Optical properties of thermally evaporated 4-(4-nitrobenzalideneamino) antipyrine Schiff base thin films

4-(4-nitrobenzalideneamino) antipyrine (NBAA) have been synthesized by refluxed ethanolic solution of 4-aminoantipyrine and p-nitrobenzaldehyde for 4 h and characterized with various physico-chemical techniques. Thin films of NBAA have been prepared by the thermal deposition technique in a vacuum of 1.5 × 10⁻⁵ mbar onto optical flat glass substrates. X-ray diffraction patterns show amorphous nature for all NBAA thin films except UV irradiated thin film which shows amorphous nature with some crystallinity but with small amount. The optical constants of thermally deposited NBAA thin film were investigated in the wavelength range 200–2500 nm. The type of optical transition near the edge of the band gap is found to be indirect allowed transition. The effect of UV irradiation as well as the effect of annealing on the optical properties of NBAA thin films was investigated. The value of the energy gap for thin films under investigation is calculated and found to be 1.56 eV for as-deposited, 1.45 eV for annealed and 1.82 eV for UV irradiation.     

Stabilization of electronic properties of (1R)-(−)-10-camphorsulfonic acid doped polyaniline by UV irradiation

Stability of electronic parameters of conducting polymers affects the overall performance of organic electronics. We show that UV light (254 nm) treatment of polyaniline (PANI) films, containing camphorsulfonic acid (CSA) as a dopant and cast from formic acid, decreases the film resistance and keeps their improved resistance stable for at least 4 months. It has been found that due to the different origins of these electronic properties, the resistance and work function of the PANI·CSA films are affected differently by the UV treatment. The long-term stability of the resistance is governed by morphological changes of the material. On the other hand the stability of the threshold voltage of the field-effect transistor (FET) which is an indirect measure of the work function, originates from the charge density equilibration at the PANI·CSA film/insulator interface. The FT-IR, UV-vis and circular dichroism data provide the evidence that after the UV treatment the polymer molecular structure remains intact, but some secondary structural re-arrangements of the PANI·CSA take place. These re-arrangements are resulting from the strong donor-acceptor interactions between the imine and/or amine groups of the PANI chains and the CO and SO₃⁻ groups of the doping CSA-anion. These interactions enhance significantly the mechanical rigidity of the PANI matrix. The increasing broad absorption band of the “free-carrier tail” in the FT-IR spectra correlates with the conductivity increase of the UV treated PANI·CSA film.     

Current-voltage characteristics of thin poly(biphenyl-4-ylphthalide) films

The paper considers the features of the charge transport near to the threshold of the transition of polymer films to the high conductive state, induced by a small uniaxial pressure. The problem has not been solved so far, how the energy structure of a wide-band-gap organic dielectric varies near this threshold. The current-voltage characteristics of poly(biphenyl-4-ylphthalide) films at different uniaxial pressures were measured and analyzed. The interpretation of the obtained results is carried out within the framework of the space charge limited conduction model. The estimation of the injection model of transport parameters such as the charge carrier mobility and concentration, trapping state concentration and others are carried out. The analysis of the obtained results allows to make the following preliminary conclusion. Pressure increase promotes formation of a narrow trap band near the quasi-Fermi level resulting from the increase in the injection. This can give rise to a sharp magnification of the charge carrier mobility and even transition to the metallic state.     

Synthesis of 10-propargylfolic acid from 2-amino-6-(bromomethyl)-4(1h)-pteridinone

6-(Bromomethyl)-2,4-pteridinediamine hydrobromide (1) is readily converted to 2-amino-6-(bromomethyl)-4(1H)-pteridinone hydrobromide (2) by treatment with 48% hydrobromic acid. Compound 2 is of interest for direct attachment of the (2-amino-3,4-dihydro-4-oxo-6-pteridinyl)methyl group to appropriate side-chain precursors of analogues of folic acid, particularly those bearing functional groups incompatible with conditions required for hydrolytic deamination of the corresponding 2,4-diaminopteridine analogues. An example of the use of 2 in this connection is demonstrated through synthesis of 10-propargylfolic acid.     

Mechanistic studies on the reactions of PhS(-) or [MoS(4)](2)(-) with [M(4)(SPh)(10)](2)(-) (M = Fe or Co)

Kinetic studies, using stopped-flow spectrophotometry, on the reactions of [M(4)(SPh)(10)](2)(-) (M = Fe or Co) with PhS(-) to form [M(SPh)(4)](2)(-) are described, as are the reactions between [M(4)(SPh)(10)](2)(-) and [MoS(4)](2)(-) to form [S(2)MoS(2)Fe(SPh)(2)](2)(-) or [S(2)MoS(2)CoS(2)MoS(2)](2)(-). The kinetics of the reactions with PhS(-) are consistent with an initial associative substitution mechanism involving attack of PhS(-) at one of the tetrahedral M sites of [M(4)(SPh)(10)](2)(-) to form [M(4)(SPh)(11)](3)(-). Subsequent or concomitant cleavage of a micro-SPh ligand, at the same M, initiates a cascade of rapid reactions which result ultimately in the complete rupture of the cluster and formation of [M(SPh)(4)](2)(-). The kinetics of the reaction between [M(4)(SPh)(10)](2)(-) and [MoS(4)](2)(-) indicate an initial dissociative substitution mechanism at low concentrations of [MoS(4)](2)(-), in which rate-limiting dissociation of a terminal thiolate from [M(4)(SPh)(10)](2)(-) produces [M(4)(SPh)(9)](-) and the coordinatively unsaturated M site is rapidly attacked by a sulfido group of [MoS(4)](2)(-). It is proposed that subsequent chelation of the MoS(4) ligand results in cleavage of an M-micro-SPh bond, initiating a cascade of reactions which lead to the ultimate break-up of the cluster and formation of the products, [S(2)MoS(2)Fe(SPh)(2)](2)(-) or [S(2)MoS(2)CoS(2)MoS(2)](2)(-). With [Co(4)(SPh)(10)](2)(-), at higher concentrations of [MoS(4)](2)(-), a further substitution pathway is evident which exhibits a second order dependence on the concentration of [MoS(4)](2)(-). The mechanistic picture of cluster disruption which emerges from these studies rationalizes the "all or nothing" reactivity of [M(4)(SPh)(10)](2)(-).     

B-[9,9-双(4-甲基苯基)-9H-芴-2-基]硼酸的合成工艺优化

以2-溴-9-芴酮为原料,经亲核加成、取代、氧化还原、氧化反应合成B-[9,9-双(4-甲基苯基)-9H-芴-2-基]硼酸,其结构经¹H NMR确证。采用响应面法重点对氧化还原步骤进行优化。确定较优合成条件为：反应时间5.4 h,催化剂用量为0.4 eq.,反应温度为108 ℃,目标产物收率92.15%,相对误差0.54%。      

High-energy 4(10)-2-fluoro-2,2-dinitroethyl and 4(10)-2,2-dinitropropyl derivatives of polynitrohexaazaisowurtzitanes

Russian Chemical Bulletin - Methods for the syntheses of a series of high-energy 4(10)-2-fluoro-2,2-dinitroethyl and 4(10)-2,2-dinitroethyl derivatives of polynitrohexaazaisowurtzitanes were...     

Thermal and environmental stability of poly(4-ethynyl-p-xylylene-co-p-xylylene) thin films

The aim of this paper was to test the thermal and environmental stability of poly(4-ethynyl-p-xylyleneco-p-xylylene) thin films prepared by chemical vapor deposition(CVD) and to optimize the reaction conditions of the polymer.Fourier transformed infrared spectroscopy(FTIR),thermogravimetric analysis(TGA) and fluorescence microscopy were employed to investigate the stability of the reactive polymer coatings in various environmental conditions.Chemical reactivity of the thin films were then tested by Huisgen 1,3-dipolar cycloaddition reaction(‘‘click' reaction).The alkyne functional groups on poly(4-ethynyl-p-xylylene-co-p-xylylene) thin films were found to be stable under ambient storage conditions and thermally stable up to 100 8C when annealed at 0.08 Torr in argon.We also optimized the click reaction conditions of azide-functionalized molecules with poly(4-ethynyl-p-xylylene-co-p-xylylene).The best reaction result was achieved,when copper concentration was 0.5 mmol/L,sodium ascorbate concentration to copper concentration was 5:1.In contrast,the azide concentration and temperature had no obvious effect on the surface reaction.     

Synthesis and Solvatochromatic properties of 9-(4-Aminophenylethynyl)-10-(4-nitrophenylethynyl)anthracene

9-(4-Aminophenylethynyl)-10-(4-nitrophenylethynyl)anthracene (2) was synthesized in high yield by using a route involving sequential Sonogashira cross coupling reactions of 9-bromo-10-iodoanthracene with 4-nitrophenylacetylene and 4-aminophenylacetylene. Solvatochromism was observed in the absorption and fluorescence spectra of 2 in a variety of solvents. In less polar solvents, such as hexane and benzene, the fluorescence emission band of 2 appears in the green to orange region while this substance does not fluoresce in polar solvents, such as acetonitrile and DMF.     

Crystal structure of thiogermanic acid H(4)Ge(4)S(10)

X-ray diffraction analysis reveals the thiogermanic acid H(4)Ge(4)S(10) possesses discrete adamantane-like Ge(4)S(10)(4)(-) complex anions. Each thioanion is composed of four corner shared GeS(2.5)(-) tetrahedral units. Crystals were grown from anhydrous liquid hydrogen sulfide reactions with glassy germanium sulfide at room temperature. The crystal structure was solved and refined from single crystal diffractometer data (Mo Kalpha radiation) obtained at 173 K. H(4)Ge(4)S(10) is triclinic, centrosymmetric space group Ponemacr;, with a = 8.621(4) A, b = 9.899(4) A, c = 10.009(4) A, alpha = 85.963(7) degrees, beta = 64.714(7) degrees, gamma = 89.501(8) degrees, and Z = 2. Average bridging and terminal d(Ge-S) distances are 2.229 and 2.206 A, respectively. Vibrational mode assignments are reported from Raman scattering and IR absorption spectra of polycrystalline samples. The nu(s)(Ge-S-Ge) and nu(s)(Ge-S(-)) stretching modes are observed at 354 and 405 cm(-)(1), respectively.     

A new synthetic route to boron-10 enriched pentaborane(9) from boric acid and its conversion to anti-(10)B(18)H(22)

Boron-10 enriched boric acid, H310BO3, was converted to the corresponding sodium borohydride, Na10BH4, in essentially quantitative yields, by using slightly modified literature methods involving the formation of butyl borate, (n-OBu)310B, first and then reacting it with NaH in mineral oil. The oxidation reaction of Na10BH4 with I2 in diglyme and subsequent addition/purification in dioxane gave Na[10B3H8]0.3(C4H8O2) that reacted further with NiCl2 in either anhydrous benzene or heavy mineral oil at 110 degrees C to produce the corresponding 10B5H9 as the first isolated 10B-enriched liquid boron hydride in a laboratory environment. Treatment of this 10B5H9 with NaH or t-BuLi in 2:1 molar ratio underwent a cage expansion reaction to produce the [M]10B9H14 that undergoes a redox reaction in situ with anhydrous NiCl2 in n-hexane to yield the corresponding fused cage anti-10B18H22 as the only solid borane product in 42% yield, thus establishing new synthetic routes for the preparation of 10B-enriched polyhedral boranes.     

Synthesis and catalysis of di- and tetranuclear metal sandwich-type silicotungstates [(gamma-SiW10O36)2M2(mu-OH)2]10- and [(gamma-SiW10O36)2M4(mu4-O)(mu-OH)6]8- (M = Zr or Hf)

The di- and tetranuclear metal sandwich-type silicotungstates of Cs10[(gamma-SiW10O36)2{Zr(H2O)}2(mu-OH)2] x 18 H2O (Zr2, monoclinic, C2/c (No. 15), a = 25.3315(8) A, b = 22.6699(7) A, c = 18.5533(6) A, beta = 123.9000(12) degrees, V = 8843.3(5) A(3), Z = 4), Cs10[(gamma-SiW10O36)2{Hf(H2O)}2(mu-OH)2] x 17 H2O (Hf2, monoclinic, space group C2/c (No. 15), a = 25.3847(16) A, b = 22.6121(14) A, c = 18.8703(11) A, beta = 124.046(3) degrees, V = 8974.9(9) A(3), Z = 4), Cs8[(gamma-SiW10O36)2{Zr(H2O)}4(mu4-O)(mu-OH)6] x 26 H2O (Zr4, tetragonal, P4(1)2(1)2 (No. 92), a = 12.67370(10) A, c = 61.6213(8) A, V = 9897.78(17) A(3), Z = 4), and Cs8[(gamma-SiW10O36)2{Hf(H2O)}4(mu4-O)(mu-OH)6] x 23 H2O (Hf4, tetragonal, P4(1)2(1)2 (No. 92), a = 12.68130(10) A, c = 61.5483(9) A, V = 9897.91(18) A(3), Z = 4) were obtained as single crystals suitable for X-ray crystallographic analyses by the reaction of a dilacunary gamma-Keggin silicotungstate K8[gamma-SiW10O36] with ZrOCl2 x 8 H2O or HfOCl2 x 8 H2O. These dimeric polyoxometalates consisted of two [gamma-SiW10O36](8-) units sandwiching metal-oxygen clusters such as [M2(mu-OH)2](6+) and [M4(mu4-O)(mu-OH)6](8+) (M = Zr or Hf). The dinuclear zirconium and hafnium complexes Zr2 and Hf2 were isostructural. The equatorially placed two metal atoms in Zr2 and Hf2 were linked by two mu-OH ligands and each metal was bound to four oxygen atoms of two [gamma-SiW10O36](8-) units. The tertanuclear zirconium and hafnium complexes Zr4 and Hf4 were isostructural and consisted of the adamantanoid cages with a tetracoordinated oxygen atom in the middle, [M4(mu4-O)(mu-OH)6](8+) (M = Zr or Hf). Each metal atom in Zr4 and Hf4 was linked by three mu-OH ligands and bound to two oxygen atoms of the [gamma-SiW10O36](8-) unit. The tetra-nuclear zirconium and hafnium complexes showed catalytic activity for the intramolecular cyclization of (+)-citronellal to isopulegols without formation of byproducts resulting from etherification and dehydration. A lacunary silicotungstate [gamma-SiW10O34(H2O)2](4-) was inactive, and the isomer ratio of isopulegols in the presence of MOCl2 x 8 H2O (M = Zr or Hf) were much different from that in the presence of tetranuclear complexes, suggesting that the [M4(mu4-O)(mu-OH)6](8+) core incorporated into the POM frameworks acts as an active site for the present cyclization. On the other hand, the reaction hardly proceeded in the presence of dinuclear zirconium and hafnium complexes under the same conditions. The much less activity is possibly explained by the steric repulsion from the POM frameworks in the dinuclear complexes.     

AC conductivity and dielectric properties of 2-(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-ylimino)-2-(4-nitrophenyl)acetonitrile thin films

The dark AC conductivity and dielectric properties of thermally evaporated 2-(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-ylimino)-2-(4-nitrophenyl)acetonitrile (DOPNA) thin films in sandwich structure employing symmetrical gold ohmic contacts have been investigated as function of temperature (303–443 K) and frequency (100 Hz–5 MHz). The AC conductivity, σ_AC(ω), is found to obey Jonscher’s universal power law, σ_AC(ω)=Aω^s (ω is the angular frequency). The AC conductivity of DOPNA thin films has been analyzed with reference to various theoretical models. The correlated barrier hopping is found to be the dominant conduction mechanism for charge carrier transport; the maximum barrier height, hopping length and the density of localized states are estimated. The temperature dependence of the AC conductivity shows Arrhenius type with two thermal activation energies. The activation energies are determined as a function of frequency. The behavior of the real and imaginary parts of the dielectric constant as a function of both temperature and frequency is discussed.     

Energy transfer in the doped poly(N-Vinylcabazole)films

The energy transfer process to guest molecule5 m poly(N-vinylcarbJZole) films WJS directly nir.isurcd In (lie film con- taining pciylencihc sandwich excimer site opcralcs as an cncrEy donor, while the evciple't si-itc composed ofthccaiba2olc- dirnettiyl IcrcphtliaJate pair is fornied by trapping tlie migrating monomer fluorescent state.     

Deracemization of a dynamic combinatorial library induced by (-)-cytidine and (-)-2-thiocytidine

A dynamic combinatorial library composed of racemic hydrazone-based dipeptides becomes deracemized on binding to the chiral analytes (-)-cytidine and (-)-2-thiocytidine through the amplification of two receptors, (SS)-dimer and (RRRR)-tetramer. The deracemization phenomenon was investigated by laser polarimetry, mass-tagged pseudo-enantiomers in conjunction with electrospray ionization mass spectrometry, HPLC/UV-MS, UPLC/UV-MS, rapid-resolution LC-MS, collision-induced dissociation MS/MS, and numerical simulations. These data were consistent with a phenomenon where (SS)-dimer and (RRRR)-tetramer selectively bind the chiral analyte in preference to their enantiomeric counterparts, which ultimately causes them to be amplified and the library to become deracemized.     

An improved solvent-free synthesis of flunixin and 2-(arylamino) nicotinic acid derivatives using boric acid as catalyst

A simple solvent-free protocol for the preparation of flunixin, a potent non-narcotic, non-steroidal anti-inflammatory drugs is reported using boric acid as catalyst. Its salt, flunixin meglumine are then prepared under reflux in EtOH. This sustainable method are then extended for the synthesis of a series of 2-(arylamino) nicotinic acid derivatives. The present protocol combines non-hazardous neat conditions with associated benefits like excellent yield, straightforward workup, and use of readily available and safe catalyst in the absence of any solvent, which are important factors in the pharmaceutical industry. The pathway for catalytic activation of 2-chloronicotic acid with boric acid was also investigated using Gaussian 03 program package.

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