The Study Of Yb-Metallofullerenes And Anomalous Fullerenes

Metallofullerenes, a new class of fullerene-based materials. Abundant researches havebeen conducted on metallofullerenes since macroscope quantity of this kind of fantasticmaterial could be obtained. In this thesis, the synthesis, isolation, structure characterizationand vibrational properties of Yb metallofullerenes have been studied.By means of promoting the synthesis DC arc discharge and HPLC isolation conditions,we synthesized and isolated a series of Yb metallofullerenes based on different fullerenecages, i.e. Yb@C₇₂, Yb@C₇₄(â… ,â…¡), Yb@C₇₆(â… ,â…¡), Yb@C₇₈, Yb@C₈₀, Yb@C₈₂(â… ,â…¡,â…¢,â…£),Yb@C₈₄(â… ,â…¡,â…¢,â…£), among which Yb@C₇₂ and Yb@C₈₂(â…£) were isolated and obtainedfor the first time. The purities of these Yb metallofullerenes were higher than 98% exceptYb@C₇₂. We characterized Yb@C₇₂ and Yb@C₈₂(â…£) through UV-Vis-NIR absorptionspectrosicopy and concluded that Yb@C₇₂ may have a non-IPR molecular structure and theelectronic structure of Yb@C₈₂(â…£) is similar to that of Yb@C₈₂(â…¡).We measured and analyzed Raman and IR spectra for Yb@C₇₄(â…¡) and Yb@C₈₂(â… ,â…¡,â…¢,â…£). Combined with the reported results of Raman and IR spectra for othermetallofullerenes, we investigated the influences of metals and carbon cages on thevibrational properties of metallofullerenes. The force constants between Yb and carbon cages(C₇₄, C₈₂) were obtained from the frequency of Yb-carbon cage vibration based on aharmonic-oscillator model, which further proved that the oxidation state of Yb is+2. Carboncages of different sizes and shapes have little effect on the metal-carbon cage vibration. Forthe vibrations of carbon cages, on one hand, their frequencies are inversely proportional to thesquare root of cage mass; on the other hand, the frequencies shift due to the interactionbetween carbon cage and the metal inside.We discovered two isomers of C₆₈ in the process of synthesizing and isolating Ybmetallofullerenes. Since there are no IPR structure for C₆₈, we inferred that both of the twoisomers of C₆₈ has a non-IPR structure. Through exploring and optimizing the experimentalconditions, we found that the best way of extracting C₆₈ is oscillation and sonication inatmosphere of nitrogen at room temperature, while refluxing in solvents is ineffective inextracting C₆₈, indicating that C₆₈ would decompose at high temperature. One isomer of C₆₈was isolated at high purity but in rather low yield, and it was characterized by UV-Vis-NIRabsorption spectrosicopy. Another isomer of C₆₈ was produced in large quantity, however, it could not be separated from C₇₀ and C₇₀O. According to the chromatogram behavior andRaman spectra of the mixture, it is reasonable that C₆₈ exsits in polymeric form with C₇₀ andC₇₀O.