SYNTHESIS, CHARACTERIZATION, AND ELECTROCHEMISTRY OF HETEROLEPTIC DOUBLE-DECKER COMPLEXES OF THE TYPE PHTHALOCYANINATO PORPHYRINATO ZIRCONIUM(IV) OR HAFNIUM(IV)

The synthesis, spectroscopic characterization, and electrochemistry of 12 different neutral, singly and doubly oxidized heteroleptic double-decker complexes of the type [M(IV)(P)(Pc)](n) where n = 0, +1, or +2, M = Zr or Hf, P = the dianion of octaethylporphyrin (OEP) or tetraphenylporphyrin (TPP), and Pc = the dianion of phthalocyanine are reported. Each neutral compound was characterized by H-1 NMR, UV-visible, and IR spectroscopy while each oxidized or reduced compound was characterized by UV-visible and/or EPR spectroscopy. The neutral compounds all undergo two reversible ring-centered oxidations and two reversible ring-centered reductions. Comparison is made with data obtained for the corresponding actinide double-decker complexes containing Th(IV) or U(IV) central metal ions and correlations examined between E(1/2) for till of the compounds and either the metal ionic radius or the absorbance band energy of the porphyrin Soret or phthalocyanine UV-band. The half-wave potentials depend upon the type of macrocycle. They also vary with the size of metal ion in the case of oxidation but not in reduction, where E(1/2) values are relatively unaffected and shift by only 20-40 mV upon going from Hf(P)(Pc) to Th(P)(Pc) as compared to a much larger 220-280 mV shift between E(1/2) for the first oxidation of the same compounds.