Chirality change

Figure 4.76 depicts an intramolecular dynamic equilibrium of a dendrimer with four blade dendrons, in the course of which the (helical) propeller conformation is inverted, i.e. the sense of the chirality changes [37a]. In such cases it was observed that all four dendrons undergo correlated motion, rather than just one dendron changing its conformation without the other three dendrons rotat-... 

In [112] the insight and accuracy of the approach has been demonstrated it has been extended afterwards to a series of molecules in view of perspective applications to molecular dynamics modeling of collision induced chirality changing processes. 

Jorio A, Saito R, Dresselhauss G, Dresselhaus MS (2004) Determination of nanotube properties by Raman spectroscopy. Phil Trans R Soc Lond A 362 2311-2336 Kobayashi K, Takagi D, Ueno Y, Homma Y (2004) Characterization of carbon nanotubes suspended between nanostructures using micro-Raman spectroscopy. Physica E 24 26-31 Dresselhaus MS, Eklund P (2000) Phonons in carbon naotubes. Adv Phys 49 705-814 Anderson N, Hartschuh A, Novotny L (2007) Chirality changes in carbon nanotubes studied with near-field Raman spectroscopy. Nano Lett 7 577-582... 

Part I of this Volume has identified chirality changes on electronic excitation as a fruitful area for further research. 

It is very peculiar that the spatial distribution of the director field of the modulated structure forms a chiral structure. This became evident much later [36] when the numerical calculations had been made in the same geometry with director components n K., rPy = co qy, = sinf/y. Thus the projections of the director on the zy plane, i.e. = Uy, rotate about the x-axis upon translation along the y-axis. The corresponding picture is demonstrated in Fig. 11.31. The calculations show that the chirality changes its handedness when the sign of the electric field applied in the z-direction inverses. Therefore, we again see the field induced break of the mirror symmetry. 

Some of the very early applications of CPL spectroscopy involved chiral polymeric systems. In particular, the CPL from achiral dye molecules dissolved in cholesteric liquid crystals has been used to probe chirality changes. CPL from chromophores attached to a chiral poly-amino acid may also be used to study exciton coupling between aromatic chromophores. In these polymeric systems, it is often observed that gijjjjj is quite large. In some cases it is so large, in fact, that detection using static quarter-wave plates is possible. 

Arg to Gln result in moderate decrease in binding, whereas substantial decreases in activity are observed in chiral changes from Gln to Leu. ... 

The role of 7i-alkene, a-alkenyl and 7i-allyl complexes in the Pd-catalysed oxidative esterification of alkenes. Changes in selectivity were affected by solvent and chirality changes in the ancillary ligand sets. " The stabilisation of p-quinone methides was achieved by coordination to the [Pd(dppe)] fragment to yield compopund 39 which was structurally characterised. ... 

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