Synthesis of derivatives of 1, 2, 4-triazole-3, 5-dicarboxylic acid

By oxidation of 3,5-dimethyl-1,2,4-triazole the monopotassium salt of 1,2,4-triazole-3,5-dicarboxylic acid was obtained. The mononitryl of 1,2,4-triazole-3,5-dicarboxylic acid was isolated during the reaction between 3-diazo-1,2,4-triazole-5-carboxylic acid and potassium cyanide in the presence of copper cyanide. Acid hydrolysis of 3-cyano-1,2,4-triazole-5-carboxylic acid leads to the formation of 3-carbamido-5-carboxy-1,2,4-trlazole, which on esterification with methanol gives rise to 3-carbamido-5-carbomethoxy-1,2,4-triazole.     

Crystallization of carbamazepine pseudopolymorphs from nonionic microemulsions

Crystallization of carbamazepine (CBZ), an antiepileptic drug, precipitated from confined spaces of nonionic microemulsions was investigated. The study was aimed to correlate the structure of the microemulsion [water-in-oil (W/O), bicontinuous, and oil-in-water (O/W)] with the crystalline structure and morphology of solid CBZ. The precipitated CBZ was studied by DSC, TGA, powder XRD, single-crystal XRD, SEM, and optical microscopy. The results suggest that the microstructure of the microemulsions influences the crystallization process and allows crystallizing polymorphs that exhibit different crystal structure and habits. W/O nanodroplets orient the crystallizing CBZ molecules to form a prismlike anhydrous polymorphic form with monoclinic unit cell and P21/n space group. Bicontinuous structures lead to platelike dihydrate crystals with orthorhombic unit cell and Cmca space group. The O/W nanodroplets cause the formation of needlelike dihydrate crystals with monoclinic unit cell and P21/c space group. The morphological features of solid CBZ remain predetermined by the basic symmetry and parameters of its unit cell. Precipitation of CBZ pseudopolymorphs from supersaturated microemulsion is discussed in terms of oriented attachment that provides perfect packing of numerous separately nucleated ordered nuclei of CBZ into microscale platelets and then into macroscopic crystals. Crystallization from microemulsion media enabling one to obtain the drug (CBZ) with predicted structure and morphology should be of great significance for pharmaceutical applications.     

New Metal Chelates with Sterically Hindered Azo Ligands: Synthesis and Physicochemical Properties

Metal chelates based on 3,5-di-(tert-butyl)-2-hydroxyazobenzene are synthesized and their physicochemical properties were studied. Four alternative structures and isomeric transformations between these structures were suggested on the basis of NMR data, electric dipole and magnetic moments, X-ray diffraction and quantum-chemical data. The change in stereochemistry of a complex through introduction of tert-butyl substituents was found to give unusual (for metal chelates with azo ligands (MN₂O₂)) dome-shaped isomers with the trans-planar coordination core at a vertex or with a distorted cis-structure.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 563–571.Original Russian Text Copyright © 2005 by Kogan, Lyubchenko, Shcherbakov, Ionov, Tkachev, Shilov, Aldoshin.     

A novel chelatofore functionalized spiropyran of the 2‐oxaindane series

A novel chelatofore functionalized spiropyran of the 2‐oxaindane series, namely 8‐formyl‐7‐hydroxy‐3′,3′‐dimethylspiro[2H‐chromene‐2,1′(3′H)‐2‐benzofuran], C₁₉H₁₆O₄, is reported. In the crystalline state, dimers are formed as a result of the π–π stacking of aromatic groups of the 2H‐chromene part of the molecule and C—H...O interactions. The C_spiro—O bond length in the pyran ring is 1.4558 (10) Å, which is longer than or equal to the bond length in thermo‐ and photochromic 2‐oxaindane spiropyrans synthesized previously, except for the 7,8‐benzo/6‐NO₂ derivative, in which this bond length is 1.465 (2) Å.     

Transition metal complexes based on 2,4-dihydroxyisophthalic anhydride and its functionalized derivative

Oligomeric complex compounds of Cu(II), Ni(II), Mn(II), Zn(II), and Cd(II) with 2,4-dihydroxyisophthalic aldehyde and its bis-hydrazone on the basis of 4-pyridinecarboxylic acid hydrazide are prepared. Probable structures of the complexes are proposed, based on the results of physico-chemical investigations by the methods of IR and ¹H NMR spectroscopy, magnetochemistry and molecular weight determining by Rast’s method.     

Reversible sorption of hydrogen on the novel hybrid material based on mesoporous chromium(<Emphasis Type="SmallCaps">iii</Emphasis>) terephthalate with included rhenium clusters

The interaction of mesoporous chromium(iii) terephthalate [Cr₃O(C₈H₄O₄)₃F(H₂O)₂] (MIL-101) with an aqueous solution of the anionic cluster [Re₄S₄F₁₂]⁴⁻ ({Re₄}) afforded a novel hybrid material {Re₄}@MIL-101. According to the elemental analysis data, one cavity of the nanoporous framework contains up to two-three tetranuclear rhenium clusters. The hybrid sorbent obtained reversibly absorbs up to 3.7 wt.% hydrogen at 77 K and 30 atm.