Comparative study of kinetics isomerization of substituted polyacetylene (Cl,F and I): Ab initio and DFT calculations

Ab initio and DFT methods were used to investigate the interconversions of substituted polyacetylene conformers C₁₀H₆X₆ (X=F, Cl and I) in the vapour phase. The rates of this geometrical isomerization have been calculated and the Arrhenius parameters evaluated. In the case of unsubstituted polyacetylene as the reference, the B3LYP Arrhenius parameters obtained are A₁=2.99 × 10¹⁷ s^–1 and E_a=17.30 kcal mol^–1. The values of the equilibrium constant for the reaction have also been determined at various temperatures between 300 and 500 K and the value of the energies change calculated. The results also suggest that the straightforward kinetics characterizing the majority of substituted polyacetylene isomerizations above 300 K. The isomerization energies are positive and the barrier heights ΔE_barrier are expected to be sensitive for the magnitude of halogens effects. According to geometries features the Cis → Trans isomerization in the gas phase occurs by a rotational mechanism.     

Preparation of a polyacetylene composite with single-walled carbon nanotubes and study of its electrochemical properties

A composite consisting of single-walled carbon nanotubes (2.4 wt %) covered by polyacetylene has been prepared. Polyacetylene synthesized directly on single-walled carbon nanotubes is a defectless long-chain polymer composed of trans and cis units with a sufficient length (60% trans and 40% cis isomers). An appreciable acceleration of the lithium ion intercalation-deintercalation corresponds to an increase in the conductivity of the composite material near the percolation threshold. The polyacetylene layer on single-walled carbon nanotubes plays the role of an electrochemically active ion-conductive membrane suitable for the transport of Li⁺ cations to the surface of nanotubes.     

Vinyltitanium as an initiator for the polymerization of acetylene

The preparation of lustrous conducting polyacetylene films by the polymerization of acetylene with vinyltitanium species as initiators was studied. Organotitanium species were generated by the alkylation of titanium vinylcarbene complexes with tert‐butyl chloride. Solid‐state ¹³C NMR and IR analyses of the obtained polyacetylene indicated that polyacetylene with a trans configuration was produced. The use of titanocene(II) species Cp₂Ti[P(OEt)₃]₂ and titanium vinylcarbene complexes for the preparation of polyacetylene films was also studied. The morphology of the films and the mechanisms of polymerization are discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2663–2669, 2002     

Lattice dynamics of polyacetylene as a one-dimensional system: Part I. The case of the trans perfect polymer

In this paper the lattice dynamics of trans-polyacetylene as a perfect one-dimensional crystal is treated. Dispersion curves, density of states and vibrational displacements are calculated. The results of the calculations are used to propose a vibrational assignment for (CH)_x, (CD)_x and (¹³CH)_x. Calculations have been made with a quadratic simplified valence force field (SVFF). The relationship between SVFF and the electron-phonon coupling model for polyacetylene, generally adopted in the literature, is discussed. Comparison with the calculations of other authors is made.     

Electronic structure of polyenes and polyacetylene

The CNDO/S2 model is applied to evaluate the molecular orbitals and ultraviolet absorption spectra of the series of polyenes C_4nH_4n+2, n = 1, 2, 3, 4; extended to encompass the infinite polyene chain, i.e., polyacetylene; and utilized to interpret the photoemission and absorption spectra of polyacetylene.     

XPS Studies of PtCl4 and H2PtCl6·6H20 doped polyacetylene

The PtCl₄ and H₂PtCl₆-6H₂O doped polyacetylene were studied by X-ray photoelection spectroscopy and transmission electron microscopy. We found that both Pt 4f and Cl 2p peaks could be resolved into two components both with a splitting of ca. 1.5 eV. The higher binding energy components of Pt 4f peak is attributed to Pt⁴⁺ and the lower binding energy one to Pt²⁺ species. From quantitative analysis of the results of decomposition of both Pt 4f and Cl 2p peaks it was found that an atomic ratio of chlorine to platinum for Pt²⁺ species is (Cl) / (Pt) = 2 and that for Pt⁴⁺ species is (Cl) / (Pt) = 6 for both PtCl₄ and H₂PtCl₆·6H₂O doped polyacetylene. The C 1s peaks could be decomposed into two components separated by ca. 1 eV. The intensity of the higher binding energy component increased with increasing dopant concentration. These indicate that the platinum salt doping proceeds through charge transfer from polyacetylene chain to platinum atom resulting in a partial reduction from Pt⁴⁺ to Pt²⁺ state. The existence of PtCl₂ cluster on the surface of the doped polyacetylene film was supported by transmission electron microscopy and electron diffraction observations. These results indicate that a random distribution of the dopant along the macromolecular chain, and the charge per carbon atom in the metallic region of doped polyacetylene has been estimated to be 0.2 |e|. From these results the mechanism of the PtCl₃ and H₂PtCl₆·6H₂O doping process in polyacetylene is clarified as follows: Thus the dopant anion in polyacetylene is PtCl,^2? for both PtCl₄ and H₂PtCl₆·6H₂O doping.     

Temperature dependence of the vibronic spectrum of cis polyacetylene

Using the Luttinger method at low temperatures, we have produced samples of cis “polyacetylene”, (CH)x, whose absorption maxima (zero phonon lines) lie between 16700 and ≈30000 cm^?1 depending upon chain length. Quite well-resolved vibronic structure has been observed for these samples, with four peaks in the vibronic spectrum clearly visible at room temperature, although degradation of this structure follows ageing at 300 K in vacuum.     

A New Disubstituted Polyacetylene for the Detection of α‐Amino Acids

New imidazole‐functionalized disubstituted polyacetylene was synthesized by utilizing the postfunctional strategy. In addition, its ability to sense copper ions and α‐amino acids by fluorescence quenching has been studied. The quenching of the fluorescence of the imidazole‐functionalized disubstituted polyacetylene was observed at a very low level of Cu²⁺ (7.0 × 10⁻⁷ mol · L⁻¹). The fluorescent intensity decreased rapidly upon the increase of the concentration of the added solution of Cu²⁺. It was expected that the addition of α‐amino acids to the solution of the polyacetylene/Cu²⁺ complex could turn on the fluorescence of the polyacetylene, if α‐amino acids could remove the copper ions from the complex. Glycine, was used for testing: upon the addition of glycine the quenched fluorescence of P1 turned on immediately. The detection limit was as low as 6.0 × 10⁻⁵ mol · L⁻¹.

     

Determination of tetracycline and related compounds using plastic membrane ion-selective electrodes

PVC membrane electrodes selective for hydrochlorides of tetracycline (TC), doxycycline (DC) and oxytetracycline (OTC) are prepared. The electrodes show a linear response with Nernstian slope over the range of 1.6 × 10⁻⁵–10⁻²M, 7.9 × 10⁻⁵–1.9 × 10⁻³M, and 6.3 × 10⁻⁵–6.3 × 10⁻³M for TC, DC, and OTC, respectively. The effects of pH of the test solution and time of soaking on the electrodes' performance are studied. The electrodes exhibit good selectivity for the investigated antibiotics with respect to a large number of inorganic cations and organic substances of biological importance. TC, DC, and OTC are determined successfully in pure solutions and in some pharmaceutical preparations using the standard additions method.     

Panaxfuraynes A and B, two new tetrahydrofuranic polyacetylene glycosides from Panax ginseng C. A. Meyer

Panaxfurayne A (1), a tetrahydrofuranic polyacetylene glycoside, was isolated from the roots of Panax ginseng C. A. Meyer (Araliaceae) together with panaxfurayne B (2) as a geometric isomer of 1. The chemical structures of these two compounds were ascertained by UV, Mass, 1D, and 2D NMR experiments. During these experiments, these tetrahydrofuranic polyacetylene compounds proved to be of biogenetically novel type.     

Selective addition of CXCR3+CCR4-CD4+ Th1 cells enhances generation of cytotoxic T cells by dendritic cells in vitro

Increasing importance is being given to the stimulation of Th1 response in cancer immunotherapy because its presence can shift the direction of adaptive immune responses toward protective immunity. Based on chemokine receptor expression, CXCR3⁺CCR4^-CD4⁺ T cells as Th1-type cells were investigated its capacity in monocyte-derived dendritic cell (DC) maturation and polarization, and induction of antigen specific cytotoxic T lymphocytes (CTL) in vitro. The levels of IL-4, IL-5 and IL-10 were decreased to the basal level compared with high production of IFN-γ, TNF-α, and IL-2 in CXCR3⁺CCR4^-CD4⁺ T cells stimulated with anti-CD3 and anti-CD28 antibodies. Co-incubation of activated CD4⁺ or CXCR3⁺CCR4^-CD4⁺ T cells with DC (CD4⁺/DC or CXCR3⁺CD4⁺/DC, respectively) particularly up-regulated IL-12 and CD80 expression compared with DC matured with TNF-α and LPS (mDC). Although there was no significant difference between the effects of the CXCR3⁺CCR4^-CD4⁺ and CD4⁺ T cells on DC phenotype expression, CXCR3⁺CD4⁺/DC in CTL culture were able to expand number of CD8⁺ T cells and increased frequencies of IFN-γ secreting cells and overall cytolytic activity against tumor antigen WT-1. These results demonstrated that the selective addition of CXCR3⁺CCR4^-CD4⁺ T cells to CTL cultures could enhance the induction of CTLs by DC in vitro, and implicated on a novel strategy for adoptive T cell therapy.     

Multifrequency EPR and DENR of polyacetylene composite

The organo-inorganic composite MoCl_{1.9 ± 0.1}(C_{30 ± 1}H_{30 ± 1}), a product of interaction of MoCl₅ with C₂H₂, has been studied by X- and W-band EPR, double electron nuclear resonance, and W-band electron spin echo spectroscopy. The composite consists of nanosized organometallic molybdenum clusters in the polyacetylene matrix. It has been shown that the composite contains three types of magnetic centers: the first is related to the existence of paramagnetic molybdenum atoms in the polyacetylene matrix, and the other two are paramagnetic defects of the matrix.     

The interaction of Co ions and sodium deoxycholate micelles

To mimic the interaction between divalent metal ions and bile slats in vivo, two groups of coordination complex compounds, crystalline and gel-like, were synthesized in vitro by mixing the aqueous solutions of CoCl₂ with sodium deoxycholate (NaDC) at various concentrations. Structures and compositions of the compounds were investigated using FT-IR, EXAFS, XRD as well as elemental and ICP analysis, respectively. Then the interaction of Co²⁺ with deoxycholate in solution was observed by laser light scattering (LLS), Transmission electronic microscope techniques and ICP analysis. Conclusions are (1) the crystalline complexes, Co (DC)₂·3H₂O were obtained by reaction of Co²⁺ with mono-molecules of NaDC, and the gel-like complexes, Na_nCo_m(DC)_n+2m formed by reaction of Co²⁺ with NaDC micelles. The gel-like complexes exhibit the non-stoichiometric character; (2) the coordination structures of carboxyl groups with Co²⁺ were different between the crystalline and gel-like complexes. In Co(DC)₂·3H₂O complex, the carboxyl groups of deoxycholate coordinated with Co²⁺ in chelating and pseudo-chelating modes, but that in bridge mode in the case of Na_nCo_m(DC)_n+2m complexes. The non-stoichiometric complexes of Na_nCo_m(DC)_n+2m are formed with a macromolecular structure through the Co²⁺ bridges; (3) NaDC can increase the solubility of Co(DC)₂·3H₂O in aqueous solution, and larger micelles (30-80 nm diameter) formed in the supernate. It is a mixed micelle formed by Co²⁺ ions bridges connecting with NaDC simple micelles. So these micelles are a new kind of micelle containing two kinds of metal ions; (4) these results are in agreement with those formed under physiological conditions in that the different states such as gel, precipitate, micelles of various structures are present in bile of gallbladder. An ideal model of the interaction between Co²⁺ and bile salts in vivo has been proposed.     

Effect of metal ion loaded in a resin towards fluoride retention

Indion FR 10 is a commercially available ion exchange resin with sulphonic acid functionality named as H⁺ form, has appreciable defluoridation capacity (DC). It has been chemically modified to La³⁺, Fe³⁺, Ce³⁺ and Zr⁴⁺ forms by incorporating respective metal ions into the resin in order to know their fluoride selectivity by measuring the DC of the respective resin. The maximum DC of these chemically modified ion exchange resins namely La³⁺, Fe³⁺, Ce³⁺ and Zr⁴⁺ forms were found to be 469.7, 467.5, 456.3 and 470.9 mg F⁻/kg respectively suggests their higher selectivity towards fluoride than H⁺ form which has the DC of only 275 mg F⁻/kg at 11 mg/L initial fluoride concentration. The higher DC of the modified resins was explained by electrostatic adsorption and complexation whereas H⁺ form retains fluoride by hydrogen bond. The functional groups present in the sorbents were identified by FTIR and the existence of fluoride onto the resins was confirmed by EDAX analysis. The experimental data was fitted with both Freundlich and Langmuir isotherms. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° indicate that the nature of sorption is spontaneous and endothermic. The applicability of reaction-based and diffusion-based kinetic models was investigated. A field trial was carried out with fluoride water collected from a nearby fluoride-endemic village to test the suitability of these sorbents at field conditions.     

Ã2Σ+ → X̃+Π Emission spectra of the phosphaethyne cations,HCP+ and DCP+

The electron impact excited òΣ⁺ → X?⁺Π emission spectra of HCP⁺ and DCP⁺ have been observed. The spin-orbit split 0-0 band has maxima at 593.7 and 599.0 nm for HCP⁺ and 593.6 and 598.8 nm for DCP⁺. Short progressions in the V₃(CP) vibration are observed. a₀, v₃ and the upper-state lifetime are determined.     

Radiation-induced Cis to Trans isomerization of poly(n-butylpropiolate) prepared with a [Rh(norbornadiene)Cl]2 complex as a stereospecific catalyst

Normal alkylpropiolate, i.e., n-butylpropiolate: HCCCOOnC₄H₉ was polymerized with [Rh(norbornadiene)Cl]₂ catalyst in methanol solvent to produce poly(n-butylpropiolate), (PBPA) polymer called polyacetylene esters in relatively high yields. The obtained polymer was characterized in detail using ¹HNMR, gel permeation chromatography (GPC), diffuse reflective UV methods. Consequently, the data showed that the resulting polymers selectively have cis-transoid form. We also found that γ-ray irradiation of the cis isomer resulted in isomerization to the trans isomer even at room temperature in air to generate the extended trans sequences which can stabilize mobile unpaired electrons as π-radicals called solitons.     

Preparation and properties of a functional polyacetylene with quinoline-based heterocyclic azo pendants

A novel functional polyacetylene with D-π-A conjugated quinoline-based heterocyclic azo pendants was designed and prepared to improve the polyacetylene properties. Its structure and properties were characterized and evaluated in details. The incorporation of D-π-A conjugated quinoline-based heterocyclic azo pendants to the polyacetylene backbone increases the polymer solubility in polar solvents. Its UV-vis absorbance is sensitive to the presence of F^? anions and results in UV-VIS spectrum red-shift by ca. 21 nm from 449 nm to 470 nm in dry DMSO.     

Cylic Voltammetric Studies on the Electrode Reaction of Polyacetylene Secondary Cell

Cells of lithium / Polyacetylene containing 0.5 · 1.5 M LiClO₄ in propylene carbonate as supporting electrolyte are constructed. The mechanism for electrochemical redox process of polyacetylene is studied using cyclic voltammetry in the potential range from ?0.8 to 0.2 volt vs. S.C.E. The electrode reactions are identified to be diffusion controlled. The difference of the peak potentials between the oxidation and reduction, ΔEp, is found to be a function of the scan time per cycle (τ sec/cycle) and is influenced by concentration of supporting electrolyte and isomeric structures of polyacetylene. However, there is a better reversible redox process of polyacetylene when the ClO₄^? - ions diffuse successfully in and out of the Polymer film, which has the cis-form structure, in concentrated supporting electrolyte solution and having a long scan time per cycle (τ). When the scan potential is extended to a more positive region, another peak is found, which may correspond to the irreversible chemical reaction caused by over-doping. The over-doping process is found to be controlled by the electrical field strength, concentration of the supporting electrolyte and isomerism of polyacetylene.     

Ab initio Hartree—Fock calculations of model polyacetylene chains using a Christoffersen basis set

Ab initio crystal orbital calculations using a Christoffersen basis set have been performed on the relative stabilities of model polyacetylene chains. Results indicate the all-trans isomer as the most stable. Among the cis structures, the cis-transoid backbone is very slightly preferred to the trans-cisoid backbone.     

Mesoporous sodium four-coordinate aluminosilicate nanoparticles modulate dendritic cell pyroptosis and activate innate and adaptive immunity

Pyroptosis is a programmed cell death widely studied in cancer cells for tumour inhibition, but rarely in dendritic cell (DC) activation for vaccine development. Here, we report the synthesis of sodium stabilized mesoporous aluminosilicate nanoparticles as DC pyroptosis modulators and antigen carriers. By surface modification of sodium-stabilized four-coordinate aluminium species on dendritic mesoporous silica nanoparticles, the resultant Na-^IVAl-DMSN significantly activated DC through caspase-1 dependent pyroptosis via pH responsive intracellular ion exchange. The released proinflammatory cellular contents further mediated DC hyperactivation with prolonged cytokine release. In vivo studies showed that Na-^IVAl-DMSN induced enhanced cellular immunity mediated by natural killer (NK) cells, cytotoxic T cells, and memory T cells as well as humoral immune response. Our results provide a new principle for the design of next-generation nanoadjuvants for vaccine applications.

Na-^IVAl-DMSN acts as both antigen carriers and modulators to “hyperactivate” dendritic cells (DCs) via potassium (K⁺) efflux dependent pyroptosis, eventually leading to enhanced adaptive and innate immunity.