Abstract 1-Methyl-, 1-ethyl-, 1,2-dimethyl-and 1,2,3,4-tetramethylimidazole react with pentacarbonyliron to yield [FeIm6][Fe(CO)8] (1), [FeIm6][Fe(CO)4]2 (2), [FeIm4][Fe(CO)4] (3) and Fe(Im)(CO)2 (4) (Im = substituted imidazole). The crystal and molecular structures of 1 and 2 have been determined by X-ray diffraction. For 1 and 2 agreement between calculated and measured Mössbauer absorption intensities was obtained by taking into account Debye-Waller-factors, which were derived from the X-ray diffraction experiments.
Durch Umsetzung von Ferroccn und Cyclopentadienyleisendicarbonyl mit Imidazol, 2‐Methyl‐, 2‐Äthyl‐ und 2‐Phenylimidazol konnten die Eisen(II)‐Derivate dieser Heterocyclen dargestellt werden. Die Verbindungen wurden thermogravimetrisch und Mössbauer‐spektrometrisch untersucht. Die Derivate der substituierten Imidazole besitzen die erwartete Zusammensetzung Fe(N2C3H2R)2 (R = CH3, C2H5, C6H5) und vierfach koordiniertes Eisen. Die Umsetzung mit nicht substituiertem Imidazol ergibt eine Verbindung Fe(N2C3H3)2 · 0,71 N2C3H4, die sowohl vierfach als auch sechsfach koordinierte Metallionen enthält.
Single crystals of myoglobin enriched on Fe57 with a diameter of about 0.5 mm were prepared. After deoxygenation crystallographic alignment and Mössbauer measurements were carried out at 77°K. In the experiment eight different orientations were selected by rotating the crystal around the b axis, thus, b axis and γ-ray propagation direction remained perpendicular to each other. From the intensity ratio of the quadrupole split spectra we derive the sign and the orientation of the principal axis of the electric field gradient. We find Vzz to be positive and forming an angle of 40° to the b axis. From two alternatives consistent with our experiments we conclude that VZZ is most likely oriented along one of the four Fe-N directions in the heme.
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