It is not that the Copper atom changes the helical chirality, it is that upon binding the systems undergo a biasing of one of the possible helical conformations.
When you oxidize/reduce the copper atom, the system undergoes a conformational change that is still chiral, but different in geometry, and thus it generates a different electro-optical response.
For more info, look at the web article I mentioned elsewhere. It is an initial report back when I was workging on my PhD at Canary's lab.
In that earlier report you can clearly see the biasing of a molecule conformation by a simple metal binding event. This was detected by optical methods.
Since them, other systems have been described by the same group, redox systems (Cu for example), in which there is a very strong conformational change affecting the optical and the electronic properties of the system. And this was very reproducible and stable.
I am a former memeber of the group, when I was doing my PhD at NYU
I am former member of the Canary lab (back when I was doing my PhD), and here is one of the first papers we published on dynamically chiral compounds: http://www.ch.ic.ac.uk/ectoc/echet96/papers/003/in dex.htm This web paper was written back in 1996, and has some animations, as well as some more background on chiral compounds (tripodal metal complexes in particular). Some of the structures need to use a plugin from www.mdli.com (ChemChime). Simple explanation: In these systems, there is equal probability of finding either conformation (left-handed or right-handed), in the systems we were working, a single point derivatization of the organic part leads to a bias towards one of the conformation w/ respect to the other, hence dynamic chiral control.
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It is not that the Copper atom changes the helical chirality, it is that upon binding the systems undergo a biasing of one of the possible helical conformations.
When you oxidize/reduce the copper atom, the system undergoes a conformational change that is still chiral, but different in geometry, and thus it generates a different electro-optical response.
For more info, look at the web article I mentioned elsewhere. It is an initial report back when I was workging on my PhD at Canary's lab.
I would refer you to the cited papers, and to an old (ca March-April 1996) web article: Dynamic Control of Topological Asymmetry
In that earlier report you can clearly see the biasing of a molecule conformation by a simple metal binding event. This was detected by optical methods.
Since them, other systems have been described by the same group, redox systems (Cu for example), in which there is a very strong conformational change affecting the optical and the electronic properties of the system. And this was very reproducible and stable.
I am a former memeber of the group, when I was doing my PhD at NYU
I am former member of the Canary lab (back when I was doing my PhD), and here is one of the first papers we published on dynamically chiral compounds: http://www.ch.ic.ac.uk/ectoc/echet96/papers/003/in dex.htm This web paper was written back in 1996, and has some animations, as well as some more background on chiral compounds (tripodal metal complexes in particular). Some of the structures need to use a plugin from www.mdli.com (ChemChime). Simple explanation: In these systems, there is equal probability of finding either conformation (left-handed or right-handed), in the systems we were working, a single point derivatization of the organic part leads to a bias towards one of the conformation w/ respect to the other, hence dynamic chiral control.