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

• Published in: Journal of molecular liquids 2023-07, Vol.382, p.121927, Article 121927
• Main Authors: Kameda, Yasuo, Amo, Yuko, Usuki, Takeshi, Umebayashi, Yasuhiro, Watanabe, Hikari, Ikeda, Kazutaka, Otomo, Toshiya
• Format: Article
• Language: English
• Subjects: Hydrogen bond; Intramolecular structure of D2O; Neutron diffraction; Ni2+ hydration
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2023.121927

[Display omitted] •The long standing “H2O(I)–H2O(II) problem” has been solved by time-of-flight neutron diffraction analysis.•O-D bond length, rg OD = 0.982 ± 0.002 Å, for D2O molecule in the first hydration shell of Ni2+ has been directly determined.•The present results are consistent with the rOD-νOD relationship reported for D2O molecule in the liquid state. 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.