A general synthetic strategy, based on a convergent approach, allowed us to prepare a series of luminescent unsymmetrical bent‐core compounds (2,5‐(disubstituted)‐1,3,4‐oxadiazole derivatives), via the Sonogashira crosscoupling reaction, all possessing a similar hockey stick shape. Their mesophases were characterized using polarizing optical microscopy and differential scanning calorimetry. The observed LC phases possess the classical textures of calamitic liquid crystals. Fluorescence in solution for these compounds exhibits strong blue emission (λmax em. = 390–460 nm) with good quantum yields (50–85%).
9 February 2017 in Angewandte Chemie International Edition
The synthesis and structural, thermal, optical and theoretical characterization of new tris[1,2,4]triazolo[1,3,5]triazines were performed to support their application as liquid crystals and advanced materials.
New fluorescent liquid crystalline (LC) compounds containing the 2,1,3-benzothiadiazole chromophore as the central core substituted with 1,2,4-oxadiazole, 1,2,3-triazole and 1,2-isoxazole heterocycles were synthesised and their mesophases characterised by polarised optical microscopy, differential scanning calorimetry and X-ray diffraction. We observed that the bent angles of the five-membered heterocyclic substituents are crucial in determining the thermal stability of the LC phases formed, indicating a delicate balance of forces involved in LC phases. The mesophases formed by all symmetrical and unsymmetrical compounds showed thermal stability in the order 1,2-isoxazole > 1,2,3-triazole > 1,2,4-oxadiazole.
The synthesis, and liquid crystalline and photophysical properties of luminescent liquid crystalline compounds based on 1,3‐bis[5‐(4‐alkoxyphenyl)‐1,3,4‐oxadiazole‐2‐yl]benzene (two‐fold symmetry) I and 1,3,5‐tris[5‐(4‐alkoxyphenyl)‐1,3,4‐oxadiazole‐2‐yl]benzene II (three‐fold symmetry) are described. The mesophases were characterized using polarizing optical microscopy and differential scanning calorimetry. In addition, all compounds showed blue fluorescence with emission maxima between 366 and 382 nm, and good quantum yields of photoluminescence (ΦPL = 45%).