Synthesis and characterization of a modified "picket fence" porphyrin complex - stronger π bonding interactions between Fe(ii) and axial ligands.

A new, modified "picket fence" porphyrin is synthesized and its bis(imidazole)-ligated iron(ii) derivative [Fe(MbenTpivPP)(1-MeIm)(2)] is investigated. X-ray structure determinations demonstrate that [Fe(MbenTpivPP)(1-MeIm)(2)] has structural features of a near planar porphyrin plane, a relative perpendicular ligand orientation, and one unusually large absolute ligand orientation (φ). The combination of these features leads to a new type of species that is different from previously reported analogues. Further structural examination reveals a strong correlation between the mutual ligand orientations (θ) and the axial Fe-N(Im) bond distances, which is detailed for the first time. Mössbauer spectroscopic characterization shows that the low spin derivative has a quadrupole splitting of 0.99 mm s(-1) at 100 K.