Centrosymmetric aliovalent KTP isomorphs KMIII0.5Nb0.5OPO4 (M = Cr and Fe)

Aliovalent KTP isomorphic compounds potassium chromium niobium oxide phosphate, KCr_0.5Nb_0.5OPO₄, and potassium iron niobium oxide phosphate, KFe_0.5Nb_0.5OPO₄, exhibit structures that differ from that of the non‐centrosymmetric KTiOPO₄. There are two crystallographically independent octa­hedral sites, M1 and M2, statistically occupied by Nb and Cr (or Fe) atoms. The M1O₆ and M2O₆ octa­hedra are connected alternately to form a chain with a cis–trans arrangement. The Nb atoms prefer the M2 sites arranged in a cis‐like configuration. Each PO₄ tetra­hedon has the P atom on a twofold axis. Site‐splitting at the K‐atom position is observed in both compounds. In the isomorphous structures, one Nb atom lies on an inversion centre and the other on a twofold axis. Similarly with the pairs of Fe/Cr sites, one is on an inversion centre and the other on a twofold axis.     

Crack resistance and atomic structure of Li2B4O7 single crystals

The nature of destruction of single crystals of lithium tetraborate Li₂B₄O₇ under the action of a concentrated load is investigated. It is established that planes of easy crack propagation in Li₂B₄O₇ single crystals are the (100), (010), (001), and {111} planes. It is found that crack propagation occurs in each case along the atomic layers that are linked by bridge oxygen atoms between main structural units (B₄O₉) and, therefore, are most weakly bound.     

Gadolinium pyrosilicate single crystals for gamma ray and thermal neutron monitoring

Bulk Gd₂Si₂O₇:Ce (GPS:Ce) single crystals obtained by Czochralski method demonstrate a high light output at γ-irradiation (3.8 times higher in comparison with Bi₄Ge₃O₁₂ (BGO)), energy resolution 13% (137Cs, 662 KeV), fast decay time (41.7 ns), and good thermal stability of light output (up to 425 K). This combination of characteristics makes this scintillator very attractive for medical imaging and high-temperature applications. Light output at thermal neutron monitoring is evaluated as twice higher in comparison with Gd₂SiO₅:Ce (GSO). The observed rather high afterglow level (0.2% after 20 ms) and moderate energy resolution (13%) certifies a room for improvement of these parameters by further optimization of crystal quality.     

Solubility of Al2O3 in some chloride-fluoride melts

Alumina solubility in chloride-fluoride melts of KCl-NaCl-NaF mixtures with ratios of 0.425:0.425:0.15 (I), 0.38:0.38:0.24 (II), and 0.35:0.35:0.30 (III) (molar fractions) was investigated in the 973-1123 K temperature range using the isothermal saturation method. Al2O3 solubility in the ionic melts studied was shown to be on the order of 0.06 g kg(-1) for system I, 0.12 g kg(-1) for system II, and 0.14 g kg(-1) for system III at 1073 K. All the "Al2O3 + melt" systems were found to demonstrate negative deviations from the ideal solutions. The solubility of Al2O3 in all the melts increases with the temperature increase; however, the dependences of -log N(Al2O3) versus T(-1) were characterized by the slopes (2.6 +/- 0.4) x 10(3) K (I and II) and (2.4 +/- 0.6) x 10(3) K (III), which were considerably less than the slope predicted by the Shreder-Le Chatelier equation (approximately 5.8 x 10(3)).     

Multi-Component Reactions of Aldehydes,Amines, and Ketones I. Synthesis and Crystal Structure Elucidation of a Novel Product of Condensation of Salicylaldehyde, 1-Methyl-4-piperidone,and Methylamine

Summary.  The condensation of salicylaldehyde, 1-methyl-4-piperidone, and methylamine has been studied as a model reaction. It was found that at a molar ratio of salicylaldehyde: 1-methyl-4-piperidone = 2:1 and an excess of methylamine the previously unknown heterocyclic compound 2-(3,6,13-trimethyl-1,2,3,4,4a,5,6,7-octahydro-7,12a-epiminopyrido[4,3-b][1,5]benzoxazocin-5-yl)-phenol was formed; its structure was elucidated by spectroscopic methods and X-ray analysis. A reaction pathway for this new multi-component condensation is suggested and discussed. Received August 20, 2001. Accepted (revised) November 15, 2001     

Molecular and crystal structure of 3-butoxy-4-(1,3,3-trimethyl-2,3-dihydro-1<Emphasis Type="Italic">H</Emphasis>-2-indolylidenemethyl)-3-cyclobutene-1,2-dione and its thio analog

X-ray investigation of 3-butoxy-4-(1,3,3-trimethyl-2,3-dihydro-1H-2-indolylidenemethyl)-3-cyclobutene-1,2-dione and its thio analog has been carried out. Replacement of the carbonyl oxygen atom by a sulfur atom causes electron density delocalization and equalization of the C-C bonds between the four-and five-membered rings.     

Onium Sulfates and Hydrogen Sulfates: Products of Reactions of Sulfur(IV) Oxide with Aqueous Solutions of Alkylamines and Aniline

The reaction products formed in the SO₂–L–H₂O–O₂ systems (L is n-propylamine, n-butylamine, tert-butylamine, n-heptylamine, n-octylamine, aniline) were isolated and identified as “onium” salts [n-C₃H₇NH₃]₂SO₄, [n-C₄H₉NH₃]₂SO₄, [t-C₄H₉NH₃]₂SO₄, [n-C₇H₁₅NH₃]₃SO₄(HSO₄), [n-C₈H₁₇NH₃]₃SO₄(HSO₄), and [C₆H₅NH₃]₂SO₄. The products were characterized by elemental analysis, IR and Raman spectroscopy, mass spectrometry, and thermogravimetry.     

Onium salts of sulfur-containing oxyanions resulting from reaction of sulfur(IV) oxide with aqueous solutions of 1,2-diamines and morpholine

Reaction products have been isolated from SO₂–L–H₂O–О2 systems (L = ethylenediamine, N,N,N′,N′-tetramethylethylenediamine, piperazine, and morpholine) as onium salts [H₃NCH₂CH₂NH₃]SO₄, [(CH₃)₂NHCH₂CH₂NH(CH₃)₂]SO₄, [(CH₃)₂NHCH₂CH₂NH(CH₃)₂]S₂O₆ ? H₂O, [C₄H₈N₂H₄]SO₃ ? H₂O, [C₄H₈N₂H₄]S₂O₆, [C₄H₈N₂H₄]SO₄ ? H₂O, [O(C₂H₄)₂NH₂]₂SO₄ ? H₂O. The prepared compounds have been characterized by X-ray diffraction analysis, X-ray powder diffraction, IR and mass spectroscopy.     

Stable 1,2,4-triazolo[1,5-a]-pyrimidinium salts

2,3-Diamino-5,7-diaryl-1,2,4-triazolo[1,5-a]pyrimidinium salts have been synthesized by the cyclocondensation of 3,4,5-triamino-1,2,4-triazole with 1,3-diaryl-2,3-propanes, and their structures and chemical properties have been studied.Kharkov State University, Kharkov 310077, Ukraine. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, 796–804 June, 1999.