<i>C</i>_3<i>v</i>-Symmetrical Tribenzotriquinacenes as Hosts for C₆₀ and C₇₀ in Solution and in the Solid State

Abstract

Various tribenzotriquinacenes (TBTQs), most of which incorporate six functional groups at the periphery of their C3v-symmetrical, rigid and convex-concave molecular framework, have been studied with respect to their ability to form supramolecular complexes with the C60 and C70 fullerenes, either in the solid state or in solution. The hexabromo derivative Br6-TBTQ was cocrystallized with C60 as [Br6-TBTQ<C60 x toluene] but, as studied by UV/vis and (1)H NMR spectroscopy, aggregation in benzene, toluene, or carbon disulfide solutions was not observed. Likewise, in contrast to the related C5v-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 C60 or C70. The novel tris(2,3-thianthreno)triquinacene (o-S2C6H4)3-TBTQ, a TBTQ derivative extended by three 1,2-benzodithiino wings, and synthesized from Br6-TBTQ, was found to form 1:1 complexes with C60 and C70 in both benzene and toluene solutions. Association constants were determined for the respective complexes, viz. (o-S2C6H4)3-TBTQ<C60 (K(assoc) = 977 +/- 56) and (o-S2C6H4)3-TBTQ<C70 (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<2 C60 x 2.5 chlorobenzene] were also determined.