Assembling nonplanar polyaromatic units by click chemistry. Study of multicorannulene systems as host for fullerenes.

Novel compounds with two or three corannulene subunits have been obtained by "click chemistry". These exotic systems were synthesized in high yields using the ethynylcorannulene as common reagent. The synergistic action as receptors for fullerenes of several corannulene blocks has been evaluated. It was found that the three-armed derivatives showed efficient complexation abilities toward C60. Furthermore, a new compound having two corannulene subunits linked to a hexahelicene scaffold has a remarkable affinity constant. Finally, theoretical calculations have been performed to evaluate the formation of their relative adducts containing a C60 molecule.

η6-Hexahelicene complexes of iridium and ruthenium: running along the helix.

The first η(6)-complexes of iridium and ruthenium coordinated to helicenes have been obtained. Hexahelicene (1), 2,15-dimethylhexahelicene (2), and 2,15-dibromohexahelicene (3) react with [Cp*IrCl(2)](2) and AgBF(4) in CD(3)NO(2) to afford quantitatively the complexes [Cp*Ir(η(6)-1)][BF(4)](2) (4A), [Cp*Ir(η(6)-2)][BF(4)](2) (5A), and [Cp*Ir(η(6)-3)][BF(4)](2) (6A), respectively. In all cases, the final thermodynamic products are similar, and they exhibit coordination between the 12 e(-) metal fragment [IrCp*](2+) and the terminal ring of the helicene. Monitoring the reaction by NMR shows formation of intermediates, some of which have been fully characterized in solution. These intermediates exhibit the metal fragment coordinated to the internal rings. We have also synthesized the bimetallic complex [(Cp*Ir)(2)(µ(2)-η(6):η(6)-2)][BF(4)](4) (7), achieving coordination between two units [IrCp*](2+) and the helicene 2. Following an analogous methodology, we have prepared the complex [(η(6)-cymene)Ru(η(6)-2)][BF(4)](2) (8), which has been studied by X-ray diffraction, confirming the preferential binding to the terminal aromatic ring.