Synthesis and Characterization of Rare Earth Corrole–Phthalocyanine Heteroleptic Triple-Decker Complexes

We
recently reported the first example of a europium triple-decker tetrapyrrole
with mixed corrole and phthalocyanine macrocycles and have now extended
the synthetic method to prepare a series of rare earth corrole–phthalocyanine
heteroleptic triple-decker complexes, which are characterized by spectroscopic
and electrochemical methods. The examined complexes are represented
as M2[Pc­(OC4H9)8]2[Cor­(ClPh)3], where Pc = phthalocyanine, Cor =
corrole, and M is Pr­(III), Nd­(III), Sm­(III), Eu­(III), Gd­(III), or
Tb­(III). The Y­(III) derivative with OC4H9 Pc
substituents was obtained in too low a yield to characterize, but
for the purpose of comparison, Y2[Pc­(OC5H11)8]2­[Cor­(ClPh)3] was
synthesized and characterized in a similar manner. The molecular structure
of Eu2[Pc­(OC4H9)8]2­[Cor­(ClPh)3] was determined by single-crystal
X-ray diffraction and showed the corrole to be the central macrocycle
of the triple-decker unit with a phthalocyanine on each end. Each
triple-decker complex undergoes up to eight reversible or quasireversible
one-electron oxidations and reductions with E1/2 values being linearly related to the ionic radius of the
central ions. The energy (E) of the main Q-band is
also linearly related to the radius of the metal. Comparisons are
made between the physicochemical properties of the newly synthesized
mixed corrole–phthalocyanine complexes and previously characterized
double- and triple-decker derivatives with phthalocyanine and/or porphyrin
macrocycles.