A convenient and high-yield synthesis for pyridinium and metal hexafluorocomplexes of vanadium, chromium, iron and cobalt

Pyridinium poly(hydrogen fluoride) reacts with the oxide of vanadium(V) and chlorides of chromium(III), iron (III) and Co(II) at room temperature forming the pyridinium salts of hexafluoro vanadate(V), hexafluorochromate(III), hexafluoroferrate(III) and hexafluorocobaltate(II) in near quantitative yields (80%). These pyridinium salts are the precursors for the preparation of the alkali metal hexafluorometallates by metathetic reactions in acetonitrile medium with the corresponding metal chlorides. The prepared salts have been identified by their infrared spectral data and elemental analysis.

Thiomalates of alkaline earth metals

Solid state 1:1 complexes of divalent Mg, Ca, Sr and Ba with thiomalic acid(tma) have been isolated and characterised by elemental analysis, IR spectra and thermal studies. It is shown that tma coordinates to the metal ions through carboxylic oxygen atoms. Thermal studies of these complexes show that desulphurisation preceeds decarbonylation reaction leading to the formation of metal carbonates in all the cases except Mg where MgO is the end product. Thermal stability of the anhydrous thiomaltes follows the order Mg not, vert, similar Ca > Sr > Ba. Structures have been proposed based on the information obtained from these studies.

Low-Temperature Fluorination Of Some Nonmetals And Nonmetal Compounds With Fluorine

Low temperature fluorination with elemental fluorine of elemental phosphorus, sulphur, silicon, amorphous carbon and phosphorus trichloride, phosphorus pentoxide, triphenylphosphine, hexafluorodisilane, hexachlorodisilane, hexabromodisilane, tetrasulphur tetranitride, sulphur dioxide, thionyl chloride and sulphuryl chloride has been carried out in freon-11 medium. The corresponding fluoro compounds have been isolated in near quantitative yields, purified by low temperature fractional condensation and characterised by IR spectroscopy and elemental analysis.

New methods for the Preparation of Nitrosyl Chloride

A pure sample of nitrosyl chloride has been prepared either by reaction of phosphorus trichloride with concentrated nitric acid or by reaction of phosphorus trichloride with sodium nitrate in presence of water. The nitrosyl chloride gas has been characterized by i.r. spectral data and elemental analysis.

New flame-retardant poly(pyromellitic imide aryl phosphoramide-ester)s

Flame-retardant poly(pyromellitic imide aryl phosphoramide-ester)s were synthesized by interfacial polycondensation of N,N?-bis(p-hydroxyphenyl)pyromellitic diimide with aryl phosphoramidic dichlorides. The polymers were characterized by IR and 1H-NMR spectroscopy. The molecular composition was confirmed by elemental analysis. The thermal stability and flammability of the polymers were studied by thermogravimetry and limiting oxygen index, respectively. Durch Grenzflächen-Polykondensation von N,N?-bis(4-hydroxyphenyl)pyromellitsäurediimid mit Dichloriden verschiedener Phosphoramide wurden flammhemmende Polymere erhalten. Diese wurden mittels IR- und 1H-NMR-Spektroskopie und Elementaranalyse charakterisiert. Thermische Stabilität und Entflammbarkeit wurden thermogravimetrisch bzw. durch Bestimmung des Sauerstoff-Indexes untersucht.

High Yield Room Temperature Synthesis And Spectral Studies Of Tri(Amino)Silanes: (R2n)3SIH

Tri(amino)silanes were prepared by the condensation of trichlorosilane with secondary amines in 1:6 molar ratio. Reactions of trichlorosilane with pyrrolidine, piperidine, hexamethyleneimine, morpholine, N-methylpiperazine and diethylamine afford the tri(amino)silanes in nearly quantitative yields. Their physical and spectroscopic properties are discussed. All these compounds are highly sensitive to moisture and hydrolyse to silica and the respective amine with the evolution of hydrogen. The compounds have been characterised by IR, 1H NMR, [1H]29Si NMR spectroscopic methods and CHN elemental analysis.

Reactions of the hexachlorocyclodiphosphazane [MeNPCl3]2 with primary aromatic amines: formation of highly basic bisphosphinimines

Reactions of hexachlorocyclodiphosphazane [MeNPCl3]2 with primary aromatic amines afforded the bisphosphinimine hydrochlorides [(RNH)2(RN)PN(Me)P(NHMe)(NHR)2]+Cl- (R = Ph 1, C6H4Me-4 2 or C6H4OMe-4 3). Dehydrochlorination of 2 and 3 by methanolic KOH yielded highly basic bisphosphinimines [(RNH)2(RN)PN(Me)P(NMe)(NHR)2] (R = C6H4Me-4 4 or C6H4OMe-4 5). Compounds 1-5 have been characterised by elemental analysis and IR and NMR (H-1, C-13, P-31) spectroscopy. The structure of 2 has been confirmed by single-crystal X-ray diffraction. The short P-N bond lengths and the conformations of the PN, units can be explained on the basis of cumulative negative hyperconjugative interactions between nitrogen lone pairs and adjacent P-N sigma* orbitals. Ab initio calculations on the model phosphinimine (H2N)3P=NH and its protonated form suggest that (amino)phosphinimines would be stronger bases compared to many organic bases such as guanidine.

High-Throughput Study of the Cu(CH3COO)(2)center dot H2O-5-Nitroisophthalic Acid Heterocyclic Ligand System: Synthesis, Structure, Magnetic, and Heterogeneous Catalytic Studies of Three Copper Nitroisophthalates

A high-throughput screening was employed to identify new compounds in Cu(CH3COO)(2)center dot H2O-NIPA-heterocyclic ligand systems. Of the compounds identified, three compounds, Cu-3{(NO2)-C6H3-(COO)(2)}(3)(C3N6H6)] (1), Cu-2(mu(3)-OH)(H2O){(NO2)-C6H3-(COO)(2)}(CN4H)]center dot-(H2O) (II), and Cu-2(mu(3)-OH)(H2O){(NO2)-C6H3-(COO)(2}-)(CN5H2)]center dot 2(H2O) (III), have been isolated as good quality single crystals by employing conventional hydrothermal methods. Three other compounds, Cu-2{(NO2)-C6H3-(COO)(2)}-(CN4H)(H2O) (IIa), Cu-2{(NO2)-C6H3-(COO)(2)}(CN5H2) (IIIa), and Cu-2{(NO2)-C6H3-(COO)(2)}{(CN5H2)(2)}2H(2)O (IIIb), were identified by a combination of elemental analysis, thermogravimetric analysis (TGA), and IR spectroscopic studies, although their structures are yet to be determined. The single crystalline compounds were also characterized by elemental analysis, TGA, IR, UV vis, magnetic, and catalytic studies. The structures of the compounds have paddle wheel (I) and infinite Cu 0(H) Cu chains (II and HI) connected with NLPA and heterocyclic ligands forming two-(II) and three-dimensional (I and III) structures. The bound and lattice water molecules in 11 and 111 could be reversibly removed/inserted without affecting the structure. In the case of II, the removal of water gives rise to a structural transition, but the dehydrated phase reverts back to the original phase on prolonged exposure to atmospheric conditions. Magnetic studies indicate an overall antiferromagnetism in all of the compounds. Lewis acid catalytic studies indicate that compounds II and HI are active for cyanosilylation of imines.

Zn(II), Cd(II) and Hg(II) complexes with 1-(p-methoxybenzyl)-2-(p-methoxyphenyl)benzimidazole: Syntheses, structures and luminescence

Five coordination compounds Zn(mbmpbi)(2)Cl-2 (1), Zn(mbmpbi)(2)Br-2 (2), Cd(mbmpbi)(2)Cl-2 (3), Hg(mbmpbi)(2)Cl-2 (4) and Hg(mbmpbi)(2)Br-2 (5) were synthesized by the reaction of 1-(p-methoxybenzyl)-2-(p-methoxyphenyl)benzimidazole (mbmpbi) with the corresponding metal halides. The complexes have been characterized by elemental analysis, conductance measurements, FT-IR, H-1 NMR and photoluminescence spectral studies. The ligand mbmpbi exhibits the N-benzimidazole coordination. The structures of 3-5 have been determined by single crystal X-ray diffraction. These three complexes are isostructural, crystallizing in the monoclinic system. P2/n space group with a distorted tetrahedral geometry around the metal ion. Zn(II) and Cd(II) complexes show strong blue emission in solid state at room temperature. (C) 2011 Elsevier Ltd. All rights reserved.

A finite element assessment of flexural strength of prestressed concrete beams with fiber reinforcement

This paper presents an assessment of the flexural behavior of 15 fully/partially prestressed high strength concrete beams containing steel fibers investigated using three-dimensional nonlinear finite elemental analysis. The experimental results consisted of eight fully and seven partially prestressed beams, which were designed to be flexure dominant in the absence of fibers. The main parameters varied in the tests were: the levels of prestressing force (i.e, in partially prestressed beams 50% of the prestress was reduced with the introduction of two high strength deformed bars instead), fiber volume fractions (0%, 0.5%, 1.0% and 1.5%), fiber location (full depth and partial depth over full length and half the depth over the shear span only). A three-dimensional nonlinear finite element analysis was conducted using ANSYS 5.5 [Theory Reference Manual. In: Kohnke P, editor. Elements Reference Manual. 8th ed. September 1998] general purpose finite element software to study the flexural behavior of both fully and partially prestressed fiber reinforced concrete beams. Influence of fibers on the concrete failure surface and stress-strain response of high strength concrete and the nonlinear stress-strain curves of prestressing wire and deformed bar were considered in the present analysis. In the finite element model. tension stiffening and bond slip between concrete and reinforcement (fibers., prestressing wire, and conventional reinforcing steel bar) have also been considered explicitly. The fraction of the entire volume of the fiber present along the longitudinal axis of the prestressed beams alone has been modeled explicitly as it is expected that these fibers would contribute to the mobilization of forces required to sustain the applied loads across the crack interfaces through their bridging action. A comparison of results from both tests and analysis on all 15 specimens confirm that, inclusion of fibers over a partial depth in the tensile side of the prestressed flexural structural members was economical and led to considerable cost saving without sacrificing on the desired performance. However. beams having fibers over half the depth in only the shear span, did not show any increase in the ultimate load or deformational characteristics when compared to plain concrete beams. (C) 2002 Published by Elsevier Science Ltd.

Peroxo-bridged divanadate as selective bromide oxidant in bromoperoxidation

Diperoxovanadate is effective only in presence of free vanadate in vanadium-dependent bromoperoxidation at physiological pH. Peroxide in the form of bridged divanadate complex (VOOV-type), but not the bidentate form as in diperoxovanadate, is proposed to be the oxidant of bromide. In order to obtain direct evidence, peroxo-divanadate complexes with glycyl-glycine, glycyl-alanine and glycyl-asparagine as heteroligands were synthesized. By elemental analysis and spectral studies they were characterized to be triperoxo-divanadates, [V2O2(O-2)(3)(peptide)(3)]. H2O, with the two vanadium atoms bridged by a peroxide and a heteroligand. The dipeptide seems to stabilize the peroxo-bridge by inter-ligand interaction, possibly hydrogen bonding. This is indicated by rapid degradation of these compounds on dissolving in water with partial loss of peroxide accompanied by release of bubbles of oxygen. The V-51-NMR spectra of such solutions showed diperoxovanadate and decavanadate (oligomerized from vanadate) as the products. Additional oxygen was released on treating these solutions with catalase as expected of residual diperoxovanadate. The solid compounds when added to the reaction mixtures showed transient, rapid bromoperoxidation reaction, but not oxidation of NADH or inactivation of glucose oxidase, the other two activities shown by a mixture of diperoxovanadate and vanadyl. This demonstration of peroxide-bridged divanadate as powerful, selective oxidant of bromide, active at physiological pH, should make it a possible candidate of mimic in the action of vanadium in bromoperoxidase proteins.

Synthesis of crystallites of carbon nitride in amorphous carbon

We report the successful synthesis of crystalline carbon nitride by chemical vapor deposition of certain nitrogen containing organic precursors. The precursor is heated and the vapors enter the hot deposition zone where they are pyrolysed and deposited in the form of thin films over pretreated substrates. The powder x-ray diffraction analysis shows clear peaks corresponding to the carbon nitride crystals of tetragonal form in addition to a broad hump corresponding to the amorphous nitrogenated carbon. The crystallites size is similar to300Angstrom and the volume fraction of the crystallites is about similar to7%. The optimum conditions of preparation are found out. The Infrared spectra of these samples also suggest the formation of Carbon Nitride crystals. The analysis reconfirms that the material contains crystallites of Carbon Nitride embedded in an amorphous matrix of nitrogenated carbon. Further the material is characterized by C,H,N elemental analysis, EDX and Raman spectra. Since all the above analyses probe the bulk material, the background amorphous matrix in this case, expecting a clear evidence of nanometer sized crystallites from these tests are unlikely. Attempts are being made to increase the yield of these carbon nitride crystallites.

Tailoring of Structural Morphology of Silver Nanowires in Electrochemical Growth

Noble metal such as Ag normally exists in an fcc crystal structure. However as the size of the material is decreased to nanometer lengthscales, a structural transformation from that of its bulk state can be expected with new atomic arrangements due to competition between internal packing and minimization of surface energy. In many previous studies, it has been shown that silver nanowires (AGNWs) grown inside anodic alumina (AAO) templates by ac or dc electrochemical deposition from silver salts or complexes, adopt fcc structure and below some critical diameter ∼ 20 nm they may acquire hcp structure at low temperature. This is, however, critically dependant on the nature of confinement, as AgNWs grown inside nanotube confinement with subnanometer diameter have been reported to have fcc structure. Hence the question of the crystal structure of metal nanowires under combined influence of confinement, temperature and deposition condition remains open. In this abstract we show that the alternative crystal structures of AGNWs at room temperature can be achieved with electrochemical growth processes under specific conditions determined by the deposition parameters and nature of confinement. We fabricated AgNWs of 4H hexagonal structure with diameters 30 – 80 nm inside polycarbonate (PC) templates with a modified dc electrodeposition technique, where the nanowires were grown at deposition potentials as low as 10 mV in 2 M silver nitrate solution[1]. We call this low-potential electrodeposition (LPED) since the electrodeposition process occurs at potential much less than the standard Nernst potential (770 mV) of silver. Two types of electrodes were used – stainless steel and sputtered thin Pt film, neither of which had any influence on the crystal structure of the nanowires. EDS elemental analysis showed the nanowires to consist only of silver. Although the precise atomic dynamics during the LPED process is unclear at present, we investigated this with HRTEM (high-resolution transmission electron microscopy) characterization of nanowires grown over various deposition times, as well as electrical conductivity measurements. These experiments indicate that nanowire growth does not occur through a three-dimensional diffusion controlled process, as proposed for conventional over-potential deposition, but follow a novel instantaneous linear growth mechanism. Further experiments showed that, (a) conventional electrochemical growth at a small over-potential in a 2 mM AgNO3 solution yields nanowires with expected fcc structure inside the same PC templates, and (2) no nanowire was observed under the LPED conditions inside hard AAO templates, indicating that LPED-growth process, and hcp structure of the corresponding nanowires depend on deposition parameters, as well as nature of confinement.

Hexa-arm star shaped hydrazone derivatives from hexakis(4-formylphenoxy)-cyclotriphosphazene core

A series of novel hexasubstituted cyclophosphazene hydrazones [N(3)P(3)(-OC(6)H(4)-p-CH=N-NH-C(O)-C(6)H(4)-p-X)(6)] (X = H, Br, Cl, F, OH, OCH(3), CH(3), NO(2), NH(2)) were prepared by a sixfold condensation reaction of [N(3)P(3)(-OC(6)H(4)-p-CHO)(6)] with para-substituted benzoic hydrazides [NH(2)-NH-C(O)-C(6)H(4)-p-X] with excellent yields (91-98%). The structures of the compounds were confirmed by elemental analysis, FT-IR, (1)H, (13)C, (31)P, 2D-HSQC NMR and mass spectrometry (MALDI-TOF). All the synthesized cyclophosphazene hydrazones exhibit high thermal stability. The crystal structure of a homogeneously substituted hexakis(4-formylphenoxy)-cyclotriphosphazene was determined by X-ray diffraction analysis. The compound crystallizes in the monoclinic system, space group P2(1)/n with a = 16.558(3) angstrom, b = 10.250(2) angstrom, c = 23.429(5) angstrom, alpha = gamma = 90.00 degrees, beta = 90.461(4)degrees, V = 3976.5(14) angstrom(3) and Z = 4. The R value is 0.0823 for 4290 observed reflections. The conformations of the 4-formylphenoxy-groups are different at the three phosphorus atoms. (C) 2011 Elsevier B.V. All rights reserved.

Reversible Formation of a Planar Chiral Ferrocenylboroxine and Its Supramolecular Structure

The boronic acid (pS)-1,2-NpFcB(OH)(2) (1) was obtained by treatment of the lithiated species (pS)-1,2-NpFcLi with B(O(i)Pr)(3), followed by acidic workup; subsequent dehydration gave the enantiomerically pure boroxine [(pS)-1,2-NpFcBO](3) (2) in 49% isolated yield. Multinuclear and 2D NMR spectroscopies, single-crystal X-ray diffraction, and elemental analysis served to confirm the structure of 2. In the solid-state structure, all three of the naphthyl groups point in one direction and all of the ferrocenyl moieties are placed on the opposite face of the boroxine ring, which is also the preferred conformation in solution according to a (1)H, (1)H-NOESY experiment. Cyclic voltammetry revealed three separate reversible oxidation events, which suggests significant communication between the ferrocenyl moieties. These redox processes experience a cathodic shift upon addition of 4-dimethylaminopyridine (DMAP) as a Lewis base. The six-membered ring is opened upon treatment with hot CHCl(3)/MeOH to form the methoxy species (pS)-1,2-NpFcB(OH)(OMe) (3), which can be converted back to the cycle 2 by dissolution in wet CHCl(3), followed by column chromatography on silica gel.