Observation of Single-Crystal-Type EPR Spectra from Monolayers of Copper-Exchanged Zeolite Na-A Crystals Assembled on Glass Plates

Single-crystal-type EPR spectra were observed for microcrystals of copper(II)-exchanged zeolite Na-A assembled on glass plates when the magnetic field was perpendicular to the glass surface. Two copper species (H and D) were identified both in the powder sample and in the assembled crystals. The g z direction of species H is parallel to [001] of the cubic crystal, while that of species D is tilted 9° away from [001]. Previously, other authors assumed the g z directions of the two corresponding species to be parallel to [111]. On the basis of the g z directions, we suggest that Cu2+ in species H is displaced 0.149 nm along [111] from the six-ring plane into the β cage and octahedrally coordinated to three zeolite oxygen atoms in the six-ring plane and three water molecules. The g z direction of Cu2+ in species D is not compatible with site II in the six-ring plane. Species D is probably a trigonal complex with Cu2+ displaced into the β cage and coordinated to three zeolite oxygen atoms.