Vuorema, A. and John, P. and Keskitalo, M. and Mahon, M.F. and Anbukulandainathan, M. and Marken, F. (2009) Anthraquinone catalysis in the glucose-driven reduction of indigo to leuco-indigo. Physical Chemistry Chemical Physics, 11 (11). pp. 1816-1824. ISSN 1463-9076

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Abstract

Anthraquinone immobilised onto the surface of indigo microcrystals enhances the reductive dissolution of indigo to leuco-indigo. Indigo reduction is driven by glucose in aqueous NaOH and a vibrating gold disc electrode is employed to monitor the increasing leuco-indigo concentration with time. Anthraquinone introduces a strong catalytic effect which is explained by invoking a molecular ‘‘wedge effect’’ during co-intercalation of Na+ and anthraquinone into the layered indigo crystal structure. The glucose-driven indigo reduction, which is ineffective in 0.1 M NaOH at 65 1C, becomes facile and goes to completion in the presence of anthraquinone catalyst. Electron microscopy of indigo crystals before and after reductive dissolution confirms a delamination mechanism initiated at the edges of the plate-like indigo crystals. Catalysis occurs when the anthraquinone–indigo mixture reaches a molar ratio of 1 : 400 (at 65 1C; corresponding to 3 mM anthraquinone) with excess of anthraquinone having virtually no effect. A strong temperature effect (with a composite EA E 120 kJ mol�1) is observed for the reductive dissolution in the presence of anthraquinone. The molar ratio and temperature effects are both consistent with the heterogeneous nature of the anthraquinone catalysis in the aqueous reaction mixture.

Item Type:	Article
Subjects:	Electroorganic
Divisions:	UNSPECIFIED
Depositing User:	ttbdu cecri
Date Deposited:	27 Feb 2012 12:28
Last Modified:	09 Mar 2012 08:49
URI:	http://cecri.csircentral.net/id/eprint/1176

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