Herbert Naarmann

Structure and conductivity of poly(acetylene)

Abstract Poly(acetylene), (CH)x, synthesized under different polymerization conditions, was investigated by means of IR and 13C NMR spectroscopy, X-ray diffraction, and conductivity measurements. The molecular structure is strongly influenced by the polymerization temperature and the catalyst system. The polymerization temperature mainly governs the cis to trans ratio. In low temperature Shirakawa (CH)x the cis crystals consist cis-transoid chains, whereas in Luttinger (CH)x the cis crystals contain cis-transoid as well as trans-cisoid chain configurations. The catalyst systems affect the degree of distortion of the conjugated (CH)x chains by sp3 hybridized carbon atoms. In Shirakawa (CH)x the sp3 content is very low. (CH)x prepared after the procedures of Luttinger and Reppe is characterized by an increasing content of sp3 hybridized carbon atoms. Hatano (CH)x exhibits the highest sp3 content of all samples under investigation. A linear relationship exists between the relative sp3 content and the X-ray crystallinity. The higher the sp3 content, the lower is the crystallinity and the less perfect are the crystals. The sp3 content and the crystallinity determine the electrical conductivity of trans (CH)x and iodine complexed (CH)x. Low sp3 content and high crystallinity of (CH)x are the preconditions for high conductivity of the corresponding iodine complexes.

E.s.r. study of the Ti(OBu)4 catalyst mixture in silicone oil with regard to the synthesis of homogeneous and highly conducting (CH)x

Abstract E.s.r. spectra of a homogeneous catalyst system based on n -butyltitanate and triethylaluminium in a Al/Ti molar ratio of four were recorded in silicone oil at temperatures ranging from 22 – 130 °C. They contained signals with G values of 1.954, 1.972, 1.977, and 1.986, whose intensities varied with the ageing temperature. It is shown that increasing the catalyst ageing temperature above 100 °C favours only the active species with G value 1.954. This could be related to the initial rate of polymerization and to the synthesis of a more homogeneous, regular and highly conducting (CH) x film after doping with a 0.25 M FeCl 3 -nitromethane solution.

New isatin derivatives: synthesis and reactions

Abstract The synthesis of new 5-substituted isatins with 2-thienyl, 3-thienyl, 2,2′-bithien-5-yl and phenyl substituents is described. The compounds were prepared via the palladium-catalysed cross-coupling reaction of 5-bromoisatin with 2-thiophene, 3-thiophene, 2,2′-bithien-5-yl and benzene boronic acids, respectively. Bis(5-isatyl) disulfide was also synthesized from the reaction of 5-isatinsulfonyl chloride with hydroiodic acid. The isatin derivatives were characterized spectroscopically and their behaviour as model compounds for the indophenine reaction was examined.

NMR studies of stable, organic free radicals

Abstract The 1H NMR spectra of verdazyls displaying magnetic interactions are examined. This is the first occasion on which the 1H NMR spectra have been reported for these particular materials and the synthesis of a number of new verdazyls is also reported. The electron-proton coupling constants have been determined from these NMR spectra. Comparison between values for the coupling constants for 1,3,5-triphenylverdazyl (TPV) and 6-methyl-1,3,5-triphenylverdazyl (Me-TPV) show excellent agreement with those calculated from ENDOR experiments. A relationship between the nature of the substituents at the C-6 position and the coupling constants for the protons on the N-phenyl groups has been observed.

Bis(thienyl) coronene and its electrochemical polymerization

Abstract 1,7-Bis(thienyl) coronene was synthesized from perylene and 2-ethynyl thiophene via the Diels-Alder reaction and was characterized spectroscopically. It was electrochemically polymerized in THF/Bu4NClO4 at a Pt electrode in N2 atmosphere using 1 mA cm−2 to obtain a new class of conjugated conducting polymers called poly(coronylene thienylene).

Approaches to a polypyrrole model

Abstract A model of the proposed macrocyclic polypyrrole has been synthesized and in discussed. Also proposed is an interesting form of polypyrrole borne from these studies with a fullerene-like structure. A possible synthetic method to it is discussed.

1,6-dipyrrol-1-yl-2,4-hexadiyne. Preparation and characterization

Abstract The synthesis of 1,6-dipyrrol-1-yl-2,4-hexadiene ( 5 ) is described. The N -alkylation of pyrrole was catalysed by crown ether and the intermediate acetylene was oxidatively coupled using cuprous chloride and oxygen.

Highly conducting polymer films by high-temperature polymerization of allenes and alkynes

Abstract Gas phase polymerization of simple allenes and alkynes at 460°C provides stable black films or coatings which become electrically conducting when doped with iodine or various Lewis acids. The range of application of this novel route to conducting polymers is discussed.