Chiral nanoscopic

Oenyuk, B., Whiteford, J.A. and Stang, P.J. (1996) Design and study of synthetic chiral nanoscopic assemblies. Preparation and characterization of optically active hybrid, iodonium-transition-metal and all-transition-metal macrocyclic molecular squares. J. Am. Chem. Soc., 118 (35), 8221-8230. 

The conformational flexibility and the lack of difference of the electronic properties of the polyether branches in 32 have been forwarded to explain this zero rotation. Therefore a similar dendrimer 34 has been prepared which carries a more sterically demanding branch, leading to a more rigid structure [66] interestingly, this dendrimer indeed exhibited a very small but measurable optical activity, which underlines the thesis that nanoscopic chirality depends on the rigidity of the investigated structure. 

Studies performed on chiral core dendrimers have provided valuable information about the influence of the achiral dendrimer scaffold on the chiroptical properties of the core unit. Yet they also show that prediction of the chiroptical properties of the dendrimer is difficult, since the chiral relationship between the local chirality of the core unit and the nanoscopic conformation of the overall dendrimer structure is influenced by numerous structural factors. Further studies will be required to attain a fuller understanding of how an individual chiral building block can induce chirality in the entire dendrimer architecture (see Section 4.2.7). 

Terms such as macroscopic, nanoscopic, and mesoscopic chirality are known from studies by Mislow [a) A. B. Buda, T. Auf der Heyde, K. Mislow, Angew. Chem. 1992, 104, 1012-1031 Angew. Chem. Int. Ed. 1992, 32, 989-1007] and Avnir [b)... 

Hu et al. [31] reported a new type of macro molecular chiral catalysts for asymmetric catalysis using Suzuki coupling polymerization and obtained optically active ephedrine-bearing dendronized polymers. Their finding showed that the optically active dendronized polymers have characteristics joined features like huge numbers of catalytic sites, more solubility and nanoscopic dimensions towards more acceptable in comparison to its existing chiral catalysts of linear polymeric and dendritic nature. 

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