Diffusive EPR line width behaviour in two-dimensional Cu(Hippurate)2 ⋅ 4H2O single crystal

XX-band EPR measurements were performed at room temperature on layered Cu(Hippurate)2⋅4H2O single crystals. Despite the dimeric molecular structure the EPR spectra are characteristic for individual Cu-complexes with square-pyramidal structure and gg-factors: gx=2.045gx=2.045, gy=2.085gy=2.085 and gz=2.346gz=2.346. The anticipated zero-field splitting from dimers with S=1S=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⋅(3cos2Θ−1)2P⋅(3cos2Θ−1)2 with P=3.03mT 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.