Temperature- and pressure-responsive properties of <Emphasis Type="SmallCaps">l</Emphasis>- and<Emphasis Type="SmallCaps"> dl</Emphasis>-forms of poly(<Emphasis Type="Italic">N</Emphasis>-(1-hydroxymethyl)propylmethacrylamide) in aqueous solutions

The structural transition of the l- and dl forms of poly(N-(1- hydroxymethyl)propylmethacrylamide (PHMPMA) in aqueous solution was studied by measuring the pressure dependence of the apparent scattering intensity, differential scanning calorimetry (DSC), and circular dichroism (CD). The thermodynamic implications of the results are discussed in relation to the chiral structure of the side chain, and differences in the thermal and barometric transitions. T-P diagrams of the transition showed characteristic ellipsoid features. Antagonism of the temperature and pressure effects was observed only for P(dl-HMPMA). For P(l-HMPMA), the transition temperature (T _tr) decreased with increasing pressure, and the highest T _tr was observed at atmospheric pressure (0.1 MPa). For both polymers, the highest P _trs were observed at the lowest temperatures. The l polymer showed a specific negative peak in its CD spectrum at around 220 nm in the lower temperature region and the temperature dependence was reproduced by a single-step transition, with the midpoint corresponding to the T _tr obtained from the scattering measurements. Coupled with the results from the DSC, the different behavior between the P(l-HMPMA) and P(dl-HMPMA) could be explained in terms of the chain states before and after the transition. The cooperative factors derived from the DSC measurement revealed that about 4 to 5 polymers of the present size were necessary to perform a thermal transition for P(l-HMPMA), and that P(dl-HMPMA) underwent its transition as an almost single molecular event.This revised version was published online in June 2005 with correction to the article category.     

Hexanuclear methanediolate bridged iron(<Emphasis Type="SmallCaps">III</Emphasis>) complex

The hexanuclear complex [Fe₆(O)₂(CH₂O₂) (OOCCMe₃)₁₂ (THF)₂]·THF was synthesized. The characteristic feature of this complex is the presence of the methanedithiolate bridge.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 795–797, March, 2005.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-(2-chloroethyl)glycine and -<Emphasis Type="SmallCaps">DL</Emphasis>-alanine esters

Two methods for the synthesis of N-(2-chloroethyl)glycine and-DL-alanine esters are proposed: 1) reductive amination of the C=O group of glyoxilic or pyruvic acids upon treatment with 2-chloroethylamine and sodium cyanoborohydride in methanol and 2) alkylation of 2-chloroethylamine with α-haloalkanoic acid esters in K₂CO₃-MeCN two-phase system. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2372–2374, December, 2007.     

Synthesis and structure of bis(1,2-diaminoethane) copper(II) bis(<Emphasis Type="Italic">o</Emphasis>-hydroxybenzoate) monohydrate and <Emphasis Type="Italic">trans</Emphasis>-diaquabis(1,2-diaminoethane)copper(II) bis(<Emphasis Type="Italic">o</Emphasis>-aminobenzoate)

X-ray structural analysis has been performed for two complex compounds: Cu(en)₂(o-HB)₂H₂O (I) (a = 16.873(4) Å, b = 8.713(2) Å, c = 14.803(3) Å, β = 91.15(2)°, V = 2175.8(8) ų, C2/c, Z = 4, R(F) = 0.0263, 1516 reflections with I > 3σ (I)) and [Cu(en)₂(OH₂)₂]²⁺(o-AB^?)₂ (II) (a = 7.488(5) Å, b = 22.122(8) Å, c = 7.856(5) Å, β = 118.77(2)°, V = 1140.7(11) ų, P2₁/n, Z = 2, R(F) = 0.0432, 1684 reflections with I > 3σ(I)) synthesized under identical conditions (en is ethylenediamine, o-HB is o-hydroxybenzoate, and o-AB is o-aminobenzoate). Although the compounds were assumed to have similar structures and the Cu-Lig bond lengths and the cis and trans angles are acceptable for an octahedral structure, the geometric parameters of o-HB suggest that the copper atom has a plane square environment.     

Mono-and bis(5-<Emphasis Type="Italic">O</Emphasis>-nitro-1,4:3,6-dianhydro-<Emphasis Type="SmallCaps">D</Emphasis>-sorbit-2-yl) phosphates: synthesis and reactions with hydroxy-and amino-containing compounds

The reaction of 1,4:3,6-dianhydro-D-sorbitol 5-nitrate with POCl₃ afforded mono-and bis(5-O-nitro-1,4:3,6-dianhydro-D-sorbit-2-yl) phosphorochloridates, whose hydrolysis resulted in phosphoric acid mono-and diesters. The subsequent treatment of these compounds with bases gave sodium and cyclohexylammonium salts. The reactions of phosphorochloridates with phenol, pentaerythritol dibromohydrin, and ethylenimine in the presence of organic bases afford mixed phosphates and phosphoramidates. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2026–2032, October, 2007.     

Inclusion of nickel(<Emphasis Type="SmallCaps">II</Emphasis>) and copper(<Emphasis Type="SmallCaps">II</Emphasis>) complexes with aliphatic polyamines in cucurbit[8]uril

The inclusion compound of macrocyclic cavitand cucurbit[8]uril (CB[8]) with the nickel(II) complex containing the tetraazamacrocyclic ligand cyclam, {[Ni(cyclam)]@CB[8]}Cl₂··16H₂O (1), and the inclusion compounds of CB[8] with the copper(II) bis-ethylene-diamine complex, {trans-[Cu(en)₂(H₂O)₂]@CB[8]}Cl₂·{CB[8]}·42H₂O (2a) and {trans-[Cu(en)₂(H₂O)₂]@CB[8]}Cl₂·17H₂O (2b), were synthesized and characterized by X-ray diffraction analysis, IR and ESR spectroscopy, and electrospray mass spectrometry. Guest—host inclusion compounds can be directly synthesized starting from a metal complex and cucurbit[8]uril, as was exemplified by the preparation of compounds 2a and 2b.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2414–2419, November, 2004.     

Fullerene complexes with bis(η6-hexamethylbenzene)chromium, hexamethylbenzene, and hexaethylbenzene

The [60]fulleride of bis(η-hexamethylbenzene)chromium(I) [(η⁶-C₆Me₆)₂Cr]^⋅+[C₆₀]^⋅−, and the complexes C₆₀·C₆Me₆ and C₆₀·C₆Et₆ were synthesized. Thermal decomposition of [(η⁶-C₆Me₆)₂Cr]^⋅+[C₆₀]^⋅− was studied. The molecular structures of C₆₀·C₆Me₆ and C₆₀·C₆Et₆ were determined. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 220—224, February, 2006.     

Molecular structure of <Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">o</Emphasis>-and <Emphasis Type="Italic">p</Emphasis>-hydroxybenzyl)cytisine

The molecular structures of N-(o-and p-hydroxybenzyl)cytisine were investigated by NMR spectroscopy, x-ray structure analysis, and molecular modeling. It was found that NMR resonances of the OH and aromatic protons in N-(o-hydroxybenzyl)cytisine were doubled because of the presence of two conformers in solution. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 165–168, March–April, 2008.     

Synthesis of (<Emphasis Type="Italic">E</Emphasis>)- and (<Emphasis Type="Italic">Z</Emphasis>)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles

Abstract  An efficient synthesis method for the preparation of a series of new (Z)- and (E)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles was developed. The reaction of (Z)- and (E)-3-styrylchromones with hydrazine hydrate afforded the corresponding (Z)- and (E)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles, except for nitro derivatives, where both (Z)- and (E)-4′-nitro-3-styrylchromones afforded (E)-3(5)-(2-hydroxyphenyl)-4-(4-nitrostyryl)pyrazoles. The reaction mechanism for these transformations is discussed and the stereochemistries of all products were established by NMR experiments. Graphical abstract        

Synthesis of substituted 7,8-di(propylsulfonyl)pyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyrazines

Heating of pyrazinium salts with E-1,2-dichloro-1,2-di(propylsulfonyl)ethene in chloro-form in the presence of three-fold excess of Et₃N regiospecifically gives rise to substituted 7,8-di(propylsulfonyl)pyrrolo[1,2-a]pyrazines in high yields. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 424–426, February, 2008.     

Synthesis and structure of (bis(3,5-dimethyl-1<Emphasis Type="Italic">H</Emphasis>-pyrazol-1-yl)methane)diiodocobalt(II)

A cobalt(II) iodide complex with bis(3,5-dimethyl-1H-pyrazol-1-yl)methane (L) CoLI₂ has been synthesized, and its single crystals have been obtained. The complex compound was characterized by electron spectroscopy and X-ray diffraction analysis. The compound crystallizes in the monoclinic system (a = 8.4044(4) Å, b = 13.3120(5) Å, c = 14.5824(7) Å; β = 94.7290(10)°; V = 1625.92(13) ų; Z = 4; ρ^calc = 2.112 g/cm³; space group P2₁/m). The structure of the complex is molecular mononuclear. L is a cyclic bidentate ligand; the coordination polyhedron of cobalt is a CoN₂I₂ tetrahedron formed by the nitrogen atoms of the pyrazole fragments L and iodine atoms. The complex has π-π stacking interactions between the pyrazole rings of CoLI₂ molecules, binding the molecules into infinite chains along the b axis.     

Synthesis and studies of spectroscopic and electrochemical properties of dinuclear ruthenium(<Emphasis Type="SmallCaps">II</Emphasis>) and manganese(<Emphasis Type="SmallCaps">II</Emphasis>) complexes

New dinuclear ruthenium manganese complexes of general composition (bpy)₂Ru(L)MnCl_x(H₂O)₂ (L is 1,10-phenanthroline-5,6-dione, 3,3′-dicarboxy-2,2′-bipyridyl, or bis(pyrazolyl); x = 2 or 4) were synthesized by the reaction of (bpy)₂Ru(L) with MnCl₂ · 4H₂O. These compounds and the starting mononuclear ruthenium complexes were studied by spectrophotometric and electrochemical methods in MeCN. The position of the charge-transfer band Ru^II → L in the spectra depends on the donor-acceptor characteristics of the ligand L. For the dinuclear complex under study, the formal potentials of reversible one-electron oxidation of Ru^II are in the range of 0.9–1.2 V (vs. the standard hydrogen electrode), whereas oxidation of Mn^II occurs at more positive (by 0.1–0.2 V) potentials. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2281–2285, October, 2005.     

Synthesis of 6-methyl-8<Emphasis Type="Italic">H</Emphasis>-dibenzo[<Emphasis Type="Italic">a</Emphasis>,<Emphasis Type="Italic">g</Emphasis>]quinolizin-8-imines <Emphasis Type="Italic">via Reissert</Emphasis> compounds

Alkylation of Reissert compounds derived from 3-methylisoquinolines with several 2-cyanobenzylbromides followed by hydrolytic cleavage provided the corresponding 1-benzyl-3-methylisoquinolines. Treatment of the latter with methylmagnesiumiodide caused cyclization to the title compounds rather than formation of 2-acetylbenzylisoquinolines.     

Crystal and molecular structure of <Emphasis Type="Italic">tris</Emphasis>(<Emphasis Type="Italic">m</Emphasis>-chlorophenyl)phosphine selenide

The crystal and molecular structure of tris(m-chlorophenyl)phosphine selenide, C₁₈H₁₂Cl₃PSe (I), was investigated by X-ray diffraction (XRD) analysis. The trigonal rhombohedral structure of I (space group \(R\overline 3 c\), a = 14.110(2) Å, c = 32.360(4) Å, Z = 12) was solved by direct methods and refined by least squares in an anisotropic approximation (R = 0.029) for 1319 averaged measured reflections (CAD-4 automatic diffractometer, λCuK_α).     

Ionic mobility in the antimony(<Emphasis Type="SmallCaps">iii</Emphasis>) fluorochloride complexes

Ionic mobility in the NaSbClF₃ · H₂O, KSbClF₃, and NH₄SbClF₃ fluorochloride complexes was studied by ¹H and ¹⁹F NMR spectroscopy in the temperature interval from 150 to 480 K. The types of ionic motions in the compounds were determined. Their physicochemical characteristics were compared with those of the earlier studied sodium, potassium, and ammonium tetrafluoroantimonates(iii). The replacement of one F atom by the Cl atom in MSbF₄ (M = Na, K, NH₄) changes both the structure of the Sb polyhedra forming the structure of the antimony(iii) fluorochloride complex and the character of ionic motions in the compounds. The ionic conductivity in the 324–436 K range was determined for NH₄SbClF₃: σ = 1.07 · 10⁻⁴ S cm⁻¹ at T = 423 K. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1353–1357, July, 2008.     

Crystal and molecular structure of 2-(<Emphasis Type="Italic">o</Emphasis>-hydroxyphenyl)-4,6-diphenylpyridine

Crystal and molecular structure of 2-(o-hydroxyphenyl)-4,6-diphenylpyridine C₂₃H₁₇NO (I) has been studied by single crystal XRD. The structure (monoclinic, space group P2₁/c, a = 8.757(2) Å, b = 20.682(4) Å, c = 9.743(2) Å, β = 108.14(2)°, Z = 4) was solved by the direct method and refined anisotropically in the full-matrix approximation to R = 0.076 using all 2660 measured independent reflections (automated diffractometer CAD-4, CuK_α). OH group of the molecule of I is disordered in the crystal over three positions with occupation factors 70%, 15% and 15%. The structure contains a very strong intramolecular hydrogen bond O-H?N disordered over three directions.     

Rapid SnCl<Subscript>2</Subscript> catalyzed phenylselenoetherification of (<Emphasis Type="Italic">Z</Emphasis>)- and (<Emphasis Type="Italic">E</Emphasis>)-hex-4-en-1-ols

A fast and efficient method for intramolecular heterocyclization of (Z)- and (E)-hex-4-en-1-ols was developed. The method does not cause side reactions of the substrates and provides the cyclic phenylselenoethers in high yields after only few minutes. A catalytic amount of SnCl₂ increased the yield, but in the presence of an equimolar amount of SnCl₂, formation of corresponding cyclic ethers were almost quantitative and reaction occurred instantaneously under extremely mild experimental conditions. Correspondence: Zorica M. Bugarčić, Department of Chemistry, Faculty of Science, University of Kragujevac, Radoja Domanovića 12, P.O.Box 60, YU-34000 Kragujevac, Serbia.     

Estimation of the specific content and nature of sorption sites of iron(<Emphasis Type="SmallCaps">III</Emphasis>) and zirconium(<Emphasis Type="SmallCaps">IV</Emphasis>) oxyhydroxides

The sorption of anions H₂PO₄ ⁻, HPO₄ ²⁻, PO₄ ³⁻, [Fe(CN)₆]³⁻, and [Fe(CN)₆]⁴⁻ from aqueous solutions on the surface of Fe^III and Zr^IV oxyhydroxide hydrogels freshly precipitated at pH 4–13 was studied. The region of sorbate concentrations was from 0.00025 to 0.06 mol L⁻¹. The plots of the anion uptakes vs. their equilibrium concentrations are represented by isotherms of the first type, which are well described by the Langmuir equation if the quantity of the amount adsorbed is expressed as mol-site g⁻¹. The maximum uptakes and constants of the Langmuir equation were calculated. The phosphate anions occupy the same number of sorption sites on the sorbents precipitated at different pH. The average specific content of sorption sites for the ferro- and zirconogels in the metastability period is independent of the pH of their precipitation, being 3.1·10⁻³ and 3.2·10⁻³ mol-site g⁻¹, respectively. The [Fe(CN)₆]³⁻ and [Fe(CN)₆]⁴⁻ anions are sorbed only on the positively charged sites of the hydrogels and occupy not more than 2·10 mol-site g⁻¹ in the studied interval of pH of precipitation. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1736—1741, August, 2005.     

The smallest Hosoya index in (<Emphasis Type="Italic">n</Emphasis>, <Emphasis Type="Italic">n</Emphasis> + 1)-graphs

A (n, n + 1)-graph G is a connected simple graph with n vertices and n + 1 edges. In this paper, we determine the lower bound for the Hosoya index in (n, n + 1)-graphs in terms of the order n, and characterize the (n, n + 1)-graph with the smallest Hosoya index.     

Preparation of nanoparticle colloids of methoxy poly(ethylene glycol)-<Emphasis Type="Italic">b</Emphasis>-poly(<Emphasis Type="SmallCaps">D</Emphasis>,<Emphasis Type="SmallCaps">L</Emphasis>-lactide): effects of surfactant and organic solvent

Nanoparticle colloids of methoxy poly(ethylene glycol)-b-poly(D,L-lactide) (MPEG-b-PDLL) diblock copolymer were prepared by a modified spontaneous emulsification solvent diffusion method using acetone/ethanol as the mixture organic solvents. The MPEG-b-PDLL was synthesized by ring-opening polymerization of D,L-lactide using stannous octoate and MPEG with molecular weight of 5,000 g/mol as the initiating system. The MPEG-b-PDLL obtained was an amorphous polymer with molecular weight of 73,600 g/mol. Influences of acetone/ethanol (v/v) ratios and Tween 80 surfactant concentrations on characteristics of the colloidal nanoparticles were investigated and discussed. Light-scattering analysis showed that average diameters of the surfactant-free colloidal nanoparticles were in the range of 86–124 nm. The nanoparticle sizes decreased as the ethanol ratio increased. The Tween 80 did not show the significant effect on the nanoparticle sizes. Scanning electron micrographs of dried nanoparticles that demonstrated the aggregation of most particles suggested they were the soft nanoparticles. However, the dried nanoparticle morphology can be observed from scanning electron microscopy as having a spherical shape and smooth surfaces.