Supramolecular structures self-assembled molecules, chirality

The foregoing studies show that chiral supramolecular modules could be obtained from self-assembly of achiral molecule components, and further assembly generates supercoil structures in a mesoscopic dimension, just like the behavior of some chiral molecules. Appropriate manipulation and combination of intermole-cular noncovalent interactions can provide new routes to constructing artificial or-... 

One core chiral system that shows dramatic amplification of its chiral structure is the substituted helicenes of Katz and coworkers [83]. In essence, this research cuts the helix into a number of six-helicene subunits that self-assemble (Figure 10). Only when these subunits, which look like lock washers, are prepared in optically pure form the material associates into supramolecular helical columns [84]. The assemblies have been synthesized with different amounts of substitution around the exterior. Depending on the helicenes substitution, the material exhibits hexagonally ordered soft-crystalline [84] or liquid-crystalline phases [85]. The liquid-crystalline versions of these molecules switch when electric fields are applied to neat and solution-phase samples and have been characterized as a dielectric response [85-87]. Upon association, these materials have enormous changes in their CD intensities and optical rotations [74]. In addition, this supramolecular chirality also significantly enhances the second-order nonlinear optical behavior of these materials in Langmuir-Blodgett films [88]. 

The formation of superlattice structures in molecular self-assembly on-surfaces provides detailed insight in how molecules act cooperatively by means of STM. By studying monolayers formed by the self-assembly of alkoxy-substituted dehydro[12] annulenes (DBAs) at the liquid-solid interface, we realized that the high adaptability of this building block led to the generation of chirality on surfaces at single molecular and supramolecular levels and formation of superlattice structures on surfaces. 

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