ZEOLITE CHEMISTRY OF CUZSM-5 REVISITED

The recently reported interesting behavior of the EPR spin intensity a s freshly prepared CuZSM-5 is dehydrated has been confirmed, and the i nterpretation offered in explanation has been tested by extending the data. Magnetic susceptibility and optical diffuse reflection spectrosc opy have been used to show that the anomalous EPR data correspond to c hanges in symmetry rather than disproportionation of [CuOH](+) into Cu + and Cu2+O- as H2O is removed, as previously suggested. Moreover, the relatively small negative Weiss constants suggest that antiferromagne tic coupling through the supposedly EPR silent conventional bridge spe cies, [Cu2+-O2--Cu2+](2+), cannot be responsible for the relatively la rge changes in observed EPR spin intensity on dehydration. EPR measure s selectively individual paramagnetic species and ignores those of low symmetry, while magnetic susceptibility integrates over all magnetic species in the sample. The changes in the EPR intensities were much la rger than those observed by magnetic susceptibility. Furthermore, thos e from EPR occurred as the first H2O was removed, before any significa nt change in susceptibility occurred. The EPR data reflected those exp ected for the decrease in symmetry accompanying dehydration. Support f or these views was found in the magnetic susceptibility and optical re flectance data. Evidence for CuO formation concomitant with dehydratio n was obtained.