Organo-functionalized activated carbons as supports for the covalent attachment of a chiral manganese(III) salen complex

• Type: Article in International Scientific Journal
• Date: 2007

Authors

Ana Rosa Silva (Author) REIT; Vitaly Budarin (Author) Other; James H Clark (Author) Other; Cristina Freire (Author) FCUP; de Castro, B (Author) FCUP

Journal

Title: Carbon

Vol. 45

Pages: 1951-1964

ISSN: 0008-6223

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 54 Citations

Scopus - 43 Citations

Scientific classification

FOS: Engineering and technology > Materials engineering

Other information

Authenticus ID: P-004-7MV

DOI: 10.1016/j.carbon.2007.06.013

Abstract (EN): A modified Jacobsen-type catalyst, possessing an hydroxyl group on the aldehyde fragment of the salen ligand, was anchored through cyanuric chloride onto: (i) an air oxidized activated carbon functionalized with 3-aminotriethoxysilane and (ii) a nitric acid activated carbon treated with thionyl chloride and functionalized with 1,8-diaminooctane. The new heterogeneous catalysts, as well as the precedent materials, were characterized by nitrogen elemental analysis, Mn ICP-AES, nitrogen adsorption at 77 K, TG-IR and XPS. The results showed that the amine derivatives, cyanuric chloride and the manganese(III) salen complex were sequentially anchored onto the two activated carbons (AC). These Mn based materials acted as active and enantioselective heterogeneous catalysts in the epoxidation of a-methylstyrene, using NaOCl as oxidant. The heterogenized complex showed higher catalytic activity than the homogeneous catalyst. The increase of distance of the manganese(III) salen complex to the carbon surface did not have a significant effect on the asymmetric inductions, which were lower than the homogeneous catalyst. Nevertheless, the catalyst bearing the shorter amine alkyl chain showed higher catalytic activity due to unique steric effects that prevent hindrances to diffusion of the substrates to the active catalytic sites.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 14