Issue 7, 2019

Ionic liquid crystals with aggregation-induced emission properties based on pyrrolo[3,2-b]pyrrole salt compounds

Abstract

The present work reports the synthesis, optical properties and mesomorphism of two viologen derivatives DPP-2Py-9 and DPP-2Py-5 of 4,4′-((2,5-diphenylpyrrolo[3,2-b]pyrrole-1,4-diyl)bis(4,1-phenylene))bis(1-pyridin-1-ium) 4-toluenesulfonate. Both DPP-2Py-5 and DPP-2Py-9 showed aggregation-induced emission (AIE) characteristics indicating that the phenyl pyrrolo[3,2-b]pyrrole core acts as an AIE unit in their salt compounds. DPP-2Py-5 did not show liquid crystalline properties due to the shorter alkoxy chains. DPP-2Py-9 was a liquid crystalline compound with smectic A mesophase, showing marble-like textures observed at 185 °C during the cooling process. DPP-2Py-9 exhibited different emission behaviors in different aggregation states controlled by the change of temperature. The PL intensity of DPP-2Py-9 gradually decreased and the wavelength showed a hypochromic shift as the temperature increased. The most obvious variation of the wavelength occurred in the liquid crystalline range. The liquid crystalline temperature range between 185 and 210 °C determined by the differential curve of PL wavelength vs. temperature was similar to that measured by the DSC technique. Therefore, PL emission spectroscopy could be used as a technical method to characterize the liquid crystalline behaviors.

Graphical abstract: Ionic liquid crystals with aggregation-induced emission properties based on pyrrolo[3,2-b]pyrrole salt compounds

Supplementary files

Article information

Article type
Research Article
Submitted
02 Apr. 2019
Accepted
29 Apr. 2019
First published
30 Apr. 2019

Mater. Chem. Front., 2019,3, 1385-1390

Ionic liquid crystals with aggregation-induced emission properties based on pyrrolo[3,2-b]pyrrole salt compounds

Z. Peng, S. Dai, Y. Ji, B. Tong, J. Shi, Z. Cai, J. Zhi and Y. Dong, Mater. Chem. Front., 2019, 3, 1385 DOI: 10.1039/C9QM00208A

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