Zeolite encapsulated Ni(ii) Schiff-base complexes: improved catalysis and site isolation

Two series of zeolite encapsulated Ni(ii) Schiff-base complexes,i.e., the Ni(ii) sal-1,2-phen and Ni(ii) sal-1,3-phen series, have been synthesized in neat and encapsulated states and characterized by using different characterization techniques such as XRD, SEM-EDS, BET, thermal analysis, XPS, IR spectroscopy, UV-vis spectroscopy and magnetic studies. UV-vis spectroscopy, XPS and magnetic studies all together reveal the structural modification of the guest complex and, thereby, the adaptation of electron density around the metal center upon encapsulation. However, encapsulation causes structural alterations for these two series differently and, hence, introduces a certain level of proficiency to these Ni(ii) complexes as catalysts for phenol oxidation reaction. However, analysis of catalytic data emphasizes site isolation as a major governing factor for the improved reactivity over the modified electron density around the metal center for phenol oxidation reaction where the heterogeneous mode of catalysis is concerned.