Electron Donor–Acceptor Interactions in Regioselectively Synthesized exTTF₂–C₇₀(CF₃)₁₀ Dyads

Abstract

The decakis(trifluoromethyl)fullerene C(1)-C(70)(CF(3))(10), in which the CF(3) groups are arranged on a para(7)-meta-para ribbon of C(6)(CF(3))(2) edge-sharing hexagons, and which has now been prepared in quantities of hundreds of milligrams, was reacted under standard Bingel-Hirsch conditions with a bis-pi-extended tetrathiafulvalene (exTTF) malonate derivative to afford a single exTTF(2)-C(70)(CF(3))(10) regioisomer in 80 % yield based on consumed starting material. The highly soluble hybrid was thoroughly characterized by using 1D (1)H, (13)C, and (19)F NMR, 2D NMR, and UV/Vis spectroscopy; matrix-assisted laser desorption ionization (MALDI) mass spectrometry; and electrochemistry. The cyclic voltammogram of the exTTF(2)-C(70)(CF(3))(10) dyad revealed an irreversible second reduction process, which is indicative of a typical retro-Bingel reaction; whereas the usual phenomenon of exTTF inverted potentials (E1ox>E2ox), resulting in a single, two-electron oxidation process, was also observed. Steady-state and time-resolved photolytic techniques demonstrated that the C(1)-C(70)(CF(3))(10) singlet excited state is subject to a rapid electron-transfer quenching. The resulting charge-separated states were identified by transient absorption spectroscopy, and radical pair lifetimes of the order of 300 ps in toluene were determined. The exTTF(2)-C(70)(CF(3))(10) dyad represents the first example of exploitation of the highly soluble trifluoromethylated fullerenes for the construction of systems able to mimic the photosynthetic process, and is therefore of interest in the search for new materials for photovoltaic applications.

Perfluoroalkylfullerenes

“…This compound can be prepared with up to 90% purity (without HPLC separation) and with up to 55 mol % yield. 68 , 99 Using a gas handling system is used with an oil bubbler serving as a pressure release, and ambient pressure of CF 3 I is maintained during the synthesis (see ref ( 101 ) for the only example of a variable-pressure closed-loop flow tube reactor). Very long residence times can be achieved if a long hot zone and a slow CF 3 I flow rate are used.…”

“…Perfluoroalkylated fullerenes are typically prepared as mixtures of multiple isomers and multiple compositions. In a few cases, higher synthetic selectivity has been realized, but even in these cases a chromatographic separation was necessary to obtain 98+% pure PFAFs (for example, see the synthesis of 70-10-1 (T1#39,72) 68 , 99 and a synthesis of the series of compounds 60-2-1 R F (T1#111,114) 101 , 104 ). Except for a few early reports that used flash chromatography and gel permeation chromatography (T1#7,9,17 10 , 14 , 17 ), reverse-phase HPLC using specialized columns designed and optimized for fullerene separation has been employed.…”

“…Structural characterizations of the C 70 (CF 3 ) 10 (C(CO 2 Et) 2 ) and C 70 (CF 3 ) 10 C 2 H 4 (C 6 H 2 (MeO) 2 ) cycloadducts (see Figure 10 ) verifed the high reactivity of that particular bond. 76 , 99 , 146 …”

Formation of Perfluoroalkyl Fullerene Alkylphosphonic Acid Self-Assembled Monolayers on Aluminum Oxide

“…The product was analyzed by 1 H, 19 F, and 31 P NMR and MALDI mass spectrometry. Two peaks were present in the mass spectrum; 1830 m/z is 14 more than desired product and unknown, 1748 m/z is C 60 (CF 3 ) 9 (malonate/phosphonic ester) + 1, which corresponds to the loss of one CF 3 group in the mass spec experiment. Yield: 14.7 mg, 32% yield based on starting 60-10-3.…”

Solution-phase perfluoroalkylation of C60 leads to efficient and selective synthesis of bis-perfluoroalkylated fullerenes

“…[1,8,17] It was also shown that PFAFs can be further derivatized chemically to form donor-acceptor diads and potentially other complex molecular systems. [18,19] The vast majority of PFAF syntheses described in the literature relied on heterogeneous high-temperature reactions between fullerenes and R F · precursors (e.g., R F I or AgOOCCF 3 , see refs. above).…”