Fixation of the 2-methylimidazole ligand and anomalous pyrrole chemical shifts in bis(2-methylimidazole) (meso-tetraalkylporphyrinato)iron(III) chloride caused by the nonplanar porphyrin ring

Dynamic NMR study of bis(2-methylimidazole)(meso-tetraalkylporphyrinato)iron(III) complexes, [Fe(TRP)-(2-MeIm)(2)](+) (R = Me, Et, iPr), has revealed that the 2-methylimidazole ligands were orientationally fixed even in less bulky methyl complex and that the pyrrole signals of the isopropyl complex appeared in a so-called diamagnetic region in spite of the S = 1/2 spin state. The anomaly was ascribed to the nonplanarity of the porphyrin ring.