Proton coordinates in Er(C2H5SO4)3⋅9H2O and ErCL3⋅6H2O from single crystal NMR studies

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Abstract
Proton coordinates have been determined for all hydrate protons in Er(C2H5SO4)3⋅9H2O and ErCl3⋅6H2O from NMR studies on single crystals. The paramagnetic NMR shift in these systems has been determined to be completely point dipolar within experimental error. In the case of Er(C2H5SO4)3⋅9H2O it was found that ’’jump rotation’’ or tunneling motion was occurring at −10 °C which averaged the NMR shift for the two water protons but left the dipolar interaction between the two protons intact. No such motion was observed for ErCl3⋅6H2O at room temperature. Methods of analysis of NMR in single crystals having rare earth ions have been developed which are capable of giving proton coordinates in a unit cell to an accuracy of 5 pm without the need of a very precise orientation of the crystal relative to the magnetic field.