Highly conductive meta derivatives of poly(phenylene sulfide)

Changes in the backbone structure of several meta derivatives of polyphenylene sulfide upon doping with AsF₅ have been investigated by IR spectroscopy. Poly(m-phenylene sulfide) does not form a conducting complex with AsF₅ unless reacted under conditions where carbon-carbon bonds form intramolecularly between phenyl rings. This assertion has been verified by comparison of the IR spectra of poly(m-phenylene sulfide) and a newly synthesized derivative, poly(thio-3,7-dibenzothiophendiyl), after doping with AsF₅. This new derivative forms a complex with AsF₅ which exhibits a conductivity of 18.5 S/cm. A sulfone-containing derivative has also been synthesized, poly[thio-3,7-(dibenzothiophene-5,5-dioxide)-diyl]. With this polymer, a much lower conductivity, 10^?3 S/cm, was obtained after exposure to AsF₅.     

Electrical properties of ion-implanted poly(p-phenylene sulfide)

Ion implantation of impurities into thin films of poly(p-phenylene sulfide) (PPS) is found to increase the conductivity of the material by up to 12 orders of magnitude. The increase is stable under exposure to ambient conditions, in contrast to the instability of the conductivity increases in PPS produced by chemical doping with AsF₅. PPS films 0.1–0.2 μm thick are spin cast from solution onto interdigitated electrodes patterned on an oxidized silicon substrate. The room-temperature interelectrode resistance is measured as a function of implantation fluence. An estimate of film conductivity is obtained from this resistance with a simple model for the electrode and film geometry. A first experiment yielded similar conductivity increases for implantation of either arsenic or krypton. At a fluence of 1 × 10¹⁶cm^?;2, which corresponds to an average impurity concentration of 2.5 × 10²¹cm^?3, the conductivity reaches an apparently saturated value of 1.5 × 10^?5 (Ω cm)^?1. Infrared spectra of the films before and after implantation suggest that crosslinking may be present in the implanted films, and Auger studies show stoichiometric changes throughout the implanted layer. These results suggest that the observed conductivity changes are the result of molecular rearrangements produced by the implantation rather than the result of specific chemical doping. Specific chemical doping may, however, explain the results of a second experiment in which implantation of bromine resulted in substantially larger conductivities found to increase at an approximate linear rate from a value of 1.0 × 10^?4 (Ω cm)^?1 at a fluence of 1 × 10¹⁶ cm^?2 to a value of 4.0 × 10^?4 (Ω cm)^?1 at a fluence of 3.16 × 10¹⁶ cm^?2.     

Electron spin resonance and optical spectroscopic studies of the conducting polymer precursor: Poly(3,4-diisopropylidene cyclobutene)

The doping process in a recently developed conducting polymer precursor, poly(3,4-diisopropylidene cyclobutene) (PDPCB)¹ was studied by electron spin resonance and optical spectroscopy. Thin films of PDPCB were exposed to several oxidants, I₂, AsF₅, or a combination of AsF₅ and AsCl₃ or AsF₃, and monitored in situ by ESR. At the initial stages of doping, the films developed broad ESR spectra with Gaussian line shape. Except in the case of doping with I₂, resolved hyperfine structures from cation radicals were observed. As the doping progressed, the ESR spectra gradually transformed to narrower line widths with a Lorentzian component. The Lorentzian component can be attributed to charge carrier species developed in the film through doping. The results of optical spectroscopy (UV-visible) are incorporated to elucidate the effect of doping on electronic transitions of the doped PDPCB.     

X–ray Single Crystal Structure and Raman Spectrum of Ammonium Hexafluoroarsenate

The structure of ammonium hexafluoroarsenate, NH₄AsF₆, has been determined by X‐ray diffraction using a single crystal grown from saturated solution in anhydrous HF. NH₄AsF₆ crystallizes rhombohedral with the KOsF₆ structure type, with a = 7.459(3) Å, c = 7.543(3) Å (at 200 K), Z = 3, space group (No. 148). No phase transition was observed in the 100 K–296 K temperature range. The structure is dominated by regular AsF₆ octahedra and disordered NH₄⁺ cations. Raman spectrum of a single crystal of NH₄AsF₆ shows the bands at 372 cm^?1, 572 cm^?1, 687 cm^?1 (AsF₆^?) and at 3240 cm^?1 and 3360 cm^?1 (NH₄⁺).     

The relationship of graphite/AsF5 intercalation compounds to Cx+AsF6− salts

Graphite intercalated by AsF₅ has been reported to give compounds of formula C_8nAsF₅ where n is the stage. It is doubtful however if materials of exact composition C_8nAsF₅ have ever been obtained. The intercalation of graphite by AsF₅ is associated with electron oxidation of the graphite according to the equation: 3AsF₅ + 2e^? → 2AsF₆^? + AsF₃. Because of the easy removal or displacement of AsF₃ the As:F ratio is readily increased beyond 5. By treating graphite with excess AsF₅, removing volatiles under vacuum and repeating the cycle seven times a first stage salt C₁₀⁺AsF₆^? (C_o = 7.96 ā) is made. Interaction of graphite with AsFs in the molar ratio 8:1, within a small volume reactor, yields a material of approximate composition C₈AsF₅. The major component of the volatiles at the onset of their removal is AsF₅,, but, at a composition close to C₁₀AsF₅, is AsF₃. ‘Graphite AsF₅’ can be prepared by adding AsF₃ to C_xAsF₆ salts. The electrical conductivities of ‘AsF₅’ and AsF₆ relatives will be compared and discussed.     

The Existence of Hexafluoroarsenic(V) Acid

The homogeneous mixture of anhydrous hydrogen fluoride aHF and antimony pentafluoride AsF₅ is known as a superacidic system. The high acidity is derived from the formation of [H₂F]⁺ [AsF₆]^?. No experimental evidence exists for the existence of the free acid molecule HAsF₆. The reaction of trimethylsilyl N,N‐dimethylcarbamate in the binary system aHF/AsF₅ led to decomposition of trimethylsilyl N,N‐dimethylcarbamate at ?50 °C to dimethylammonium hexafluoridoarsenate and cocrystallization of HAsF₆. The single‐crystal X‐ray structure displays an HAsF₆ molecule involved in an asymmetric hydrogen bridge to the hexafluoridoarsenate anion. As a result of the incalculable situation in the crystal lattice, the molecular structure of HAsF₆ is calculated by quantum chemical structure optimization of the extreme cases of [FHF‐AsF₅]^? (strong hydrogen bond) and HAsF₆ (no hydrogen bond) at the PBE1PBE/6‐311G(3df,3pd) level of theory.     

Properties of polyphenylene films deposited electrochemically in an HF-benzene system

Free-standing polyphenylene films, prepared by the electrochemical oxidation of benzene in an HF-benzene, two-phase system, were investigated. From electron microscope pictures, x-ray diffraction patterns, and infrared (IR) spectra of polyphenylene films and commercial polyphenylene powder it is concluded that the films, which are largely para linked, contain in addition a substantial amount of meta and possibly ortho linkages and are amorphous in nature. Doping with AsF₅ increases the electrical conductivity of the otherwise insulating films to 10^?4?10^?2ohm^?1cm^?1; doped films are relatively stable in air. The lower conductivity of doped films with respect to reported values for chemically synthesized poly-p-phenylene appears to be the result of the amorphous nature of the films.     

X-ray crystal structure and raman spectrum of tribromine(1+) hexafluoroarsenate(V), Br3+AsF6−, and raman spectrum of pentabromine(1+) hexafluoroarsenate(V), Br5+AsF6−

A single crystal of Br₃⁺AsF₆^? was isolated from a sample of BrF₂⁺AsF₆^? which had been stored for 20 years. It was characterized by x-ray diffraction and Raman spectroscopy. It is shown that Br₃⁺AsF₆^? (triclinic, a = 7.644(7) Å, b = 5.641(6) Å, c = 9.810(9) Å, α = 99.16(8)°, β = 86.61(6)°, γ = 100.11(7)°, space group P1 R(F) = 0.0608) is isomorphous with I₃⁺AsF₆^?. The structure consists of discrete Br₃⁺ and AsF₆^? ions with some cation-anion interaction causing distortion of the AsF₆^? octahedron. The Br₃⁺ cation is symmetric with a bond distance of 2.270(5) Å and a bond angle of 102.5(2)°. The three fundamental vibrations of Br₃⁺ were observed at 297 (ν₃), 293 (ν₁), and 124 cm^?1 (ν₂). The Raman spectra of Cl₃⁺AsF₆^? and I₃⁺AsF₆^? were reinvestigated and ν₃(B₁) of I₃⁺ was reassigned. General valence force fields are given for the series Cl₃⁺, Br₃⁺, and I₃⁺. Reactions of excess Br₂ with either BrF₂⁺AsF₆^? or O₂⁺AsF₆^? produce mixtures of Br₃⁺AsF₆^? and Br₅⁺AsF₆^?. Based on its Raman spectra, the Br₅⁺ cation possesses a planar, centrosymmetric structure of C_2h symmetry with three semi-ionically bound, collinear, central Br atoms and two more covalently, perpendicularly bound, terminal Br atoms.     

Trityl-initiated copolymerizations of propylene oxide with tetrahydrofuran. VIII. Influence of reaction parameters

The copolymerization of propylene oxide (PO) with tetrahydrofuran (THF) in dichloroethane (DCE) has been studied at ?10, 0, +10, and +20°C. The reactions were initiated by triphenylmethyl cations associated with the following gegenions: PF₆^?, SbF₆^?, and AsF₆^?. The overall energies of activation (E_α of PO and E_a of THF) obtained with the three gegenions increase as one passes from PF₆^? to AsF₆^? then to SbF₆^?, though the magnitude of the increase in each case is not substantial. On the other hand, the associated frequency factors A show a considerable variation with the gegenion. The bimodal distributions of the molecular weights, obtained by GPC with the copolymer produced from reactions initiated with triphenylmethyl hexafluorophosphate, show that the proportions of the lower molecular weight component (L) decrease as the solvent is changed from DCE to toluene, and this is even more marked when bulk polymerization conditions are adopted. The proportions of the higher molecular weight component (H) however increase, as does its molecular weight. The GPC molecular weight distributions of the copolymers initiated with triphenylmethyl hexafluorophosphate in DCE to which water has been added, show that the molecular weight of component H decreases with increasing concentration of water, while that of component L remains practically unchanged at a value of 308. This corresponds to an average degree of polymerization (DP ) of 4 to 5. The NMR and infrared spectra of copolymers prepared in the presence of still higher initial water concentrations indicate that the PO-based polymer segments are present in excess of those required for a 1:1 copolymer.     

NSF3 und NSF2NMe2 als Liganden in der metallorganischen Chemie

Thiazyltrifluoride NSF₃ and Thiazyldifluoridedimethylamide NSF₂NMe₂: Ligands in Organometallic Chemistry From the reaction of [Re(CO)₅SO₂]⁺AsF₆^? ( 1 ) and [CpFe(CO)₂SO₂]⁺AsF₆^? ( 6 ) with NSF₃ ( 2 ) and NSF₂NMe₂ ( 4 ) the complexes [Re(CO)₅NSF₃]⁺AsF₆^? ( 3 ), [Re(CO)₅NSF₂NMe₂]⁺AsF₆^? ( 5 ), [CpFe(CO)₂NSF₃]⁺AsF₆^? ( 7 ), and [CpFe(CO)₂NSF₂NMe₂]⁺AsF₆^? ( 8 ) were obtained. The compounds have been characterised by X-ray crystallography, the ligand properties of 2 and 4 are discussed.     

Oligomers from biphenyl,biphenyl-d10, or p-terphenyl with aluminium chloride-cupric chloride: Mechanism,ESR, and conductivity

Biphenyl and biphenyl-d₁₀ were coupled by aluminum chloride-cupric chloride. For the two systems, the yields of p-quaterphenyl, p-sexiphenyl, and sublimation residue were compared. The results, which have mechanistic significance, are similar to those reported earlier for benzene versus benzene-d₆; that is, a decrease in DP for the deuterated substrate. p-Sexiphenyl, obtained from biphenyl or p-terphenyl and aluminum chloride-cupric chloride, displayed a concentration of 3 × 10¹⁷ spins/g in ESR. There was little or no change in spin density after sublimation or crystallization. Even after drastic purification by a variety of techniques the radical character persisted. Biphenyl was polymerized by aluminum chloride-cupric chloride at temperatures in the 50–155°C range. Processable polymers with m- and p-phenylene linkages were produced. When doped with AsF₅, the highest conductivity obtained was 7.3 × 10^?2 Ω^?1 cm^?1.     

The reaction of arsenic pentafluoride with graphite fluorosulfate

The reaction of graphite fluorosulfate with an excess of arsenic(V) fluoride produces the new intercalation compound C₁₄⁺ [AsF₅(SO₃F)]^?. Identification as a first stage compound rests on the observed interlayer separation of 7.92 Å and the position of ν_E2g at 1636 cm^?1 in the Raman spectrum. Evidence for [AsF₅(SO₃F)]^? as intercalant is based on ¹⁹F NMR spectra of the solid material. C¹⁴⁺[AsF₅(SO₃F)]^? is found to exhibit high electrical conductivities in the basal plane.     

Poly(2-methoxyphenylene vinylene): Synthesis,electrical conductivity,and control of electronic properties

Poly(2-methoxyphenylene vinylene) has been synthesized by a four step reaction sequence beginning with the bromination of 2,5-dimethylanisole and proceeding to the formation of an intermediate sulfonium salt precursor polymer. The infrared and UV-visible spectra of the PPV derivative asymmetrically substituted on the phenyl ring are presented. Films of poly(2-methoxyphenylene vinylene) can be doped with iodine to give a conductivity of 1 S cm^?1. Films doped with AsF₅ exhibited activated charge transport behavior with room temperature conductivities of about 100 S cm^?1.     

Über die Darstellung der Dichlormethylen-halogensulfenium-Salze Cl2CSCl+ AsF6− und Cl2CSBr+ AsF6− [1]

The Synthesis of the Dichloromethylene-halogenosulfenium Salts Cl₂CSCl⁺ AsF₆^? and Cl₂CSBr⁺ AsF₆^? The sulfenium salts Cl₂CSCl⁺ AsF₆^? and Cl₂CSBr⁺ AsF₆^? are synthesized by oxidative halogenation of thiophosgene, Cl₂CS with X₂/AsF₅ (X = Cl, Br) at 195 K and are characterized by vibrational as well as NMR spectroscopy.     

Crystalline phases of electrically conductive poly(p-phenylene vinylene)

Poly(p-phenylene vinylene) (PPV) undergoes a first-order crystal-crystal phase transition when chemically doped with AsF₅, SbF₅, or H₂SO₄ or electrochemically oxidized with ClO^-₄ as the counterion. These structures have been observed using wide-angle x-ray diffraction. Doping with these agents does not disrupt the original orientation of the PPV crystallites. The crystalline phases obtained with all dopants employed here are similar in character, indicating a closely related family of electrically conductive structures having orthorhombic symmetry. An electrically conductive phase consisting of layers of polymer chains separated by a layer of the chemical dopant is proposed.     

Autooxidation and stabilization of undoped and doped polyacetylenes

Autooxidations of polyacetylene have been measured by volumetric, infrared, and isothermal TGA weight uptake techniques. The rate of oxygen uptake is 9 × 10^?7 mol (g s)^?1 at 70°C and the overall activation energy is about 10 kcal mol^?1. The maximum oxygen uptake corresponds to [CHO_0.25]_x. Above 100°C there is oxidative degradation of the polymer completely to volatile products. The rate constant for the oxidative degradations at 160°C is ca. 1.5 × 10^?5s. Autooxidation does not result in formation of significant amounts of crosslinking because there are not carbonaceous residues. TGA under a stream of oxygen showed the degradation to be complete at ca. 420°C leaving no residues. Autooxidation is much slower if the polymer is compressed to higher bulk density. Radical scavengers such as BHT and 4010 are effective stabilizers. Hydroperoxide decomposers, such as DSTDP, does not help in the stabilization; spin trap BPN accelerates the oxidation of polyacetylene. Iodine and AsF₅ doped polyacetylenes are oxidatively much more stable than undoped polymers. Perchlorate doped polyacetylenes begin to lose weight as soon as heated above room temperature. Even in an inert atmosphere the polymers often undergo explosive decomposition.     

SN-conducting polymers with heterocyclic spacer groups

Polymer-containing alternating sulfur nitrogen moieties separated by heterocyclic groups have been synthesized and characterized. The polymers have undoped conductivities of 10^?6 to 10^?9 (Ω cm)^?1; the intrinsic carriers are negatively charged as shown by thermopower coefficient of ?1.4 × 10³ to ?1.9 × 10³ μV K^?1. The polymers are degraded by AsF₅ and cannot be doped by iodine. Exposure to bromine resulted in reversible p-doping of the SN polymers to the thermopower values of +400 to +820 μV K^?1 and conductivities of 0.01 to 0.002 (Ω cm)^?1. Removal of dopant by evacuation returns most of the properties of the polymers to the undoped states. Magnetic properties of the materials have been studied.     

Dithiadiazolium salts as initiators for the cationic ring-opening polymerization of tetrahydrofuran

Mono-, bis- and tris-(1,3,2,4-dithiadiazolium) salts [R-(CNSNS ⁺)_n]_n+[AsF^-₆]_n (R = aryl, n = 1, 2, 3) were found to initiate the cationic ring-opening polymerization of tetrahydrofuran (THF) at room temperature to give clear gels from which the pure polymer was precipitated. 1,3,2,4-Dithiadiazolium cations associated with the hard [AsF₆]^- anion thus constitute a new class of cationic polymerization initiators. The poly(THF) formed by initiation with 1,3,2,4-dithiadiazolium cation was characterized by gel permeation chromatography, infrared spectrophotometry, and ¹³C-NMR spectroscopy. Number-average molecular weights of 198 700 g mol^-1 (polydispersity 1.96) and 190 000 g mol^-1 (polydispersity 1.61) were obtained using [PhCNSNS ] [AsF₆] and [C₆H₃-1,3,5-(CNSNS )₃][AsF₆]₃, respectively, as initiators. The use of multifunctional dithiadiazolium salts as initiators suggests that they may be useful in the preparation of starburst and dendritic polymers. © 1992 John Wiley & Sons, Inc.     

Zur Chemie des Xenons, 3. Mitt. Xenon(II)-fluorid-pentafluoro-orthotellurat als Fluoridionen-Donor: [XeOTeF5]+[AsF6]−

Interactions of Xenon(II)-fluoride-pentafluoro-orthotellurate, FXeOTeF₅, with the fluoride ion acceptors BF₃, GeF₄, PF₅, VF₅, and AsF₅ have been studied. An adduct with a molar ratio of 1∶1 is formed with AsF₅. The Laser-Raman spectrum proves it to be the salt [XeOTeF₅]+[AsF₆]^?. The pale yellow solid (M.P. 160°C) can be sublimed in vacuo at room temperature and is thermally stable up to at least 200°C in prefluorinated Monel-vessels. The fluoride ion donor strengths of FXeOTeF₅ and XeF₂ are comparable. XeF₂ however is capable of displacing FXeOTeF₅ out of [XeOTeF₅]+[AsF₆]^?. Therefore the following order of the relative fluoride ion donor strength of Xenon compounds can be given: $$XeF_4 \ll FXeOTeF_5< XeF_2< XeF_6 $$      

Dihalogen(pentafluorphenyl)sulfonium(IV)-hexafluoroarsenat C6F5SX2+AsF6− (X = Cl,Br) und Kristallstruktur von Di(pentafluorphenyl)sulfan (C6F5)2S

Dihalogen(Pentafluorophenyl)sulfonium(IV) Hexafluoroarsenate C₆F₅SX₂⁺AsF₆^? (X = Cl, Br) and Crystal Structure of Di(pentafluorophenyl)sulfane (C₆F₅)₂S The preparation and spectroscopic characterisation of the halogensulfonium salts C₆F₅SCl₂⁺AsF₆^? and C₆F₅SBr₂⁺AsF₆^? is reported. The new salts are much more stable than their trifluoromethyl derivatives. In addition the crystal structure of (C₆F₅)₂S is reported. Space group P4₃2₁2, Z = 4, 478 unique observed diffractometer data, R_int. = 0.07, lattice constants: a = 569.0(5) pm, c = 3785.8(22) pm, V = 1225 times; 10^?30 m³.