Comparative Study of Structure−Properties Relationship for Novel β-Halogenated Lanthanide Porphyrins and Their Nickel and Free Bases Precursors, as a Function of Number and Nature of Halogens Atoms^⊥

The synthetic route of partially β-halogenated via a “metal-assisted” reaction and perhalogenated terbium complexes is described. This protocol allows the facile insertion of the halogens (bromines or chlorides) to the porphyrin peripheral positions. The electronic absorption spectra and the redox potentials of the free porphyrins as well as the terbium complexes are dramatically affected as the number of halogen atoms increase. In fact, two antagonistic effects are responsible for that, the inductive and the distortion effects on the porphyrin ring. They result in a red shift for the Soret band and a stabilization/destabilization of the HOMOs/LUMOs which in turn is manifested by variations on the redox potentials. The novel crystal structure of the Ni(Cl₈TPP) is discussed in great detail and compared with the previously reported structures of Tb(Cl₈TPP) (OAc)(DMSO)₂·3PhCH₃·MeOH and H₂(Br₈TPP), as well as with other perhalogenated nickel porphyrins available in the literature.