Solvent‐Assisted Organized Structures Based on Amphiphilic Anion‐Responsive π‐Conjugated Systems

Abstract

The synthesis of amphiphilic pi-conjugated acyclic oligopyrroles and the formation of solvent-assisted aggregates are reported. We have prepared various types of BF(2) complexes of 1,3-dipyrrolylpropane-1,3-diones bearing aryl rings substituted with hydrophilic polyethyleneglycol (PEG) chains, both as acyclic anion receptors and as building subunits for organized architectures based on pi-pi stacking. The formation of supramolecular H-type assemblies of these "amphiphilic" derivatives in aqueous solution was suggested by UV/Vis and fluorescence spectroscopy and further supported by (1)H NMR and dynamic light scattering (DLS) analyses. Cryogenic transmission electron microscopy (cryo-TEM) analyses of the aqueous solutions suggest that the fabrication of nanoscale network structures and vesicles depends on the peripheral substituents. The H-aggregates in aqueous solution are sensitive to the conditions required for transformation into monomers through replacement with miscible solvents such as alcohols and into J-type aggregates by water evaporation and freeze-drying procedures. However, they are fairly stable and sustainable to anion binding, whereas on CH(2)Cl(2) extraction they are transformed into other assembled modes but remain in the aqueous solution. The metastable states of affairs for distributions between two immiscible solvents are controlled by the orders of solution preparation; this also suggests that the formation of stable assemblies is assisted by water molecules. Furthermore, assemblies in which the stacking modes depend on the aliphatic side chains are also observed in a nonpolar hydrocarbon solvent.

Self‐Assembly and Aggregate‐Induced Enhanced Emission of Amphiphilic Fluorescence Dyes in Water and in the Solid State

“…Similar TEM images were also observed for another amphiphilic compound reported previously. [12] Compounds 2 and 3 were confirmed to have different structures in the solid state by TEM observations.…”

Fullerene Derivatives That Bear Aliphatic Chains as Unusual Surfactants: Hierarchical Self‐Organization, Diverse Morphologies, and Functions

“…[22] In other cases, systems with p-conjugated amphiphiles as a nonpolar tail group were self-assembled to study their potential use for organic electronics. [23][24][25][26] Newer types of the compounds are macromolecular, in which dendrimers and block copolymers display amphiphilicity. The unusual supramolecular assemblies composed of giant amphiphiles exhibit unique geometries such as hollow nanospheres, pores, and single and double helices.…”

Control of the Optical Properties of a Star Copolymer with a Hyperbranched Conjugated Polymer Core and Poly(ethylene glycol) Arms by Self‐Assembly

“…[6] For linear rod-coil block conjugated polymers, the opto-A C H T U N G T R E N N U N G electronic properties can be improved by changing their aggregation behavior (H-or J-aggregates). [7] In the solid state, the electroluminescent properties can also be enhanced by the evolution of the phase structure. [5b] Unfortunately, nonradiative decay occurs in the supramolecular self-assembly of linear rod-coil block conjugated copolymers as a result of interchain electronic interactions of rigid segments through p-p stacking.…”

“…For linear rod–coil block conjugated polymers, the optoelectronic properties can be improved by changing their aggregation behavior (H‐ or J‐aggregates) 7. In the solid state, the electroluminescent properties can also be enhanced by the evolution of the phase structure 5b.…”