Bis(thf)(porphyrinato)iron(III) complexes with highly S₄-ruffled and S₄-saddled porphyrin cores are determined to be very pure intermediate spin complexes on the basis of NMR, EPR, Mössbauer, and magnetic data.

Combined analyses using NMR, EPR and Mössbauer spectroscopy as well as SQUID magnetometry have revealed that highly saddle shaped Fe(OETPP)I adopts an essentially pure intermediate spin state in spite of the coordination of an iodide ligand.

A novel spin transition between S = and S = has been observed for the first time in five-coordinate, highly saddled iron(III) porphyrinates by EPR and SQUID measurements at extremely low temperatures.