DOUBLE-DECKER ACTINIDE PORPHYRINS AND PHTHALOCYANINES - SYNTHESIS ANDSPECTROSCOPIC CHARACTERIZATION OF NEUTRAL, OXIDIZED, AND REDUCED HOMOLEPTIC AND HETEROLEPTIC COMPLEXES

The synthesis, spectroscopic characterization, and electrochemistry of 26 different neutral and singly-oxidized homoleptic and heteroleptic actinide double-decker complexes are reported. The investigated compou nds are represented as [M(P)2]n, [M(P)(P')]n, [M(Pc)2]n, and [M(P)(Pc) ]n where n = 0 or 1+, M = U or Th, Pc = the dianion of phthalocyanine, and P or P' = the dianions of octaethylporphyrin (OEP), tetraphenylpo rphyrin (TPP), or tetra-p-tolylporphyrin (TpTP). Each neutral compound was characterized by H-1 NMR, UV-visible, and IR spectroscopy and com parisons made to the cationic singly-oxidized double-decker derivative s which were chemically generated and isolated as a SbCl6-salt. The in itial neutral species can undergo up to six reversible one-electron tr ansfers in nonaqueous media, and U(IV) or Th(IV) compounds with a give n set of porphyrin or phthalocyanine macrocycles could be electrogener ated in up to seven different oxidation states. Some of these species were characterized by UV-visible or FTIR thin-layer spectroelectrochem istry and the resulting spectral data then used along with the redox p otentials to assign the site of each electron transfer. The first two reductions of M(P)(Pc) occur mainly at the Pc ring while the first two oxidations of the same heteroleptic compound involve primarily orbita ls of the porphyrin macrocycle. This result contrasts with the homolep tic M(P)2 and M(Pc)2 derivatives which undergo initial one-electron ox idations and reductions which are localized not at a single porphyrin or phthalocyanine ring but rather at orbitals involving both macrocycl es. The ESR spectra of [Th(OEP)(Pc)]+ and [Th(TPP)(Pc)]+ show triplet character in toluene or methylene chloride and give data consistent wi th the presence of dimers held together by pi-pi interactions between two Pc macrocycles. The calculated distance between the two electrons in the dimer varies between 8.8 and 9.0 angstrom, which is consistent with the hole of [Th(P)(Pc)]+ being localized on the porphyrin ring an d the two cation radicals being separated in the pi-pi complex by an a verage of about 3.3 angstrom. No pi-pi interactions are observed for t he singly-oxidized homoleptic species, and the ESR spectra of [Th(P)2] + and [Th(Pc)2]+ suggest simple monomeric cation radicals, both-as SbC l6- salts in the solid state and in frozen solutions of CH2Cl2 or pyri dine at 110 K.