Synthesis and characterization of di- and trivalent pyrazolylborate β-diketonates and cyanometalates

The syntheses, structures, and magnetic properties of a series of di- and trivalent hydridotris(3,5-dimethylpyrazol-1-yl)borate (Tp*) cyanomanganates are described. Treatment of tris(acetylacetonate)manganese(III) [Mn(acac)(3)] with KTp* and tetra(ethyl)ammonium cyanide affords [NEt(4)][(Tp*)Mn(II)(κ(2)-acac)(CN)] (1), as the first monocyanomanganate(II) complex; attempted oxidation of 1 with iodine affords {(Tp*)Mn(II)(κ(2)-acac(3-CN))}(n) (2) as a one-dimensional chain and bimetallic {[NEt(4)][(Tp*)Mn(II)(κ(2)-acac(3-CN))](2)(μ-CN) (3) as the major and minor products, respectively. A fourth complex, [NEt(4)][(Tp*)Mn(II)(η(2)-acac(3-CN))(η(1)-NC-acac)] (4), is obtained via treatment of Mn(acac(3-CN))(3) with KTp* and [NEt(4)]CN, while [NEt(4)](2)[Mn(II)(CN)(4)] (5) was prepared from manganese(II) trifluoromethanesulfonate and excess [NEt(4)]CN. Tricyanomanganate(III) complexes, [cat][(Tp*)Mn(III)(CN)(3)] [cat = NEt(4)(+), 7; PPN(+), 8], are prepared via sequential treatment of Mn(acac(3-CN))(3) with KTp*, followed by [NEt(4)]CN, or [cat](3)[Mn(III)(CN)(6)] with (Tp*)SnBu(2)Cl. Magnetic measurements indicate that 1, 2, and 4 contain isotropic Mn(II) (S = (5)/(2); g = 2.00) centers, and no long-range magnetic ordering is found above 1.8 K. Compounds 7 and 8 contain S = 1 Mn(III) centers that adopt singly degenerate spin ground states without orbital contributions to their magnetic moments.     

Syntheses and characterizations of trinuclear and dinuclear “half-sandwich” zirconocene phosphates and phosphonates

A series of six-coordinate “half-sandwich” zirconocene phosphates and phosphonates have been synthesized by the reaction of Cp₂ZrCl₂ with (diphenyl-, dibenzyl-)phosphate and methylphenylphosphinic acid under different conditions. All of the complexes were characterized by elemental analysis, FT-IR and NMR (¹H, ¹³C) spectroscopy. Except for complex 3, the structures of complexes 1, 2, 4, 5, and 6 were confirmed by X-ray crystallography. The structure analyses reveal that complexes 1, 2, and 3 are trinuclear complexes with fascinating μ₃-oxygen bridging ligands, central to a Zr–O backbone (Cp₂ZrCl₂:ligand is 1:1) while complexes 4, 5, and 6 are centrosymmetric dinuclear complexes built up about the trapezoidal Zr₂(μ₂-OH)₂ unit (Cp₂ZrCl₂:ligand is 1:2).     

Synthesis and electrochemical properties of mono- and (±)-1,2-dialkylferrocenes and alkylferrocenium hexafluorophosphates in aqueous and micellar media

Absract Simple methods have been developed for the preparation of a series ofn-alkylferrocenes H(CH₂) _n Fc (n = 3, 5–8, or 12) based on Friedel-Crafts acylation of ferrocenes followed by reduction of the corresponding ketones with Zn amalgam. The properties of H(CH₂) _n Fc and the corresponding ferrocenium ions in micellar aqueous solutions and the behavior of water-soluble cations H(CH₂) _n Fc⁺ in the absence of micelles were studied by cyclic voltammetry. In all cases, the formal redox potentials of ferrocenes (E ^o) increase linearly asn increases up to 8. Whether micelles are present or not, the corresponding correlation equation has the following form:E ^o= + n, where = 29 mV in all cases. The synthesis of (±)-1-ethyl-2-methylferrocene from racemic -dimethylaminoethylferrocene is reported.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2575–2581, October 1996.     

Short and efficient hemisynthesis of α-eudesmol and cryptomeridiol

The aerial part of Dittrichia viscosa yielded two sesquiterpenes, isocostic acid (1) and ilicic acid (2), on multigram scale. These acids are appropriate starting materials for short and facile syntheses of α-eudesmol (5) and cryptomeridiol (6), natural products featuring anti-Alzheimer and anti-spasmodic properties. Compounds 5 and 6 were obtained in three steps in overall yields of 70% and 52%, respectively.     

Synthesis and Sweetness of Pseddo-β-D and L-Frdctopyranose

Abstract

Pseudo-β-D (D-2) and L-fructopyranose (L-2), 1(S) and (1R)-(1,2/-3,4)-4-C-hydroxymethyl-1,2,3,4-cyclohexanetetrol, have been synthesized, starting from optically active endo-adducts of furan and acrylic acid, following the modified procedure used for the preparation of the racemic modification. It has been demonstrated that the D and L-enantiomers are nearly as sweet as D-fructose, and the former is somewhat sweeter than the latter.     

Synthesis and properties of cross-conjugated ��,�ء�-bis-dimethylamino ketones and dinitriles with N-acetyl- and N-benzylpiperidine cycles

Reactions of N-acetyl- and N-benzyl-4-piperidones with aminal of ??-dimethylaminoac-rolein yielded ketocyanines bearing piperidine cycle. Reaction of 3-dimethylamino-1,1,3-trimethoxypropane with 1-acetylpiperidin-4-ylidenemalononitrile in the presence of ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF₄), resulted in cross-conjugated ??,???-dimethylamino dinitrile. Protonation of ketocyanines bearing N-acetyl- and N-benzyl-piperidine cycles with Et₂O·HBF₄ (1 equiv.) furnished piperidinium salts, while protonation of the latter with Et₂O·HBF₄ (2 equiv.) afforded doubly charged 4-hydroxypolymethine salts. Unlike protonation, reaction of 3,5-bis(3-dimethylaminoprop-2-enylidene)-1-acetylpiperidin-4-one with Me₂SO₄ involved only the oxygen atom and led to a singly charged 4-methoxypolymethine salt. Methylation of 3,5-bis(3-dimethylaminoprop-2-enylidene)-1-benzylpiperidin-4-one with Me₂SO₄ (1 equiv.) involved cyclic nitrogen atom and resulted in piperidinium salt; heating of the latter with the excess of Me₂SO₄ afforded doubly charged bis-methoxysulfonate. Starting from 4-methoxytetrahydropyridinium salts, meso-methoxythiapentacarbocyanine dyes were synthesized.     

Di- and Trinuclear σ-Aryl Iron and Manganese Complexes

Reactions of p- and m-diiodobenzenes, p,p'-diiodobiphenyl, and 1,3,5-triiodobenzene with anions derived from dicarbonyl(cyclopentadienyl)iron and pentacarbonylmanganese, catalyzed by palladium complexes, provide a successful route to mono-, di-, and trinuclear -aryl iron and manganese complexes.     

Structures and Properties of 1,2,3-Triazoles and 1,2,4-Triazoles

1 INTRODUCTION In the energetic material field, extensive attention was paid to insensitive compounds possessing not only high energetic density but also good stability. Previous studies[1] have shown that some small mo- lecular compounds such as azoles are good candi- dates for excellent explosives. For example, explo- sives containing triazole rings have the advantages of less molecular weight, high nitrogen content and density, good thermal stability, low impact sensiti- vity and large …     

Photoinduced intermolecular and intramolecular actions between eosin and porphyrin

Two dyads of eosin and porphyrin linked with a semi-rigid (-CH2phCH2-) or flexible (-(CH2)4-) bridge and their reference model compounds were synthesized and characterized The intermoleccular interaction and intramolecular photoinduced singlet energy transfer and electron transfer were studied by their absorp tion spectra,fluorescence emission,excitation spectra and fluorescence lifetime The model compounds,ethyl ester of eosm (EoEt) and porphyrin (PorEt),could form complexes in the ground state.When the eosin moieties in dyads were excited,they could transfer some singlet energy to the porphyrins; in the meantime,they could also ndsce electron transfer between two chromophores.Exciting the porphyrin moieties in dyads could induce electron transfer from eosin moieties to porphyrin moieties.The efficiencies (EnT,ET) and rate constants (kEnT,kET) were related to the polarity of solvents and mutual orientation of the two chromophores in dyads.     

Identification and Determination of Nicorandil and its Degradation Products by HPLC and GC/MS

Nicorandil [N-(2-hydroxyethyl)-nicotinamide nitrate NIC] is a novel kind of compound in the treatment of angina pectoris. NIC can be degraded easily in storage. The degradation products include N-(2-hydroxyethy) nicotinamide (HN), nitrate ion (NI), and ni…     

Cloning and Sequencing of Trichosanthin Gene and Its Expression in Escherichia coli and Tobacco Plant

A Trichosanthin gene was cloned from Trichosanthes kirilowii genomic DNA by polymerase chain reaction (PCR). Nucleotide sequence data indicated that we obtained the coding region of the mature Trichosanthin peptide as well as its signal peptide at the N-terminus. Comparisons of our sequence with the previously reported nucleotide sequences of this gene showed 99.25% homology, yet there were notable differences between the previously reported amino acid sequence and our deduced result. This gene was subcloned into a highlevel expression plasmid (pJLA502) of E. coli under the control of a P_RP_L promoter, and we observed the gene product after temperature induction. The gene was further cloned into plant intermediate vector pE3 under the control of a CaMV 35S promoter, and transferred into a tobacco genome using the agrobacterium-mediated gene transfer system. Western blotting analysis of the protein extracted from Escherichia coli and transgenic tobacco plants proved that the Trichosanthin gene has been     

Paradigms and Paradoxes: Electronegativity and Bond Energies—Living Legacies of Linus and Lee

In this paper we will discuss Pauling's classic Eq. (1) that relates bond energies, "D," and electronegativities, "x." Recast to be applicable to enthalpies of formation and reaction, we apply it to the study of hydrogenolysis reactions of dienes, diynes, and alkanes, halogenolysis reactions (with chlorine, bromine, and iodine) and metathetical reactions of organosulfur species (sulfides, sulfoxides, and sulfones). It is with great regret that this equation is found wanting.     

Synthesis and Properties of Polyetherketones Containing Sulfide and Phthalazinone

High molecular weight copoly(ether ketone)s (PEK) based on 4-(4-hydroxyphenyl)-1-phthalazinone (DHPZ)/4,4′-thiobisphenol (TBP)/4,4′-diflourodiphenylketone (DFK) were prepared by nucleophilic substitution polycondensation. The copolymers were characterized by FT- and ^1H-NMR. Thermal properties and solubility of copolymers were studied.     

Are isatin and isatoic anhydride antiaromatic and aromatic respectively? A combined experimental and theoretical investigation

This paper reports the results of our thermochemical/calorimetric determination of the enthalpies of combustion, phase change, and formation of isatin, isatoic anhydride, and N-methylisatin. The density functional calculations accompanied by vibrational and thermal corrections were also performed for these compounds and N-methylisatoic anhydride. Through a combination of theoretical calculations and associated isodesmic reactions, we have deduced that isatin has some antiaromatic character and isatoic anhydride enjoys some aromatic stabilization.     

Theoretical Study of the Molecular and Electronic Structures of CPDT-TCNQ and Its Difluoro and Dimethyl Derivatives

1 INTRODUCTION Since the discovery of one-dimensional metallic behavior of tetrathiafulvalene (TTF) with tetracyano- quinodimethane (TCNQ)[1], organic charge-transfer (CT) complexes and CT salts have been intensively studied in search of electrically conducting and superconducting properties[2 ～ 6] which are most unusual for an organic material. The most intriguing property is that it is excellent metal with conducti- vity similar to that of metals at room temperature[7, 8]. In these…     

Hückel theory and distinguishing between isospectral molecules: 1,4-divinylbenzene and 2-phenylbutadiene,and tetramethylenemethane and cyclobutadiene + carbon

Structural Chemistry - Although Hückel molecular orbital theory (HMO) has been generally outdated as a computational method for the energetics of organic molecules, there is still much we can...     

Syntheses and transformations of α-azido ketones and related derivatives

Organic azides are known and utilized in the synthetic organic chemistry as amine precursors, potential sources of nitrenes, dipoles useful in 1,3-dipolar cycloadditions and starting materials of phosphoranes for a long time, and their literature has been overviewed by several authors. On the other hand, there are some special subclasses within the azides which possess peculiar and interesting properties differing from those of the majority and offering extra synthetic possibilities. In this critical review we wish to give an exhaustive overview on the synthesis and synthetic potential of α-azido ketones and related systems, an underestimated group of compounds. The enhanced acidity of the α-hydrogen offers various new synthetic applications including the creation of a new C-C bond, while the joint presence of the carbonyl and vinyl functions of α-azido-α,β-unsaturated ketones results in a special reactivity, too. Chemo- and stereoselectivity issues also represent important points which are discussed in detail. Finally, the usefulness of the titled derivatives in the synthesis of various heterocycles is reviewed (273 references).     

Synthesis and properties of polyfluorene copolymers bearing thiophene and porphyrin

To search for more wider absorption and higher charge carriers mobilities materials of polymer solar cell, a series of soluble alternating polyfluorene copolymers were synthesized by palladium-catalyzed Suzuki coupling reaction. Their structures were determined by 1H NMR, IR and UV-vis. And their UV-vis absorption spectra indicated that they had strong absorption over 600 nm spectral range and nearly cover 400-700 nm visible region. The band gaps of copolymers calculated according to cyclic voltammetry （CV） were between 1.96 and 2.03 eV. Polymer：TiO2 bulk-heterojunction films were made from mixtures of polymer and titanium isopropoxide, a precursor for TiO2, via hydrolysis in air overnight. The photoluminescence at 380-800 nm of the blend film of PT-TPP20 （5 mg/mL）：Ti（OC3H7）4 （80 μL/mL） （20% volume fraction） was significantly quenched in the 50% Ti（OC3H7）4 blend film, indicating that rapid and efficient separation of photoinduced electron-hole pairs.