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Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
Published on: May 15, 2017
7.2K
Two host-guest grown ether supramolecules show switchable phase transition, dielectric and second-harmonic generation
Xing Ye1, Wenhui He1, Jing Wei1
1School of Chemistry and Chemical Engineering, Nanchang University, Nanchang, 330031, People's Republic of China. weizh@ncu.edu.cn.
Dalton Transactions (Cambridge, England : 2003)
|September 16, 2022
Summary
Novel host-guest crown ether supramolecules were synthesized, exhibiting enhanced phase transition temperatures and nonlinear optical properties. Substituting perchlorate with perrhenate ions induced a non-centrosymmetric structure, enabling a switchable second-harmonic generation effect.
Area of Science:
- Supramolecular Chemistry
- Materials Science
- Crystallography
Background:
- Host-guest crown ether complexes show promise for phase transition, dielectric, and nonlinear optical applications.
- Designing supramolecular structures with tailored properties is crucial for advanced materials development.
Purpose of the Study:
- To synthesize novel host-guest crown ether supramolecules incorporating 2,6-difluorobenzylamine (DFBA).
- To investigate the impact of anion substitution (perchlorate vs. perrhenate) on phase transition temperatures and nonlinear optical properties.
Main Methods:
- Synthesis of supramolecular complexes [(DFBA)(15-crown-5)]X where X is ClO4- or ReO4-.
- Differential scanning calorimetry (DSC) for phase transition temperature determination.
- X-ray diffraction analysis to determine crystal structures and space groups.
Main Results:
- Two novel supramolecular compounds, [(DFBA)(15-crown-5)]ClO4 (1) and [(DFBA)(15-crown-5)]ReO4 (2), were successfully prepared.
- Phase transition temperatures were significantly increased to 377 K for 1 and 391 K for 2.
- Compound 2 crystallized in a non-centrosymmetric (NCS) Pca21 space group, exhibiting switchable second-harmonic generation (SHG) properties, unlike the centrosymmetric (CS) P2/c of compound 1.
Conclusions:
- The introduction of DFBA as a guest cation effectively elevates phase transition temperatures in crown ether supramolecules.
- Anion engineering, specifically replacing ClO4- with ReO4-, can induce a transition from a centrosymmetric to a non-centrosymmetric crystal structure.
- This structural change enables desirable nonlinear optical properties like SHG, demonstrating a method for tuning crystal properties through anion-cation interactions.
