Thermo‐Induced Bathochromic Emission in Columnar Discotic Liquid Crystals Realized by Intramolecular Planarization

Abstract

Most organic thermochromic fluorescent materials exhibit thermo-induced hypsochromic emission due to the formation of excimers in ordered molecular solids; however, it is still a challenge to endow them with bathochromic emission despite its significance in making up the field of thermochromism. Here, a thermo-induced bathochromic emission in columnar discotic liquid crystals is reported realized by intramolecular planarization of the mesogenic fluorophores. A three-armed discotic molecule of dialkylamino-tricyanotristyrylbenzene was synthesized, which preferred to twist out of the core plane to accommodate ordered molecular stacking in hexagonal columnar mesophases, giving rise to bright green monomer emission. However, intramolecular planarization of the mesogenic fluorophores occurred in isotropic liquid increasing the conjugation length, and as a result led to thermo-induced bathochromic emission from green to yellow light. This work reports a new concept in the thermochromic field and provides a novel strategy to achieve fluorescence tuning from intramolecular actions.

Bioinspired polymeric supramolecular columns as efficient yet controllable artificial light-harvesting platform

“…13 ), thereby supporting the proposition of a Col h structure with p 6 mm symmetry, similar to related columnar discotic systems (Fig. 3g ) 50 , 51 . Additionally, the electron density map confirmed the formation of columns via a helical stacking manner of three-armed MTCS molecules (Supplementary Fig.…”

“…1b ). Both PTCS and MTCS formed thermotropic hexagonal columnar (Col h ) LC phases due to the discotic shape of the TCS core with aliphatic surroundings, which was reminiscent of the columnar structures generated by TCS derived LC compounds 50 , 51 . The temperature range of PTCS was significantly expanded across room temperature from below 0 °C to 123 °C, compared to MTCS that exhibited a LC range between 80 °C and 110 °C (Supplementary Fig.…”

2-Aryl-1,3,4-trifluoro-6,7,10,11-tetrakis(alkoxy)triphenylene: a remarkable and highly inclusive mesomorphic platform

“…Fluorescent and light-emitting large, π-conjugated DLCs still attract the interest of scientists not only for academic reasons but also for their potential applications and uses in OLEDs, biological probes, chemical sensors, stimuli responses and circularly polarized light-emitting materials. 47–54 Large aromatic systems containing pyrene ( PY 8) and tetraphenylethene ( TPE 8) are particularly important as potential fluorescent and aggregate-induced light-emitting functional materials, respectively. 55…”

“…Fluorescent and light-emitting large, p-conjugated DLCs still attract the interest of scientists not only for academic reasons but also for their potential applications and uses in OLEDs, biological probes, chemical sensors, stimuli responses and circularly polarized light-emitting materials. [47][48][49][50][51][52][53][54] Large aromatic systems containing pyrene (PY8) and tetraphenylethene (TPE8) are particularly important as potential fluorescent and aggregateinduced light-emitting functional materials, respectively. 55 The UV-Vis absorption and fluorescence emission of the synthesized molecules were studied in both dilute solutions and in thin films (emission) to understand the effects of the pconjugation extension, intermolecular interactions and coplanarity on the optical properties.…”