Association of Keggin-type anions with cationic meso-substituted porphyrins: synthesis, characterization and oxidative catalytic studies
authors Santo, ICMS; Rebelo, SLH; Balula, MSS; Martins, RRL; Pereira, MMMS; Simoes, MMQ; Neves, MGPMS; Cavaleiro, JAS; Cavaleiro, AMV
nationality International
journal JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
author keywords polyoxometalates; cationic porphyrins; metalloporphyrins; manganese(III); oxidation; hydrogen peroxide; monoterpenes; cyclooctene
keywords BY-LAYER METHOD; HYDROGEN-PEROXIDE; OXOMANGANESE(V) PORPHYRIN; SELECTIVE OXIDATION; DIOXYGEN REDUCTION; CRYSTAL-STRUCTURE; SILICA-SUPPORT; HYBRID FILM; COMPLEXES; METAL
abstract New compounds based on the association of polyoxometalates and cationic porphyrins or metalloporphyrins were prepared with the aim of obtaining new bi-functional catalysts. A combined study on the syntheses, characterization and catalytic activity of these compounds was performed. The new compounds have the general formula (porphyrin)xHy[XM12O40](.)z solv, x=0.75 or 1, X=P or Si and M=W or Mo. The porphyrins used were 5. 10, 1 5,20-tetrakis(4-pyridyl)porphyrin, 5,10,15,20-tetrakis(1 -methyl-4-pyridinio)porphyrin, 5,10,15-tris(2,6dichorophenyl)-20-(4-pyridyl)porphyrin, and 5,10,15 -tris (2,6-di chlorophenyl)-20-(1 -methyl -4-pyridinio)porphyrin, either as free bases or complexed with Mn-III (one case with Zn-II). A few compounds with metal substituted Keggin anions ([PW11Y(H2O)O-39](n-,) Y=Mn, Fe, Ni, Zn) were also prepared. All compounds were characterized by spectroscopic and analytical techniques. The oxidation of cis-cyclooetene, geraniol and (+)-3-carene by hydrogen peroxide catalysedby the polyoxometalate/Mn(III)porphyrin associations and co-catalysed by ammonium acetate was examined. Some of the associations significantly increased the percentage of conversion of the substrates relatively to the respective metalloporphyrin alone. However, the regio-, chemo- and stereoselectivity of the oxidation reactions catalysed by metalloporphyrins were alobally preserved: cis-cyclooctene was selectively epoxidised to epoxycyclooctane; geraniol gave 6,7-epoxygeraniol as the major product and (+)-3-carene was preferably oxidised to the alpha-3,4-epoxycarane. In the conditions studied, the polyoxoanions seem to contribute mainly to stabilise the metalloporphyrin against deactivation during catalytic cycles. (c) 2004 Elsevier B.V.. All rights reserved.
publisher ELSEVIER SCIENCE BV
issn 1381-1169
year published 2005
volume 231
issue 1-2
beginning page 35
ending page 45
digital object identifier (doi) 10.1016/j.molcata.2004.12.021
web of science category Chemistry, Physical
subject category Chemistry
unique article identifier WOS:000227966600004
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