Immobilization of a copper-Schiff base complex in a Y-zeolite matrix: Preparation, chromogenic behavior and catalytic oxidation

• Published in: Polyhedron 2007-02, Vol.26 (3), p.563-571
• Main Authors: Saha, Pratap Kumar, Dutta, Buddhadeb, Jana, Sreyashi, Bera, Rajesh, Saha, Sandip, Okamoto, Ken-ichi, Koner, Subratanath
• Format: Article
• Language: English
• Subjects: Catalytic oxidation; Heterogeneous catalysis; Immobilization; Schiff base; Zeolite
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2006.08.018

To mimic the catalytic activity of metalloenzymes, a copper Schiff base complex has been immobilized in Y zeolite. A spectacular color change (green to red) has been observed when the complex [Cu(MeO-salen)(H 2O)] ( 1) is immobilized in a zeolitic matrix. While the prepared catalyst shows excellent catalytic activity and product selectivity, the complex itself remains virtually inactive. A new zeolite-immobilized hybrid catalyst Cu(MeO-salen)-NaY has been prepared by encapsulating [Cu(MeO-salen)(H 2O)] ( 1) [where MeO-salenH 2 = N, N′-(ethylene)-bis-(3-methoxysalicylaldimine)] in a NaY zeolite matrix. The hybrid material has been characterized by UV–Vis, IR and EPR spectrometry and by X-ray powder diffraction analysis. The pristine complex [Cu(MeO-salen)(H 2O)] ( 1) has also been synthesized and characterized by all the spectrometric methods mentioned above as well as by single crystal X-ray diffraction analysis. A brilliant color change (green to red) has been observed when the complex [Cu(MeO-salen)(H 2O)] ( 1) is immobilized in the zeolitic matrix. X-ray powder diffraction analysis of Cu(MeO-salen)-NaY reveals that the structural integrity of the mother zeolite in the hybrid material remains intact upon immobilization of the complex. The coordination geometry around the Cu II ion in [Cu(MeO-salen)(H 2O)] is found to be square pyramidal. Spectroscopic studies indicate that coordination geometry of the complex undergoes a significant distortion when it is entrapped in the zeolite cavity. While Cu(MeO-salen)-NaY shows excellent catalytic activity and product selectivity in the hydroxylation of phenol and 1-naphthol, [Cu(MeO-salen)(H 2O)] ( 1) remains virtually catalytically inactive in these reactions.