Alleno-acetyllenic scaffolding for the construction of axially chiral C-60 dimers

作者：Tzirakis Manolis D; Gisselbrecht Jean Paul; Boudon Corinne; Trapp Nils; Diederich Francois^*

来源：Tetrahedron, 2014, 70(36): 6193-6202.

DOI：10.1016/j.tet.2014.02.088

• Allenes
• Chirality
• Circular dichroism
• Fullerene
• Dimerization

The preparation of enantiopure dumbbell-type dimeric fullerenes consisting of two C-60 units connected by axially chiral alleno-acetylenic spacers is reported for the first time. As a key step, the attachment of the terminal alkyne moiety of the spacers to C-60 was efficiently accomplished by employing an in situ C-60-ethynylation methodology. In addition to spectral analyses, single-crystal X-ray crystallographic studies allowed for the unambiguous structural assignment of two C-60-alleno-acetylene conjugates. Circular dichroism measurements showed that the axial chirality of the allene moieties linked to the fullerene sphere is able to perturb the intrinsic symmetry of the fullerene pi-system. Large characteristic Cotton effects were observed for two bisfullerenes in the 200-350 nm spectral region. UV/Vis absorption spectroscopic studies showed improved molar absorptivity of these dimeric fullerenes, but no strong evidence for a significant through-space electronic communication between the two C-60 spheres; electrochemical investigations further confirmed this conclusion.

• 出版日期2014-9-9