Photochemical Route to the Production of Fullerene Allotropes

A photochemical route to the formation of two C₆₀ molecules which are bridged by one and up to eighteen carbon atoms to form bucky-dumbbell shaped molecules, i.e., C₆₀ > C < C₆₀ to C₆₀ > C = C = C = C = C = C = C = C = C = C < C₆₀, etc. is described. Irradiation of C60 in solutions of chloroform and iodine (magenta color) with pulsed laser light from the frequency tripled (355 nm) Nd:YAG laser produced a dark crimson color. Matrix assisted laser desorption ionization (MALDI) negative ion mass spectroscopy was used to examine the irradiated fullerenes. Irradiation of solutions under low laser power for short periods of time (∼ 1 hr) gave exclusively C₆₀ > C < C₆₀ as evidenced from the negative ion spectrum. Higher power and longer irradiation times (∼ 3 hrs) produced C₆₀ > C_n < C₆₀ samples yielding negative ions with n = 1 to l8. Ions for even n bucky-dumbells are more abundant than for odd n which may represent the greater electron affinity anticipated for even n species. High performance liquid chromatography was used to separate the bucky-dumbbells from the dominant C₆₀ molecules as well as C₆₀ > C < C₆₀ from the remaining clusters, confirming that the dumbbells were produced in the solution and not in the MALDI process. High Resolution TEM pictures and Raman spectra of the bucky-dumbells are also presented.