Nanoaggregates of Mn(III)tetraperfluorophenylporphyrin: a greener approach for allylic oxidation of olefins

Abstract

Organic nanoparticles of metalloporphyrins can be a versatile catalyst for the selective oxidation of alkenes and other hydrocarbons. The catalytic activity of the metalloporphyrin depends on the nature of the central metal atom, peripheral groups, and the architecture of the porphyrin macrocycle. Herein, we report the catalytic activity of organic nanoparticles of 5,10,15,20-tetrakis-(2,3,4,5,6pentafluorophenyl)porphyrinato manganese(III), Mn(III)TPPF 20 , for the oxidation of cyclohexene using molecular oxygen as an oxidant in aqueous solvent under ambient conditions. While the solvated metalloporphyrins catalytically oxidize alkenes to the corresponding epoxide with a modest turn-over numbers, ca. 30 nm organic nanoparticles of Mn(III)TPPF 20 have enhanced catalytic activity with up to a two-fold greater turn-over number and yields only allylic oxidation products. The activity of organic nanoparticles is slow compared to the solvated metalloporphyrins. These organic nanoparticles catalytic systems facilitate a greener reaction since ca. 89% of the reaction medium is water, molecular oxygen is used in place of man-made oxidants, and the ambient reaction conditions require less energy. This organic nanoparticle catalytic system also avoids using halogenated solvents commonly used in solution phase reactions. The enhanced catalytic activity of these organic nanoparticles is unexpected because the metalloporphyrins in the nanoaggregates are in the close proximity and the turn-over number should diminish by self-oxidative degradation.

Fluorinated porphyrinoids as efficient platforms for new photonic materials, sensors, and therapeutics

“…Supramolecular Por catalysts are designed to prevent self-oxidative degradation and to enhance substrate selectivity for quicker catalysis and better TON. 52,53 To minimize oxidative damage and to develop metalloPors 139–143 with more robust structures, our group prepared aggregated metalloPors into organic nanoparticles (ONP). 52,53 …”

“…Our group 52,53 has published a green chemistry approach to develop ONP from substituted metalloPors for oxidative catalysis of olefins and alkenes. These 10–30 nm ONP are easily formed by injecting the metalloPor into a host solvent such as DMSO or DMF into water while vigorously mixing.…”

“…42,48–51 Appending exocyclic motifs onto the redox active metalloporphyrinoids results in molecules and materials with improved catalytic properties for organic transformations. 52,53 This review will focus mainly on the nucleophilic substitution of fluorine analogues belonging to Pors, Pcs, Chls, Cors, Bacs and Ibacs. We will discuss their physicochemical as well as biomedical and material properties and applications.…”

Nanoaggregates of Simple Mn Porphyrin Complexes as Catalysts for the Selective Oxidation of Hydrocarbons

“…Notably, in almost all reports perfluoro aryl or alkyl porphyrins, which stabilize the porphyrin nanoparticles toward self‐oxidative degradation, have been used. However, in some conditions they decomposed completely even in the presence of O 2 8d,16. Moreover, invaluable oxyfunctionalization of less reactive saturated hydrocarbons has not been reported in these studies.…”

Applications of Fluorous Porphyrinoids: An Update†

“…Formation of supramolecular systems of porphyrinoids is another approach to increase their robustness toward selfoxidative degradation, while also enhancing substrate selectivity for better TON (49)(50)(51)(52). To this end, we have reported the formation of aggregates of various metalloporphyrinoids to form organic nanoparticles (ONP) and investigated their catalytic activity for olefinic oxidation reactions (50)(51)(52)(53)(54). We have also investigated the catalytic activities of TPPF 20 derivatives prepared by substituting the parafluoro group with a long fluorinated alkyl chain (Fig.…”