An Unconventional Approach to Induce Liquid‐Crystalline Phases of Triazine‐Based Dendrons by Breaking Their Self‐Assembly into Dimers

Abstract

Three triazine-based dendrons (1 a-c) were successfully prepared in 70-83 % yields. These newly prepared dendrons are found to be liquid crystalline (LC). Computational investigations on molecular conformations and dipoles of triazine-based dendrons reveal that the substituent on the central triazine unit interrupts strong dipole or H-bond interactions to avoid dimeric formation. The obtained dendrons, not favouring self-assembly into dimers but showing LC behaviours, provides evidence for an approach contrary to the conventional method of inducing LC behaviours of dendrons by dimer or trimer formation, mostly through H-bond interactions.

Converting Nonliquid Crystals into Liquid Crystals by N-Methylation in the Central Linker of Triazine-Based Dendrimers

“…The synthesis of dendrons 2a and 2b is shown in Scheme . Dendron G 3 Cl was prepared according to literature . ( N,N -Dimethylamino)­ethane was allowed to react with 1 equiv of G 3 Cl in THF at 70 °C for 24 h. Then another 1 equiv of G 3 Cl , followed by 3 equiv of K 2 CO 3 , was added, and the resulting mixture was heated at 170 °C for 72 h in a sealed tube.…”

“…G 3 -Cl (0.3 g, 0.1 mmol), prepared according to our previous procedure, and the corresponding ( N , N -dimethylamino)­alkane (0.1 mmol) were dissolved in dry THF (15 mL) in a sealed tube and then heated at 70 °C for 24 h. Potassium carbonate (0.04 g, 0.3 mmol) and G 3 -Cl (0.3 g, 0.1 mmol) were then added, and the tube was sealed. The resulting mixture was heated at 170 °C for 72 h. Water (20 mL) was added to the mixture, and the solution was extracted with CH 2 Cl 2 (20 mL × 2).…”

“…Instead of traditional LC dendrimers, − we are more interested in the synthesis and study of unconventional triazine-based LC dendrimers, which contain rigid cores, rigid linkages, and flexible peripheral chains, because their morphology is controlled by restricted conformational freedom and cavities may thus be created in the dendritic frameworks to incorporate guest molecules as demonstrated in other dendritic systems . Previously, we prepared unconventional triazine-based dendrimers 1a and 1b , which contain the −NH­(CH 2 ) 2 NH– and the −NH­(CH 2 ) 4 NH– linkers between two G 3 dendrons, respectively.…”

Design of a Peripheral Building Block for H-Bonded Dendritic Frameworks and Analysis of the Void Space in the Bulk Dendrimers

“…t - Bu - G n Cl (1 mmol; n = 1 or 2) and t - Bu - G n NH (1 mmol; n = 1 or 2), prepared according to our previous procedure 71 – 75 , were dissolved in dry THF (20 mL) in a sealed tube. Potassium carbonate (0.5 g, 5 mmol) was then added and sealed.…”