Synthesis and Electrochemical Study of an Original Copper(II)-Capped Salen-Cyclodextrin Complex

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TitreSynthesis and Electrochemical Study of an Original Copper(II)-Capped Salen-Cyclodextrin Complex
Type de publicationJournal Article
Nouvelles publications2010
AuteursDeunf, E, Zaborova E, Guieu S, Bleriot Y, Verpeaux JN, Buriez O, Sollogoub M, Amatore C
JournalEuropean Journal of Inorganic Chemistry
Année de publicationOct
Accession NumberISI:000283836300019

A new metallocapped cyclodextrin (CD) was synthesized by the regioselective debenzylation, induced by diisobutylaluminium hydride (DIBAL-H), of perbenzylated cyclodextrins. This reaction allowed for the efficient preparation of an unprecedented CD-salen type copper(II) complex. The electrochemical behavior of both the bound and unbound CD-salen compounds was investigated by cyclic voltammetry. Notably, it was shown that the presence of tert-butyl groups at the ortho- and para-positions of the salen aromatic rings stabilized the copper(II) phenoxyl radical species that was generated upon the one-electron oxidation of the starting compound. Importantly, this stabilization remained effective when the salen-type ligand was covalently attached to the CD. This allowed for investigations of the reactivity of the copper(II) phenoxyl radical complex towards a primary alcohol to be performed by cyclic voltammetry. This reaction can be considered as mimicking the behavior of galactose oxidase. However, under these conditions, no reactivity was observed in the presence of benzyl alcohol. This may be due to distortion, either of the initially square planar salen ligand after its grafting to the CD primary face, and/or of the CD itself. On the other hand, the electrochemical reduction of the un-grafted copper(II) salen-type ligand led to a transient anionic species that exhibited significant stability on the time-scale of the slow cyclic voltammetry measurement in the absence of the CD, but was unstable in the presence of the CD. In the latter case, it was demonstrated that the anionic species was protonated by the CD. Importantly, this protonation was not fast enough to prevent catalytic activation of iodomethane by the electro-generated copper(I)capped salen CD complex.

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Importer un fichierSynthesis and Electrochemical Study of an Original Copper(II)-Capped Salen-Cyclodextrin Complex
Unité de rattachement: 
UMR 8640