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The spectroscopic properties of poly(3,4-ethylenedithiathiophene) (PEDTT) which is a sulfur analogue of poly(3,4-ethylenedioxythiophene) (PEDOT) are studies by in situ techniques like IR, Vis and electron spin resonance (ESR) spectroelectrochemistry. Despite the topological equivalence of PEDTT and PEDOT, their IRAV signatures are found to be different and the results suggest very different conformations for the two materials.

Studies have shown that the most important intermediate formed during aniline polymerization, the p-aminodiphenylamine, has formed a [pi]-dimer under oxidation at room temperature in acidified organic solvents that are used in electropolymerization. The [pi]-dimer is used for interpreting the ultraviolet visible (UV-vis) spectra of higher oligomers and polyaniline.

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. [ABSTRACT FROM AUTHOR]

The electrode reactions during the initial stages of Fe electrodeposition on GaAs from a sulfate-based aqueous electrolyte, were investigated. Electrochemical quartz microbalance measurements were carried out to distinguish hydrogen evolution from Fe deposition. For conditions with a lower hydrogen evolution rate, hemispherical Fe nanoparticles with negligible in-plane magnetic anisotropy are obtained. In contrast, when hydrogen evolution dominates over Fe electrodeposition, the deposited nanoparticles exhibit a defined faceted shape, crystallographic alignment and magnetic in-plane anisotropy. This beneficial impact of hydrogen evolution on the epitaxy is discussed with regard to the role of hydrogen adsorption during Fe/GaAs interface formation. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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–t. The hyperfine coupling constants determined for the adduct were a N =1.285mT, and in accord to those reported in literature. [Copyright &y& Elsevier]

The diethyl ester of o-phenylenebis(oxamic acid) (opbaH2Et2) was treated with an excess of RNH2 in MeOH to cause the exclusive formation of the respective o-phenylenebis(N(R)-oxamides) (opboH4R2, R = Me , Et , (n)Pr ) in good yields. Treatment of with half an equivalent of [Cu2(AcO)4(H2O)2] or one equivalent of [Ni(AcO)2(H2O)4] followed by the addition of four equivalents of [(n)Bu4N]OH resulted in the formation of mononuclear bis(oxamidato) type complexes [(n)Bu4N]2[M(opboR2)] (M = Ni, R = Me , Et , (n)Pr ; M = Cu, R = Me , Et , (n)Pr ). By addition of two equivalents of [Cu(pmdta)(NO3)2] to MeCN solutions of , novel trinuclear complexes [Cu3(opboR2)(L)2](NO3)2 (L = pmdta, R = Me , Et , (n)Pr ) could be obtained. Compounds have been characterized by elemental analysis and NMR/IR spectroscopy. Furthermore, the solid state structures of and have been determined by single-crystal X-ray diffraction studies. By controlled cocrystallization, diamagnetically diluted and (1%) in the host lattice of and (99%) (@ and @), respectively, in the form of single crystals have been made available, allowing single crystal ESR studies to extract all components of the g-factor and the tensors of onsite (Cu)A and transferred (N)A hyperfine (HF) interaction. From these studies, the spin density distribution of the [Cu(opboEt2)](2-) and [Cu(opbo(n)Pr2)](2-) complex fragments of and , respectively, could be determined. Additionally, as a single crystal ENDOR measurement of @ revealed the individual HF tensors of the N donor atoms to be unequal, individual estimates of the spin densities on each N donor atom were made. The magnetic properties of were studied by susceptibility measurements versus temperature to give J values varying from -96 cm(-1) () over -104 cm(-1) () to -132 cm(-1) (). These three trinuclear Cu(II)-containing bis(oxamidato) type complexes exhibit J values which are comparable to and slightly larger in magnitude than those of related bis(oxamato) type complexes. In a summarizing discussion involving experimentally obtained ESR results (spin density distribution) of and , the geometries of the terminal [Cu(pmdta)](2+) fragments of determined by crystallographic studies, together with accompanying quantum chemical calculations, an approach is derived to explain these phenomena and to conclude if the spin density distribution of mononuclear bis(oxamato)/bis(oxamidato) type complexes could be a measure of the J couplings of corresponding trinuclear complexes.

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.

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.

The crystalline, spinless π dimer (1 . + ⋅PF 6 ) 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., (© 1999 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.)