Synthesis and Structure of Transition-Metal Bis(porphyrinato) Complexes. Characterization of Zr(TPP)2 and Zr(OEP)2

Kimoon Kim, Won S. Lee, Hee Joon Kim, Sung Hee Cho, Gregory S. Girolami, Philip A. Gorlin, Kenneth S Suslick

Research output: Contribution to journalArticlepeer-review

Abstract

Treatment of Zr(NEt2)4 with the free-base porphyrins 5,10,15,20-tetraphenylporphyrin (H2TPP) or 2,3,7,8,12,13,17,18-octaethylporphyrin (H2OEP) gives the transition-metal bis(porphyrinato) complexes Zr(TPP)2 and Zr(OEP)2. The hafnium analogue Hf(OEP)2 may be prepared similarly from Hf(NEt2)4. The complexes have been characterized by UV-vis and 1H NMR spectroscopy, and the molecular structure of Zr(TPP)2 has been determined crystallographically. The Zr-N distances of 2.40 (1) Å and the porphyrin-porphyrin interplanar spacing of 2.56 Å are the shortest such distances in all known M(porphyrinato)2 complexes. The cyclic voltammograms indicate that Zr(TPP)2 and Zr(OEP)2 each undergo two oxidations and two reductions; the redox potentials suggest that there is significant overlap between the π-systems of the two porphyrin rings. Chemical oxidation of the Zr(porphyrinato)2 complexes with phenoxathiinylium hexachloroantimonate has led to the isolation of the π-radical-cation complexes [Zr(TPP)2+] [SbCl6-] and [Zr(OEP)2+][SbCl6-]. The UV-vis, near-IR, EPR, and IR spectra of these cations are consistent with oxidation of the porphyrin-porphyrin ir-system; most notable are the unusually high energy near-IR bands at 1110 and 962 nm in the TPP and OEP complexes, respectively. The high energy of these bands with respect to those of other [M(porphyrinato)2+] cations with larger metal atoms again can be rationalized on the basis of unusually strong overlap between the π-systems of the two porphyrin rings. Crystallographic data for Zr(TPP)2·C5H12: monoclinic, space group C2/c, with a = 21.183 (3) Å, b = 21.263 (4) Å, c = 18.688 (3) Å, β = 124.57 (1)°, V= 6930.9 Å3, Z = 4; RF = 0.077 and RwF = 0.083 for 1578 independent reflections with I > 3τ(I).

Original languageEnglish (US)
Pages (from-to)2652-2656
Number of pages5
JournalInorganic Chemistry
Volume30
Issue number12
DOIs
StatePublished - Jun 1 1991

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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