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The one-electron reduction of a diiron cationic complex revealed unique features: cleavage of the diiron structure occurred despite a multidentate bridging C3ligand and was accompanied by the clean dissociation of one η5-cyclopentadienyl ring and one iron as isolated units. Thus, the iron(II)–iron(II) μ-vinyliminium complex [Fe2Cp2(CO)(μ-CO){μ-η1:η3-C3(Et)C2HC1N(Me)(Xyl)}][SO3CF3] ([1a]SO3CF3) reacted with cobaltocene in tetrahydrofuran (THF), affording the iron(II) vinylaminoalkylidene [FeCp(CO){C1N(Me)(Xyl)C2HC3(Et)C(═O)}] (2a) in 77% yield relative to the C3ligand. Analogously, [FeCp(CO){C1N(Me)(Xyl)C2HC3(CH2OH)C(═O)}] (2b) was obtained in 64% yield from the appropriate diiron precursor and CoCp2. The formation of 2ais initiated by the one-electron reduction of [1a]+, followed by a reversible intramolecular rearrangement terminating with the irreversible release of CpH (NMR and gas chromatography–mass spectrometry) and Fe [electron paramagnetic resonance (EPR) and magnetometry]. The key intermediate iron(I) ferraferrocene (3) was detected by EPR and IR spectroelectrochemistry, while the related species 3-H-3was isolated after the addition of a hydrogen source and then identified by X-ray diffraction. A plausible mechanism for the route from [1a]+to 3was ascertained by density functional theory calculations. The dication [1a]2+, displaying both carbonyl ligands in terminal positions, and the anion [3]−were electrochemically generated. The functionalized diiron compounds 4(52% yield) and 5(62%) were afforded through the activation of O2and S8by a radical intermediate along the reductive pathway of [1a]+. The reaction of [Fe2Cp2(CO)(μ-CO){μ-η1:η3-C(SiMe3)CHCN(Me)(Xyl)}][SO3CF3] ([1c]SO3CF3) with CoCp2in THF afforded [Fe2Cp2(C≡CSiMe3)(CO)(μ-CO){μ-CNMe(Xyl)}] (6) in 65% yield.

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Das Salz der Erde: Eine Reaktion, in der Niobpentafluorid als Oxidationsmittel (Bildung von NbF4) und als Fluoridakzeptor (Bereitstellung des Gegenions [Nb2F11]−) fungiert, lieferte Radikalkationensalze von monocyclischen Arenen, einschließlich Benzol (siehe Bild). Anion‐π‐Wechselwirkungen sind entscheidend für die einzigartige Inertheit der Radikalkationen.

The polymerization of norbornene in the presence of different bis(salicylaldiminate)copper(II) complexes and methylalumoxane has been investigated. In all cases a high molecular weight vinyl-type polymer was obtained. The presence of electron-withdrawing nitro groups on the chelate ligand markedly increased the activity of the catalyst. The influence on the catalytic performances and polymer characteristics as a function of reaction parameters, such as temperature, duration, and content of free trimethyl aluminum in the commercial MAO, was studied.

M(η6-arene)2species (M = Cr, arene = 1,3,5-Me3C6H3; M = Mo, arene = 1,3,5-Me3C6H3, 1,3,5-iPr3C6H3), have been prepared by a modified Fischer–Hafner synthesis or by metal vapour techniques. The reaction of Cr(η6-1,3,5-Me3C6H3)2with the fulvene derivatives pentacarbomethoxycyclopentadiene (pcmcpH), 1-benzoyl-6-hydroxy-6-phenylfulvene (dbcpH), or 1-benzoyl-3-nitro-6-hydroxy-6-phenylfulvene (dbncpH) proceeds with evolution of dihydrogen and formation of the ionic derivatives [Cr(η6-1,3,5-Me3C6H3)2][E], where E = pcmcp, dbcp, or dbncp. Mo(η6-arene)2derivatives (arene = toluene, 1,3,5-Me3C6H3, 1,3,5-iPr3C6H3) are oxidized to [Mo(η6-arene)2]+by pcmcpH. The crystal and molecular structures of [M(η6-1,3,5-R3C6H3)2][pcmcp] (M = Cr, R = Me; M = Mo, R = Me, iPr) have been solved by X-ray single crystal diffraction.

A response when wheat is grown in excess copper is an altered lipid composition of the root plasma membrane (PM). With detailed characterisation of the root PM lipid composition of the copper-treated plants as a basis, in the present study, model systems were used to gain a wider understanding about membrane behaviour, and the impact of a changed lipid composition. PMs from root cells of plants grown in excess copper (50 μM Cu) and control (0.3 μM Cu) were isolated using the two-phase partitioning method. Membrane vesicles were prepared of total lipids extracts from the isolated PMs, and also reference vesicles of phosphatidylcholine (PC). In a series of tests, the vesicle permeability for glucose and for protons was analysed. The vesicles show that copper stress reduced the permeability for glucose of the lipid bilayer barrier. When vesicles from stressed plants were modified by addition of lipids to resemble vesicles from control plants, the permeability for glucose was very similar to that of vesicles from control plants. The permeability for protons did not change upon stress. Electron paramagnetic resonance (EPR) of the lipid vesicles spin probed with n -doxylstearic acid (nDSA) was used to explore the lipid rotational freedom at different depth of the bilayer. The EPR measurements supported the permeability data, indicating that the copper stress resulted in more tightly packed bilayers of the PMs with reduced acyl chain motion.

HSA and BSA, human and bovine serum albumins, react with a reactive dye, C.I. Reactive Blue 29 (levafix brillant blue EB) giving adducts containing two dye molecules per protein molecule. While cysteine was able to react with the dye, the cysteine(s) present in the proteins was not. The dye-protein adducts reveal strong circular dichroism in the 300-720 nm spectral region where only absorption bands of the achiral dye molecule are active. The intensity of these bands depends on the conformation of the protein: particularly the 530-720 nm band. On tuning the denaturation degree by means of SDS addition and removal, the intensity of this band varies between zero and a maximum when the protein is in fully denaturated and native conditions, respectively. This behavior evidences a chiral label function of the dye that can be useful in studying processes regarding proteins.

A solitonic regime has been found in a γ-irradiated single crystal of the malonic acid-urea 1 : 1 adduct. The study has been performed on the α-protons of the radicals by taking advantage of the high resolution of ENDOR spectroscopy and by a careful reproduction of the lineshapes. A solitonic density corresponding to 40 per cent of the radicals present in the single crystal has been obtained. The soliton can be equally ascribed to an incommensurate crystallographic phase or to a solitonic wave excited and sustained by a double-well hydrogen bond present in the crystal. The 1 : 1 adduct seems to have a high electrical conductivity when measured in the crystallographic plane containing the adduct itself.

The oxidative polymerization of furan, 3-methylfuran and 2,2',5',2'-terfuran, induced by iodine in organic solvents having different donicity, was investigated by time-resolved electron paramagnetic resonance (EPR) spectroscopy. The reaction was monitored starting from the onset of the process and radical species arising from the monomers in early stages of the polymerization reaction were detected. The comparison between experimental and theoretical hyperfine coupling constants, obtained by simulated EPR spectra and theoretical ab initio calculations, respectively, allowed one to structurally characterize the above radical species, thus enabling mechanistic conclusions about oxidative coupling. Moreover, the analysis of the time evolution of EPR spectrum during the oxidative polymerization process was used for evaluating the relative amount of localized and mobile radical species along the polymer backbone, thus getting preliminary information about conjugation extent and electroconducting properties of the final material. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1901–1910, 1998

The ENDOR spectra of γ-irradiated single crystals of the urea-malonic acid 1 : 1 adduct were recorded at room temperature. The hyperfine coupling tensor of the α proton of the HOOC-CH-COOH free radical formed by irradiation were measured as well as the hyperfine coupling tensors of a number of hydrogen bonded protons. The tensor elements are compared with values calculated according to the McConnell and Strathdee procedure taking into account the spin distribution in a π- orbital extending over the whole molecule. The position of the proton belonging to a very short hydrogen bond is discussed on the basis of its dipolar and isotropic interaction.

The crystal structure of a 1 : 1 stoichiometric adduct of urea and malonic acid, has been investigated in connection with an ENDOR study of the paramagnetic centre which is formed by γ-irradiation of a single crystal. It is found that the crystal structure consists of a two-dimensional network of hydrogen bonded urea and malonic acid molecules. Interesting features are the planarity of the acid molecule induced by the presence of an intramolecular hydrogen bond, and the presence of a very short hydrogen bond between the carboxylic group and an urea molecule. The position of the proton in this bond is discussed.

The results of a room temperature ENDOR investigation of the secondary radicals formed after X-irradiation in a single crystal of α-calcium formate are reported and discussed. 39 different proton hyperfine tensors have been determined, belonging to magnetically or structurally different radicals. The hyperfine tensors are typical of α-protons in π-radicals, with a spin density ρc = 0·75 on the central carbon atoms. The radicals are identified therefore -O-ĊH-O-CO2- in twelve slightly different conformations. The mechanisms giving rise to the reactions of primary σ-radicals CO2- with the neighbouring undamaged molecules through cooperative rotations around the Ca-O bonds are discussed. It is shown that the experimentally determined C-H directions are very well reproduced by rotations of the formate groups around a Ca-O bond.