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Updated: Jan 7, 2026

Probing the Structure and Dynamics of Interfacial Water with Scanning Tunneling Microscopy and Spectroscopy
Published on: May 27, 2018
Water-Induced Reversible Structural Transition Enables Dual Cooperative Switching of Second-Harmonic Generation and
Zhuo Huang1, Zhi-Rui Li1, Hai-Xia Zhao1
1State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
None:
A reversible single-crystal-to-single-crystal (SCSC) dehydration-rehydration phase transition was realized between [C6H12NO][FeCl4(H2O)]0.5[FeCl4]0.5·0.5H2O (1) and [C6H12NO][FeCl4] (2). Compound 1 crystallizes in the centrosymmetric space group P21/m. Upon the loss of both coordinated and guest water molecules, cooperative rotational and translational rearrangements of the [FeCl4]- anions and [C6H12NO]+ cations occur, accompanied by reconstruction of the hydrogen-bonding network. This transformation breaks the inversion symmetry of 1, yielding compound 2, which crystallizes in the noncentrosymmetric space group Cm. The reversible phase transition involves a distinct symmetry change and induces a switchable second-harmonic generation response. Moreover, due to the reorganization of the hydrogen-bonding network, compound 2 exhibits a proton conductivity 2 orders of magnitude lower than that of 1, demonstrating a pronounced switching behavior in proton transport.
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