Self-Assembly of Aromatic-Functionalized Amphiphiles:  The Role and Consequences of Aromatic−Aromatic Noncovalent Interactions in Building Supramolecular Aggregates and Novel Assemblies

Abstract

This feature article presents an overview of a study of several different aromatic-functionalized amphiphiless fatty acid and phospholipid derivatives. These amphiphiles form organized assemblies when the fatty acids are spread as monolayers at the air-water interface or when the phospholipids are dispersed in aqueous solutions. For a wide range of aromatic chromophoresstrans-stilbene derivatives and a series of "vinylogues" (1,4-diphenyl-1,3-butadiene and 1,6-diphenyl-1,3,5-hexatriene), diphenylacetylenes, and azobenzenes such as phenyl, biphenyl, and terphenyl derivatives and modified stilbenes (styryl thiophenes and styryl naphthalenes)sassembly formation is accompanied by formation of aggregates of the aromatic groups. Results of experimental studies and simulations indicate that in many cases the aromatics form a small, stable "unit aggregate" characterized by strong "noncovalent" edge-to-face interactions among adjacent aromatics. Although the unit aggregates exhibit characteristic spectral shifts and strong induced circular dichroism indicating a chiral "pinwheel" aggregate structure, they may be packed together in pure films or dispersions to form an extended glide or herringbone structure. Although the "pinwheel" unit aggregate and the extended glide structure is favored for the majority of aromatics studied, for certain aromatics (styrenes, styrylthiophenes, and R-styrylnaphthalenes) a translation layer, characterized by face-to-face noncovalent interactions, is preferred. The glide or herringbone aggregates are readily distinguished from the translation aggregates by different spectral signatures and different photochemical and photophysical behavior. Factors controlling the type of aggregate and hence extended structure formed from different aromatic functionalized aromatics include shape and steric factors and strength of the competing noncovalent edge-face and face-face interactions.

The density of humic acids and humic like substances (HULIS) from fresh and aged wood burning and pollution aerosol particles

“…These interactions have multiple points of intermolecular contact with variable geometries and may contain a vast range of different functional groups (Hunter et al, 2001). Moreover, these interactions play a crucial part in biomolecules and pure organics selfassembly (Azriel and Gazit, 2001;Hunter et al, 2001;Whitten et al, 1998). Harmata and Barnes (1993) who also studied the packing and density of a complex organic substance concluded that the high densities observed indicate the efficiency of the packing, which are dominated by edge-to-face stacking of aromatic moieties.…”

Solvent‐Polarity‐Tunable Dimeric Association of a Fullerene (C60)–N,N‐Dimethylaminoazobenzene Dyad: Modulated Electronic Coupling of the Azo Chromophore with a Substituted 3D Fullerene

“…[31][32][33][34][35][36][37][38] Azobenzenes of donor-acceptor type have been found to form characteristic aggregates depending on the solvent composition, polarity, and the solute concentration. Studies directed towards aggregation of azobenzenes have mainly concentrated on: 1) simpler azobenzene molecular entities of donor-acceptor and electronically symmetric type; [39,40] 2) surfactant-like azobenzene derivatives functionalized with long alkyl chains and apexed with a polar head group; [41,42] and 3) azo moieties with polar or nonpolar head groups, appended as side chains on polymeric backbones. [43,44] With the aim of developing photomodulated phthalocyanine J-aggregates, a-aryl/ alkoxy-substituted zinc phthalocyanine dyads (3-azo-ZnPc and 4-azo-ZnPc) have been synthesized by LiHong Niu et al [45] In noncoordinating solvents, the 3-azo-ZnPc could be effectively photocontrolled as a result of changes in the geometry and dipole moment of azobenzene on the dyad framework.…”

Replicator Dynamics in Protocells

“…In contrast to other proposals, the proto-genes directly interact with the lipid; this requires a less sophisticated spatial organisation than vesicles (see e.g. (Apel et al, 2002)), making micelles (Whitten et al, 1998) or even less organized lipid aggregates plausible. A scheme of the replication mechanism is shown in Fig.…”