938
Nucleotidic and Peptidic Multi-Porphyrinic Devices: When the Desired Conformation Is Determined By Chiral Flexible Linkers
An octapeptide3 and an hexadecapeptide4 derived from the L-lysine and functionalized with porphyrins have been prepared. Beyond a certain degree of oligomerisation, we observed the development of a secondary structure such as a 310 helix which forces the porphyrins to arrange in a defined spatial arrangement. Due to the overlap of the porphyrins in such a conformation, the chromophores undergo a sufficient electronic coupling to favor a good exciton migration.5
The ability of these peptides to accomodate guests was investigated through ligand binding studies carried out in dichloromethane with DABCO as bidentate base. The complexation of DABCO by these peptides was monitored by UV-visible spectrophotometric titration in CH2Cl2. We showed that the enhanced stability of the complexe octapeptide/DABCO can be ascribed to a pre-organization of the octapeptide forming cavities, and provides convincing evidence that the bidentate base is inserted into the cavities of the octapeptide viahost/guest interactions.
We also investigated the ability of oligonucleotides to orientate porphyrins in space, and the capability of this type of backbone to generate multi-porphyrinic hosts able to complex multiple bidentate guests.
Acknowledgements
This work was supported by the CNRS and the French Ministry of Research.
References
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