Related Experiment Video
Updated: Jan 14, 2026

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water
Published on: August 2, 2012
Concentration-Dependent Structures and Ultrafast Dynamics within Aqueous BeF2: From Ion Complexes to Extended
Zhou Liang1, Peng Jiahui2, You Min3
1State Key Laboratory of Thorium Energy, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
None:
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 [BeFx(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.
Related Concept Videos
Formation of Complex Ions
Complexation Equilibria: Overview
The equilibrium constant of the complexation reaction is represented as the formation constant...
Resonance and Hybrid Structures
Resonance Structures and Resonance Hybrids
The Lewis structure of a nitrite anion (NO2−) may actually be drawn in two different ways, distinguished by the locations of the N–O and N=O bonds.
Complexation Equilibria: Factors Influencing Stability of Complexes
Valence Bond Theory
Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...

