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Journal of Catalysis, Vol.257, No.2, 233-243, 2008
Synthesis, characterization, and catalytic activity of anionic iron(III) porphyrins intercalated into layered double hydroxides
The first generation free-base anionic porphyrin [H-2(TSPP)](4-), its iron(III) porphyrin [Fe(TSPP)](3-), and the second generation anionic complexes [Fe(TDFSPP)](3-) and [Fe(TDCSPP)](3-) were intercalated into the layered double hydroxide ZnnAl-LDH (n = 2, 4 or 5) by coprecipitation at constant pH. The materials were characterized by X-ray powder diffraction, UV/visible spectroscopy in glycerin mull, attenuated total reflectance Fourier transform infrared spectroscopy, and electron paramagnetic resonance. Results revealed that the coprecipitation method led to intercalation of the free-base porphyrin and the iron(III) porphyrins between the ZnnAl-LDH layers. The materials were used as catalysts in the oxidation of cyclooctene, cyclohexene, and cyclohexane by iodosylbenzene. The catalytic activity of [Fe(TDCSPP)]-Zn2Al-LDH was higher than that of the homogeneous [Fe(TDCSPP)](3-), but the opposite effect was observed in the case of [Fe(TDFSPP)]-Zn2Al-LDH. Although [Fe(TDFSPP)](3-) and [Fe(TDCSPP)](3-) are structurally similar, their intercalation into Zn2Al-LDH likely results in different chemical environments, leading to distinct catalytic activities. (c) 2008 Elsevier Inc. All rights reserved.