Synthesis and thermal, emission and dielectric properties of liquid crystalline Eu(III), Sm(III) and Tb(III) complexes based on mesogenic 4-pyridone ligands functionalized with cyanobiphenyl groups
| Autor: | Viorel Cîrcu, Paul C. Ganea, Doina Manaila Maximean, Laura F. Chiriac, Iuliana Pasuk |
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| Rok vydání: | 2019 |
| Předmět: |
Lanthanide
Polarized light microscopy Materials science Mesogen 02 engineering and technology Dielectric 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Thermotropic crystal Atomic and Molecular Physics and Optics 0104 chemical sciences Electronic Optical and Magnetic Materials Dielectric spectroscopy Crystallography Differential scanning calorimetry Liquid crystal Materials Chemistry Physical and Theoretical Chemistry 0210 nano-technology Spectroscopy |
| Zdroj: | Journal of Molecular Liquids. 290:111184 |
| ISSN: | 0167-7322 |
| Popis: | New thermotropic lanthanidomesogens based on Eu(III), Sm(III) and Tb(III) with N-alkylated 4-pyridones mesogenic ligands, having two cyanobiphenyl groups attached via long alkoxy spacers, with 6, 9 and 10 carbons atoms in 3,5 - positions of a benzyl unit, have been designed and investigated. The liquid crystal behavior was assessed by differential scanning calorimetry, the mesophases being assigned by polarized light microscopy based on their characteristic textures and confirmed by variable temperature X-ray powder diffraction analysis. The three N-alkylated 4-pyridones nematic ligands reacted with lanthanide nitrates to yield new lanthanidomesogens with a stable and reproducible smectic A phase up to 125 °C. The emission spectra of the complexes have shown the characteristic emission of the lanthanide trivalent ions, over the entire temperature range of SmA phase up to isotropic state. The dielectric spectroscopy measurements performed in the temperature range of existence of the liquid crystal phase, both in the low frequency (LF) domain 0.01–10 MHz and in the high frequency (HF) range, 1 MHz–3 GHz, revealed three dipolar relaxation processes. The characteristic times have been obtained by fitting the spectra of the dielectric loss with a two component Havriliak-Negami function. The activation constant/energy was determined from the Vogel-Fulcher-Tammann law. |
| Databáze: | OpenAIRE |
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