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Columnar Liquid Crystals of Copper(I) Complexes with Ionic Conductivity and Solid State Emission.
Viorel Cîrcu1, Constantin P Ganea2, Mihail Secu2
1Department of Inorganic and Organic Chemistry, Biochemistry and Catalysis, University of Bucharest, 4-12 Regina Elisabeta Bld., Sector 5, 030018 Bucharest, Romania.
Molecules (Basel, Switzerland)
|May 27, 2023
Summary
New copper(I) halide complexes exhibit liquid crystalline, emission, and proton conduction properties. These metallomesogens demonstrate potential for advanced materials due to their thermal stability and unique structural characteristics.
Area of Science:
- Materials Science
- Supramolecular Chemistry
- Coordination Chemistry
Background:
- Copper(I) halide complexes are of interest for their diverse properties.
- Thiourea ligands can form complex supramolecular structures.
- Liquid crystalline materials offer unique self-assembly and electronic properties.
Purpose of the Study:
- To synthesize and characterize novel neutral copper(I) halide complexes.
- To investigate the supramolecular, liquid crystalline, emission, and ionic conduction properties of these complexes.
- To explore the potential of these materials in advanced applications.
Main Methods:
- Synthesis via reduction of copper(II) halides with benzoylthiourea (BTU) ligand.
- Structural characterization using ESI-MS, elemental analysis, IR, and NMR spectroscopy.
- Mesomorphic behavior analysis via DSC, POM, and XRD.
- Thermal stability assessment using TG analysis.
- Emission properties measured via solid-state spectroscopy.
- Electrical properties investigated by variable temperature dielectric spectroscopy.
Main Results:
- Two neutral copper(I) halide complexes, [Cu(BTU)₂X] (X = Cl, Br), were successfully synthesized.
- The complexes exhibit 2D supramolecular structures and liquid crystalline behavior with a hexagonal columnar mesophase over a wide temperature range (>100 K).
- Good thermal stability was observed up to isotropization temperatures.
- Solid-state emission with quantum yields up to 8% was detected.
- Anhydrous proton conduction was facilitated by hydrogen-bonding networks within the liquid crystal phases, achieving conductivities of 2.97 × 10⁻⁷ S·cm⁻¹ (Cl) and 1.37 × 10⁻⁶ S·cm⁻¹ (Br) at elevated temperatures.
Conclusions:
- The synthesized copper(I) complexes possess a unique combination of properties including liquid crystallinity, emission, and proton conductivity.
- The hydrogen-bonding networks in the BTU ligand play a crucial role in enabling proton conduction within the mesophase.
- These metallomesogens show promise for applications in functional materials requiring self-assembly and ion transport.
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