Electrical conductive AsF5-complexes of poly (2, 5-Thiophenediyl)

Abstract

Poly (2,5-thiophenediyl) (2) reacts with AsF₅ in a gas phase reaction yielding Poly (2,5-thiophenediyl) complexes with cationic centers and AsF₆ counterions (1). Polymeric complexes of the same structure are formed by gas phase reactions of AsF₅ with thiophene (3) and 2,2-bithienyl (4) via an oxidative poly-condenzation reaction. Treatment of the polymeric complexes 1 with aqueous ammonia yields 2. These complexes are stable materials due to the strong electron donating property of the thiophene system. They may be handled without any special precaution. They have electrical conductivities as high as 0.02 Ω^?1 cm^?1 (activation energy: E = 0.04eV). A possible mechanism for the formation of the polymeric complexes 1 is proposed according to the KOVACIC polycondenzation reaction of aromatic hydrocarbons.     

Microstructure of Polyphenylacetylene and Other Acetylenic Polymers

¹H- and ¹³C-NMR studies carried out on poly(phenylacetylene)s and poly(pentadeutero-phenylacetylene)s prepared with Ziegler and metathesis type catalysts, revealed two different mechanisms which control the microstructure of acetylenic polymers.

For the Ziegler-type catalysts, thermal induced reactions (intramolecular cyclization, aromatization, chain scission and cis-trans isomerization) of the cis-double bonds (isomerization after double bond formation) are responsible for the polymer microstructure. (For a review see: Progr. Polym. Sci., 8, 133 (1982).) Both isomerization "after” double bond formation as well as isomerization “before^” double bond formation are responsible for the microstructure of polymers obtained with metathesis type catalysts. In both cases, the polymer molecular weight is controlled by the intramolecular cyclization of the cis-polymer chain end. Under reaction conditions where isomerization occurs mainly "before double bond formation, “pure” trans polymers having very high molecular weight are obtained (Polym. Prepr., 24 (1), 239 (1983); Polym. Bull., 9, 548 (1983)).

The microstructure of several other acetylenic polymers will be commented on in relation with the polymerization mechanism and with the microstructure of (CH)_x.     

CNDO/2-FPP Polarizabilities

Polarization functions have been added to the CNDO/2 basis set to reproduce a minimal set of experimental polarizability tensors for 13 model molecules containing H, C, N, O, F, P, S, Cl, Se, and Br without affecting occupied molecular orbital energies or atom-in-molecule charges. The resulting CNDO/2-FPP program yields excellent molecular and atom-in-molecule polarizability tensors for almost any molecule containing these elements.     

Thermal Isomerization of Polyacetylene Films

Isomerization of the as-formed (-78°C) cis-polyacetylene to the trans isomer is relevant to the electronic structure, the crystal structure and the electrical properties of this prototypical conductive polymer. We have studied the process using Fourier transform infrared (FTIR) and 13_C magic angle nuclear magnetic resonance (NMR) spectroscopies at temperatures between 80 and 110°C. The observed kinetics will be discussed in terms of three basic processes: a second order process which randomly converts cis-cis-cis (CCC) sequences to trans-cis-trans (TCT) sequences via a pair of biradicals, a fourth order process that converts CTCC sequences to TCTT sequences via four biradicals, and two fourth order processes which allow sequential migration along the chain. The correlation of observed electron spin resonance and x-ray results, among others, with these mechanisms will be shown.     

Thermal Expansion in TMTSF-Dmtcnq & (TMTSF)2PF6

We have measured the anisotropic thermal expansion of TMTSF-DMTCNQ and (TMTSF)₂PF₆ in the temperature range 10-300 K using an X-ray diffraction technique with a relative accuracy of 3 parts in 10⁴. Between 10 K and 300 K we find expansion in the a*, b* and c* directions to be respectively 2.5%, 0.2% and 1.7% for TMTSF-DMTCNQ and 3.7%, 1.6% and 1.3% for (TMTSF)₂PF₆     

Frequency Dependent Conductivity of Polyacetylene

We report on an extensive study of the frequency and temperature dependent conductivity of largely cis- (CH)_x trans- (CH)_x, and NH₃ compensated and iodine doped materials. The results reveal a strongly temperature (T) dependent dc conductivity and weakly T-dependent ac conductivity for largely cis- (CH)_x and for NH₃ compensated samples, similar to the behavior that is observed in many crystalline and amorphous semiconductors. The trans- (CH)_x and lightly iodine doped trans- (CH)_x have larger dc and ac conductivity and a strongly T-dependent ac conductivity. These latter results contrast with the usual expectations of variable range hopping and polaronic hopping, but are in good agreement with the predictions of Kivelson's Theory of charge transport via intersoliton electron hopping.     

Polyacetylene and Relativistic Field Theory Models

Connections between continuum, mean-field, adiabatic Peierls-fröhlich theory in the half-filled band limit and known field theory results are discussed. Particular attention is gi en to the Φ⁴ model and to the solvable N +2 Gross-Neveu model. The later is equivalent to the Peierls system at a static, semi- classical level. Based on this equivalence we note the prediction of both kink and polaron solitions in models of trans-(CH)_x. Polarons in cis-(CH) are compared with those in the trans isomer. Optical absorption from polarons is described, and general experimental consequences of polarons in (CH)_x and other conjugated polymers is discussed.     

Stimulation of the Electrohydrodynamic Instability in the Smectic a Phase

The electrooptical properties of 4-n-octyl-4′-cyano-biphenyl (8CB) in the smectic A phase were investigated. The electrohydrodynamic instability in the smectic A phase was observed, when a small quantity of any homologue (C₇, C₈, C₉) of 4-n-alkoxyben-zoic acid was adzed to this material. After the electrical field is turned off, the stable focal-conic texture is formed. A reverse focal-conic to homeotropic transition can be as well induced by means of an electric field.     

Electrical Characteristics of an Aluminum: Trans- (Ch)X Photodiode and Possible Defect-Related Current Transport

We have measured the electrical characteristics of photodiodes made by vacuum deposition of aluminum onto fibrous trans-(CH)_x. The trans-(CH)_x was not intentionally doped. The polymer surface was rough, so the Al overlayers were irregular. They were thick, to have low resistance, and had gaps that allowed some light into the junction. A simple equivalent circuit was fitted to the dark and illuminated current-voltage characteristics. The room temperature diode quality factor, n, was 1.9 for the junction in this circuit. This result is consistent with several mechanisms for the forward diode current, including that of charge carrier recombination at defects in the junction space charge region of the trans-(CH)_x.     

Investigation of the Homologous Series of 4-Propionyl–4′-n-Alkanoyloxyazobenzenes by X-Ray Diffraction

A study of the homologous series of liquid cristalline 4-propionyl-4′-n-alkanoyloxyazobenzenes was performed by x-ray diffraction. Two indipendent parame ters were used, namely the temperature and the paraffinic chain length, in order to obtain some structural in formation. In particular the molecular layer thickness was obtained as a function of the temperature for the different phases and different homologous. A linear de pendence of the molecular layer thickness as a function of chain length was found for the crystalline phase as it was previously observed for the smectic A phase. By comparison of the present data with those of the series 4-acetyl-4′-n-alkanoyloxyazobenzenes, a bilayer molecular organization similar to that of the smectic A phase appears as very probable also for the crystalline phase.     

Prediction of Leslie Coefficients for Rodlike Polymer Nematics

Doi's molecular theory for the dynamics of rod-like polymers in concentrated solutions is here extended to include the effect of a molecular field. The resulting expression for the stress tensor is then linearized so as to obtain the Leslie coefficients in the nematic phase. Each of these coefficients takes the form of a basic viscosity - dependent on rod concen tration and rotational diffusion constant - times a different function of the equilibrium order parameter. The predicted ordering of the three Miesowicz viscosi ties is in agreement with the experimental evidence.     

Some Novel Nematic Liquid Crystals of Negative Dielectric Anisotropy

A number of ether and ester derivatives of 1-(trans-4-n-alkylcyclohexyl)-2-(4-hydroxyphenyl)ethane bearing lateral substituents on the phenyl ring are reported. Several of the novel compounds exhibit enantiotropic nematic phases at room temperature. All of the liquid crystals described are of negative dielectric anisotropy (-0.5 -3.5). The effect of lateral substituents on the liquid crystal transition temperatures of these ethanes has been studied.     

The molecular structure of dibutylbis(2-pyridinethiolato-5-ethyl ester)tin(IV), [SnBu2(TNEE)2]

The crystal structure of [SnBu₂(TNEE)₂], (HTNEE=5-ethyl ester of 2-mercaptopyridine-5-carboxylic acid) has been determined by X-ray single crystal diffraction study. The crystal is triclinic, space groupP,a=10.042(1),b=18.421(2),c=7.979(1) Å, =98.7(1), =107.3(1), =87.7(1)^o,V=1393(1) ų, and Z=2 The tin center is coordinated to two butyl groups and to the nitrogen and the sulfur atoms of two ligand molecules in a very distorted trapezoidal bipyramid.     

The crystal structure of a novel product from the acid-catalyzed condensation of 1-benzylindole with acetone

The acid-catalyzed condensation of 1-benzylindole with acetone in the presence of N-phenylmaleimide gave a tetrahydrocarbazole, (4,5,10,10b-tetrahydro-5-methyl-2-phenyl-10-(phenylmethyl)pyrrolo[3,4-a]carbazole-1,3[2H, 3aH]-dione (1), as the major product and a novel spiro compound, 1,3,4,4-tetrahydro-1,1,3,3-tetramethyl-4,4-bis(phenylmethyl)-1,3(2H, 2H)-spiro[cyclopent[b]indole] (2), as the minor product. The structure of the spiro compound was determined by an X-ray crystallographic determination. The acid-catalyzed condensation of 1-benzylindole with acetone in the absence of N-phenylmaleimide gave a bisindole, (1,1-bis(phenylmethyl)-3,3-(1-methylethylidene)diindole (3), as the major product and the spiro-compound as the minor product.     

X-ray structures of new substituted 2-(pyrazol-1-yl)-2′-nitroacetanilides with pharmacological activity

The X-ray structures of four pharmacologically active lidocaine analogs, containing substituted pyrazole moieties as the basic residue and an o-nitrophenyl moiety as the hydrophobic residue, have been determined. They are 2-(pyrazol-1-yl)-2-nitroacetanilide (1), 2-(3,5-dimethyl-pyrazol-1-yl)-2-nitroacetanilide (2), 2-(3,5-dimethyl-4-iodo-pyrazol-1-yl)-2-nitroacetanilide (3), and 2-(3,5-dimethyl-4-nitro-pyrazol-1-yl)-2-nitroacetanilide (4). Crystal data are 1: space group Pn with a = 4.6944(1), b = 22.3890(3), c = 15.7481(2) Å, = 96.810(1)°, Z = 6; 2: P with a = 4.7277(2), b = 11.6878(5), c = 12.0355(6) Å, = 87.689(2), = 85.048(2), = 85.975(2)°, Z = 2; 3: I2/a with a = 24.108(5), b = 4.7321(9), c = 25.337(5) Å, = 96.09(3)°, Z = 8; 4: P2₁ with a = 5.7788(2), b = 8.9844(3), c = 14.0304(5) Å, = 101.611(1)°, Z = 2. Molecules of compound 1 adopt a unique, folded conformation stabilized by intramolecular hydrogen bonds and the crystal structure lacks significant intermolecular interactions. In contrast, molecules of 2–4 adopt common, extended conformations and their crystal structures are based on linear arrays of hydrogen bonded (N—H...O=C) molecules. Compound 3 displayed the highest local anesthetic activity while 2 was the most active in tests for anti-arrhythmic effects.     

Towards The Synthesis of Electroactive Block Copolymers Via Anionic-To-Ziecler-Natta Transformation Reactions

Styrene/acetylene diblork copolymers have been prepared by alkylating Ti(OBu)₄ with polystyryl lithium (Li/Ti = 3) in THF followed by exposure to acetylene. Homopolystyrene can be separated from the soluble, blue-violet diblock copolymer by extraction with 10% THF/acetone, the latter being soluble in THF. Infrared spectroscopy confirmed the presence of polystyrene and (CH)_x components. Gel permeation chromatography of copolymers in which the (CH)_x portion has been converted to poly(l,2-dibromoethylene unambiguously demonstrates that block copolymers have been synthesized. The yields of block copolymer based on the total weight of polystyryl Li used initially is estimated to be ca 5%.     

Mesomorphic Behavior of Some New Fluorene Compounds

Several new fluorene derivatives have been synthesized and their liquid crystalline polymorphic behavior examined. Specifically, 2-fluorenylmethylidene-4′-n-alkylanilines with different alkyl groups are compared with corresponding compounds wherein the alkyl groups have been replaced either by the alkoxy or other different groups. In addition, some of the 4-alkyl and alkoxybenzylidene-2-aminofluorenes have also been prepared for comparison. Many of these compounds show not only the nematic phase but also two smectic phases. The presence of a lateral substituent in analogous compounds decreases the nematic-isotropic transition by about 60[ddot]C.     

Molecular structure of 1-phenyl-1-dimethylamino-4,4-bis(trimethylsilyl)-2-aza-3λ3-phosphabutadiene-1,3

The crystal and molecular structure of 1-phenyl-1-dimethylamino-4,4-bis(trimethylsilyl)-2-aza-3³-phosphabutadiene-1,3, Me₂N(Ph)C=N—P=C(SiMe₃)₂ (1), has been determined. Crystal data: triclinic, P1¯, a = 8.975(4), b = 10.001(5), c = 12.440(6) Å, = 79.04(4), = 77.98(4), = 73.07(4)°, V = 1034.7 ų, Z = 2, and D _c = 1.08 g cm^–3. The main geometrical parameters of 1 as well as ab initio (HF/6-31+G**) calculations of the model systems show no clear evidence of high efficiency of the (C=N)— (P=C) conjugation.     

Synthesis and crystal structures of 4,4′-bipyridinium and 2,2′-bipyridinium pentachloro complexes containing the polynuclear anions [Bi2Cl10]4− and [Bi4Cl20]8−

The compounds 4,4-bipyridinium(2+) pentachloro-bismuthate(III) (1), [4,4-(C₁₀H₈N₂)BiCl₅] and 2,2-bipyridinium(2+) pentachloro-bismuthate(III) (2), [2,2-(C₁₀H₈N₂)Bi₂Cl₁₀] have been obtained by reacting bismuthate oxide and 4,4-bipyridine or 2,2-bipyridine in HCl acid medium. They have been characterized by single crystal X-ray analysis. (1) crystallizes in the triclinic space group with a = 9.776(2), b = 11.009(3),c = 8.346(1) Å, = 101.58(2), = 98.63(2), and = 112.86(2)°. (2) crystallizes in the monoclinic space group P2₁/c with a = 14.239(2), b = 14.226(2), c = 16.275(3) Å, and = 110.15(2)°. The crystal structure of (1) consists of 4,4-bipyridinium(2+) cations interacting through hydrogen bonding with [Bi₂Cl₁₀]^2– dimers giving rise to endless double chains, while that of (2) is formed by 2,2-bipyridinium(2+) cations and [Bi₄Cl₂₀]^8– tetramers extensively interacting through hydrogen bonding. The different polynuclearity of the anions seems related to the different directions along which each cation can form hydrogen bond interactions.     

ESR and Theoretical Studies of Bis-Benzene-1, 2-Diselenolate Nickel and Related Complexes

Abstract

ESR and theoretical studies of the transition metal complexes of [Co and Ni (Se₂C₆H₄)₂]^? (n-C₄H₉)₄N⁺ are reported and compared with closely related systems. Room temperature single crystal X-ray studies reveal the Nickel complex is orthorhombic. ESR studies of the polycrystalline powders of the Ni complex as a function of temperature from 108 K to room temperature show a series of spectral envelopes which can arise only from a paramagnetic site which possesses axial symmetry. At ca 160 K, there is an abrupt change in the value of the principal components of the anisotropic g-tensor of the Ni complex which is discussed. Low temperature ESR studies of polycrystalline samples of the ground state triplet Cobalt complex which is isomorphous with the Nickel complex reveal an orthorhombic g-tensor. From the field position of the half-field resonance, it is possible to calculate a mean separation, of the two electrons which make up the triplet state, of 4.3 (±0.5) A.