[Show abstract][Hide abstract] ABSTRACT: Five potential charge transfer complexes of trimeric perfluoro-o-phenylene mercury (I) with tetrathiafulvalene (TTF) and tetramethyltetraselenefulvalene (TMTSF) were grown from different solvent mixtures. The adducts (I)2∙TTF (1) and I∙TTF (2) were grown by slow evaporation from the 1:1 mixture of dichloromethane (CH2Cl2, DCM) and carbon disulfide (CS2). Use of the different 1 : 1 solvent mixture of dichloromethane (CH2Cl2, DCM) and dichloroethane (C2H4Cl2, DCA) has led to the crystalline adducts I∙TTF( 3) and I∙TTF∙DCA (4). Adduct I.TMTSF ( 5) was grown by the interface crystallization on the borderline of two immiscible layers, ethyl acetate, and carbon disulfide. The co-crystals differ by the donor-acceptor ratio, molecular packing and the solvent inclusion. The components in 1-5 form the mixed donor-acceptor stacks. The stacks are stabilised by the Hg∙∙∙S and Hg…C short contacts, while the lateral interactions between stacks include F…F, CH…F, and S/Se…F short contacts.
[Show abstract][Hide abstract] ABSTRACT: The molecular and crystal structures of two energetic fused furazans, 4H,8H-bis-furazano[3,4-b:3',4'-e]pyrazine (1) and 4H,9H-bisfurazano[3,4-b:3',4-g]-pyrazino[2,3-e]pyrazine (2), have been studied by single crystal X-ray diffraction analysis. These materials were found to have rather high crystal densities for organic compounds (2.032 and 1.882 g.cm(-3)). Very short interplanar distances between overlapping molecules in crystals (less than 3.15 angstrom) suggest the presence of stacking interaction between planar rings. High-resolution low-temperature X-ray diffraction data for both compounds were used to analyze the electron density distribution in the area of stacking interaction and hydrogen bonds, as interpreted through the framework of Baders AIM theory. A weak accumulation of the electron density, and (3, -1) bond critical points were found in the area of this interaction between overlapping molecules in the crystal. It was established that the energy of the stacking interactions in 1 and 2 are 3.9 and 3.2 kcal/mol, which is in good agreement with previous experimental and theoretical works. On the basis of our results and literature data we analyzed the correlation between the interatomic distance and the electron density in critical point (3, -1). This analysis revealed that the stacking interaction is a partial case of other specific interactions.
No preview · Article · Nov 2014 · Crystal Growth & Design
[Show abstract][Hide abstract] ABSTRACT: Adducts of cobalt(II) bis(salicylaldiminates) and 2,4,6,8-tetra-tert-butylphenoxazin-1-one were synthesized and their molecular and crystal structures were determined. According to the ESR and magnetochemical data, the metal atom is in the low-spin trivalent state (CoIII) due to the intramolecular electron transfer to the redox-active ligand. In the solid state, the mixedligand complexes are stable in air for several months, but in solution at elevated temperatures they dissociate to the starting components. Such a behavior detected by the temperature dependence of the effective magnetic moment is explained by the quantum chemical DFT calculations of the energy barriers of possible valence tautomeric dynamics, whose values were found to be higher than the enthalpy of dissociation.
No preview · Article · Aug 2014 · Russian Chemical Bulletin
[Show abstract][Hide abstract] ABSTRACT: A convenient express method for obtaining palladium nanoparticles on the graphene oxide support was developed. The data of transmission electron microscopy and X-ray diffraction analysis indicated the formation of palladium nanoparticles with an average size of 2 nm. The obtained nanocomposite material showed high catalytic activity in the cross-coupling reaction of bromobenzene with phenylboronic acid. The efficiency of the catalyst increases when using a mixture of organic solvents with water.
No preview · Article · Sep 2013 · Russian Chemical Bulletin
[Show abstract][Hide abstract] ABSTRACT: Here, we report the synthesis, characterization, and properties of novel nanohybrids formed by self-assembly of negatively charged MoS2 nanoplates and positively charged iron oxide nanoparticles (NPs) of two different sizes, 5.1 and 11.6 nm. Iron oxide NPs were functionalized with an amphiphilic random copolymer, quaternized poly(2-(dimethylamino)ethyl metacrylate-co-stearyl metacrylate), synthesized for the first time using atom transfer radical polymerization. The influence of the MoS2 fraction and the iron oxide NP size on the structure of the nanohybrids has been studied. Surprisingly, larger NPs retained a larger fraction of the copolymer, thus requiring more MoS2 nanoplates for charge compensation. The nanohybrid based on 11.6 nm NPs was studied in oxidation of sulfide ions. This reaction could be used for removing the dangerous pollutant from wastewater and in the production of hydrogen from water using solar energy. We demonstrated a higher catalytic activity of the NP/MoS2 nanohybrid than that of merely dispersed MoS2 in catalytic oxidation of sulfide ions and facile magnetic recovery of the catalyst after the reaction.
Full-text · Article · Jun 2013 · Chemistry of Materials
[Show abstract][Hide abstract] ABSTRACT: In the title co-crystal, 2C6H5NO·C4H4O4, two crystallographically different hydrogen-bonded trimers are formed, one in which the components occupy general positions, and one generated by an inversion centre. This results in the uncommon situation of Z = 3 for a triclinic crystal. In the formula units, mol-ecules are linked by O-H⋯N hydrogen bonds.
Full-text · Article · Jun 2013 · Acta Crystallographica Section E Structure Reports Online
[Show abstract][Hide abstract] ABSTRACT: Co-crystallization of 4-nitrophenol (I) with five aminopyridines (4-aminopyridine 1, 3,4-diaminopyridine 2, 2,3-diaminopyridine 3, 3-aminopyridine 4, 2-amino-6-methylpyridine 5) and 2,4-diaminopyrimidine 6 resulted in six adducts with the ratio of components 2:1 in five and 1:1 in one final compounds. Single crystals were grown by slow evaporation technique using ethanol as a solvent. Five adducts with 1–5 crystallize in acentric P21 and Pna21 space groups, and one, 2(I)·6 – in centrosymmetric P21/c space group. Compounds 2(I)·1, 2(I)·2, 2(I)·3 are isomorphous, and demonstrate similar H-bonding patterns despite the differences in aminopyridine molecules. Compound 2(I)·5 is isomorphous to two previously reported compounds. Adducts 2(I)·1, 2(I)·2, 2(I)·3, 2(I)·5, 2(I)·6 represent organic salts composed of pyridinium/pyrimidinium cation, 4-nitrophenolate anion, and 4-nitrophenol neutral molecule. The H-bonded 4-nitrophenol–4-nitrophenolate anionic dimers were found in all compounds with 2:1 molar ratio. In adduct I·4 both molecules are in neutral form. The IR spectral data support crystallographic conclusions on salts formation. Plane wave pseudopotential density functional theory calculations were used to predict hyperpolarizability tensor components. Our calculations suggest 2(I)·3 as the best candidate for nonlinear optical materials (14 times more active than urea).
[Show abstract][Hide abstract] ABSTRACT: In the title salt, C5H8N3
−, the 3,4-diaminopyridinium cation is almost planar, with an r.m.s. deviation of 0.02 Å. The conformation of the hydrogen malonate anion is stabilized by an intramolecular O—H⋯O hydrogen bond, which generates an S(6) ring. In the crystal, N—H⋯O hydrogen bonds link cations and anions into layers parallel to the ab plane.
Full-text · Article · May 2013 · Acta Crystallographica Section E Structure Reports Online
[Show abstract][Hide abstract] ABSTRACT: The product of exfoliation and restacking of MoS2 in acidic conditions is studied in detail using X-ray powder diffraction, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The temperature dependence of powder patterns reveals that the heating of exfoliated-restacked MoS2 is a way to a new nanostructured MoS2-based layered material that remains nanosized even upon heating to 850 °C. Previously this material has been described as 2H-MoS2, but according to the X-ray diffraction (XRD) data, its structure cannot be correctly described by any of the ?usual? MoS2 polytypes. A model of the structure of the material describing its XRD patterns and thermal behavior is discussed in detail.
[Show abstract][Hide abstract] ABSTRACT: The title natural compound, isolated from var. King Alfred crystallizes as a hemihydrate, CHNO·0.5HO, with four crystallographically independent dioxolophenanthridinone mol-ecules and two crystallographically independent solvent water mol-ecules in the asymmetric unit. All four crystallographically independent dioxolophenanthridinone mol-ecules are geometrically very similar and differ only in the orientations of the three hy-droxy groups at the terminal cyclo-hexene rings. The five-membered dioxolane ring has a planar conformation (the r.m.s. deviations are 0.010, 0.019, 0.025 and 0.004 Å, for the four crystallographically independent molecules), and the six-membered dihydro-pyridone and cyclo-hexene rings adopt sofa conformations in each mol-ecule. The flattened structure of each dioxolophenanthridinone mol-ecule is supported by a strong intra-molecular O-H⋯O hydrogen bond. The N atom has a slightly pyramidalized configuration. In the crystal, the dioxolophenanthridinone mol-ecules form layers parallel to (101) with O-H⋯O and N-H⋯O hydrogen bonds linking the dioxolophenanthridinone mol-ecules both within and between the layers and the water mol-ecules, forming a three-dimensional framework. The absolute configurations of the chiral centers are 2, 3, 4 and 4a.
Full-text · Article · Mar 2013 · Acta Crystallographica Section E Structure Reports Online
[Show abstract][Hide abstract] ABSTRACT: Chiral nonracemic 3-substituted cis- and trans-4-aminopiperidines, which are precursors of anilidopiperidine analgesics, were obtained by diastereoselective synthesis from 1-methyl- and 1-benzyl-4-[(S)-1-phenylethyl]iminopiperidines, using the following reaction sequence: metalation with lithium diethylamide, alkylation with alkyl halides, and hydride reduction or hydrogenation over Raney nickel. The steric direction of the reaction, three-dimensional structure, preferred conformation, and absolute configuration of the resultant aminopiperidines were determined.
No preview · Article · Feb 2013 · Chemistry of Heterocyclic Compounds
[Show abstract][Hide abstract] ABSTRACT: The structure of methyl 4-[(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)methyl]-1-methyl-1H-pyrazol-5-
carboxylate is determined by X-ray crystallography and further used to elucidate the structure of methyl
4-[(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)methyl]-1-methyl-1H-pyrazol-3-carboxylate, using the data of
homo- and heteronuclear 2D NMR correlation spectroscopy.
Full-text · Article · Feb 2013 · Journal of Structural Chemistry
[Show abstract][Hide abstract] ABSTRACT: Poly(meth)acrylates of three types, namely, regular homopolymers containing side-chain tetraalkylammonium ionic groups with alkyl radicals of various lengths (C6 and C16), a copolymer with statistically distributed ionic and long-chain (C18) alkyl groups, and a block copolymer of the same composition in which alkylammonium and alkyl groups are located in separate blocks, are synthesized with the use of controlled radical polymerization processes. The interaction of the polymers with molybdenum disulfide singlelayer dispersions yields self-organized organic-inorganic nanocomposites containing up to 40% polymer. As evidenced by powder X-ray diffraction and high-resolution transmission electron microscopy structural studies of the composites, they possess a crystalline layered structure with interlayer distances depending on the composition and structure of the polymer. Structures with the most regular alternation of organic and inorganic layers are formed in the case of homopolymers. The orientation of their alkylammonium fragments relative to MoS2 layers depends on the length of the alkyl radical and corresponds to their parallel (C6) or perpendicular (C16) arrangement.
Full-text · Article · Jan 2013 · Polymer Science Series B
[Show abstract][Hide abstract] ABSTRACT: A new restraint scheme for Rietveld refinement based on Morse bond energy potential is introduced, in which the asymmetry of the Morse potential allows the refinement to `break' the incorrectly placed bonds. The analysis of bond‐length distributions at different values of restraint strength reveals a visible difference in behavior of wrong and correct structures, which can be detected using robust statistical methods. This fact is employed as a basis for a novel structure verification criterion. The approach is demonstrated on known difficult cases of acetolone and γ‐quinacridone and used for the Rietveld refinement of N‐(6‐phenylhexanoyl)glycyl‐L‐tryptophanamide, an organic molecule of a potential anxiolytic containing 32 non‐H atoms and 14 single bonds. The results are verified using density functional theory calculations with periodic boundary conditions.
Full-text · Article · Dec 2012 · Journal of Applied Crystallography
[Show abstract][Hide abstract] ABSTRACT: Quantum chemical calculations and topological analysis of the electron density distribution r(r) were performed in the framework of the “Atoms in molecules” theory for a series of 22,5-substituted phosphacymantrene derivatives. The electronic structure of the cyclic π-ligand caused by the donor-acceptor properties of the substituents determines the preferential orientation of the Mn(CO)3 fragment relative to the heterocycle. The change in the number of bond paths between the Mn atom and heterocycle affects “fine” changes in the character of the M-π-interaction, depending on the nature of the substituents and orientation of the carbonyl groups.
No preview · Article · Dec 2012 · Russian Chemical Bulletin
[Show abstract][Hide abstract] ABSTRACT: In the title mol-ecule, CHN, intra-cyclic angles cover the range 117.15 (10)-124.03 (11)°. The N atoms of the amino groups have trigonal-pyramidal configurations deviating slightly from the pyridine plane by 0.106 (2) and -0.042 (2) Å. In the crystal, the pyridine N atom serves as an acceptor of an N-H⋯N hydrogen bond which links two mol-ecules into a centrosymmetric dimer. Inter-molecular N-H⋯N hydrogen bonds between the amino groups further consolidate the crystal packing, forming a three-dimensional network.
Full-text · Article · Dec 2012 · Acta Crystallographica Section E Structure Reports Online
[Show abstract][Hide abstract] ABSTRACT: In the title mol-ecule, CHN, the endocyclic angles are in the range 118.43 (9)-122.65 (10)°. The mol-ecular skeleton is planar (r.m.s. deviation = 0.007 Å). One of the two amino H atoms is involved in an N-H⋯N hydrogen bond, forming an inversion dimer, while the other amino H atom participates in N-H⋯π inter-actions between the dimers, forming layers parallel to (100).
Full-text · Article · Dec 2012 · Acta Crystallographica Section E Structure Reports Online
[Show abstract][Hide abstract] ABSTRACT: The spatial and electronic structure studies of nitramide NH2NO2 suggest that the change in its molecular geometry upon transition from the gas phase to the condensed state is caused by an increase in the contribution of conjugation between functional groups. According to the analysis of the Bader atomic charges, the effects of such conjugation are to a considerable extent governed by intramolecular charge transfer from the amino to the nitro group. From estimation of the contribution of conjugation to the charge transfer it follows that conjugation remains in the isolated molecule. The influence of hydrogen bonding on the increase in the contribution of conjugation and the corresponding charge redistribution in the molecule was considered. Despite the presence of conjugation between functional groups, the planar configuration of the molecule in the crystal is not realized and the crystallographic twofold axis corresponds to superposition of two molecular configurations with C
No preview · Article · Nov 2012 · Russian Chemical Bulletin