1H-NMR spectroscopic studies of paramagnetic superstructured iron(III) porphyrins

Abstract

The electronic properties of several superstructured iron(III) porphyrins, in which the two faces of the porphyrin are protected by two chains linked at the opposite phenyl rings, have been investigated. The paramagnetic ¹H NMR spectra of three iron(III) “basket-handle” porphyrins such as Fe^III[e-BHP(C₁₂)₂], Fe^III[a-BHP(C₁₂)₂] and Fe^III[e-BHP(C₁₂)(ImC₁₁)] in organic solvent have been assigned. The ¹H T₁ values of the signals were measured and resonance assignments made based on NOESY and COSY experiments. The electronic structure of the iron(III) is discussed on the basis of the temperature dependence of the isotropic shifts and relaxation times. The hyperfine-shifted resonances in these spectra are compared with those of unhindered iron(III) porphyrins.