The Remarkable Chemistry of Trannulenes: Green Fluorinated Fullerenes with Unconventional Aromaticity

Abstract

We report the first reaction of trannulenes involving their thermal isomerization to a new class of compounds termed "triumphenes". The thermodynamically controlled conversion of trannulenes into triumphenes is accompanied by an unprecedented migration of three organic addends from one hemisphere of the fullerene cage to another. The reaction products, bearing aliphatic substituents, might find applications in materials science as strong electron acceptors due to the presence of fifteen electron-withdrawing fluorine atoms in their molecular framework. It was revealed that the isomerization of trannulenes can be affected by the presence of unsaturated compounds in the reaction mixture. Heating of trannulenes C(60)F(15)R(3) with C(60), C(70), anthracene, or pentacene at reflux in 1,2-dichlorobenzene yields fluorinated derivatives C(60)F(14)R(2)A, which possess a fused cyclic addend A. The products of this reaction have "triumphene-type" addition patterns and seem to be formed through an unprecedented sequence of elimination, addition, and isomerization steps. The molecular structure of a representative triumphene was proven unambiguously by X-ray single-crystal diffraction analysis and by NMR spectroscopy. The reactions revealed here open up numerous opportunities for chemical derivatization of fluorinated fullerenes. This method promises to provide a new path towards valuable photoactive materials and a new generation of fullerene-based compounds that are suitable for biomedical applications.

Near-Infrared Absorbing Compounds Based on π-Extended Tetrathiafulvalene Open-Cage Fullerenes

“…Chemical modification of the spherical π-system has been proven an effective method to prepare fullerene-based NIR materials. Fullerene multiadducts C 60 F 15 R 3 and C 60 R 6 show NIR absorption as a result of the change of the spherical π-system. Introduction of a heteroatom into the fullerene cage can also shift the absorption into the NIR region as in the case of azafullerenes .…”

Fullerenes

“…42 A remarkable isomerisation of trannulene fullerene derivatives C 60 F 15 [CX(COOR) 2 ] 3 (X = Br, COOR; R = Alkyl) to the corresponding triumphenes through an unprecedented migration of three organic addends from one hemisphere of the fullerene cage to the other has been described. 43 Perfluoroalkylation of C 60 and C 70 with the use of the linear-chain…”