Síntese, caracterização e atividade catalítica de novos catalisadores metaloporfirínicos suportados / Synthesis, characterization and catalytic activity of novel anchored metalloporphyrin catalysts
André Luiz de Faria
DATA DE PUBLICAÇÃO
In this work the second generation metalloporphyrin Me(TFPP)Cl (Me = Fe and Mn) [5,10, 15, 20 ? tetrakis(pentafluorophenyl) porphyrin iron (III) or manganese (III) chloride] was covalently anchored to aminofunctionalyzed supports, through nucleophilic substituition of the para-fluorine atoms of the pentafluorophenyl meso-aryl groups, with the objective of obtaining selective solid catalysts for oxidation reactions of organic molecules. The supports montmorillonite (modified with aminopropyltrietoxysilane, Mont1, and chloropropyltrietoxysilane followed by 1,6 ? diaminohexil, Mont2) and silica modified with 1,6 ? diaminohexil (DAHS) were initially synthesized; aminofunctionalyzed polystyrene, PS, was given by Prof. Dr. John Lindsay Smith, York ? England; hybrid magnesium phyllosilicates, Silx and Talx, were previously synthesized by Prof. dr. Cláudio Airoldi´s research group, UNICAMP ? Campinas; and 3 ? aminopropylsilica, APS, was purchased from Aldrich. The supports Mont1, Mont2, DAHS and metalloporphyrins were firstly synthesized and characterized, followed by the anchoring reactions. The solid catalysts were characterized by UV/Vis, IR, EPR, TGA, X-ray. The catalytic activity of these solid catalysts was investigated in the oxidation of cyclooctene, cyclohexane and styrene, using PhIO and H2O2, as oxidants. These systems possibilities the study of the effects: distance between the metalloporphyrin and the supports surface (?arm? size); polarity; support?s structures (amorphous or lamellar, organic or inorganic, rigid or flexible); metalloporphyrin´s central metal ion; protection of the free NH2 on the support. In general way, the investigated systems show to be efficient catalysts for all substrates, mainly from the supports, proving that the covalent bond is an efficient method for the preparing of anchored catalysts. The stability of these systems was also investigated through developing four reaction cycles with the same solid catalyst, with reproducible products yields. The FeP were more efficient catalysts than the MnP, even using imidazole as co-catalyst for the MnP. The better catalysts were FeAPS, FeMont1, FeDAHS, FeTal2 and FeSil2. All these solid catalysts are rigid and inert, with an intermediary ?arm? size (4-7 atoms). The protection of the support?s free NH2 groups is fundamental to improve the catalytic efficiency of metalloporphyrins anchored on aminofunctionalized supports, because it avoids the bis-coordenation of the NH2 groups to the metal ion, effect responsible for the blocking of the catalytic site. Although the oxidation products yields using H2O2 have been lower than these using PhIO, some systems were more efficient when compared to the homogeneous systems both in product yield and selectivity. These results open the possibility for utilization of the system for drugs and poluents oxidation.
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