Direct determination of intramolecular structure of D2O in the first hydration shell of Ni2+

Abstract

Time-of-flight (TOF) neutron diffraction measurements have been carried out for aqueous 6 mol% NiCl2 solution in D2O in order to obtain experimental information on intramolecular structure of D2O molecules involved in the first hydration shell of Ni2+. The O-D bond length, rg OD = 0.982 ± 0.002 Å has been determined through the least squares fitting analysis of the observed difference interference term between the NiCl2 solution and pure D2O in the high-Q region (14 ≤ Q ≤ 40 Å−1). The present O-D bond length is significantly longer than that determined for pure liquid D2O (rg OD = 0.978 ± 0.001 Å), confirming strong hydrogen bonds between D2O molecules in the first- and the second hydration shell of Ni2+. These results are in good agreement with the νOD-rOD relationship obtained from infrared spectra for uncoupled O-D stretching frequency of HDO and O-D bond length of D2O molecule in aqueous solutions determined by neutron diffraction.