Proton ENDOR Studies on Zinc-Doped Copper(II) Acetate Monohydrate Single Crystal

Abstract

Abstract The proton ENDOR spectra of the zinc-doped copper(II) acetate monohydrate single crystal were measured at 20 K. Hyperfine coupling tensors have been determined for the two protons of the water molecule at the axial position of the paramagnetic copper ion and a proton of the water forming the hydrogen bond with carboxylate oxygen at the equatorial plane of the copper ion. The axial water protons have small positive isotropic hyperfine couplings owing to the pseudo-contact interaction, and the equatorial water proton has a small negative one due to the spin polarization effect of the positive spin on the acetate oxygen through the hydrogen bond. The anisotropic hyperfine tensors of the former protons are interpreted by the dipolar interaction with the unpaired spin on the copper dx2−y2 orbital. The anisotropic interaction of the latter protons indicates that the spin delocalizes onto the oxygen atoms of the acetate bridges. Based on these observed hyperfine interactions, the mechanism of the spin–spin interaction in the dimer complex is discussed.