal atom, which is coordinated by two H-Im^tBu ligands and one cyclooctadiene group. The new iridium carbene complex has a pair of hydrogen wing tips. The Ir−C_carbene bond lengths are 2.066(5) and 2.052(5) Å, and the bond angle C−Ir−C between these bonds is 95.54(19)°. The dihedral angle between two imidazol-2-ylidene rings is 86.42°.

A series of 2-arylidenebenzocycloalkanones containing heterocyclic rings 1–8 were prepared and characterized by IR, ¹H NMR and elemental analyses. X-ray diffraction study of 6 reveals that the cyclohexyl ring of the 3,4-dihydronaphthalen-1(2H)-one adopts a chair conformation with a maximum deviation of 0.547(3) Å and makes dihedral angles of 52.24(17)° and 11.23(16)°, respectively, with the benzene plane and the mean plane of the benzimidazole ring.

Five derivatives of curcumin analogue (R = OCH₂CH₃ (1), R = N(CH₃)₂ (2), R = 2,4,5-OCH₃ (3), R = 2,4,6-OCH₃ (4), and R = 3,4,5-OCH₃ (5)) were synthesized and characterized by ¹H NMR, FT-IR and UV–Vis spectroscopy. The synthesized derivatives were screened for antityrosinase activity, and found that 4 and 5 possess such activity. The crystal structure of 1 was determined by single crystal X-ray diffraction: monoclinic, sp. gr. P2₁/c, a = 17.5728(15) Å, b = 5.9121(5) Å, c = 19.8269(13) Å, β = 121.155(5)°, Z = 4. The molecule 1 is twisted with the dihedral angle between two phenyl rings being 15.68(10)°. In the crystal packing, the molecules 1 are linked into chains by C−H···π interactions and further stacked by π···π interactions with the centroid–centroid distance of 3.9311(13) Å.

Two organic salts of 1,2,3,4-tetrahydro-1,10-phenanthroline (tphen), namely (oaH)(tphenH) (1) and (ssa)(tphenH)·H₂O (2) (oaH₂ is oxalic acid, ssaH is 5-sulfosalicylic acid), were synthesized and structurally characterized. Both compounds contain tphenH⁺ cations but illustrate different crystal structures. The tphenH⁺ cations show a cross-stacking packing model in 1 but display a herringbone packing model in 2.

The thermal effect on lead clusters with radii up to 5.5 nm has been investigated by the molecular dynamics method using a modified tight-binding potential TB-SMA. The melting of Pb nanoparticles of these sizes is strictly homogeneous, without the formation of a surface liquidlike layer. The primary fcc phase in the particles is retained upon heating in the overwhelming majority of model experiments. An analysis of the structure formation during crystallization has shown that structures with pentagonal symmetry are preferred for lead clusters in this case. It is noted that an increase in the nanoparticle size leads to the dominance of the dodecahedral structure over the icosahedral one.

In this work, high aspect ratio zinc oxide nanowires are synthesized using templated one-step electrodeposition technique. Electrodeposition of the nanowires is done using a handcrafted electronic system. Nuclear track-etched polycarbonate membrane is used as a template to form the high aspect ratio nanowires. The result of X-ray diffraction and scanning electron microscopy shows that nanowires with a good crystallinity and an aspect ratio of more than 30 can be achieved in a suitable condition. The height of electrodeposited nanowires reaches to about 11 μm. Based on the obtained results, high aspect ratio ZnO nanowires can be formed using inexpensive electrodeposition setup with an acceptable quality.