Highly Fluorescent Crystalline and Liquid Crystalline Columnar Phases of Pyrene-Based Structures

Abstract

A concept for highly ordered solid-state structures with bright fluorescence is proposed: liquid crystals based on tetraethynylpyrene chromophores, where the rigid core is functionalized with flexible, promesogenic alkoxy chains. The synthesis of this novel material is presented. The thermotropic properties are studied by means of differential scanning calorimetry (DSC), cross-polarized optical microscopy (POM), and X-ray diffraction. The mesogen possesses an enantiotropic Colh phase over a large temperature range before clearing. The material is highly fluorescent in solution and, most remarkably, in the condensed state, with a broad, strongly red shifted emission. Fluorescence quantum yields (ΦF) have been determined to be 70% in dichloromethane solution and 62% in the solid state. Concentration- and temperature-dependent absorption and emission studies as well as quantum-chemical calculations on isolated molecules and dimers are used to clarify the type of intermolecular interactions present as well as their influence on the fluorescence quantum yield and spectral properties of the material. The high luminescence efficiency in the solid state is ascribed to rotated chromophores, leading to an optically allowed lowest optical transition.

Electrofluorochromism in π-conjugated ionic liquid crystals

“…It is worth highlighting that compounds 1 and 2 exhibit high fluorescent quantum yields (F) either in the liquid crystalline phases or in the solid state at room temperature (Table 1), among the highest ever reported [19][20][21][22] .…”

“…However, the synthesis of fluorescent liquid crystal including ionic ones, is challenging because of aggregation-caused fluorescent quenching [19][20][21][22] . Thus, electrofluorochromic liquid crystals have not been reported yet.…”

A Stimuli‐Responsive, Photoluminescent, Anthracene‐Based Liquid Crystal: Emission Color Determined by Thermal and Mechanical Processes

“…Our aim has been the development of a new class of photofunctional liquid crystals that change the emission properties on order-order phase transitions through external stimuli. [14] Recently, intensive work has been focused on photoluminescent liquid crystals [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] as they may be used for materials such as polarizing electroluminescent materials and laser devices. However, a change of the photoluminescent color based on the dynamic change of the LC assembled structures has not been observed, except for a few examples.…”

Self-assembled 1D Semiconductors: Liquid Crystalline Columnar Phase

“…However, majority of the DLCs discussed so far (except for some perylene derivatives) are only weakly fluorescent in their mesophases. Recently, pyrenebased DLCs have been synthesized in order to induce strong fluorescence in the columnar mesophase [89,90]. Shimizu and co-workers reported ambipolar charge transport in the Col h phase of a pyrene derivative 33 ( Fig.…”