ELECTRON-PARAMAGNETIC RESONANCE INVESTIGATION OF COPPER(II) COMPLEXES WITH REVERSED G VALUES IN A AND Y ZEOLITES

The electron paramagnetic resonance (EPR) spectra of evacuated low ion exchanged copper(II) Y and A zeolites are presented, in which reversed g values are observed. The EPR parameters for CuY-10 and CuA-6 are g⊥=2.32 with=2.00 (102) and g⊥=2.30 with g⨉=1.99 (85), respectively, where the numbers in parentheses are the hyperfine splitting values (in gauss). It is proposed that these reversed spectra are due to pentacoordinated copper(II) ions held in the trigonal sodalite cage windows with water molecules in the axial positions to yield trigonal-bipyramidal complexes. Using a reoxidation technique, a similar diammine complex has been formed, which has EPR parameters of g⊥=2.32 and g⨉=1.97 (131). The latter values are similar to those previously reported for an amminecopper(II) complex formed by an evacuation procedure. Only part of the divalent copper in the zeolites form the bipyramidal complexes that are decomposed by thermal treatments. © 1979, American Chemical Society. All rights reserved.