Synthesis of C60 Dimer C120

The reaction of cyanide ion with C60 in a solution of o-dichlorobenzene (ODCB)-DMF gives a stable (CN)C-0 anion, which can be quenched with various electrophiles to afford cyanated C60 derivatives [46]. In sharp contrast to the reaction in liquid phase, the solid-state reaction of C60 with KCN under HSVM conditions for 30 min unexpectedly and selectively afforded the formal [2 + 2]-type dimer C120 (6) in 18% other than the cyanated C60 derivative 5, along with 70% of unconsumed C60 (Fig. 2) [47]. The X-ray crystal structure unequivocally showed that the dumbbell-shaped C120 is connected by a cyclobutane ring and this four-membered ring is square rather than rectangular as predicted theoretically. Furthermore, the [2 + 2] structure of C120 is stable and does not rearrange to other C120 isomers such as those with peanuts-shaped structure.

The amount of KCN need not necessarily be equivalent to that of C60; a small amount such as 0.2 molar equivalent

Figure 2. Synthesis of C120 from C60 and KCN under HSVM conditions [47].

Figure 2. Synthesis of C120 from C60 and KCN under HSVM conditions [47].

is enough [28]. Apparently, the solid-state reaction of C60 with cyanide proceeds in a quite different reaction pathway from the solution reaction. Formation of C120 can also be obtained by the reaction of C60 with potassium salts such as K2CO3 and CH3CO2K, metals such as Li, Na, K, Mg, Al, and Zn, and organic bases such as 4-(dimethylamino)-and 4-aminopyridine [28]. This mechanochemical reaction appears to reach an equilibrium state with a ratio of C60 to C120 in about 7:3 either starting from a mixture of C60 and a chosen reagent or from pure C120. For these reactions, the formation of C120 was most probably initiated by electron transfer reaction. Once the radical anion C60 is formed, it would couple with a neutral C60 to give C120, which would transfer one electron to another C60 to afford the neutral C120. Helium-3 labeled C60 dimer, [email protected] (7) (Fig. 3), was prepared by the above-mentioned HSVM reaction using a helium-3 labeled C60 sample in which the approximate ratio of [email protected] to empty C60 is about 1:1000 [28]. [email protected] and its derivatives can be monitored by helium-3 nuclear magnetic resonance (3He NMR) [48]. Similarly, [email protected] has been synthesized by the mechanochemical reaction of C60 containing approximately 0.01% of [email protected] with additives such as KCN, CuSO4, CaCl2, and P2O5 [49]. [email protected] has been measured by electron paramagnetic resonance (EPR).

[60] Fullerene dimer was also obtained as the main product from the HSVM reaction of C60 and C70 with 4-aminopyridine, which was designed to synthesize cross dimer C130 [50]. Dimerization of C60 was also found to occur without the presence of any catalyst. Treatment of C60 itself under HSVM conditions resulted in a small amount of C120 and a large amount of insoluble C60 polymers; the latter was not formed in the reaction of C60 and KCN [28]. A similar phenomenon was observed by prolonged mechanical milling in a conventional horizontal ball mill at a rotational speed of 95 ± 1 rpm [51, 52].

Shinohara and coworkers described the preparation of C120 in 15% overall yield by simply hand-grinding a mixture of C60 and K2CO3 [53]. The same research group also reported that C120 was obtained as the main product (8%) from a hand-ground reaction mixture of C60 and C70 with K2CO3 aiming to synthesize cross dimer C130, which was isolated in 3% yield [54].

It should be mentioned that C120 has been synthesized in high yield (~80%) by squeezing the organic molecular crystal (ET)2C60 at 5 GPa and 200 °C using a wedge-type cubic anvil high-pressure apparatus [55]. While C60 powder itself was squeezed in a simple piston-cylinder pressure cell at 1 GPa and ~200 °C for a few minutes, only ca. 3% of C120 and mainly insoluble residue of C60 oligomers and polymers along with 15-20% unchanged C60 were obtained [56]. Longer treatment resulted in a decrease in the yield of C120 and an increase in the insoluble portion.

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Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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