Synthesis and Characterization of Fluorescent, Low-Symmetry Triphenylene Discotic Liquid Crystals:  Tailoring of Mesomorphic and Optical Properties

Abstract

A series of monofunctionalized triphenylene-based discotic liquid crystals were synthesized starting from 2-hydroxy-3,6,7,10,11-pentakis(pentyloxy)triphenylene. These compounds are unique in that they possess a single electron-withdrawing group (and consequently a large dipole moment) connected directly to the polyaromatic core. All of the new liquid crystals show a significantly broader range of mesogenicity relative to the parent compound 2,3,6,7,10,11-hexakis(pentyloxy)triphenylene. Moreover, some of the new mesogens exhibit a more ordered mesophase relative to the hexagonal columnar phase (D h ) at lower temperatures. Monofunctionalization of the triphenylene core has a dramatic effect on the photophysical properties of the mesogens such as the color and efficiency of fluorescence.

Diskotische Flüssigkristalle: Von der maßgeschneiderten Synthese zur Kunststoffelektronik

“…[115] Die induzierte Abnahme der Molekülabstände um 6 % für Drücke bis 17 kbar ist jedoch zu klein, um die elektronische Struktur und damit die optoelektronischen Eigenschaften zu modifizieren. Dagegen fanden die Arbeitsgruppen um Ringsdorf, [116] Kumar [117] und Bushby [118] unabhängig voneinander, dass stark elektronenziehende Bromoder Cyansubstituenten (in 48 e bzw. 48 f) nicht nur die Mesophasen stabilisieren, sondern auch die Fluoreszenzquantenausbeuten erhöhen, die für die Entwicklung optoelektronischer Bauteile wichtig sind.…”

Influence of mesogenic core polarity and position of chains attachment on columnar phase stability

“…On the contrary, when in the I-2d compound the exchange is done at meta position -meta-pentoxy chain is replaced with the meta-hexyl substituentthe resulting I-2a compound shows the lower clearing point, about 33°C. The meta-alkyl group is more likely to be situated nearly perpendicular to the phenyl ring [37] and it seems this is the case. When orthooctyloxy substituent (R4) in the compound I-2g is converted into ortho-nonyl chain, the clearing temperature in I-2f compound falls drastically about 130°C.…”

Self-assembled 1D Semiconductors: Liquid Crystalline Columnar Phase

“…Reproduced with permission from [31] mobility on transition from mesophase to crystal phase is a common feature of a number of discotics and is ascribed to the greater short-range structural order within the crystal packing of the molecules. It is found that molecular order within the columnar phase of discotic triphenylenes can also be changed by the variation of the lateral chain or by direct polar substitutions (compound 4) on the aromatic core [41,42]. van de Crats et al reported TOF and PR-TRMC hole mobilities of about 0.01 cm 2 V −1 s −1 in the columnar phase of triphenylene dimer 5 [43].…”