Helical aggregates chirality sensing

Keywords Chiral amplification Chirality sensing Helical aggregates ... 

Figure 6.9 Schematic representation of hierarchical self-assembly process for chiral phthalocya-nine 64. Phthalocyanine molecules self-assembly into helical columns with right-handed screw sense (left). These right-handed helices subsequently aggregate to give left-handed super-helices.

Poly (PDBF) s synthesized by helix-sense-selective polymerization using FlLi-Sp and FlLi-DDB complexes did not show detectable CD or optical activity in solution. However, a thin film made by drop-casting the solution onto a quartz plate indicated intense CD absorptions. The spectra of the polymers synthesized with (+)- and (-)-DDB were almost mirror images. The CD spectra are not due to film anisotropy but to conformational chirality of polymer chains. Because the polymers showing clear CD bands in film did not show chiroptical properties in solution, molecular aggregation may amplify and stabilize the single-handed helical conformation induced... 

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