Copper(II) complexes of 12-membered macrocyclic ligands having three different donating atoms (N2O2, N2S2 and N-4) in the macrocyclic ring have been encapsulated in the nanocavity of zeolite-Y by the fexible-ligand method. Copper(II) complexes with macrocyclic ligands were entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of precursor ligand; 1,2-di(o-aminophenyl-, amino, oxo, thio)ethane, N2X2; in the supercages of the Cu(II)-NaY, and (ii) in situ condensation of the Cu(II) precursor complex; [Cu(N2X2)](2+); with glyoxal or biacetyl. The new host-guest nanocomposite materials (HGNM); [Cu([R](2)-N2X2)](2+)-NaY (R = H, CH3; X = NH, O, S); have been characterized by FT-IR, DRS and UV-vis spectroscopic techniques, XRD and elemental analysis, as well as nitrogen adsorption. The "neat" and encapsulated complexes exhibited good catalytic activity in the oxidation of ethylbenzene at 333 K, using tert-butylhydroperoxide (TBHP) as the oxidant. Acetophenone was the major product though small amounts of o- and p-hydroxyacetophenones were also formed revealing that C-H bond activation takes place both at benzylic and aromatic ring carbon atoms. Ring hydroxylation was more over the "neat". complexes than over the encapsulated complexes. (C) 2008 Elsevier B.V. All rights reserved.