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Synthesis of metallotetraphenyl-porphyrin in the presence of zeolite
502 Abstracts
179
SYNTHESIS OF METALLOTETRAPHENYL-PORPHYRIN IN THE PRESENCE OF ZEOLITE S. Nakagaki~ A.S. Mangrich, C. R. Xavier and A. M. Machado Departamento de Quimica, Centro Polit~cnico- UFPR; C.P. 19081, CEP81531990, Curitiba- PR BRAZIL Inorganic compounds such as silica gel, clays and zeolites have been investigated as matrix for immobilization of metalloporphyrins, acting as biomimetic catalysts, because of their stability to oxidative degradations reactions and to temperature. Moreover the matrix can be easily recovered after a catalitic cycle. The zeolite structure (zeolite supercage) in particular, can be an interesting selective ambient for a bether approach of the substrates into the active sites of the metallocomplex present in the zeolitic matrix, where the selective catalytic oxidations of current interest take place. Recently we prepared the tetraphenylporphyrin (TPP) in the presence of zeolite NaY impregnated with Cu (II) ions in propionic acid in a template way [1]. The CuTPP obtained in the reaction solution was characterized by UV-VIS spectra after a few hours of the reaction suggesting that, in the presence of zeolites, the synthesis of this porphyrin is quite efficient. The Cu-complex formed in the zeolite surface was removed after washing exhaustively with dichloromethane in a soxhlet extractor. In order to detect the intrazeolitic Cu-Complex formed during CuTPP synthesis , the whashed zeolite was dissolved in concentrated snlphuric acid. The resulting green acid solution exhibit a broad band at 440 nm in the UV-Vis ~ suggesting the presence of CuTPP. Now we have also studied the EPR spectra at room temperature and at 77 K of the Cu complex formed inside the zeolite cages. The spectrum at room temperature showed a organic radical signal at g = 2.00 and a large signal at g = 2.21, probably due to Cu - Cu interaction [2]. At 77 K the large signal at g = 2.21 desappeared suggesting that at low temperatures the Cu-Cu interactions have been reduced. At 77 K the EPR parameters observed, gl = 2.46, g~ = 2.06, A I = 132 G and g = 2.00 (radical signal), indicate formation of Cu-complex intra zeolitic cavity. The EPR spectrum of the TPP reaction solution (containing CuTPP and characterized by UVVis) was different, showing the EPR parameters, gl =2.19, &= 2.06, AI= 201 G and Ar~ = 18 G. The lower A I and higher gl values observed in the intra zeolitic Cu-Complex compared of CuTPP (from the reaction solution) togheter with low resolution of the nitrogen hyperfine splitting can be a consequence of the low symmetry (or distortion) of this Cucompound produced intra zeolitic These results indicate that the Cu-compounds presented in the zeolitic cavity has lower symmetry in this synthetic way. Similarly, TPP was also synthesized in the presence of zeolite NaY but impregnated with Fe(III) ions. The EPR spectrum at room temperature of the zeolite solid after the reaction, and being washed in a soxhlet showed a broad signal at g = 2.47 suggesting the interaction between Fe-Fe center inside the zeolite cage. It was also observed a radical signal at g = 2.00 assigned to a zeolite polypyrrol radical formed in the zeolitic cavity [3]. At 77 K the EPR spectrum presented gl = 6.04 due to Fe (III) high spin in an axial symmetry (commonly observed in iron(III)porphyrin ); g = 4.30, due to Fe (III) high spin in a rhombic symmetry and g = 2.00 (radical signal). At this temperature the broad signal observed at room temperature desappered similarly to that observed for Cu systems. 1- S.Nakagaki, A.S.Mangrich, C.R.Xavier and A.M.Machado; XVIII Meeting of Brasilian Chemistry Society (1995) - Brazil. 2- H.Yokoi et al.; J.Am.Chem.Soc.; 108, 3361 (1986). 3- G.L.Haller et al.; J.Phys.Chem.;96, 4145 (1992).
179
SYNTHESIS OF METALLOTETRAPHENYL-PORPHYRIN IN THE PRESENCE OF ZEOLITE S. Nakagaki~ A.S. Mangrich, C. R. Xavier and A. M. Machado Departamento de Quimica, Centro Polit~cnico- UFPR; C.P. 19081, CEP81531990, Curitiba- PR BRAZIL Inorganic compounds such as silica gel, clays and zeolites have been investigated as matrix for immobilization of metalloporphyrins, acting as biomimetic catalysts, because of their stability to oxidative degradations reactions and to temperature. Moreover the matrix can be easily recovered after a catalitic cycle. The zeolite structure (zeolite supercage) in particular, can be an interesting selective ambient for a bether approach of the substrates into the active sites of the metallocomplex present in the zeolitic matrix, where the selective catalytic oxidations of current interest take place. Recently we prepared the tetraphenylporphyrin (TPP) in the presence of zeolite NaY impregnated with Cu (II) ions in propionic acid in a template way [1]. The CuTPP obtained in the reaction solution was characterized by UV-VIS spectra after a few hours of the reaction suggesting that, in the presence of zeolites, the synthesis of this porphyrin is quite efficient. The Cu-complex formed in the zeolite surface was removed after washing exhaustively with dichloromethane in a soxhlet extractor. In order to detect the intrazeolitic Cu-Complex formed during CuTPP synthesis , the whashed zeolite was dissolved in concentrated snlphuric acid. The resulting green acid solution exhibit a broad band at 440 nm in the UV-Vis ~ suggesting the presence of CuTPP. Now we have also studied the EPR spectra at room temperature and at 77 K of the Cu complex formed inside the zeolite cages. The spectrum at room temperature showed a organic radical signal at g = 2.00 and a large signal at g = 2.21, probably due to Cu - Cu interaction [2]. At 77 K the large signal at g = 2.21 desappeared suggesting that at low temperatures the Cu-Cu interactions have been reduced. At 77 K the EPR parameters observed, gl = 2.46, g~ = 2.06, A I = 132 G and g = 2.00 (radical signal), indicate formation of Cu-complex intra zeolitic cavity. The EPR spectrum of the TPP reaction solution (containing CuTPP and characterized by UVVis) was different, showing the EPR parameters, gl =2.19, &= 2.06, AI= 201 G and Ar~ = 18 G. The lower A I and higher gl values observed in the intra zeolitic Cu-Complex compared of CuTPP (from the reaction solution) togheter with low resolution of the nitrogen hyperfine splitting can be a consequence of the low symmetry (or distortion) of this Cucompound produced intra zeolitic These results indicate that the Cu-compounds presented in the zeolitic cavity has lower symmetry in this synthetic way. Similarly, TPP was also synthesized in the presence of zeolite NaY but impregnated with Fe(III) ions. The EPR spectrum at room temperature of the zeolite solid after the reaction, and being washed in a soxhlet showed a broad signal at g = 2.47 suggesting the interaction between Fe-Fe center inside the zeolite cage. It was also observed a radical signal at g = 2.00 assigned to a zeolite polypyrrol radical formed in the zeolitic cavity [3]. At 77 K the EPR spectrum presented gl = 6.04 due to Fe (III) high spin in an axial symmetry (commonly observed in iron(III)porphyrin ); g = 4.30, due to Fe (III) high spin in a rhombic symmetry and g = 2.00 (radical signal). At this temperature the broad signal observed at room temperature desappered similarly to that observed for Cu systems. 1- S.Nakagaki, A.S.Mangrich, C.R.Xavier and A.M.Machado; XVIII Meeting of Brasilian Chemistry Society (1995) - Brazil. 2- H.Yokoi et al.; J.Am.Chem.Soc.; 108, 3361 (1986). 3- G.L.Haller et al.; J.Phys.Chem.;96, 4145 (1992).