Match or mismatch? Steady state and ultrafast spectroscopy reveal the decisive role of the benzothiazole orientation in the Intramolecular Charge Transfer and excited state dynamics of octupolar molecules of the D-(π-Α)3 type. <...
Nematic Phase of Polar Unsymmetrical Bent‐Core Molecules
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Polar bent-core molecules: Unsymmetrical polar bent-core molecules exhibiting cybotactic clustering in the nematic phase are reported, and substantiated by temperature-dependent XRD studies, dielectric spectroscopy, and birefringence measurements. DFT calculations reveal that the antiparallel arrangement of the polar molecules is favored that minimizes the large net dipole moment of the system.
In liquid crystalline systems, the presence of polar groups at lateral or terminal positions is fundamentally and technologically important. Bent-core nematics composed of polar molecules with short rigid cores usually exhibit highly disordered mesomorphism with some ordered clusters that favourably nucleate within. Herein, we have systematically designed and synthesized two new series of highly polar bent-core compounds comprised of two unsymmetrical wings, highly electronegative −CN and −NO2 groups at one end, and flexible alkyl chains at the other end. All the compounds showed a wide range of nematic phases composed of cybotactic clusters of smectic-type (Ncyb). The birefringent microscopic textures of the nematic phase were accompanied by dark regions. Further, the cybotactic clustering in the nematic phase was characterized via temperature-dependent XRD studies and dielectric spectroscopy. Besides, the birefringence measurements demonstrated the ordering of the molecules in the cybotactic clusters upon lowering the temperature. DFT calculations illustrated the favourable antiparallel arrangement of these polar bent-core molecules as it minimizes the large net dipole moment of the system.Zum Volltext
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