Copper(II)-purine complexes encapsulated in NaY zeolite

Y-encapsulated Cu-II-purine complexes were synthesized, characterized and studied in the catalytic oxidation of cyclohexene. Encapsulation was achieved by ion-exchanging the complex from aqueous solutions containing both the purine ligand, 9-methyl-6-(methylaniino)purine, and copper, in different pH, with a purine/Cu-II molar ratio of 5:1. The resulting materials were characterized by surface analysis (XPS, SEM and XRD), chemical analysis, spectroscopic methods (EPR, FTIR and UV/Vis) and thermal analysis (TGA), which indicated that the Cu-II-purine complexes were effectively encapsulated in NaY, most probably inside the supercages, without any modification of the morphology and structure of the zeolite. Different Cu-II-purine complexes were formed, depending on the pH during synthesis. The coordination geometry of Y-encapsulated Cull-purine complexes was obtained with preferentially 1:2 and 1:3 Cu/L stoichiometry: complexes A and B (1:2) and complex C (1:3). Complex A was formed at pH >= 7, and complexes B and C (Scheme 2) were formed at pH = 5.4. Oxidation of cyclohexene with tBuOOH (TBHP) as the oxygen source, gave 2-cyclohexene-l-one, 2-cyclohexene-1-ol, cyclohexene oxide and 3-tert-butylcyclohexenyl peroxide. (C) Wiley-VCH Verlag GmbH & Co.