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Research paper thumbnail of ChemInform Abstract: Electrochemical Properties

Cheminform, 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Research paper thumbnail of Doped Polymers by Oxidative Polymerization. 4.†Oxidative Coupling of Methylated Oligothiophenes by FeCl3·6H2O as a Model Reaction for the Oxidative Polymerization of Thiophene Derivatives

Macromolecules, 1996

Methylated bi-and terthiophenes (monomers, 1, 3, 5, 8) with one free R-position can be oxidized w... more Methylated bi-and terthiophenes (monomers, 1, 3, 5, 8) with one free R-position can be oxidized with FeCl3‚6H2O. An irreversible dimerization reaction forms dimers of the expected structure. The radical cations of the monomers also react with free -positions of the formed dimers (6, 9) having two methylated R-positions. The products of these reactions show R, ′ linkages (7, 10, 11). Different -positions in end-capped dimers show a graduated reactivity against radical cations of the monomers; the free -position with the higher electron spin density can be attacked preferably by an R-position of a radical cation of a monomer molecule. No products with , ′ linkages were found. Electrochemical investigations using fast-scan voltammetry show the formation of R,R′ linkages of methylated oligothiophenes. For bithiophene derivatives, rate constants of the dimerization process in the range of 10 9 L‚mol -1 ‚s -1 were determined. In comparison with a terthiophene derivative, it was found that the dimerization rates decrease with increasing chain length of the oligomers. † For part 3, see ref 15.

Research paper thumbnail of Reversible dimerization of 3,3′,5,5′,-tetramethyl-2,2′-bithiophene cations

Journal of Electroanalytical Chemistry, 1997

Cyclic voltammetric measu~ments at dil'l~rent temperatures, concentrations and scan rates give ev... more Cyclic voltammetric measu~ments at dil'l~rent temperatures, concentrations and scan rates give evidence ior the reversible dimerization of 3,3°,5,5',tetramethyl-2,2'-bithiophene radical cations. The analysis of the experimental data confirm the mechanistic concept of a RR dimerization. The rate constants and equilit~rium constants were determined from working curves and digital simulations. The reaction enthalpy is -60 kJ mol-~. The weak temperature dependence of the rate constants for the dimerization results in values of the activation enthaipy that is close to zero or even negative. © 1997 Elsevier Science S.A.

Research paper thumbnail of ChemInform Abstract: Studies on β-Methylated End-Capped Bithiophenes

Cheminform, 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Research paper thumbnail of Disubstituted oligothiophenes, a new oligomeric approach towards the synthesis of conducting polymers

Journal of Electroanalytical Chemistry, 1998

The electropolymerization of methylthio-substituted oligothiophenes 2-4 has been studied. Theoret... more The electropolymerization of methylthio-substituted oligothiophenes 2-4 has been studied. Theoretical and experimental results reveal that only 4,4%-disubstituted derivatives yield polymeric films. The reason for this is that electron-donating methylthio (= methylsulphonyl) substituents in the 'outer' i-positions of the starting compounds 2-4, which cause high spin densities at the corresponding h-C atoms, favour fast coupling steps between the reacting oligomers during all stages of the electropolymerization. All data clearly indicate that the electropolymerization of donor-substituted thiophenes is not a chain propagation process but a series of successive 'dimerization' steps. The resulting polymers have been characterized by voltammetric measurements, in situ conductivity experiments and spectroelectrochemistry.

Research paper thumbnail of Voltammetry of fullerenes C60 and C70 in dimethylamine and methylene chloride

Journal of Electroanalytical Chemistry, 1993

Research paper thumbnail of The oligomeric approach – the electrochemistry of conducting polymers in the light of recent research

Journal of Solid State Electrochemistry, 1998

Electrochemical investigations on oligomeric model compounds (β-carotenoids) of polyacetylene var... more Electrochemical investigations on oligomeric model compounds (β-carotenoids) of polyacetylene varying the chain length in the range between 5 and 23 double bonds provide deeper insights into the redox properties of such systems. Furthermore, cyclic voltammetric studies of α,ω-diphenylpolyenes and phenylenevinylenes give clear evidence that the formation of the radical ions is followed by a rapid reversible dimerization between the oligomeric chains. The thermodynamic and kinetic parameters of the chemical reaction are presented. Applying these results to the properties of conducting polymers opens up new perspectives for interpreting charge storage and conductivity.

Research paper thumbnail of A Method for the Construction of Ultramicroelectrodes

Analytical Chemistry, 1995

Research paper thumbnail of Studies on β-methylated end-capped bithiophenes

Journal of The Chemical Society-perkin Transactions 2, 1998

Research paper thumbnail of ChemInform Abstract: Electrochemical Properties

Cheminform, 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Research paper thumbnail of Doped Polymers by Oxidative Polymerization. 4.†Oxidative Coupling of Methylated Oligothiophenes by FeCl3·6H2O as a Model Reaction for the Oxidative Polymerization of Thiophene Derivatives

Macromolecules, 1996

Methylated bi-and terthiophenes (monomers, 1, 3, 5, 8) with one free R-position can be oxidized w... more Methylated bi-and terthiophenes (monomers, 1, 3, 5, 8) with one free R-position can be oxidized with FeCl3‚6H2O. An irreversible dimerization reaction forms dimers of the expected structure. The radical cations of the monomers also react with free -positions of the formed dimers (6, 9) having two methylated R-positions. The products of these reactions show R, ′ linkages (7, 10, 11). Different -positions in end-capped dimers show a graduated reactivity against radical cations of the monomers; the free -position with the higher electron spin density can be attacked preferably by an R-position of a radical cation of a monomer molecule. No products with , ′ linkages were found. Electrochemical investigations using fast-scan voltammetry show the formation of R,R′ linkages of methylated oligothiophenes. For bithiophene derivatives, rate constants of the dimerization process in the range of 10 9 L‚mol -1 ‚s -1 were determined. In comparison with a terthiophene derivative, it was found that the dimerization rates decrease with increasing chain length of the oligomers. † For part 3, see ref 15.

Research paper thumbnail of Reversible dimerization of 3,3′,5,5′,-tetramethyl-2,2′-bithiophene cations

Journal of Electroanalytical Chemistry, 1997

Cyclic voltammetric measu~ments at dil'l~rent temperatures, concentrations and scan rates give ev... more Cyclic voltammetric measu~ments at dil'l~rent temperatures, concentrations and scan rates give evidence ior the reversible dimerization of 3,3°,5,5',tetramethyl-2,2'-bithiophene radical cations. The analysis of the experimental data confirm the mechanistic concept of a RR dimerization. The rate constants and equilit~rium constants were determined from working curves and digital simulations. The reaction enthalpy is -60 kJ mol-~. The weak temperature dependence of the rate constants for the dimerization results in values of the activation enthaipy that is close to zero or even negative. © 1997 Elsevier Science S.A.

Research paper thumbnail of ChemInform Abstract: Studies on β-Methylated End-Capped Bithiophenes

Cheminform, 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Research paper thumbnail of Disubstituted oligothiophenes, a new oligomeric approach towards the synthesis of conducting polymers

Journal of Electroanalytical Chemistry, 1998

The electropolymerization of methylthio-substituted oligothiophenes 2-4 has been studied. Theoret... more The electropolymerization of methylthio-substituted oligothiophenes 2-4 has been studied. Theoretical and experimental results reveal that only 4,4%-disubstituted derivatives yield polymeric films. The reason for this is that electron-donating methylthio (= methylsulphonyl) substituents in the 'outer' i-positions of the starting compounds 2-4, which cause high spin densities at the corresponding h-C atoms, favour fast coupling steps between the reacting oligomers during all stages of the electropolymerization. All data clearly indicate that the electropolymerization of donor-substituted thiophenes is not a chain propagation process but a series of successive 'dimerization' steps. The resulting polymers have been characterized by voltammetric measurements, in situ conductivity experiments and spectroelectrochemistry.

Research paper thumbnail of Voltammetry of fullerenes C60 and C70 in dimethylamine and methylene chloride

Journal of Electroanalytical Chemistry, 1993

Research paper thumbnail of The oligomeric approach – the electrochemistry of conducting polymers in the light of recent research

Journal of Solid State Electrochemistry, 1998

Electrochemical investigations on oligomeric model compounds (β-carotenoids) of polyacetylene var... more Electrochemical investigations on oligomeric model compounds (β-carotenoids) of polyacetylene varying the chain length in the range between 5 and 23 double bonds provide deeper insights into the redox properties of such systems. Furthermore, cyclic voltammetric studies of α,ω-diphenylpolyenes and phenylenevinylenes give clear evidence that the formation of the radical ions is followed by a rapid reversible dimerization between the oligomeric chains. The thermodynamic and kinetic parameters of the chemical reaction are presented. Applying these results to the properties of conducting polymers opens up new perspectives for interpreting charge storage and conductivity.

Research paper thumbnail of A Method for the Construction of Ultramicroelectrodes

Analytical Chemistry, 1995

Research paper thumbnail of Studies on β-methylated end-capped bithiophenes

Journal of The Chemical Society-perkin Transactions 2, 1998