EPR studies of iron substitution in the molecular sieve VPI-5

Abstract

The X-band EPR spectra of iron-containing VPI-5 were recorded at room temperature and liquid nitrogen temperature. An intense signal at g/sub ///=2.0 and gperpendicular to =6.0 characteristic of high-spin Fe3+ ions in axial symmetry was observed at both temperatures. A splitting of these components due to superhyperfine interaction indicated the presence of these Fe3+ ions in the network-forming position. An anisotropic line at G=4.3 and weak superhyperfine lines centred at g=1.7 characteristic of high-spin Fe3+ ions in orthorhombic symmetry were also observed at liquid nitrogen temperature. These signals may also be attributed to the presence of Fe3+ ions, most probably in the network-forming position. Lastly, the very weak signal at g=3.1 was tentatively assigned to traces of occluded compounds of iron outside the framework.