Exciton-coupled circular dichroism signal

Further evidence for the existence of a helical conformation for meta-linked CPEs comes from circular dichroism (CD) studies of j-PPE-C02 (Figure 14.10). The basis for this experiment lies in the fact that a helix is an inherently chiral structure. Because the helix is chiral, one would expect that if an enantiomeric excess (ee) of the right- or left-handed forms (the P and M forms) exists in solution, then the CD spectrum would feature a bisignate signal due to exciton coupling of the backbone chromophores which are in a chiral environment [35]. However, when a polymer folds into a helical structure, because the polymer itself is achiral, the ensemble of helically folded polymers exists as a... 

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