(Invited) Concave Host Molecules Containing Phosphorus Atoms for Fullerenes

Abstract

The recognition of fullerenes (C60 and its higher analogues) is one of the most intensive research subjects in supramolecular and host-guest chemistry. Bowl-type p-conjugated molecules, for example, corannulene or sumanene, are promising host molecules because their concave surfaces closely resemble fullerene segments and can fit precisely to the convex surface of C60. In particular, these molecules are attractive because of their potential to function as chiral hosts based on “bowl-chirality”. However, racemization easily underwent in many of chiral bowl-type molecules. We envision a strategy for the design of a chiral concave molecule using a phosphorus-doping method, which can play a crucial role in construction of the concave structure. We now report the synthesis of the chiral concave molecule by extension of the p-surface ofphosphorus-containing concave molecule. We synthesized the C 3-symmetric chiral concave mole-cule having a phosphorus atom at the center and resolved the enantiomers. The chiral concave structure was revealed by X-ray analysis. The concave molecule exhibited strong CD signals with a large anisotropy, the detail of which was confirmed by TD DFT calculation. In the co-crystal with C60, four molecules of enantiopure perfectly wrapped the surface of C60. MALDI-TOF mass and NMR spectra also supported the concave-convex interaction between the host molecule and C60. Furthermore, the observa-tion of the ICD signal of the guest fullerene indicates the transfer of the chiroptical properties of the host molecule to the guest. These results suggest that the chiral host is a component of a chiral self-assembled host for C60. The self-assembly of the concave molecules and the properties of the host-guest complex with fullerene will be presented. Figure 1