Synthesis of Triphenylene Discotic Liquid Crystal Dimers: Click Chemistry As an Efficient Tool

Abstract

Click chemistry between alkynes and azides high efficiently produces triazoles and would be a convenient tool for synthesis of discotic liquid crystal dimers, oligomers and polymers. In this report, triphenylenes containing terminal alkynes and azides were prepared, and the cycloaddition reaction (click chemistry) between them catalyzed by CuI-Et 3 N in toluene produced discotic liquid crystal dimers in high yield and good selectivity. The dimers and intermediates have been fully characterized by 1 H NMR and high resolution MS. Polarized optical microscopy (POM) and differential scanning calorimetry (DSC) results show the dimers possess columnar mesophase in wide temperature range from very low temperature. The triazole moiety in the dimer can act as electron and hydrogen bond acceptor, and ionic forming part, rich chemical and physical properties can be expected from these new structure discotic dimers.

Discotic liquid crystalline tris(hexahexyloxytriphenylene)triazines with separate columns of triphenylene and triazine cores

“…The resulting compounds 3-R were reacted with a dibromoalkane to afford compounds 4-n-R, which were converted in high yield (typically 90-95%) into the azides 5-n-R. [14,15,27] These azideterminated alkoxytriphenylenes were clicked under standard CuAAC conditions [23] to tris(propynyloxy)triazine 6 to afford the final compounds of the series 7-n with typically 35% yields. In order to study the influence of an alkyl tail near the spacer group on the ordering properties, a compound with a methoxy instead of a hexyloxy group at the ortho-position of the triphenylene core was also prepared and investigated (8-3; 50% yield).…”

“…This reaction has recently already been applied to prepare liquid crystalline materials. [22][23][24][25][26] In the present article, a series of discotic liquid crystalline materials was devised in which three HAT units are 'clicked' to a central 1,3,5-triazine unit ( Figure 1). This triazine unit was chosen as a model for an electron-poor aromatic moiety that has the potential for significant stacking interactions that can contribute to formation of separate columns without involving H-bond stabilisation.…”

Synthesis of disk-rod-disk liquid crystal trimers by using click chemistry

“…1,4-Disubstituted 1,2,3-triazole heterocyclic ring could act as the hydrogen bond acceptor [28], precursor of ionic compounds [29] and ligands for metal coordination complexes [30].…”

“…When azido and alkynyl connect to alkyl chains, the triazole ring formed by click chemistry acts as the spacer and its effect on mesomorphism remains unclear. However, liquid crystals with 1,2,3-triazole rings as the linkage could be readily synthesized, and the unique properties of the N atom of 1,4-disubstituted 1,2,3-triazole ring to act as the hydrogen bond acceptor [28], precursor of ionic compounds [29] and ligands for metal coordination complexes [30] have made this material even more attractive. Herein, we report the synthesis and mesomorphic properties of a new series of disk-rod-disk triphenylene discotic liquid crystal trimers linked via 1,4-disubstitute-1,2,3-triazole using click chemistry.…”

“…We synthesized new triphenylene discotic liquid crystalline dimers composed of two triphenylene discogens and a triazole moiety using the same method [28]. In the case of aryl azide reacting with aryl alkyne, the triazole ring formed is part of the rigid conjugating mesogen system and it is not harmful to the formation of the mesophase.…”