The University of Southampton
University of Southampton Institutional Repository

Incorporation of transition-metal complexes in functionalized mesoporous silica and their activity toward the oxidation of aromatic amines

Evans, J., Zaki, A. B., El-Sheikh, M. Y. and El-Safty, S. A. (2000) Incorporation of transition-metal complexes in functionalized mesoporous silica and their activity toward the oxidation of aromatic amines Journal of Physical Chemistry B, 104, (44), pp. 10271-10281. (doi:10.1021/jp000564p).

Record type: Article

Abstract

The highly ordered mesoporous material HISiO2 was prepared at room temperature and low pH utilizing a high concentration of nonionic surfactant to achieve a hexagonal ordered phase with a pore size of similar to3.5 nm. The grafted amino ligand was covalently bonded to the internal pore surface of HISiO2 through a silanation procedure. Thereby, immobilized transition-metal-aquo complexes such as Mn-II-aquo (I), Cu-II-aquo (II), Co-II-aquo (III), and Zn-II-aquo (IV) were coordinated to the supported wall without impregnation on the surface. Diffuse reflectance spectroscopy (DRS) and electron paramagnetic resonance (EPR) studies observed that a proportion of the Mn-II complex was oxidized to a higher oxidation state, particularly Mn-IV. The kinetics and mechanism of redox reactions between o-aminophenol, o-phenylenediamine, and p-pheneylenediamine and the incorporated transition-metal-aquo-propylamine complexes have been investigated. The oxidation products of the amines have been monitored by UV-vis spectroscopy. The reaction follows first-order kinetics, and the rate constant of the oxidation of amines decreases in the following order: Mn-IV/Mn-II --> Cu-II --> Con --> Zn-II. This trend is attributed to the reduction potential of the metal ions in the reaction medium. The most obvious feature of the oxidation reaction of amines with complexes III and IV is that there is a well-defined induction time, whose rate depends on the reactivity and the initial concentration of these amines, prior to a rapid growth in the production of the oxidation product of amines. The experimental results indicate that the outer-sphere mechanism is probably followed in this redox system. Extensive studies of the transition-metal complexes on HISiO2 have been conducted before and after the redox reaction by a wide variety of characterization techniques which include powder X-ray diffraction, DRS, the Bnxnauer-Emmett-Teller method for nitrogen adsorption and surface area measurements, NMR, EPR, and IR.

Full text not available from this repository.

More information

Published date: 9 November 2000
Keywords: electron-spin-resonance, mcm-41 type silicas, molecular-sieves, hydrogen-peroxide, aqueous-solution, o-phenylenediamine, synthasemodel, mechanism, catalysts, kinetics

Identifiers

Local EPrints ID: 19002
URI: http://eprints.soton.ac.uk/id/eprint/19002
ISSN: 1089-5647
PURE UUID: c54df946-3601-43b8-a54c-28b78d1f2a77

Catalogue record

Date deposited: 05 Jan 2006
Last modified: 17 Jul 2017 16:34

Export record

Altmetrics

Contributors

Author: J. Evans
Author: A. B. Zaki
Author: M. Y. El-Sheikh
Author: S. A. El-Safty

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×