Desymmetrization of 3,3′‐Bis(acylamino)‐2,2′‐bipyridine‐Based Discotics: The High Fidelity of Their Self‐Assembly Behavior in the Liquid‐Crystalline State and in Solution

Abstract

Two novel nonsymmetrical disc-shaped molecules 1 and 2 based on 3,3'-bis(acylamino)-2,2'-bipyridine units were synthesized by means of a statistical approach. Discotic 1 possesses six chiral dihydrocitronellyl tails and one peripheral phenyl group, whereas discotic 2 possesses six linear dodecyloxy tails and one peripheral pyridyl group. Preorganization by strong intramolecular hydrogen bonding and subsequent aromatic interactions induce self-assembly of the discotics. Liquid crystallinity of 1 and 2 was determined with the aid of polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. Two columnar rectangular mesophases (Col(r)) have been identified, whereas for C(3)-symmetrical derivatives only one Col(r) mesophase has been found. In solution, the molecularly dissolved state in chloroform was studied with (1)H NMR spectroscopy, whereas the self-assembled state in apolar solution was examined with optical spectroscopy. Remarkably, these desymmetrized discotics, which lack one aliphatic wedge, behave similar to the symmetric parent compound. To prove that the stacking behavior of discotics 1 and 2 is similar to that of reported C(3)-symmetrical derivatives, a mixing experiment of chiral 1 with C(3)-symmetrical 13 has been undertaken; it has shown that they indeed belong to one type of self-assembly. This helical J-type self-assembly was further confirmed with UV/Vis and photoluminescence (PL) spectroscopy. Eventually, disc 2, functionalized with a hydrogen-bonding acceptor moiety, might perform secondary interactions with molecules such as acids.

Hierarchical Self‐Assembly of Supramolecular Helical Fibres from Amphiphilic C3‐Symmetrical Functional Tris(tetrathiafulvalenes)

“…As expected, we obtain a CD signal image of the one obtained for the precursor B (for a description of the main electronic transitions that involve contributions from both the TTF and bipyridine units, see Ref. 32).…”

“…Although so far only hydrophobic chains have been attached at the periphery of the disk‐shaped platform, the possibility of using hydrophilic polyether chains is also envisaged. Moreover, desymmetrisation of the C 3 core through the well‐established strategy32, 33 would possibly allow for the modulation of the helical pitch of the mesoscopic size fibres.…”

“…29 The chirality of the peripheral groups controls the helicity, M or P , of the primary fibres, and, moreover, non‐linear effects, that is, “sergeants‐and‐soldiers”30 and “majority rules”,31 have been evidenced by CD studies. Desymmetrisation of the C 3 platform allowed the modulation of the number of chiral units, the nature of the appended groups, and, ultimately, the self‐assembly properties 32. 33 To prepare electroactive supramolecular aggregates, we have recently attached thioalkyl containing TTF units to the 3,3′‐bis(acylamino)‐2,2′‐bipyridine‐substituted benzene‐1,3,5‐tricarboxamide (BiPy‐BTA) moieties.…”

Formation of Columnar Liquid Crystals on the Basis of Unconventional Triazine‐Based Dendrimers by the C3‐Symmetric Approach

“…Interestingly, the molecular conformation of (G 2 N–N) 3 T is arranged as a three‐leaf fan and leads to less π–π interaction between molecules. According to a detailed study of Percec and co‐workers,15g dendrimers with C 3 symmetry and three‐leaf fan conformation efficiently assemble into a columnar stacks like traditional disk‐shaped compounds with C 3 symmetry do 15a–f. Thus, (G 2 N–N) 3 T shows a columnar LC phase during thermal treatment.…”

Chirality Transfer and Modulation in LB Films Derived From the Diacetylene/Melamine Hydrogen‐Bonded Complex

“…Introduction of hydrogen‐bonding interaction into π‐conjugated systems is an especially promising strategy, since the highly selective and directional hydrogen‐bonding can increase the binding strength, provide enhanced stability to the assemblies, and position the π‐conjugated molecules in a desired arrangement . Variation of the peripheral flexible chains and the aromatic core is decisive for the tuning of coassembly in both solution and bulk .…”