The binding of a chiral ligand to a racemic transition-metal complex can be used to control the conformation around the metal centre. This local event has the potential to govern global conformation over much larger distances. This mimics allosteric enzymes and proteins, where binding of a molecule at one position affects the shape of a remote site.This work uses the binding of an enantiopure carboxylic acid to a metal centre to control the orientation of both the metal and an attached peptide. These dynamic foldamers form stable helices so are excellent signal transducers that can communicate information across nanometre distances.Binding of chiral amino acids such as N-Boc-proline was used to bias the conformation of a zinc propeller complex (Figure 1), as observed by exciton-coupled circular dichroism (ECCD). The stereochemical information is then relayed through the attached helical peptide to the remote glycine residue, which consequently appears in the NMR spectrum as an ABX system.The high-affinity binding of carboxylates to the zinc centre, as well as the availability of both L- and D-amino acids, provide an ideal system to develop as a switchable receptor. Furthermore, the well-defined conformation of the whole scaffold allows its application in controlling the conformation of other structures. Work is ongoing to use these systems to achieve the transmission of a signal across a membrane.

Ligand-induced control of molecular helicity over nanometre distances

248th National Meeting (2014)

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