ESR of Cu2+ (H2O)6. I. The oxygen-17 superhyperfine tensors in 63Cu2+ doped zinc Tutton's salt at 20 °K

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Abstract
The X-band ESR spectrum of 63Cu2+ doped zinc Tutton's salt enriched to 16 at.% in oxygen-17 isotope was studied in a completely deuterated single crystal at 20°K. Satellites from both singly and doubly labelled molecules were observed and the oxygen-17 superhyperfine tensors were found to differ for the two trans pairs of equatorial oxygens. The two tensors are −21.0, −11.9, and −10.9×104 cm−1 and −16.1, −9.9, and −8.8×104 cm−1, where the largest principal value in each case is directed along the copper-oxygen bond and the tensors are associated, respectively, with the shorter and longer of the equatorial copper-oxygen bonds. The tensors, after correction for a distant dipolar contribution from the metal, were shown to imply a value of 1/6 for the ratio 2s0/2p0 in the molecular orbital containing the unpaired electron. This result is discussed in terms of the known geometry of the Cu2+(H2O)6 complex in Tutton's salts.