| Abstract
| - This paper describes the self-assembly of a new class of foldamer-based molecular tweezers,whose rigid folded conformations are stabilized by intramolecular hydrogen bonding. Two zinc porphyrinunits are introduced to the ends of molecular tweezers Zn21 and Zn22, while three zinc porphyrin units areincorporated to the S-shaped bi-tweezers Zn33, which may be regarded as a combination of two Zn21molecules. Due to the preorganized U-shaped feature, Zn21 and Zn22 are able to strongly complex C60,C70, and C60 derivative 25 in chloroform or toluene in a 1:1 binding stoichiometry, whereas Zn33, whichpossesses two tweezer units, complexes the guests in a 1:2 stoichiometry. More stable complex Zn33·24is formed between Zn33 and 24, a linear molecule bearing two C60 moieties at the ends, as a result of thecooperative interaction of two binding sites. Chiral induction is observed for all the three receptors uponcomplexation with C60-incoporated chiral phenylalanine derivative 29, although the complexation of 29 bythe folding receptors is pronouncedly weaker than that of C60 and 25 due to increased steric hindrance.The driving force for the formation of the complexes is the well established π−π stacking between the zincporphyrin and fullerene units. The 1H and 13C NMR, UV−vis, fluorescent, and circular dichroism spectroscopyhave been used to investigate the complexing behavior of the folding receptors and the fullerene guests.The association constants of the corresponding complexes in toluene and chloroform (if possible) havebeen evaluated with the UV−vis and fluorescent titration experiments.
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