Synthesis and study of trannulene derivatives of fullerenes

Abstract

A series of trannulenes C60F15[CX(COOR)2]3 (X = COOMe, Br; R = Me, Et, Prn, n-Hex, But, (CH2)3NHCOOBut) was synthesized. The first water-soluble trannulenes containing six carboxyl groups (C60F15[C(COOMe)(COOH)2]3) or six protonated amino groups (C60F15[C(COOMe)(COO(CH2)3NH3+CF3COO−)2]3) were obtained. The compositions and structures of all compounds were proved by mass spectrometry, 1H, 13C, and 19F NMR spectroscopy, and other physicochemical methods. The reactivity of trannulenes was studied for the first time. The unique isomerization of trannulenes to triumphenes accompanied by the migration of three organic addends from one hemisphere of the fullerene cage to another hemisphere was discovered. The structures of the isomerization products were proved using single-crystal X-ray diffraction analysis and 1H, 13C, and 19F NMR spectroscopy. The concerted cascade of isomerization, elimination, and addition reactions was accomplished, which made it possible to obtain photoactive dyads C60F14R2=A (R = C(X)(COOR)2, A is a fragment of fullerenes C60 or C70, anthracene, or pentacene). These dyads contain the electron-deficient fluorofullerene core and electron-donor (with respect to the fluorofullerene core of the molecule) addend A. Photoinduced charge separation can occur in these systems, which makes them analogs of natural photosynthetic antennas.