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15N-NMR chemical shifts, spin-lattice, and spin-spin relaxation times of the four pyrrole nitrogen nuclei in complexes of low-spin ferritetraphenylporphyrin with pyridine and 1-methylimidazole in chloroform have been studied. Although deviations from an axial symmetry are observed at 4K by EPR and ENDOR spectroscopy, only one 15N-NMR absorption signal can be detected at T < 200 K indicating that rhombic distortions are averaged out at temperatures where NMR is observed. From an analysis of the 15N-NMR relaxation behavior it was possible to determine the magnitude of the hyperfine coupling constant A, from which the Fermi contact term to the chem­ical shift was obtained. For a calculation of the pseudocontact shift, which is of the same size as the contact term, not only the shifts arising from the ‘orbital term’ but also bonding effects be­tween the pyrrole nitrogen orbitals and the Fe3+ orbitals have to be considered.

Proton spin-lattice relaxation times of pyridine and 1-methylimidazole complexed on Fe(III)protoporphyrin IX dimethyl ester, Fe(III)tetraphenylporphyrin in chloroform and on metmyoglobin in 2H2O have been measured. Caused by chemical exchange of the ligand molecules into the bulk solvent phase, the decay of their MZ-magnetization is given by a superposition of two exponentials from which the mean lifetime of the complexed species can be determined. This method offers the possibility to study exchange kinetics of ligand molecules from a well defined molecular configuration. The present data are compared with the results from linewidth measurements of the bulk phase molecules. From both sets of parameters a detailed picture of the ligand exchange can be gained, particularly if spin transition of the paramagnetic organic metal complex occurs, as is the case for some ferriporphyrins. For metmyoglobin, the NMR result is compared with relaxation times extracted from temperature jump experiments under similar conditions.

Changes of the solvation sphere of N,N′-dibenzoyl-m-phenlyenediamine (as a model substance for aromatic polyamides) in N,N′-dimethylacetamide caused by electrolytes such as LiCl, LiBr or BeCl2 were studied by 13C NMR chemical shift measurements. The observed variations of the chemical shift data were interpreted by a stronger interaction of the solvent molecules with the carbonamide group. The relation of the carbonyl and the amide group interaction with the solvent or the solvated cations depends on the kind of electrolyte. It is not possible to correlate the obtained results with the influence of these electrolytes upon the molecular weight of the aromatic polyamides prepared in N,N′-dimethylacetamide. Therefore some possible explanations are discussed.

Synthesis of a Bifunctional Spin-label for Cross-linking of Proteins The nitroxyl radical 4 of the pyrrolidine series with two functional iodoacetamido groups was synthesized. It appears to be useful for cross-linking of proteins and subsequent conformational studies by the ESR method.