The fascinating story of axial ligand dependent spectroscopy and redox-properties in iron(ii) phthalocyanines

Iron phthalocyanines play crucial fundamental and applied roles ranging from bulk colorants to components of advanced materials. In this Frontier article, we discuss four aspects concerning the influence of the axial ligands on spectroscopic and redox properties of iron(ii) phthalocyanines: (i) iron versus macrocycle oxidation cite as a function of Lever's E-L parameter; (ii) energy of the metal-to-ligand charge-transfer transitions as a function of Lever's E-L parameter; (iii) iron versus macrocycle reduction in iron(ii) phthalocyanines; (iv) Mossbauer quadrupole splitting as a function of axial ligand binding through the prism of d(z)2 orbital population.