This review describes the effects of highly deformed porphyrin ring on the electronic structures of iron(III) porphyrinates, which includes (i) the electron configurations in low-spin (S = 1/2) ruffled complexes, (ii) the contribution of the intermediate-spin (S = 3/2) state in the spin-admixed (S = 5/2, 3/2) complexes with ruffled and saddled porphyrin ring, and (iii) the novel spin crossover (S = 1/2, S = 3/2) phenomenon in saddled complexes, with a special emphasis on the use of H-1 NMR, C-13 NMR, and EPR spectroscopy. (c) 2006 Elsevier B.V All rights reserved.