For 67Zn NMR lines of solutions of ZnCl2, ZnBr2, and Znl2 in H20 and D20 an anomalous solvent isotope effect is reported. In D20 solutions the lines are shifted to higher frequencies. The difference between the shieldings in H20 and D20 is e.g. o (H 20) -o(D20) = (13.1 ±0.7) ppm for a concentration of 0 .0 2 moles zinc bromide per mole solvent.The frequency of the NMR signal (Larmor fre quency) of a nucleus in an ion in aqueous solution can depend on the isotopic composition of the sol vent. Such a behaviour has been found for alkali 1-4, halide 115,6 and several other nuclei7-11 in aqueous salt solutions. The largest effect was observed for 20"Pb in aqueous lead salt solutions". The differ ence between the shieldings in H20 and D20 is ö (H20) -o (D20) = -(31 + 3) ppm for a concen tration of 0.004 moles lead nitrate per mole solvent. These shielding differences are presumably due to the different vibronic states of the H20 and D20 molecules surrounding the ions 5.For i n Cd an indication for a shift to higher frequency was found in a cadmium chloride solu tion n , whereas in perchlorate and nitrate solutions the usual solvent isotope effect was observed.During a NMR investigation of II b elements, 6'Zn NMR signals were observed in aqueous solu tions for a determination of the shielding constant12. The 6'Zn studies were done at 4.841 MHz in a field of 1.807 Tesla with a Fourier Transform Spectro meter basing on a Bruker pulse spectrometer KR 322 s. For experimental details see for example2.The dependence of the Larmor frequency of 67Zn on the concentration of aqueous zinc chloride, bro mide, and iodide solutions was measured. The ob served linewidths are in the range between 20 Hz for low and 170 Hz for high concentrations. For all these salts an anomalous shift to higher frequencies
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