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The great prospects for low-power magnetoelectronic devices trigger significant research activity aiming at voltage-control of magnetism. In this field, ion migration and reversible electrochemical reactions currently open a pathway to voltage-reprogrammable magnetic materials. Up to now, such electrochemical manipulation of oxide/metal heterostructures is mainly reported for thin films prepared by physical methods. The present study describes an all-electrochemical route by utilizing electrodeposited FeOx/Fe nanoislands as a starting state. Repeatable electrochemical conversion between ferromagnetic Fe and FeOx is achieved in KOH solution and exploited for voltage control of the magnetization of the nanoislands. For the smallest nanoislands, exhibiting dimensions of a few nanometers, almost complete voltage-induced ON/OFF switching of magnetism at room temperature is detected by in situ transport and ferromagnetic resonance measurements. The observed effects are enhanced in comparison to those of continuous films, which points at the morphology as an influencing factor of electrochemical voltage control of magnetism. The all-electrochemical approach is decisive for extending the application possibilities for voltage-programmable magnetic materials, because, by electrochemical deposition, geometry restrictions can be overcome and 3D structures can be functionalized.

The electrochemical reduction of cobalt dibromide 2,2′-bipyridine (bpy) complexes (Co/bpy molar ratio 1:1) results in the formation of cobalt nanoparticles (CoNP) formed by the disproportionation reaction of the electrochemically generated cobalt(I) mononuclear complexes. The process of the electrochemical generation of CoNP was monitored by in situ EPR-spectroelectrochemistry where the signals of the ferromagnetic resonance (FMR) have been observed for these species. According to small-angle X-ray scattering (SAXS) analysis the average diameter and the average length of the formed cylindrical CoNP is varied from 9 to 10 nm and 30–32 nm, respectively, and correlates to the g-value and the broadness of the FMR signal observed by in situ EPR-spectroelectrochemistry during electrochemical process.

Aligned, individual iron square cuboid nanoparticles have been achieved by taking advantage of epitaxial, three-dimensional-island growth on GaAs(001) during electrodeposition at low deposition rates. The nanoparticles exhibit lateral dimensions between 10 and 80 nm and heights below 40 nm. Surface {100} facets predominate with a thin crystalline oxide shell that protects the nanoparticles during prolonged storage in air. The single crystallinity of the iron in combination with structural alignment leads to an in-plane magnetic anisotropy. These immobilized, oriented, and stable nanoparticles are promising for applications in nanoelectronic, sensor, and data storage technologies, as well as for the detailed analysis of the effect of shape and size on magnetism at the nanoscale.

The organonickel complex [NiBr(Mes)(phen)] (1) (Mes = 2,4,6-trimethylphenyl, phen = 1,10-phenanthroline) was synthesized by oxidative addition of MesBr to nickel(0) complexes, obtained from [Ni(COD)2] (COD = 1,5-cyclooctadiene) and phen, or electrochemically generated from [NiBr2(phen)], and by ligand exchange reaction from [NiBr(Mes)(PPh3)2]. The electrochemical properties of [NiBr(Mes)(phen)] were investigated by cyclic voltammetry and in situ EPR spectroelectrochemistry. The cathodic reduction of 1 resulted in formation of the neutral radical complex [Ni(Mes)(phen −)] with a 1,10-phenanthroline radical anion bound to a nickel(II) centre. The electrochemical generation of the free 1,10-phenanthroline radical anion from 1,10-phenanthroline is also described.

Poly(2-methoxynaphthalene) (P2MN) belongs to the category of fused ring organic semiconductors that due to their planar structure have very interesting optical and electrical properties like a reduced band gap and easiness of undergoing both oxidation and reduction. Here, we present a spectroelectrochemical study by means of simultaneous recording of electron spin resonance–UV–vis–near infrared spectra (ESR–UV–vis–NIR) to probe the nature of the charge carriers in both p- and n-doped P2MN. As shown earlier P2MN is both p- and n-dopable, however, further information of the nature of both types of charge carriers is needed. In this work we demonstrate that the dominant charge carrier in p- and n-doped P2MN is positive and negative polarons, respectively. The material under study constitutes an example of an ambipolar organic conjugated polymer capable to conduct both holes and electrons. This is a unique property worthy to be further studied since only a few organic conducting polymers can reversibly be both p- and n-doped.

For the first time, the superoxide anion radical was formed by electrochemical reduction of oxygen and detected in situ by EPR spectroscopy without changing the temperature. The spin susceptibilities of solid superoxide solutions were measured between 280 and 4 K showing Curie behavior. The EPR results were explained in the frame of an ion association and support the formation of a loose ion pair between the superoxide anion radical and the potassium crown ether complex. An alternative explanation for the large EPR line width of the superoxide anion radical at higher temperatures is given.

The superoxide anion radical, O2•−, induced C60 electropolymerization mechanism was refined by simultaneous cyclic voltammetric (CV) and vis-NIR spectroelectrochemical as well as mass spectrometric (MALDI-TOF) characterization of the one- and two-electron reduction products of C60 in the presence of O2 in a mixed organic solvent solution. The C60 polymer (C60-O) film was also investigated by Raman spectroscopy and imaged by atomic force microscopy (AFM) both at the early and advanced polymerization stage. While the spectroelectrochemical behavior of the C60/C60•− couple in the presence of O2 was similar to that in its absence, at more negative potentials corresponding to C602− and O2•− formation C602− participated in a chemical follow-up reaction resulting in a product lacking any diagnostic absorption band in the vis-NIR range. Although the main peak in the MS spectrum of the one-electron reduction product was that of C60 at m/z of 720, several additional peaks in the m/z range of 739−760 appeared, indic...

Superoxide radical (O2 −) was both electrochemically generated and detected at room temperature. In situ ESR spectroelectrochemistry with spin trapping was used for the radical detection. That is, the O2 − radical was obtained in a DMSO solution under cyclic voltammetry conditions as soon as the potential of the dioxygen electroreduction was reached. This radical reacted then with a 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) spin-trap reagent present in solution to form the DMPO– OOH adduct. The hyperfine coupling constants determined for the adduct were aN = 1.285 mT, a H β = 1.042 mT and a H γ = 0.142 mT in accord to those reported in literature.

It is shown for the first time that the most important intermediate formed during aniline polymerization, the p-aminodiphenylamine, forms a pi-dimer under oxidation at room temperature in acidified organic solvents that are used in electropolymerization. N-Phenylquinonediimine, which is generally assumed to be formed under oxidation, is only formed in basic solutions and in ionic liquids. Most of the mechanistic studies reported so far take the formation of N-phenylquinonediimine under consideration, although it is not consistent with the UV-vis spectra measured during oxidation of p-aminodiphenylamine. The formation of a pi-dimer is very well consistent with the electronic spectra of the oxidation product. In this way the pi-dimer is very important for the interpretation of the UV-vis spectra of higher oligomers and polyaniline as well. Furthermore, it offers a new interpretation of the redox behavior of p-aminodiphenylamine as found by cyclic voltammetry and has to be considered in the mechanism of the electrochemical polyaniline formation.

Simultaneous electron spin resonance (ESR) and UV−vis−NIR measurements have been carried out during oxidation of a poly[N-methyl(aniline)] (PNMA) film, which was prepared electrochemically in aqueous solutions containing 1 M trifluoroacetic acid. In situ conductance measurements were also performed during the electrochemical doping of PNMA. The combination of the different experimental techniques allows a simultaneous elucidation of optical and electrochemical properties of the conducting polymer film. Although there are a lot of predictions and discussions on the free charge carriers of poly(aniline) (PANI) and its derivatives, there is no direct evidence of the correlation between polarons and conductance for PANI and its derivatives during doping. This article provides the correlation between the spin and spinless species and the conductance of PNMA during the electrochemical doping in acidic aqueous solutions. PNMA differs from other conjugated polymers (e.g. polypyrrole) in that the results from ESR ...

Poly(3,4-ethylenedithiathiophene) (PEDTT) is a polythiophene-like conjugated polymer in which each thiophene ring is functionalized with an ethylenedithia bridge. As such, PEDTT is the sulfur analogue of the well-known poly(3,4-ethylenedioxythiophene) (PEDOT). Substituent effects, namely the presence of sulfur atoms in PEDTT replacing the oxygen atoms of PEDOT, do not provide a simple explanation for the different electronic properties of the two polymers in the neutral state. This paper reports the spectroscopic properties of PEDTT, studied by in situ techniques such as IR-, Vis-, and electron spin resonance (ESR) spectroelectrochemistry. The differences observed upon electrochemical oxidation of PEDTT and PEDOT (e.g., the different infrared active vibrational band patterns in IR spectroelectrochemistry as well as the different nature of the charged states) are even more marked than those observed in the neutral state. These results, with AM1 calculations, indicate conformational effects as a possible explanation for the different electronic and spectroscopic properties of PEDTT and PEDOT.

The temperature dependence of the magnetic susceptibility of polyaniline at significant different doping levels has been investigated. The samples cover the conducting as well as the insulating region. The conductivity varies from 10−4 to 5 S cm−1. A temperature independent behaviour of the spin susceptibility is found in all cases. While the interpretation of the temperature dependence was formerly done by assuming metallic properties (Pauli paramagnetism) we give an alternative explanation of the results here based on the temperature dependence of a chemical equilibrium.

Triphenylamine was electrochemically polymerized in a mixture of toluene and acetonitrile with different electrolyte salts. The poly(triphenylamine) (PTPA) films are insoluble in polar solvents and show high stability and no degradation or loss in electrochemical properties when stored in a laboratory atmosphere. The PTPA films were characterized in situ by FTIR external reflection spectroscopy and by Raman spectroscopy.

Poly(dithienothiophene)s (PDTTs), low band-gap conjugated polymers with polythiophene-like chain where an aromatic thienothiophene moiety is fused to each thiophene ring, were studied using Raman spectroscopy, photoinduced infrared absorption, as well as attenuated total reflection Fourier transform infrared (ATR-FTIR) and electron spin resonance (ESR) spectroelectrochemistry. The spectroelectrochemical studies were performed in situ during p- and n-doping (electrochemical oxidation and reduction, respectively). Raman lines of the pristine polymers are compared to infrared active vibration (IRAV) bands due to the charge carriers injected by the electrochemical doping processes or by illumination. The different π-electron distribution along the polythiophene-like chain, which determines the different band-gap sizes, also account for the different lattice relaxations and vibrational behaviors shown by these polymers. By means of in situ ESR spectroscopy, the formation of paramagnetic positive and negative c...

The electrochemical synthesis of poly(p-phenylenevinylene) (PPV) and different modifications in the electronic distribution upon electrochemical p-doping (oxidation) and n-doping (reduction) of this polymer film have been studied in situ by resonance Raman spectroscopy, optical absorption spectroscopy and ESR spectroscopy. The polymer film has been prepared by electrochemical reduction of α,α,α′,α′-tetrabromo-p-xylene in dimethylformamide using tetraethylammonium tetrafluoroborate as the electrolyte salt. During electrochemical polymerization the position and relative intensities of the Raman bands change regularly as the chain length increases and finally converge on values reported for chemically prepared PPV. The Raman spectra for electrochemically polymerized PPV is compared to infrared-active vibration bands for electrochemically n-doped PPV. When the polymer undergoes redox reactions (doping-dedoping), shifts and broadening of Raman bands, compared to neutral PPV, are observed. Interpretation of the Raman spectra and the ESR results led to the conclusion that charge transfer in this system is mainly accomplished by polaron species formed upon doping of the polymer. In this reaction the quinoid structure is formed rather than the benzenoid structure.

The oxidation of aniline and some derivatives of 1,2-phenylenediamine was performed by the system Pb(CH3COO)4—CF3COOH—CH2Cl2. An ESR investigation of the oxidized aniline confirmed the presence of secondary cation radical. Its structure was determined by comparison of its ESR spectrum with those of cation radicals prepared from derivatives of 1,4-phenylenediamine. The oxidation of 1,2-phenylenediamine and its derivatives leads to the formation of either primary or secondary cation radicals, the latter having the character of substituted dihydrophenazinium cation radicals.

The electrochemical redox process to charge and discharge polyaniline layers is studied by simultaneous Electron Spin Resonance (ESR) and UV–vis spectroscopic measurements. For this purpose, optically transparent electrodes were applied under potential-controlled conditions. The use of a calibrated manganese ESR standard ensures the calculation of the absolute numbers of free spins in the polymer layer during electrochemical doping. A general procedure is given to analyse the simultaneously recorded electrochemical and spectroscopic data. The procedure proposed following the time dependence of charge, ESR absorption and the absorbance demonstrates that the electrochemical charging/discharging mechanism of polyaniline can be described on the base of three oxidation states. In this way, the separated UV–vis spectra and the time/potential dependence of each redox state can be shown. Only little changes are observed in the shape of the separated spectra using the polaron/bipolaron model in comparison to the polaron/ σ -dimer model. A square ladder scheme of the redox mechanism is discussed, considering neutral, polaronic and bipolaronic states and the protonation equilibria. Furthermore, experimental evidence for the Faradaic nature of the “capacitive” current plateau is presented.

The electrochemical oxidation of polyaniline (PAni) films on gold electrodes is studied by simultaneous electron spin resonance (ESR) and UV−vis spectroelectrochemistry. The technique permits the separation of the superimposed UV−vis spectra of three redox states: the protonated reduced polyaniline chains, the deprotonated polaronic state, and the bipolaronic state. The separated UV−vis spectra as well as the potential dependence of each redox state concentration enables a more precise determination of the energy levels and the stability of paramagnetic species.

The redox behaviour of polypyrrole layers prepared by the electrochemical oxidation of pyrrole in acetonitrile solutions was studied using insitu EPR/UV–VIS spectroelectrochemistry. Various supporting electrolytes: p-toluene sulfonic acid, tetrabutylammonium perchlorate (TBAP) and tetraethylammonium p-toluene sulfonate (TEATos), were used. Optically transparent indium tin oxide (ITO)-coated glass and gold mesh electrodes were used as electrode materials. Using the calibrated manganese EPR standard, the quantitative time dependences of the three oxidation states in the polymer layer were obtained during redox cycling. The separation of the superimposed UV–VIS spectra was carried out by a least-squares method. The different mechanisms of the polymer oxidation, the polaron/bipolaron route and polaron/dimer route, are compared.

The electrochemical reduction of 2,5-diphenyl-1,3,4-oxadiazole has been studied by both cyclic voltammetry and spectroelectrochemistry. The in situ spectroscopic techniques were applied to obtain structural information on the products of the follow-up reactions. Time-resolved UV-vis spectroscopy, with spectra measured on a time scale of 20ms by a diode array spectrometer, was used in cyclic voltammetry to obtain up to 60 single spectra in the forward and backward scans. The radical anion of 2,5-diphenyl-1,3,4-oxadiazole, which is formed in the electron transfer reaction at the electrode, was studied by ESR spectroscopy. Furthermore, paramagnetic products of the follow-up reactions were detected. A reaction mechanism is formulated that includes an irreversible protonation reaction and, in parallel, a reversible ion-pairing reaction with the supporting electrolyte cation for the electrochemically generated radical anion and an irreversible follow-up reaction for the dianion of 2,5-diphenyl-l,3,4-oxadiazole.

Simultaneous in situ measurements by both ESR and UV-vis spectroscopy have been carried out at the same electrode for the first time during a single electrochemical experiment in order to spectroscopically characterize the electrochemical reaction products. The experimental technique, including a special TE102 optical ESR cavity and an electrochemical cell for both ESR and UV-vis spectroscopy in transmission, is described. It is shown that the UV-vis absorbance measured in situ, as well as the ESR intensity characteristics of the electrochemical system under study, can be understood in terms of the faradaic current. The reliability of this system is proved by measuring the organic redox couple of methyl-substituted p-phenylenediamine and by comparing calculated and experimental curves.

We have studied the molecular orientation of well-known representatives of organic semiconductors from the family of the phthalocyanines [copper phthalocyanine (CuPc) and its perfluorinated relative (CuPcF16)] on a conducting polymer thin film using polarization-dependent x-ray absorption spectroscopy. As a polymer substrate PEDOT:PSS [a mixture of poly-3,4-ethylenedioxy-thiophene (PEDOT) and polystyrenesulfonate (PSS), which is often applied as an electrode material in (all-)organic semiconductor devices] was spin coated onto indium-tin-oxide substrates. Even if the interfaces themselves are relatively ill defined (we found recently a mixing of the two organic materials and charge-transfer processes), a very high degree of molecular ordering is observed in the 20–50nm thick phthalocyanine films.

We studied the electronic properties of technically relevant organic/organic interfaces using photoemission spectroscopy. Representatives of organic semiconductors from the family of the phthalocyanines were evaporated onto PEDOT:PSS [mixture of poly-3,4-ethylenedioxy-thiophene and polystyrenesulfonate] thin films, which are often applied as electrode material in organic semiconductor devices. Besides the formation of interface dipoles we observe energetic shifts of the electronic levels of the semiconductors, which are explained by a doping of the organic semiconductor near the interface due to a mixing of the two organic materials within the interface region.

The treatment of the diethyl ester of o-phenylenebis(oxamic acid) (opbaH(2)Et(2)) with 2/3 of an equivalent of MeNH(2) in MeOH does not result in the formation of the methyl ester of o-phenylene(N'-methyloxamide)(oxamic acid) (opooH(3)Me, 1) in pure state, as reported previously. The colourless crude material formed by this reaction was confirmed to be composed of 1 (89% content), the dimethyl ester of o-phenylenebis(oxamic acid) (opbaH(2)Me(2), 2, 6%), 1,4-dihydro-2,3-quinoxalinedione (3, 3%) and o-phenylenebis(N'-methyloxamide) (opboH(4)Me(2), 4, 1%), respectively. The identities of 1-4 have been verified by IR, (1)H and (13)C NMR spectroscopy as well as elemental analysis. In addition, the solid state structures of 1 and 2·2DMSO, respectively, were determined by single-crystal X-ray diffraction studies. Successive recrystallization of the crude material from MeOH and MeOH : THF (1 : 1), respectively, does not give pure 1, but a mixture of 1 and 2. It is shown further that out of this mixture pure bis(oxamato) complexes cannot be obtained, as previously reported. Instead, treatment of the mixture with Ni(II) or Cu(II) salts, followed by the addition of [(n)Bu(4)N]OH, results in the formation of two mixtures of [(n)Bu(4)N](2)[Ni(opba)] (5) and [(n)Bu(4)N](2)[Ni(opooMe)] (6) as well as [(n)Bu(4)N](2)[Cu(opba)] (7) and [(n)Bu(4)N](2)[Cu(opooMe)] (8), respectively. The simultaneous formation of 5/6 and 7/8, respectively, has been verified by crystallization of the obtained mixtures and X-ray diffraction studies of the obtained single crystals. Co-crystallization of mixtures of 5/6 (99 mass%) and 7/8 (1 mass%), respectively, results in the formation of single-crystals of diamagnetically diluted 7 in the host lattice of 5 (7@5) accompanied by single-crystal formation of diamagnetically diluted 8 in the host lattice of 6 (8@6), as verified by EPR spectroscopy. It is finally shown that the ethyl ester of o-phenylene(N'-methyloxamide)(oxamic acid) (opooH(3)Et, 9), a homologue of 1, can be obtained in pure state by the treatment of opbaH(2)Et(2) with 5/6 of an equivalent of MeNH(2) in EtOH.

3,3-Dimethyl-1-(4-R-phenyl)- [R = (CH3)2N, C2H5O, CH3O, CH3; 3] and 3-Methyl-1-(4-R1-phenyl)-3-(4-R2-phenyl)triazenes [R1 = (CH3)2N, CH3O, NO2, R2 = CH3O, H, 4] are oxidized electrochemically and chemically to their one-electron oxidation products. Cyclic voltammograms of the triazenes are discussed, and ESR as well as UV/Vis spectra of the radical cations are presented. The stability of the triazene radical cations generated depends on the substituents on the aryl rings. 4-R-Benzenediazonium ions are identified as one of the decay products of the radical cations by means of cyclic voltammetry and UV/Vis spectroelectrochemistry.

The electrochemical reduction of isatoic anhydride and its derivatives was studied by simultaneous electrochemical and ESR-measurements. For the first time 9 new radicals were characterized by its formal redox potentials, hyperfine coupling constants, g-factors and lifetimes. The advantage of measuring the kinetic data in stagnant and renewed electrolyte combined with accumulation of the ESR-spectra is demonstrated in the case of shortlived radicals. It is shown that the electrochemical reduction of isatoic structures follows a self protonation mechanism.

The reaction of [NiBr(2)(bpy)(2)] (bpy = 2,2'-bipyridine) with organic phosphinic acids ArP(O)(OH)H [Ar = Ph, 2,4,6-trimethylphenyl (Mes), 9-anthryl (Ant)] leads to the formation of binuclear nickel(II) complexes with bridging ArP(H)O(2)(-) ligands. Crystal structures of the binuclear complexes [Ni(2)(μ-O(2)P(H)Ar)(2)(bpy)(4)]Br(2) (Ar = Ph, Mes, Ant) have been determined. In each structure, the metal ions have distorted octahedral coordination and are doubly bridged by two arylphosphinato ligands. Magnetic susceptibility measurements have shown that these complexes display strong antiferromagnetic coupling between the two nickel atoms at low temperatures, apparently similar to binuclear nickel(II) complexes with bridging carboxylato ligands. Cyclic voltammetry and in situ EPR spectroelectrochemistry show that these complexes can be electrochemically reduced and oxidized with the formation of Ni(I),Ni(0)/Ni(III) derivatives.

Strongly electron-deficient (n-type) main-chain π-conjugated polymers are commonly prepared via well-established step-growth polycondensation protocols which enable limited control over polymerization. Here we demonstrate that activated Zn and electron-deficient brominated thiophene-naphthalene diimide oligomers form anion-radical complexes instead of conventional Zn-organic derivatives. These highly unusual zinc complexes undergo Ni-catalyzed chain-growth polymerization leading to n-type conjugated polymers with controlled molecular weight, relatively narrow polydispersities, and specific end-functions.

In this paper the electrochemical synthesis of polytriphenylamine is shown for the first time. The electrochemical oxidation of triphenylamine (TPA) in nonpolar solvents leads to the formation of oligomers of TPA in solution and the formation of a polymer film with TPA as repeating unit. Cyclic voltammetry of these electrochemically produced TPA films is compared to that of chemically produced polytriphenylamine what demonstrates a similar electrochemical behaviour. From FTIR spectra of the polymer film it is concluded that the electrochemically formed polymer is more crosslinked than the chemically produced one. Therefore, it is a very stable redox polymer and a promising candidate for application in batteries, electrochromic displays, sensors or organic electronic devices.

The influence of molecular inclusion and separation of radical guests inside the amorphous β-cyclodextrin host polymer (β-CDP) matrices on the motion and stability as well as controlled potential release of radicals was studied by electron spin resonance spectroscopy (ESR) and simultaneous electrochemistry and electron spin resonance (SEESR) spectroscopy. A pronounced restriction of rotational motion was observed for the included stable protonated form of the 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO) free radical and a partial restriction of motion of the NN,N',N'-tetramethyl-1,4-phenylenediamine (TMPD.+) radical (generated ex situ by controlled potential electrolysis), while virtually no restriction was found in the case of the methyl (MV.+) and heptyl viologen (HV.+) monocation radicals as well as of the 2-nitrotoluene anion radical (2NT.− ). The MV.+, HV.+ and 2NT.− unstable radicals were electrochemically generated inside the β-CDP film coat at a Pt flag electrode. The rate of the open-circuit decay of the included unstable radicals was markedly decreased as compared with their decay at the bare electrode. It was also found that the extent of inclusion of alkyl viologens was governed by their ionic charge, i.e. the higher the charge of the ion the weaker its inclusion.

In situ spectroelectrochemistry is of high importance for the characterization of doping reactions in pi-conjugated polymers. In this paper we present the results of simultaneous ESR and UV-vis-NIR measurements performed in situ during electrochemical p- and n-doping of polyazulene (PAz). In previous studies on p-doping of PAz the assignment of the optical absorption bands to specific charge carriers have been somewhat controversial, therefore the aim of this study is to clarify the nature of the doping-induced charge carriers and their corresponding optical absorption bands by in situ ESR-UV-vis-NIR spectroelectrochemistry. PAz was polymerized in two different potential ranges in order to obtain films with different structures and morphologies. On the basis of our spectroelectrochemical results we propose that polarons and polaron pairs are formed during p-doping in the two different types of PAz films electrodeposited on ITO. For studying n-doping of PAz, a Pt electrode was used. The ESR signal first decreased in intensity at low doping levels and then increased in intensity at higher doping levels pointing to the formation of new paramagnetic species. At high negative potentials there occurred an additional line broadening of the ESR signal indicating the existence of rather localized negative charge carriers.

The nitroso labeling method (1) has been used to demonstrate its possibilities for the characterization of irradiated polyethylene (LDPE) with respect to its crosslinkings and oxygen functionalities.

Photoemission studies of interfaces between molecular organic semiconductors and the conducting polymer PEDOT:PSS [mixture of PEDOT (poly-3,4-ethylenedioxy-thiophene) and PSS (polystyrenesulfonate)] demonstrate that it is impossible to control the charge injection barriers at such contacts by either a systematic change of the work function of the conducting polymer or that of the organic semiconductor. Instead, these interfaces are, in all cases, characterized by a charge transfer across the interface and a resulting Fermi level pinning. Thus interfacial charge barriers do not explain observed changes in device parameters as a function of the work function of the polymer electrode.

The crystalline, spinless π dimer (1.+ ⋅PF6 )2 was obtained by the oxidation of bipyrrole 1 with ferrocenium hexafluorophosphate. The diamagnetic species generated electrochemically in solution was identified as the σ dimer by NMR spectroscopy.

Treatment of the diethyl ester of o-phenylenebis(oxamic acid) (opbaH(2)Et(2), 1) with 5/6 equivalent of MeNH(2) in abs. EtOH results in the exclusive formation of the ethyl ester of o-phenylene(N′-methyl oxamide)(oxamic acid) (opooH(3)EtMe, 2) in ca. 50% yield. Treatment of 2 with four equivalents of [Me(4)N]OH followed by the addition of Cu(ClO(4))(2)·6H(2)O gave [Me(4)N](2)[Cu(opooMe)]·H(2)O (3A) in ca. 80% yield. As 3A appears to be a hygroscopic solid, the related [(n)Bu(4)N](+) salts [(n)Bu(4)N](2)[M(opooMe)]·H(2)O (M = Cu (3B), Ni (4)) have been synthesized. By addition of two equivalents of [Cu(pmdta)(NO(3))(2)] to a MeCN solution of 3B the novel asymmetric trinuclear complex [Cu(3)(opooMe)(pmdta)(2)](NO(3))(2) (5) could be obtained in ca. 90% yield. Compounds 2, 3A, 3B, 4 and 5 have been characterized by elemental analysis and NMR/IR spectroscopy. Furthermore, the solid state structures of 3A in the form of [Me(4)N](2)[Cu(opooMe)]·MeOH (3A′), 3B in the form of [(n)Bu(4)N](2)[Cu(opooMe)] (3B′), 4 in the form of [(n)Bu(4)N](2)[Ni(opooMe)]·1.25H(2)O (4′) and 5 in the form of [Cu(3)(opooMe)(pmdta)(2)] (NO(3))(2)·3MeCN (5′), respectively, have been determined by single-crystal X-ray diffraction studies. By controlled cocrystallization, diamagnetically diluted 3B (1%) in the host lattice of 4 (99%) in the form of single crystals have been made available, allowing single crystal EPR studies to extract all components of the g-factor and the tensors of onsite (Cu)A and transferred (N)A hyperfine interaction. Out of these studies the spin density distribution of the [Cu(opooMe)](2-) complex fragment could be determined. The magnetic properties of 5 were studied by susceptibility measurements versus temperature. An intramolecular J parameter of -65 cm(-1) has been obtained, unexpectedly, as 5 should possess two different J values due to its two different spacers between the adjacent Cu(II) ions, namely an oxamate (C(2)NO(3)) and an oxamidate (C(2)N(2)O(2)) fragment. This unexpected result is explained by a summarizing discussion of the experimentally obtained EPR results (spin density distribution) of 3B, the geometries of the terminal [Cu(pmdta)](2+) fragments of 5 determined by X-ray crystallographic studies and accompanying quantum chemical calculations of the spin density distribution of the mononuclear [Cu(opooMe)](2-) and of the magnetic exchange interactions of trinuclear [Cu(3)(opooMe)(pmdta)(2)](2+) complex fragments.

In this work PPV films were prepared by electrochemical reduction of α,α,α,α-tetrabromo-p-xylene in dimethylformamide and tetraethylammonium tetrafluoroborate. To get more information about the mechanism behind electrochemical polymerization of PPV and its doping reaction, in situ ESR- UV-VIS measurements were made on the electrochemically synthesized conducting polymer PPV.

Conducting polymers can form both polarons and bipolarons in redox reactions at electrodes surfaces. Both of these species can be studied by UV-Vis-NIR spectroscopy. To follow the polaron by the in situ ESR spectroscopic technique and the bipolaron formation by the UV-Vis-NIR spectroscopy in electrochemical studies a special equipment is required. For this purpose an optical ESR cavity is applied to do transmission spectroscopy at optically transparent electrodes in an ESR spectrometer. The advantages of the in situ ESR/UV-Vis-NIR spectroelectrochemical measurements is presented in the study of different polymeric structures like polypyrrole, polythiophene, polyaniline and oligothiophenes.

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