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Metal Complexes with Tetrapyrrole Ligands. 47. Yttrium(III) Bis(octaalkylporphyrinate)s: Synthesis and Electron Spin Resonance Spectra of Earth Metal Porphyrin Sandwich Compounds

1988; Oxford University Press; Volume: 61; Issue: 1 Linguagem: Inglês

10.1246/bcsj.61.71

1348-0634

Johann W. Buchler, Jürgen Hüttermann, Jürgen Löffler,

Analytical Chemistry and Sensors

Abstract Reaction of tris(2,4-pentanedionato)yttrium(III) with octaethylporhyrin, H2oep in refluxing 1,2,4-trichlorobenzene (TCB) produces a trace (2%) of the double-decker, Y(oep)2 (3A) besides major amounts (72%) of the yttrium(III) monoporphyrinate, Y(oep)(acac) which are separated by chromatography. Appreciable yields of Y(oep)2 (3A) (25%) are obtained from dilithium octaethylporphyrinate, Li2(oep), formed in situ and Y(oep)(acac) in refluxing TCB. The constitution of the double-decker 3A is proved by UV/VIS, IR, 1H NMR, ESR, ENDOR, and mass spectra. The well-defined composition Y(oep)2 requires that one of the porphyrin rings is electron-deficient, i.e. the charge of the YIII ion is compensated by the normal porphyrinate dianion and a porphyrinate monoanion radical. The magnetic moment in the solid state, μeff=1.5 B.M. (5–100 K), demonstrates the radical nature of 3A as well. Under the time resolution of the methods used, the unpaired electron is delocalized between the two porphyrin rings. The wavenumber of the internal charge transfer absorption band in the near infrared (λCTI 1175 nm) agrees well with the value expected for the ionic radius of YIII according the linear relationship of the energy of the CTI band and the ionic radius which has been established for the series of lanthanoid octaethylporphyrinates, Ln(oep)2 (Ln=La···Lu). 3A can be reduced to the diamagnetic sandwich anion, [Y(oep)2]−. YIII double-decker radicals Y(omp)2 (3B; λCTI 1100 nm) or Y(hbp)2 (3C, λCTI 1100 nm) containing octamethylporphyrin or hexadecahydrotetrabenzoporphyrin have also been prepared.