An EPR study on oxygen molecule adduct of Co(II)-phthalocyanines encapsulated into zeolites

An electron paramagnetic resonance (EPR) study was carried out for O2 molecule adducts formed on cobalt-phthalocyanine encapsulated into Y-type zeolite (CoPc-in-Y). The EPR spectrum, which is characteristic of a superoxide-type O2-adduct to CoPc-in-Y, was observed when O2 molecule was introduced into CoPc-in-Y with either ammonia (NH3) or n-butylamine (n-BuNH2) as an axial ligand. The number of the O2-adduct was found to strongly depend on measurement temperature as well as on the axial ligand employed. The maximum spin concentration of (O2-Co)2+Pc(n-BuNH2)-in-Y was about one order of magnitude higher than that of (O2-Co)2+Pc(NH3)-in-Y. The results are discussed in terms of the size of the axial ligands and of the magnetic interaction of the O2-adduct with paramagnetic O2 adsorbed on zeolite.