Advanced Paramagnetic Resonance Studies on Manganese and Iron Corroles with a Formal d4 Electron Count

Metallocorroles wherein the metal ion is MnIII and formally FeIV are studied here using field- and frequency-domain electron paramagnetic resonance techniques. The MnIII corrole, Mn(tpfc) (tpfc = 5,10,15-tris(pentafluorophenyl)corrole trianion), exhibits the following S = 2 zero-field splitting (zfs) parameters: D = −2.67(1) cm–1, |E| = 0.023(5) cm–1. This result and those for other MnIII tetrapyrroles indicate that when D ≈ – 2.5 ± 0.5 cm–1 for 4- or 5-coordinate and D ≈ – 3.5 ± 0.5 cm–1 for 6-coordinate complexes, the ground state description is [MnIII(Cor3–)]0 or [MnIII(P2–)]+ (Cor = corrole, P = porphyrin). The situation for formally FeIV corroles is more complicated, and it has been shown that for Fe(Cor)X, when X = Ph (phenyl), the ground state is a spin triplet best described by [FeIV(Cor3–)]+, but when X = halide, the ground state corresponds to [FeIII(Cor•2–)]+, wherein an intermediate spin (S = 3/2) FeIII is antiferromagnetically coupled to a corrole radical dianion (S = 1/2) to also give an S =...