Simultaneous aluminium oxide pillaring and copper(ii) Schiff base complexes encapsulation in a montmorillonite

Abstract

Copper(II) acetylacetonate and two complexes with pentadentate N₃O₂ Schiff-base ligands derived from acetylacetone–bis(acetylacetonate)-3-amino-bis(propyldiimine), ([Cu(acac)₂trien]), and bis(acetylacetonate)-3-methylamino-bis(propyldiimine), [Cu(acac)₂Metrien], were encapsulated into a pillared clay (PILC) using a new methodology that involves simultaneous oligomer pillaring and complex encapsulation: in the present work the pillaring oligomer was [Al₁₃O₄(OH)_24+x(H₂O)_12−x]^(7−x)+ and the starting clay was a Portuguese montmorilonite. All the materials were characterised by X-ray photoelectron spectroscopy, powder X-ray diffraction, adsorption of nitrogen at low temperature and infrared spectroscopy and, for copper-based materials, by chemical analysis. Data indicate that all three complexes have been immobilised within the matrix, but only for [Cu(acac)₂] and [Cu(acac)₂trien], did metal complex immobilisation take place concomitantly with aluminium pillar intercalation. Furthermore, the encapsulation of the latter complexes induced an increase in the PILC basal distance when compared with the pillared clay prepared without complex present. Finally, in all the materials the encapsulated complexes exhibit structural properties that are different from those of the free complexes, a consequence of the steric effects imposed by the porous structure of the PILC.