Manfred D. Zeidler

N-2-(Azol-1(2)-yl)ethyliminodiacetic acids: a novel series of Gd(III) chelators as T2 relaxation agents for magnetic resonance imaging

The synthesis, physicochemical properties, and toxicological implications of a novel series of N-2-(azol-1(2)-yl)ethyliminodiacetic acids, useful as contrast agents for magnetic resonance imaging are reported. Compounds were prepared by alkylation of methyl iminodiacetate with N-2-bromoethylazoles and subsequent hydrolysis. Stability constants of the corresponding Gd(III) complexes and T1 and T2 relaxivities were determined and interpreted in terms of optimized geometries obtained by semiempirical PM3 calculations. Compounds show increased T2 relaxivity and decreased toxicity in vitro as compared to EDTA-Gd(III) complexes.

Self-diffusion in binary mixtures: The system benzene/cyclohexane at high pressures

Pulsed-gradient spin-echo proton NMR measurements were performed on a 1 : 1 mixture of benzene and cyclohexane at pressures between ambient and 200 MPa and temperatures between 298 and 333 K. A high-pressure probe head was constructed for this purpose. Since the resolution was sufficient to differentiate between the protons of both components, it was possible to obtain the single self-diffusion coefficients for benzene and cyclohexane in the mixture. The results are discussed on the basis of different theories (Thorne–Enskog, Jacucci–McDonald, Enninghorst–Wayne–Zeidler) applicable to mixtures.

The deuterium quadrupole coupling constant in liquid ammonia

The presence of hydrogen bonds in liquid ammonia is not without controversy. Probes for hydrogen bonds are the gas to liquid shift and the temperature dependence in the liquid of the deuterium quadrupole coupling constant (DQCC). Using a new NMR method, the first reliable results for the DQCC in liquid heavy ammonia were obtained for six temperatures between 237 and 293 K. The value of 232(1) kHz at 237 K amounts to only 80% of the gas phase value. A small temperature dependence of about 0.1 kHz K−1 in the liquid is observed. These results support the hypothesis that hydrogen bonds play an important role in liquid ammonia, similar to the situation in water.

High-pressure NMR study of liquid propanol up to 3 GPa

Longitudinal 1H-relaxation rates 1/T1 for the methyl and hydroxy protons of propanol have been recorded at 300 MHz over the pressure range 0.12 GPa to 3.1 GPa at three temperatures 293 K, 308 K and 313 K. A maximum of the relaxation rate as a function of pressure was detected. The probe head is constructed on the basis of an anvil cell with in situ pressure measurement by ruby fluorescence. The probe is pressurised and then transferred to the fluorescence spectrometer and the NMR spectrometer for the respective measurements.

Reduction of the isolated double bond in bis(N-alkenylbenzimidazole)Pd(II) complexes with KBH4

Abstract Palladium(II)-promoted vicinal diamination of N -alkenylbenzimidazoles has been investigated. Dichlorobis(1-(alkenyl)benzimidazole)palladium(II) complexes were identified as initial reaction products which proved to be rather inert to the subsequent oxidative diamination required in the process. Instead, they were readily reduced by KBH 4 to give the corresponding 1-alkylbenzazoles as the main reaction products. The crystal structure of the isolated complex trans -dichlorobis(1-(3-butenyl)benzimidazole)palladium(II) was determined by X-ray diffraction analysis.

Molecular dynamics of hydantoins and barbiturates assessed by 1H, 13C and 15N relaxation data

The molecular dynamics of hydantoin,5,5-dimethylhydantoin,5,5-diphenylhydantoin, barbituric acid and 5-ethyl-5-phenylbarbituric acid in solution are determined to investigate the molecular basis for the activity of these neuroactive drugs. From dipolar 13C and 15N spin-lattice relaxation times the correlation times for the rotational dynamics of specific bond vectors are evaluated. Conclusions can be drawn concerning the anisotropy of the overall molecular rotational motion and the internal rotations of molecular segments. The translational molecular diffusion coefficients are obtained from self diffusion measurements by the pulsed gradients method. The observed differences in the dynamics as well as structural differences may account for the variation in the neuroactivity of the studied compounds.