Modified silicas covalently bounded to 5,10,15,20-tetrakis(2-hydroxy-5-nitrophenyl)porphyrinato iron(III): synthesis, spectroscopic and EPR characterization. Catalytic studies

Abstract

Neste trabalho estudamos a epoxidação do cicloocteno com PhIO utilizando uma nova porfirina 5,10,15,20-tetraquis(2-hidroxi-5-nitrofenil) In this work we have studied cyclooctene epoxidation with PhIO, using a new iron porphyrin, 5,10,15,20-tetrakis(2-hydroxy-5-nitrophenyl)porphyrinato iron(III), supported on silica matrices via eletrostatic interaction and / or covalent bonds as catalyst. These catalysts were obtained and immobilized on the solid supports propyltrimethylammonium silica (SiN species in all of the three obtained catalysts. In the case of (Z)-cyclooctene epoxidation by PhIO the yields observed for cis-epoxycyclooctane were satisfactory for the reactions catalyzed by the three materials (ranging from 68% to 85%). Such results indicate that immobilization of metalloporphyrins onto solid supports via groups localized on the ortho positions of their mesophenyl rings can lead to efficient catalysts for epoxidation reactions. The catalyst 1-CPS is less active than 1-SiN and 1-SiN(IPG), this argues in favour of the immobilization of this metalloporphyrin onto solids via electrostatic interactions, which is easier to achieve and results in more active oxidation catalysts. Interestingly, the activity of the supported catalysts remained the same even after three successive recyclings; therefore, they are stable under the oxidizing conditions.

Metalloporphyrin-functionalized hexagonal mesoporous silica: Synthesis, structural properties and catalytic activity as cytochrome P450 model

“…In this sense, an approach has been to immobilize metalloporphyrins (MePs) onto solid matrices. The immobilization of MePs onto solid supports can be achieved via coordination [25], electrostatic interactions [26][27][28], or covalent binding to silica gel and modified silicas [16,[29][30][31]; encapsulation into the silica matrix through the sol-gel process [31,32]; and encapsulation into zeolite [33,34] or MCM41, for instance [35][36][37]. The solid matrix confers stability to the MeP during the oxidation reaction and allows for control of the reactivity of the system through the microenvironment created by the support [38].…”

Chemical Reactions Catalyzed by Metalloporphyrin-Based Metal-Organic Frameworks

“…Chemical processes generally involve formation of a chemical (electrostatic or covalent) bond between the support and the catalyst; physical processes include adsorption, intercalation, and encapsulation. Compared with physical interactions, an effective chemical interaction is expected to render a more robust and resistant solid catalyst; it should avoid catalyst leaching and allow it to be reused several times [52,53,54,55].…”

Recent Advances in Solid Catalysts Obtained by Metalloporphyrins Immobilization on Layered Anionic Exchangers: A Short Review and Some New Catalytic Results

“…Since then, a large number of inorganic solids have been studied as supports for MPs and many other complexes for catalytic purposes. Examples of these solids include clay minerals [19,20,21], silica [22,23], and metal oxides [24,25], among others [26]. Besides, polymeric matrixes like isocyanide [15], poly(vinyl alcohol) [27], and polystyrene [28] have also been employed to immobilize MPs and obtain efficient catalysts for oxidation reactions.…”