Diffusive EPR line width behaviour in two-dimensional Cu(Hippurate) 2 ⋅ 4H 2O single crystal

Abstract

X -band EPR measurements were performed at room temperature on layered Cu(Hippurate) 2⋅4H 2O single crystals. Despite the dimeric molecular structure the EPR spectra are characteristic for individual Cu-complexes with square-pyramidal structure and g -factors: g x = 2.045 , g y = 2.085 and g z = 2.346 . The anticipated zero-field splitting from dimers with S = 1 is averaged out by interdimer exchange coupling within the layers. The dimers in adjacent layers are not exchange coupled as we determined from the two-component EPR spectra. Thus, the crystal is an ideal 2D magnetic system and shows a strong spin diffusion effect in the EPR line width. The spin diffusion contribution to the line width is described as P ⋅ ( 3 cos 2 Θ − 1 ) 2 with P = 3.03 mT which is much higher compared to other 2D copper(II) crystals. The background line width is due to dipolar coupling and non-resolved hyperfine structure. Exchange coupling was determined from the exchange narrowing effect as of about 0.1 cm −1.