Charge-based and charge-free molecular assemblies comprising π-extended derivatives of anion-responsive acyclic oligopyrroles

Abstract

Assemblies comprising anion complexes of π-extended oligopyrrole derivatives and counter cations, as well as those of anion-free receptor molecules, exhibited the formation of mesophases based on columnar structures using electrostatic and π-π interactions.

Ionic Liquid Crystals: Versatile Materials

“…Col squ phases have been observed, for instance, for supramolecular ionic dendritic complexes of alkanoic acids or T-shaped facial amphiphilic carboxylic acids with firstto fifth-generation DAB PPI dendrimers; 416,417 for ionic dendritic complexes of anionic lipids with cationic dendronized polymers; 418,419 for an ionic complex of ethyl orange and N,N-bis(n-hexadecyl)-N,Ndimethylammonium; 156 for ionic complexes of negatively charged DNA with positively charged PPI dendrimers; 167 and for an ionic complex of a planar, π-conjugated, negatively charged (oligopyrrole receptor)-anion complex and a planar 4,8,12trialkyl-4,8,12-triazatriangulenium (TATA) cation. 420 Nematic phases are very uncommon for ILCs, as the orientationally ordered nematic phase is stabilized by weak, anisotropic dispersion forces, and not by strong, isotropic electrostatic forces that cause strong intermolecular interactions. 2,292,421 In the case of type (a) compounds (Figure 3), excluded volume effects induced by a rigid anisometric molecular core, which constitute an important driving force for nematic phase formation in conventional LCs, can play no role.…”

“…The Maeda group also investigated other β-substitution patterns for the π-conjugated receptor−anion complexes (362• Cl − , 363•Cl − , and 364•Cl − ). 420 β-Aryl and β-(n-alkyloxy) substituents appeared to be unsuitable for the induction of mesomorphism in combination with a planar TATA cation, probably because of less efficient stacking of the different planar components. A Col squ phase was however found for β-benzofused 362•Cl − in combination with 369-3, in contrast to the Col hex phase previously observed for 361-a-H•Cl − /369-3 (see above).…”

Chirality Induction by Formation of Assembled Structures Based on Anion‐Responsive π‐Conjugated Molecules

“…Assembly behavior of receptor–anion complexes in solution was also examined. Planar cations such as a tripropyl‐substituted triazatriangulenium cation (TATA + )11 are effective at forming charge‐by‐charge assemblies by combining with planar receptor–anion complexes 9a,d,e,g. Broad and severely diminished signals in the 1 H NMR spectrum of the TATA + salt of 2 b⋅ Cl − in [D 18 ]octane and CD 2 Cl 2 (1 m M ) suggest the formation of aggregates at lower temperatures.…”

The supramolecular assemblies based on heteroatom-containing triangulenes

“…For example, the benzo[c]-fused analogues of 15 were studied in this context. 54 The p-electronic salts (14a)(16ÁCl) were prepared and studied with respect to their self-assembly behavior. In the case of (14a)(16bÁCl), a tetragonal Col t mesophase was identified by POM imaging and XRD measurements (Fig.…”

“…Bottom: (a and b) POM image and synchrotron XRD pattern of (14a)(16bÁCl), respectively (both measurements were conducted at 80 1C); the proposed supramolecular stacking within the Col t structure is also shown. 54 were employed for the complexation of chloride ions and, subsequently, the formation of p-electronic salts with TATA + cations. 56 The anion-receptor molecules featured an increased affinity towards halide anions (attributed to additional C-HÁ Á ÁCl interactions with the phenanthroline unit) and, as result, the (17ÁCl) À were of highly planar structure.…”