The use of polythiophene films for the immobilization of enzymes at electrodes is shown to have advantages over other conducting polymer films. Two methods by which the enzymes can be immobilized—entrapment and covalent immobilization at the surface—are described and compared. The improved stability of polythiophene against oxidation in ambient environments is expected to enable the construction of biosensors with improved sensor characteristics and lifetime.

A method for the experimental determination of ligand-field (LF) energy splitting in mononuclear lanthanide complexes, based purely on variable-temperature NMR spectroscopy, was developed. The application of this method in an isostructural series of anionic lanthanide bis(cyclooctatetraenide) double-decker compounds bearing large rigid substituents is demonstrated. Using the three-nuclei plot approach devised by Reilley, the isostructurality of the compound series and the identical orientation of the magnetic main axis of all Ln ions in the series Tb to Tm are demonstrated. Measurement of the H NMR spectra of partially deuterated analogues of the complexes permitted determination of the axial magnetic susceptibility anisotropies χ for all five ions in the temperature range from 185 to 335 K. For this purpose, analysis of the hyperfine shifts was combined with structural models derived from density functional theory calculations. In a final step, the temperature dependence of the χ values was used for determination of the three axial LF parameters, adapting a method employed previously for phthalocyanine-based systems. The temperature dependence dictated by the LF parameters determined by this NMR-based approach is compared to the results of recently published ab initio calculations of the system, indicating reasonable agreement of both methods. For all ions except Dy, the NMR method determines the same m ground state as the calculations and the order and energies of the excited states match well. However, the sign of the magnetic anisotropy of the dysprosium complex in the temperature range evaluated here is not correctly predicted by the published calculations but can be described accurately by the NMR approach. This shows that our experimental method for determination of the LF parameters is an ideal complementation to other theoretical and experimental methods.

Polarization transfer efficiency in liquid-state dynamic nuclear polarization (DNP) depends on the interaction between polarizing agents (PAs) and target nuclei modulated by molecular motions. We show how translational and rotational diffusion differently affect the DNP efficiency. These contributions were disentangled by measuring 1 H-DNP enhancements of toluene and chloroform doped with nitroxide derivatives at 0.34 T as a function of either the temperature or the size of the PA. The results were employed to analyze 13

Communications ylide was consumed between successive additions. When no color change was observed upon addition of the base the reaction mixture was diluted with an equal volume of water. The mixture was extracted with diethyl ether three times, the combined organic layers were washed with water several times, dried over anhydrous magnesium sulfate and the solvent distilled. The pure all-trans isomer was obtained by heating the olefins inp-xylene with a catalytic amount of iodine. The pure product was obtained after repeated crystallization from THFimethanol. Yield 1.42 g, 71 %. 'H-NMR (CDC13): 6 0.89(t,CH3), 1.(2,5-Bis(4-styryl)styryl) 1 ,4dioctyloxybenzene (2) was prepared according to the same procedure as described for (1) from (4-(styryl)benzyltriphenylphosphonium bromide (3.5 g, 6.5 mmol) and 2,5-dioctyloxyterephthaldialdehyde (1.0 g, 2.6 mmol). Yield 1.48 g, 77%. 'H-NMR: 60.91(t,CH3), 1.33(m,5CHz), 1.54(m,y-CH2), I.90(m,P

Reported are the syntheses, structures and magnetic properties, also by NMR spectroscopy in solution, of a series of 13 linear trinuclear 3d-4f compounds with a lanthanide(iii) surrounded by two Ni ions, NiLn, where the central Ln is hexacoordinate. For three of the crystal structures, an additional HO molecule is coordinated to the central Ln ion, leading to a monocapped trigonal prismatic structure. However, NMR spectroscopy indicates that in solution, these complexes also have a hexacoordinate Ln center. The solution magnetic anisotropies, determined by NMR spectroscopy, indicate that the axial components of the anisotropies are relatively small and that the Dy derivative might therefore not exhibit single molecule magnetism. The axial anisotropies determined by NMR spectroscopy are in good agreement with the expectations based on the distorted trigonal prismatic ligand field.