C3v-Symmetrical Tribenzotriquinacenes as Hosts for C60 and C70 in Solution and in the Solid State

Various tribenzotriquinacenes (TBTQs), most of which incorporate six functional groups at the periphery of their C-3v-symmetrical, rigid and convex-concave molecular framework, have been studied with respect. to their ability to form supramolecular complexes with the C-60 and C-70 fullerenes, either in the solid state or in solution. The hexabromo derivative Br-6-TBTQ was cocrystallized with C-60 as [Br-6-TBTQ subset of C60 center dot toluene] in benzene, toluene, but, as studied by UV/vis and H-1 NMR spectroscopy, aggregation in benzene, toluene, or carbon disulfide solutions was not observed. Likewise, in contrast to the related C-5v-symmetrical decakis(alkylthio)corannulenes, neither the parent hydrocarbon, nor a related hexamethoxy, or two hexakis(alkylthio) derivatives exhibited color, or complexation-induced chemical shift (CIS) changes with C-60 or C-70. The novel tris(2,3-thianthreno)triquinacene (o-S2C6H4)(3)-TBTQ, a TBTQ derivative extended by three 1,2-benzodithiino wings, and synthesized from Br-6-TBTQ, was found to form 1:1 complexes with C-60 and C-70 in both benzene and toluene solutions. Association constants were determined for the respective complexes, viz. (o-S2C6H4)(3)-TBTQ subset of C-60 (K-assoc = 977 +/- 56) and (o-S2C6H4)(3)-TBTQ subset of C-70 (463 +/- 49, both in benzene). The X-ray single crystal and molecular structures of the pure host and of the aggregates [(o-S2C6H4)(3)-TBTQ subset of 2 C-60 center dot 2.5 chlorobenzene] were also determined.