The electrooxidation of , -coupled thiophene oligomers with terminal a-(CH3)3Si groups ( -TMS) and i8-CH3 groups was studied in methylene chloride at room temperature. The oligomers with four, five, six, seven, and eight thiophene rings undergo two stepwise oxidations to produce the radical cation and dication, respectively, as confirmed by the ESR spectra. The redox waves are chemically reversible and separated by 180 mV for the hexamer, heptamer, and octamer, suggesting that the same electrochemical behavior should be observed with the next higher oligomers or with the «--conjugated segments of polythiophene. Thus it is proposed that the broad, featureless voltammogram observed with films of polythiophene is not an inherent property of the polymer segments but may reflect complications from the solid-state nature of the film. Radical cations and dications of some of the oligomers were succesively generated with stoichiometric amounts of FeCl3 in CH2C12 and characterized by vis-near-IR. The energies of the sharp absorption bands in the visible and near-infrared of the neutral and oxidized oligomers are found to scale linearly with the inverse of the oligomer size. Extrapolation of the absorption energy to infinite chain length leads to excellent agreement with the values for neutral poly(methylthiophene), but significant differences are observed with those for the oxidized forms. The implications of this difference on the delocalization length of the polymer radical cation and dication are discussed. Some of the electronic transition assigments for the oxidized thiophene oligomers which appear i:

No abstract

The chemical polymerization of aniline and sodium diphenylamine-4-sulfonate produces poly-(aniline-co-JV-(4-sulfophenyl)aniline) (PAPSA), copolymers which have high molecular weights and are recovered as a dark green powder. The PAPSA copolymers have a monomer composition like the composition in the reaction mixture. They have conductivities which range between the conductivities of the poly(JV-(4-sulfophenyl)aniline) homopolymer (0.0035 S/cm) and polyaniline (5.2 S/cm). While the homopolymer poly (JV-(4-sulfophenyl)aniline) is ID3 times less conductive than polyaniline, it is still 10* times more conductive than other polyaniline polymers with sulfonate groups. The conductivity and the ESR signal both decrease with the phenylsulfonic acid content in the copolymer. The PAPSA copolymers are soluble in aqueous NH4OH but not in aqueous HC1 solutions. The color of the resulting solutions varies with the copolymer monomer composition. Films of the PAPSA copolymers on an electrode show two reversible redox reactions for the aniline units and one for the pendant phenylsulfonic acid groups between 0.2 and 0.8 V vs Ag/AgCl reference electrode, when immersed in aqueous acid solutions. During the redox process, the PAPSA films exhibit reversible color changes from pale yellow to green to dark blue.

Zeolite cations lying on the intracrystalline pore surface of the Linde X and Y molecular sieves are linked to only three oxide ions and consequently are not well shielded electrically. They therefore create very large electrostatic fields, extending into the main zeolitic cavities, causing carboniogenic catalytic activity. This activity follows in magnitude the changes in the field, and is independent of the presenceof OH groups ; nochange in activity is observedeven after 99 %of OH protons present after ordinary activation in vacuum at 500°C are removed. Bivalent cations exposed on the surface of the main intracrystalline cavities adsorb carbon monoxide with infra-red frequencies specific to cation ; the adsorption follows Langmuir isotherms, suggesting that a single carbon monoxide molecule can be independently attached to every surface cation. Certain transitionmetal zeolites adsorb carbon monoxide much more tenaciously than alkaline earth cations, indicating a highly significant difference in their ability to form co-ordination bonds.Univalent nickel ions can be prepared both on the intracrystalline surface and at fully coordinated positions by heating NiIIY with alkali metal vapour. The surface NiI ions are chemically very reactive but thermally unstable ; those at fully co-ordinated positions are thermally stable even at 400"C, and are inert to H2, NH3, and CO although they react with oxygen to form 0;.The alkali-metal X and Y zeolites react with alkali metal vapour to form coloured products of non-stoichiometric compositions containing the paramagnetic centres Na 2 + and Naa +. The Na 2 + centres are stable up to 500°C and they react reversibly with gases ; with oxygen they form 0 , radicals. U.S.A. STRUCTURAL FRAMEWORKDespite differences in origin, composition, and chemical and physical properties, the mineral faujasite and the synthetic zeolites of interest in this paper-Linde Molecular Sieve Type X and Linde Molecular Sieve Type Y-are related in crystal structure to the extent that the basic framework is the same for all three. Their structures have been described in their general aspects 1-4 but are all too little known in their detail. Because the basic framework of these materials is primarily involved in the variations in the properties that are here our principal concern, namely, the net electric fields, valences, and electron affinities of the zeolitic (exchangeable) cations, its relevant aspects will now be reviewed. We must emphasize, however, that the only anhydrous material that has been studied by X-ray diffraction is single-crystal faujasite that had been repeatedly exchanged with calcium ion and then dehydrated. We of course cannot be sure of the extent to which we are justified in applying the resulting information to the synthetic materials. Any speculation on fine details of the structures, for example on the ordering of A1 relative to Si, immediately leads one to recognize many probable differences among faujasite, X and Y. As a probable result of the chemical as well as structural dif...

N,N-Bis(4-phenylsulfonate)-l,4,5,8-naphthalenetetracarboxylic diimide was prepared as the disodium and bis(tetrabutylammonium) salts. It was reduced electrochemically in DMF or water and by dithionite in water to a form an anion radical. On the basis of visible, NIR, IR, and ESR data, the anion radical is shown to be monomeric in DMF, dimeric in water, and aggregated in aqueous NaCl. The aggregates contain -stacks that are spectroscopically similar to the stacks found in a solid film of the anion radical.The field of organic metals is dominated by two types of molecular structures: linearly conjugated -systems such as polyacetylene, and charge-transfer complexes that form stacks of -systems in the solid state.1 In one case electrons move rapidly along a partially oxidized or reduced molecular chain. In the other, electrons move along a partially oxidized or reduced stack of molecules. In either case the electrical, optical, and magnetic properties are a complex function of the solid-state structure, and efforts have been made to prepare and study model compounds in solution. Examples of linear -conjugated systems are oligothiophenes,2 an oligoaniline,3 and oligoarylenes,4 which were oxidized in solution or in zeolites to permit investigation of the intramolecular, single-chain spectroscopic properties of the cation radicals and dications. More pertinent to the present study, which concerns -stacks in solution, is a long-chain-aryl derivatized cation radical that forms a diskotic liquid-crystal phase.5 In this case there is spectral evidence for -interactions between cation radicals, but solid salts have low conductivity and there is no evidence for extensive delocalization along the stack.In general it seems that ion radicals do not organize into delocalized -stacks in dilute solution.It is well-known, however, that ion radicals have a propensity to form -dimers in solution. The examples that have received considerable attention include Wurster's Blue (the cation radical of tetramethyl-1,4-diaminobenzene, l),6 viologen cation radicals (e.g., 2),7 and TCNQ anion radical (3).8 9In each of these cases a -complex formed at relatively high concentration in solution, which CH3X+',CH3 NC^CN 1 3

The microwave spectra of six isotopic species of dimethyl ether were investigated from 8–48 Gc. From the changes in moments of inertia with C13 and O18 substitutions the CO distance and <COC were found to be 1.410±0.003 Å and 111°43′±20′, respectively. The conformation of the methyl groups was determined from the (CH2D) (CH3)O species. Dimethyl ether has C2v symmetry and the methyl groups are staggered with respect to the opposite CO bonds. The data from deuterium substitutions could only be satisfactorily fit by a structure containing asymmetric methyl groups. The two CH distances in this structure differ by 0.009 Å, the < HCH by 49′, and the angle between the CO internuclear line and a perpendicular to its respective hydrogen plane is 2°31′±40′. If an average CH distance of 1.0956 Å is assumed the average <HCH is 109°29′. The structure of the asymmetric methyl groups is shown to be consistent with s and p hybridization of the carbon orbitals. In this scheme the carbons form ``bent bonds'' with the oxygen. From the Stark effect the dipole moment of dimethyl ether was determined to be 1.31±0.01×10—18 esu.

Thermal degradation of commercial perfluoropolyethere (Fomblin Z and Y, Krytox, and Demnum) and PFPEO (perfluoropoly(ethy1ene oxide)) in the presence of Lewis acids (metal oxides and halides) was examined. It is shown that the degradation is dominated by the intramolecular disproportionation process of the following scheme. (q+) ((q+)+W R-CF? -0-CF, 0 . &O-R I [Lewisacid] 3.

It was found that perfluoropolyethers (PFPE) with carboxylic acid end groups, PFPE-COOH, and their sodium salts, PFPE-COONa, afford an anhydrous fluid medium in which the direct pair-wise interaction of these end groups may be examined. An IR study (of the carbonyl band) of these materials revealed not only the dimerization of acid units, but also the formation of salt dimers, (salt)2, and mixed dimers, (acid)(salt). The carbonyl spectra of PFPE-acid/salt mixtures exhibit temperature-dependent broadening, shift, and, in some cases, coalescence of the bands which are attributed to the pseudocoalescence phenomenon stemming from the presence of relatively low energy cation exchange passages among the three possible dimers. Examination of the corresponding CH3COOH/CH3COONa system by ab initio calculations (6-31G) yielded the heat of dimerization of ∼20, ∼50, and ∼35 kcal/mol for the acid−acid, the salt−salt, and the acid−salt dimers, respectively. The calculated dimer structures are shown and discussed. The calculations also yielded the carbonyl stretching frequencies in good accord, and in support of the analyses/postulates made for the PFPE-acid/salt system.