Intramolecular Dynamics of Lanthanide(III) Tetraoxadiaza Macrocycle Complexes in Solution as Studied by NMR

¹H and ¹³C NMR and ¹H NMR relaxation spectroscopy (RS)measurements are reported for the CDCl₃ and CD₂Cl₂ solutions of [La(NO₃)₃(diaza-18-crown-6)] ({bf I}), [Pr(NO₃)₃(diaza-18-crown-6)] ({bf II}) and [Nd(NO₃)₃(diaza-18-crown-6)] ({bf III}) complexes. Temperature dependencies of the ¹H NMR spectra of II have been analyzed using the dynamic NMR methods for multi-site exchange. Enantiomeric isomer interconversion in II is characterized by H = 21.5 ± 4 kJ mol^-1. Studies of the values of the lanthanide-induced shifts and the longitudinal relaxation rate enhancement revealed that the structure of complexes in solution is similar to that reported for the [La(NO₃)₃(18-crown-6)] complex in the crystal state. Nevertheless, it appears that the principal values of the molar paramagnetic susceptibility tensor (_i) significantly differ in complexes II and III. The possible reasons for the different characteristics of these complexes are discussed.     

Template-induced control of stereochemistry for the synthesis of linear vinyl polymers

Asymmetric cyclocopolymerization of judiciously designed bifunctional monomers with a number of common comonomers affords optically active vinyl polymers with main chain chirality. Tacticity and sequence of comonomeric units can be controlled and thus complicated structures built up. Under different reaction conditions the same bifunctional monomer 1 can undergo cyclization involving a 19-, a 21-, or an 18-membered ring. With monomer 3 an 11-membered ring is formed.     

Ueber die Bestimmung der St?rke in Cerealien, Kartoffeln und in der Handelsst?rke

Ohne Zusammenfassung     

Calculation of the Knight shift in palladium

The direct and the exchange core polarization (ECP) contributions of the conduction electrons to the Knight shift of palladium are evaluated. To obtain the wave functions for the conduction electrons and the partial densities of states at the Fermi surface a KKR energy band calculation was performed. The contributions of the core electrons to the Knight shift were determined by using the moment perturbation method (MP). Electron-electron interactions are taken into account by individual enhancement factors for thed ands electrons. The agreement between the theoretical results and the available experimental data is quite satisfactory.     

A Mössbauer investigation of diamagnetic,semiconducting alpha-FeP4

Measurements of the magnetic and electrical properties show the ambient pressure (α) modification of FeP₄ to be diamagnetic and semiconducting. Its ⁵⁷Fe Mössbauer spectra were recorded at room temperature and liquid nitrogen temperature. They are discussed together with the Mössbauer spectra of the other iron phosphides. There is a significant difference between the isomer shifts of the intermetallic-like phosphides with high coordination for all atoms and the polyanionic phosphides with low coordination numbers.