Clay Minerals (1996) 31,491-500 CLAY INTERCALATED Cu(II) AMINO ACID COMPLEXES" SYNTHESIS, SPECTROSCOPY AND CATALYSIS

ABSTRACT: Complexes of Cu(lysine) 2+ and Cu(histidine) 2+ have been intercalated between the layers of saponite clays by a simple cation exchange procedure from aqueous olutions of preformed Cu(amino acid)2-complexes. Successful immobilization was obtained with an amino acid:Cu 2 § ratio of 5, and a pH of 10 and 7.3 for lysine and histidine, respectively. The synthesized materials were investigated as powders and as thin films by electron spin resonance (ESR), diffuse reflectance spectroscopy (DRS) and X-ray diffraction (XRD). The light blue clays are characterized by an axially symmetric ESR spectrum with A// = 192 G, g// = 2.23 and g • = 2.07, and a d-d absorption band around 600 nm, due to the intercalated planar Cu2*-complexes. Ammonia interacts reversibly with these intercalated complexes, suggesting the presence of a free coordination site. The novel synthesized materials are active in various oxidation reactions with t-butyl hydroperoxide asoxidant. Studies of the immobilization of transition metal ion complexes on inorganic surfaces have funda-mental and practical importance. At the funda-mental level, researchers want to establish the sorption mechanism, the geometry of the adsorbe