Concentration-Dependent Structures and Ultrafast Dynamics within Aqueous BeF₂: From Ion Complexes to Extended Networks.

Authors

Zhou Liang, Peng Jiahui, You Min, Yue Jianing, Fu XiaoBin, Shen Miao, Bian Hongtao, Qian Yuan

Published in

The journal of physical chemistry. B. Oct 18, 2025. Epub Oct 18, 2025.

Abstract

Salt-concentration effects on the structural dynamics of aqueous beryllium fluoride (BeF₂) must be elucidated to advance the separation and dehydration processes. This study systematically investigates BeF₂-solution concentration-dependent structures and dynamics using nuclear magnetic resonance and ultrafast spectroscopy. Be²⁺ primarily exists as the tetrahedral complex [BeF₂(H₂O)₂] in a BeF₂ solution, with small [BeF(H₂O)₃]⁺ and [BeF₃(H₂O)]^- complex contents. At BeF₂ concentrations exceeding 8.3 mol %, an extended Be-F network becomes prominent. Fourier transform infrared spectroscopy with a thiocyanate (SCN^-) vibrational probe reveals two SCN^- peaks: a bulk-water-associated peak and a Be²⁺-coordinated peak from the SCN^- substitution in [BeF_x(H₂O)₄-_x] complexes. The Be²⁺ peak full width at half-maximum exhibits nonlinear broadening at concentrations exceeding 8.3 mol %, consistent with network formation. Polarization-selective pump-probe measurements demonstrate that increased salt concentration accelerates vibrational energy relaxation and suppresses rotational diffusion. The rotational diffusion time is related to the macroscopic viscosity via the Stokes-Einstein-Debye model. The Be-F complexes cause non-Newtonian behavior of the BeF₂-solution viscosity. At concentrations exceeding 8.3 mol %, the formed network structures exponentially increase the viscosity, negating the classical Jones-Dole model. These macroscopic viscosity changes can be explained microstructurally. A coherent molecular mechanism linking the microscopic coordination structure to macroscopic transport properties is established.

PMID:
41108630
Bibliographic data and abstract were imported from PubMed on 19 Oct 2025.

Read full publication at:
Please sign in to see all details.

Stats

1-terrible, 9-excellent. How would you rate this publication? Sign in in to submit your rating.

Post a comment

You need to be signed in to post comments. You can sign in here.

Comments

There are no comments yet.