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1994
Metal-catalyzed coupling reactions in the synthesis of new conducting polymers.
Journal of Macromolecular Science, Pure and Applied Chemistry,vol.A31,p.1893–1902,1994A review with 22 refs. primarily on the authors’ work, discussing the use of transition metal-catalyzed coupling reactions in the synthesis of conducting thiophene-based and ladder polymers. [on SciFinder(R)] -
1994
Synthesis of Diacetylene Macrocycles Derived from 1,2-Diethynyl Benzene Derivatives: Structure and Reactivity of the Strained Cyclic Dimer.
Journal of Organic Chemistry,vol.59,p.1294–1301,1994Diacetylene macrocycles I (R = H, C4H9, C6H13, C10H21, C12H25, OC10H21; n= 1-3) were prepd. from the oxidative coupling of 1,2-diethynylbenzene derivs. I can be produced in useful quantities and are of interest as precursors to novel conjugated org. polymers. The reported results indicate that when the R groups are large the dimeric macrocycle (n = 1) can be prepd. in as high as 74% yield from the corresponding 1,2-diethynylbenzene in a 1-step procedure. An alternate multistep procedure was found to produce the tetrameric macrocycle I (n = -
1994
Conducting Pseudopolyrotaxanes: A Chemoresistive Response via Molecular Recognition.
Journal of the American Chemical Society,vol.116,p.9347–9348,1994The synthesis and electrochem. properties of the macrocycle-contg. polythiophene I are described. I forms a self-assembled pseudopolyrotaxane in the presence of $π$-deficient guests such as paraquat and 1,1′-bis(4-fluorobenzyl)-2,2′-bipyridyl. Pseudopolyrotaxane formation results in both an anodic shift in the oxidn. potential of the polymer as well as a significant decrease in its max. cond. (ca. 52% at 45 mM guest). This effect is completely reversible. For comparative purposes, a nonmacrocyclic model polymer was also studied and showed no significant change in max. cond. under identical conditions. The results clearly demonstrate that the chemoresistive response is a direct result of host-guest complexation. Such a chemoresistor approach is an attractive route into conducting polymer-based sensors wherein resistivity is attenuated by perturbations arising from host-guest interactions. [on SciFinder(R)] -
1994
Fused Polycyclic Aromatics via Electrophile-Induced Cyclization Reactions: Application to the Synthesis of Graphite Ribbons.
Journal of the American Chemical Society,vol.116,p.7895–7896,1994The development of a novel reaction for the synthesis of fused polycyclic benzenoid arom. hydrocarbons is reported. In the reaction’s simplest form, the attack of an electrophile on a substituted 2-(ethynyl)biphenyl would provide a substituted phenanthrene. To demonstrate the utility of the reaction the authors have synthesized in all carbon conjugated ladder polymer or graphite ribbon. En route to this target, model systems of the general structure 2′,5′-di(4-alkoxyphenylethynyl)-p-terphenyl were synthesized for characterization and optimization purposes. Cyclization to give substituted dibenz[a,h]anthracenes consistently proceeded in very high to quant. yield. The graphite ribbon polymer, a yellow-orange material, was synthesized by TFA treatment of the colorless poly[2,5-di(dodecyl)-2′,5′-di(4-(dodecyloxy)phenylethynyl)-p-biphenylene]. All compds. were characterized using 1H and 13C NMR, IR, UV-VIS and luminescence spectroscopy, high resoln. mass spectrometry, and elemental anal. [on SciFinder(R)] -
1994
Octahedral Metallomesogens: Liquid Crystallinity in Low Aspect Ratio Materials.
Journal of the American Chemical Society,vol.116,p.761–762,1994A new class of metallomesogens contg. $beta$-diketone derivs. with octahedral structures are described. The observation of liq. crystallinity in these materials was unexpected as a result of their low aspect ratios. To better understand these materials, the dependence of the mesomorphism on the no. of sidechains (N) and metal center was investigated. [on SciFinder(R)] -
1993
Designing conducting polymer-based sensors: selective ionochromic response in crown ether-containing polythiophenes.
Journal of the American Chemical Society,vol.115,p.12214–12215,1993The synthesis and ionochromic properties of polythiophenes functionalized with macrocyclic crown ether groups are described. These polymers are designed to be sensitive to alkali metal ions and chelation of the ion induces a twisting of the polymer’s backbone from planarity. These conformational changes are of interest since they should ultimately lead to cond. changes which can be used to construct new sensory devices. Twisting of the polymer’s backbone from planarity will also reduce the effective conjugation lengths, and polymers in which two of the crown ether oxygens are directly attached to the thiophene rings (I; X = O; x = 1, 2) exhibit large ionochromic responses which are easily detected visually. Only small responses are detectable for I (X = CH2O; x = 1, 2) which exhibit smaller assocn. consts. The large ionochromic responses are mainly the result of twisting at a no. of sites along the polymer chain; however electrostatic factors may also play a role. The ion selectivity is similar to that obsd. for simpler crown ether macrocycles and the smaller rings give the largest response for Na+ ions and the larger rings are most sensitive to K+. [on SciFinder(R)] -
1993
Controlling intermolecular associations with molecular superstructure: polar discotic linear chain phases.
Journal of the American Chemical Society,vol.115,p.8879–8880,1993This report demonstrates the interrelationships between liq. cryst. superstructure and the strength of linear chains (–V-O…V = O–)n, exhibited by vanadyl-based discotic liq. crystals. The effect of mol. superstructure was detd. by studying related compds. which due to their shapes display liq. crystal phases with specific intermol. correlations between nearest neighbors. In superstructures which do not exhibit steric interactions, the strength of assocn. in the linear chain structure was controlled by the groups bridging between the Schiff-base nitrogens. Compds. with bridging group a are monomeric, compds. with bridging group b are the strongest linear chains, and compds. with bridging group c are somewhat weaker linear chains. The relative strength of the linear chains was detd. by monitoring the V=O stretching frequency and is sensitive to mesophase superstructures which produced specific steric repulsions and/or orientational preferences. Linear chain structures also influence the nature of the mesophases and produced novel polar mesophases with high intercolumnar order yet liq.-like order within the columns. This increased intercolumnar order is ascribed to an increase in the rigidity of the linear chain which holds the mesogens in a tighter registry. [on SciFinder(R)] -
1993
Rigid bowlic liquid crystals based on tungsten-oxo calix[4]arenes: host-guest effects and head-to-tail organization.
Journal of the American Chemical Society,vol.115,p.1159–1160,1993New bowl-shaped (bowlic) liq. crystals with rigid W-oxo calix[4]arene (I; Z = N:NC6H2-3,4-(O(CH2)12H)2-5-R where R = H, O(CH2)12H) based mesogens 1a and 1b, resp., are reported. These compds. exhibit discotic columnar phases which are stable over approx. a 200° temp. range. The uncomplexed tetra-phenol ligand displays only a transient mesophase on the first heating, and the conformational rigidity provided through W-oxo complexation is necessary for well behaved mesomorphism. For 1a, the clearing point is at 320° which leads to decompn. in the isotropic phase. The addn. of 4 more sidechains to form 1b results in a lower clearing point (267°) and a stable isotropic phase. Polarized optical microscopy and DSC indicate that 1b displays a bowlic Dho phase (also known as PA or Bho), whereas studies on 1a’s mesophase were less definitive. Both 1a and 1b exhibit a pronounced tendency to bind Lewis base guests in their cavities, and DMF forms very strong complexes which were spectroscopically characterized. The DMF guest produces large effects on the phase behavior by suppressing mesomorphism and lowering the isotropic points of 1a and 1b to 115 and 84°, resp. This extreme sensitivity of the DMF guest suggests that the mols. organize in head-to-tail structures in the mesophases and that the W-oxo group of one mol. protrudes into the cavity of the neighboring mol. [on SciFinder(R)] -
1993
The development of polar discotic metallomesogens: vanadyl 1,3-diketone complexes.
Liquid Crystals,vol.14,p.1421–1429,1993The dependence of mesomorphism of 1,3-diketonate V-oxo (vanadyl) complexes on the no. of side chains was studied. These complexes have a large dipole normal to the disk plane and are under study in an effort to generate discotic phases with polar order. Relatively complex phase behavior is obsd. when the vanadyl 1,3-diketonate complexes are appended with 4 chains. These complexities are most likely related to the order/disorder assocd. chains were prepd. by replacement of 2 of the Ph groups with Me or trifluoromethyl groups, and these complexes displayed only crystal phases. Complexes with 2 trialkyloxy phenyls and 2 dialkyloxy phenyls were synthesized and found to display a very stable Dhd phase. The presence of addnl. alkyloxy groups was found also to promote a linear chain structure, (i.e.-V=O–V=O–), in the crystal phase. [on SciFinder(R)] -
1992
Discotic bimetallomesogens: building blocks for the formation of new columnar arrangements of transition metals.
Journal of the American Chemical Society,vol.114,p.7948–7949,1992New discotic bimetallic liq. crystals, I, II, (r = (CH2)n -
1992
Tuning the intermolecular dative interactions in vanadium-oxo linear chain compounds: formation of a new type of liquid crystalline polymer.
Journal of the American Chemical Society,vol.114,p.1887–1889,1992A series of liq. cryst. vanadyl 5-alkoxy-N,N’-disalicylidenediamine complexes are reported with ethylene (salen), propylene (salpn), and 2,2-dimethylpropylene (Me2salph) groups connecting the Schiff-base nitrogens. These compds. are under investigation as potential ferroelec. and second order nonlinear optical materials. The n(salen)VOs (n = no. of carbons in the alkoxy chain) are monomeric in the solid state and display highly disordered smectic A and smectic C structures as detd. by optical textures and x-ray powder diffraction. In the case of the (n(salpn)VO)s, the compds. exhibit a linear chain structure (e.g. (-V = O -V = O)n) in the solid state. For n(salpn)VO, the linear chain structure is too restrictive to allow a liq. cryst. state and these compds. melt at ∼300° with decompn. The n(Me2salpn)VOs also exhibit a linear chain structure as detd. by an x-ray crystal structure and IR spectroscopy, but steric repulsions weaken the linear chain structure sufficiently to allow melting into the liq. cryst. state. Variable temp. IR shows that the fluid liq. cryst. phase of these compds. exhibits a linear chain structure and becomes monomeric at temps. above their clearing point. X-ray powder diffraction and optical texture anal. show the thermotropic phases of the n(Me2salpn)VO complexes to display smectic structures. These results demonstrate that the n(Me2salpn)VO complexes comprise a new type of low-viscosity liq. cryst. polymer which assembles into a unidirectional linear chain structure. [on SciFinder(R)] -
1990
Polyquinone bisketals: precursors to new conductive polymers.
New Polymeric Materials,vol.2,p.1–10,1990Polymers contg. quinone bisketal groups were synthesized by ring-opening metathesis polymn. of I and II. These polymers were investigated as sol. precursors to insol. conductive polymers. Hydrolysis produced the corresponding quinones which underwent tautomerization of hydroquinones. This process resulted in extended conjugation and elec. conduction. Thermolysis of quinone bisketals of 200° resulted in MeOH elimination to give red materials. Preliminary cond. studies of the doped hydrolyzed and thermolyzed polymers revealed conds. in the semiconductive region. [on SciFinder(R)] -
1989
Electron spin resonance and optical spectroscopic studies of the conducting polymer precursor: poly(3,4-diisopropylidenecyclobutene).
Journal of Polymer Science, Part B: Polymer Physics,vol.27,p.443–463,1989The doping process in a recently developed conducting polymer precursor, poly(3,4-diisopropylidenecyclobutene) (PDPCB) was studied by ESR 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 a Gaussian line shape. Except in the case of doping with I2, resolved hyperfine structures from cation radicals were obsd. 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. [on SciFinder(R)] -
1989
New morphologies of polyacetylene from the precursor polymer polybenzvalene.
Journal of the American Chemical Society,vol.111,p.4413–4422,1989The synthesis and properties of the polybenzvalene and its conversion to polyacetylene are presented. This conversion is performed by treating polybenzvalene with Lewis acid catalysts. The highest quality material was obtained from the isomerization with HgCl2. The polyacetylene produced by this precursor route has a morphol. that is considerably more amorphous than other forms of polyacetylene that have been previously reported. Orientation of the precursor polymer by stretching induced crystallinity and chain alignment as detd. by x-ray diffraction. The unoriented polyacetylenes exhibited a cond. of 1 $Ømega$-1 cm-1 with I doping. Materials stretched to elongations of l/l0 = 2.3 and l/l0 = 6 displayed conductivities of 13 $Ømega$-1 cm-1 and 49 $Ømega$-1 cm-1, resp. Block copolymers of polynorbornene and polybenzvalene were produced. [on SciFinder(R)] -
1989
The synthesis of low crystallinity polyacetylene from the precursor polymer polybenzvalene.
Synthetic Metals,vol.28,p.D57–D62,1989The synthesis and properties of the conductive polymer precursor polybenzvalene (I) and its conversion to polyacetylene (II) are presented. I was synthesized by ring-opening metathesis polymn. of benzvalene with non-Lewis acidic tungsten alkylidene catalysts. Treatment of I with solns. of HgCl2, HgBr2, ZnI2, and AgBF4 resulted in a C-C bond rearrangement and produced II. The II films produced with HgCl2 displayed the highest conductivities and the best mech. properties. The II produced was of low crystallinity and upon treatment with iodine exhibited conductivities of 1 S/cm. Oriented II was produced by stretching I and converting it to II. With iodine doping, the oriented II (6-fold stretching) displayed a cond. of 49 S/cm. [on SciFinder(R)] -
1988
Strained rings as a source of unsaturation: polybenzvalene, a new soluble polyacetylene precursor.
Journal of the American Chemical Society,vol.110,p.2973–2974,1988Polyacetylene (I) was prepd. by ring-opening metathesis polymn. of benzvalene in the presence of non-Lewis acidic W alkylidene catalysts to give polybenzvalene, followed by isomerization in the presence of HgCl2. I had low crystallinity and elec. cond. 1 s/cm upon doping with iodine. [on SciFinder(R)] -
1987
Synthesis and properties of a novel cross-conjugated conductive polymer precursor: poly(3,4-diisopropylidenecyclobutene).
Journal of the American Chemical Society,vol.109,p.894–896,1987The polymer [104584-99-8] which is synthesized by ring opening olefin-metathesis polymn. of 3,4-diisopropylidenecyclobutene, is sol., transparent, and forms conductive materials (up to 200 $Ømega$-1cm-1) when doped with iodine. The characterization of the material by CP-MAS 13C NMR, ESR, and UV-vis spectroscopy is reported. The electronic structure and the possible mechanisms of conduction are discussed. [on SciFinder(R)] -
1986
Synthesis and properties of a novel conductive polymer: poly-3,4-diisopropylidenecyclobutene.
Polymeric Materials Science and Engineering,vol.55,p.323–327,1986Ring-opening metathetical polymn. of 3,4-diisopropylidenecyclobutene in the presence of titanocene methylidene [83876-46-4] catalysts yielded elec. conducting polymer which was sol. in C6H6 and CHCl3 in its undoped form and exhibited high elec. cond. in its doped form. Thermoelec. power measurements on I2-doped films showed that the charge carriers were pos. charged. [on SciFinder(R)] -
1985
Temperature dependence of the bulk modulus of solids in the magnesium oxide-aluminum oxide (AlO1.5)silicon dioxide system.
Journal of Physical Chemistry,vol.89,p.2682–2687,1985The relation between the bulk modulus (K) and the coeff. of thermal expansion implied by the Murnaghan logarithmic equation of state are explicitly derived. Values for dK/dT can be obtained from thermal expansion measurements. These values are consistent with, and generally more accurate than, direct compressibility measurements. The equations are confirmed by calcns. for MgO AlO1.5, MgAl2O4, and MgSiO3. The temp. dependence of the bulk modulus can be predicted for solids for which there are no high-temp. compressibility measurements. [on SciFinder(R)] -
1985
Native American food and medicinal plants. Part 4. Coumarins from Musineon divaricatum.
Phytochemistry (Elsevier),vol.24,p.805–813,1985A chem. investigation of M. divaricatum has resulted in the isolation of 19 coumarins, 5 of which are novel compds. and 18 are khellactone derivs. The coumarins were isolated from the crude exts. by a combination of adsorption chromatog., gel permeation and HPLC; the more successful HPLC sepns. utilized a nitrile bonded phase column. The structures were detd. by 1H NMR and mass spectral studies and by comparisons with literature data. The relative configuration for the entire series was secured from 1H NMR data, while the abs. configuration could be assigned with any certainty only in the cases of 2 of the compds. [on SciFinder(R)]
