Polyynes and cyanopolyynes synthesis from the submerged electric arc: about the role played by the electrodes and solvents in polyynes formation

The products of the electric arc between graphite electrodes have been investigated by high performance liquid chromatography-diode-array detector (HPLC-DAD) analysis in various media: distilled water, liquid nitrogen, methanol, ethanol, n-hexane and benzene. In distilled water, hydrogen capped polyynes H-(CC)_n-H were the unique products demonstrating that carbon is supplied by the graphite electrodes while hydrogen is supplied by the solvent plasmalysis (in this case water plasmalysis). Arcing graphite electrodes in liquid nitrogen produces cyanopolyynes: NC-(CC)_n-CN demonstrating that in this case the end groups of the polyyne chains are supplied by molecular nitrogen plasmalysis caused by the electric arc. Graphite arcing in methanol and ethanol produces very clean solutions (by-products negligible or absent) of hydrogen-capped polyynes with C₈H₂ as the main product accounting for more than 70 mol percent of the total polyyne concentration. By replacing graphite electrodes with titanium electrodes in methanol or in ethanol, polyynes are not formed at all; only trace amounts of polycyclic aromatic hydrocarbons (PAHs) were detected. When arcing with graphite electrodes is conducted in n-hexane or in benzene, polyyne formation is accompanied by a significant production of PAH, especially in benzene. These results have been rationalized in terms of carbonization or coking tendency of a given solvent. The effect of using titanium electrodes in place of graphite electrodes has been investigated also in n-hexane and in benzene as well as the effects of very high electric current intensity employed to ignite and sustain the submerged electric arc.     

Determination of six polyynes in Oplopanax horridus and Oplopanax elatus using polyethylene glycol modified reversed migration microemulsion electrokinetic chromatography

A PEG‐modified reversed migration MEEKC method was developed for simultaneous determination of six polyynes, including oplopandiol, falcarindiol, oplopandiol acetate, (11S, 16S, 9Z)‐9,17‐octadecadiene‐12,14‐diyne‐1,11,16‐triol,1‐acetate, oplopantriol B, and oplopantriol A, in Oplopanax horridus and Oplopanax elatus. The running buffer containing 0.8% v/v ethyl acetate, 3.8% w/v SDS, 6.6% v/v n‐butanol in 20 mM phosphate buffer (pH 2.5), followed by mixing with propan‐2‐ol at 30% v/v and PEG‐1000 at 15% w/v, was applied in the analysis. The proposed method was successfully applied to determine the six polyynes in five samples of Oplopanax horridus and one of O. elatus. The result showed that the types and amounts of polyynes present were obviously different when comparing the two herbs. Besides, the developed PEG‐modified reversed MEEKC method might be suitable for the analysis of hydrophobic analytes in herbal medicines.     

Review of quantitative spectroscopy of polyynes

We propose a review of quantitative spectroscopy of polyynes in the infrared and ultraviolet domain focusing on essential spectroscopic parameters for the interpretation of observed spectra in the infrared and ultraviolet domain and for photochemical modeling. We point at the lacking data in both wavelength domains for C₂H₂, C₄H₂, C₆H₂, C₈H₂ and propose downloadable files of the ultraviolet absorption coefficient ready to use for photolysis rate calculations. For longer polyynes, we calculate extrapolated ultraviolet spectra and calculate their photolysis rate. Using a simplified photochemical model of the polyynes in Titan and CRL618, we predict their relative abundance and compare them with the observed ones. This also leads us to predict the abundances of the longer polyynes.     

Polyynes from Toona ciliata var. ciliata and Related Cytotoxic Activity

A phytochemical investigation of Toona ciliata var. ciliata afforded three new polyynes, 1 – 3 . Their structures were elucidated on the basis of spectroscopic analysis and chemical methods. Only compound 3 exhibited potent cytotoxicity against the HL‐60 cell line with an IC₅₀ value of 6.7±0.27 μM .     

聚炔烃电子吸收光谱的理论研究

应用DFT/B3LYP方法,在6-31G水平上计算了HC2nH(n=1～13)的基态平衡几何构型和振动频率.在基态平衡构型下,通过TD-B3LYP/cc-PVTZ计算,确定了HC2nH(n=1～5)体系电子跃迁的能量和对应的振子强度.根据计算结果并结合先前的价键研究导出了HC2nH聚炔烃体系电子跃迁能与体系大小n有关的解析表达式.     

New ε-caprolactone diyne monomers aiming for biodegradable polymers

A substitution reaction of cyclohexane-1,4-diol with propargyl bromide gave 4-(prop-2-yn-1-yloxy)cyclohexanol. This compound was oxidized to the corresponding ketone (2-C₂H) and then to acetylene γ-substituted ε-caprolactone (3-C₂H). The latter compound was chain-extended to two butadiynyl monomers: symmetrical 5,5′-[hexa-2,4-diyne-1,6-diylbis(oxy)]bis(oxepan-2-one) (3-C₄-3) and unsymmetrical 5-{[5-(trimethylsilyl)penta-2,4-diyn-1-yl]oxy}oxepan-2-one (3-C₄TMS) via Eglinton and Cadiot–Chodkiewicz couplings, respectively. Both compounds were obtained through an alternative Baeyer–Villiger oxidation of immediate ketone precursors 2-C₄-2 and 2-C₄TMS.     

β-Halovinylsilanes in oligoyne synthesis: a fluoride-catalysed unmasking of alkynes from β-fluorovinylsilanes

A stereoselective halodestannylation of (E)-β-stannylvinylsilane 6 has been used to access a range of (E)-β-halovinylsilanes. Most notably, the β-fluorovinylsilane 14 was accessed in high yield using the Selectfluor^® reagent, and subsequently converted into a masked hexayne 22. Release of the hexayne 25 was achieved by exposing 22 to sub-stoichiometric quantities of fluoride.     

Stability of polyynes in air and their degradation by ozonolysis

Polyyne solutions in n-hexane or other aliphatic hydrocarbons having C₆H₂, C₈H₂ and C₁₀H₂ as main components were found to be unstable at relatively high concentration (≈10⁻² M) and to separate in few hours a brown precipitate. This phenomenon does not occur in more dilute solutions. The precipitate recovered from the mentioned solutions was analysed by FT-IR spectroscopy and thermogravimetry and found to be constituted by polyyne chains crosslinked and oxidized by oxygen resembling in some way the product obtained by photolysing acetylene in water solution and in presence of air. Polyynes react very quickly with ozone producing as main product polymeric ozonides which are insoluble in hydrocarbons and which have been studied with FT-IR spectroscopy. The oxidized nature of the chains highly crosslinked by ozonides, peroxide and oxygen bridges has been confirmed. The oxidized polyyne fraction remaining in solution after ozonolysis was studied by electronic absorption spectroscopy and by liquid chromatography. Extensive chain breaking was found as expected although some degree of unsaturation was preserved even in the final oxidized products.     

Synthesis, characterization and photovoltaic properties of a low-bandgap platinum(II) polyyne functionalized with a 3,4-ethylenedioxythiophene-benzothiadiazole hybrid spacer

The synthesis, characterization and optical spectroscopy of a deep blue platinum(II) polyyne functionalized with the (3,4-ethylenedioxythiophene)-benzothiadiazole hybrid spacer (P1) and its dinuclear platinum molecular model complex (M1) are described. This metalated polymer P1 exhibits good thermal stability and possesses a narrow bandgap of 1.76 eV. Optical spectroscopic measurements of these materials reveal a substantial donor-acceptor interaction along the rigid backbone of the organometallic polyynes through the interaction of metal center and the conjugated tricyclic ligand. Preliminary study shows that P1: methanofullerene acceptor blend can be used as an active layer of bulk-heterojunction polymer solar cells. Photoexcitation of this blend layer in some yet-to-be optimized cells results in a photo-induced electron transfer from the π-conjugated metallopolyyne electron donor to [6,6]-phenyl C₆₁-butyric acid methyl ester with a power conversion efficiency (PCE) close to 0.30% under air mass (AM1.5) simulated solar illumination. The power dependencies of the solar cell parameters (including the short-circuit current density, open-circuit voltage, fill-factor and PCE) were also studied.     

Macromolecular polyyne-containing benzoxazines for cross-linked polymerization

A Mannich condensation of 2,4-di-tert-butylphenol, p-bromophenethylamine, and formaldehyde followed by a Sonogashira coupling of the resulting 3-(4-bromophenethyl)-6,8-di-tert-butyl-3,4-dihydro-2H-benz[1,3]oxazine (1-Br) with TMSCCH gave acetylenic benzoxazine 1-C₂TMS which was a precursor for polyynic derivatives. Firstly, it was deprotected with K₂CO₃ in iPrOH/MeOH to give the terminal acetylene 1-C₂H, which was subsequently dimerized to the symmetrical diyne 1-C₄-1. Next, 1-C₂H was transformed to 1-C₄TMS via a Cadiot-Chodkiewicz coupling, and then 1-C₄TMS was homocoupled with in situ deprotection to give octatetrayne 1-C₈-1. X-ray diffraction studies of 1-C₈-1 showed distinctive chain bending and a packing analysis revealed the potential for 1,n-topochemical polymerization that implies a cross-linking opportunity.