Homogeneous and heterogenized copper(II) complexes as catechol oxidation catalysts

✍ Scribed by Maria Louloudi; Katerina Mitopoulou; Elisavet Evaggelou; Yiannis Deligiannakis; Nick Hadjiliadis

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 159 KB
• Volume: 198
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/s1381-1169(02)00692-1

✦ Synopsis

Two macroacyclic ligands represented as L 1 and L 2 with 3N 2 O and 5N donor atoms, respectively, have been synthesized by Schiff base condensation. They were subsequently grafted on a silica surface via covalent bonds. The organic ligands L 1 and L 2 as well as the heterogenized ligands L 1 •SiO 2 and L 2 •SiO 2 reacted with copper(II) leading to the formation of dinuclear copper(II) complexes. Catalytic oxidation of 3,5-di-t-butylcatechol (DTBC) by dioxygen was studied using as catalysts the homogeneous Cu 2 (L 1 ) and Cu 2 (L 2 ) and the heterogenized Cu 2 (L 1 )•SiO 2 and Cu 2 (L 2 )•SiO 2 complexes. These complexes were found to be very effective catalysts for DTBC oxidation producing mainly 3,5-di-t-butylquinone (DTBQ). During the catalytic process the formation of an o-semiquinone radical has also been confirmed. The immobilized on modified silica surface copper(II) complexes gave significantly higher DTBC conversion than the homogeneous copper(II) complexes.