Theoretical And Experimental Studies On Fullerenes And Their Derivatives

The reactions properties of fullerenes that produce three kinds of derivates, i. e. exohedral, substitutional and endohedral doping fullerenes were studied both experimentally and theoretically.The gas-phase ion-molecule reactions of C₆₀ with methyl ethers, trimethylsilyl methyl ethers, hexamethyldisiloxane and CS₂ were studied in the ion source of a mass spectrometer. [CH₂O=CH₃]⁺, [CH₂=O-CH₂CH₃]⁺, [CH₂=O-(CH₂)₂CH₃]⁺ and [CH₂=O-(CH₂)₃CH₃]⁺ generated under the self-chemical-ionization (self-CI) conditions of alkylmethyl ethers can adduct with C₆₀ to produce the adduct ions [C₆₀C₂H₅O]⁺. These ethers are good protonating reagents to C₆₀ and [C₆₀H]⁺ are abundant in the resulted mass spectra. [C₆₀(CH₃)₂SiOCH3]⁺ and [C₆₀(CH₃)₂SiOSi(CH₃)₃]⁺, the reaction products of C₆₀ with dimethylsiloxymethyl ion [(CH₃)₂SiOCH₃]⁺ and the trimethylsiloxydimethylsilyl ion [(CH₃)₃SiOSi(CH₃)₂]⁺ were also observed as the major adduct ions. The ab initio and density functional theory molecular orbital calculations were carried out on all the possible structures of the adduct ions. The calculated results showed that the most stable structure among the possible isomers of [C₆₀C₂H₅O]⁺ is the 6-6 [3+2] cycloadduct. To [C₆₀(CH₃)₂SiOCH3]⁺ and [C₆₀(CH₃)₂SiOSi(CH₃)₃]⁺, the most stable structure is the σ_si adduct. According to experimental and theoretical results, the pathway for the formation of the adducts was presented. C₆₀S⁺ was synthesized through the gas-phase ion-molecule reaction of C₆₀ with the plasmas of carbon disulfide. Among the two reactions C₆₀+S⁺→C₆₀S⁺ and C₆₀⁺+S→C₆₀S⁺, the first one is the main reactions that produce C₆₀S⁺. Semi-empirical PM3-UHF and density functional B3LYP levels of theory with 6-31G(d) basis set calculations were performed on all the possible structures and electronic properties of the product. The results showed that the most stable structure among the possible isomers was the 6/6 closed derivative. These studies provided fundamental information on the understanding of the chemical properties of C₆₀ and the synthesis of novel fullerene derivatives.Substitutional doping makes many changes on the properties of C₆₀. Structural andelectronic properties of S-doped fullerene C58 were calculated systematically via Hartree-Fock self-consistent field and density functional B3LYP levels of theory with 6-31G(d) basis set. S@C58 was also calculated for comparing. The most stable C58S represents an open cage structure with a nine-member ring orifice that the longest and shortest axis lengths are 3.199 and 4.256 A respectively, far larger than that of C6o. Thus provides a large hole for atoms or small molecules to pass through into the cage. The most stable endohedral S@C5s has the S atom seated 0.667 A off the center of the C58 cage and near the 6-6 bond of the 7-member ring. The IR spectrum profile of S@C58 is similar to that of C58, while the IR spectrum profile of CssS is different from them. The most possible reaction sites of C5gS are on the C atoms and to S@C58 they are on the 7-member ring of the C58 cage. Compared with C60, both the abilities of electron accepting and donating of the S-doped hetrofullerenes are strengthened. Our results may aid in the design of experimental methods for controlling the nature of fullerene cages-for example, doping, opening, and reclosing them.The chemical properties of the internal cage of fullerenes were different from their external surface. The structural and electronic properties of atom endohedral doped fullerenes C@C6o and small neutral molecules H2, N2, CO endohedral doped C32, C36, C50 and C6o fullerenes were studied via Hartree-Fock self-consistent field (SCF) and density functional B3LYP levels of theory with the STO-3G, 6-31G(d) and 6-31G(d, p) basis sets. To C@C6o, the triplet structure with C on the center of the C60 cage was proved to be global minimum on the C@C6o molecular potential energy surface. Similar to N@C6o and P@C6o, there are no charge transfer between the encaged C atom and the fullerene cage. And no covalent bond is formed. Which is different from endohedral metallofullerens. In H2, N2, CO endohedral doped C32, C36, C50 and C60 fullerenes, the small molecules are seated near the center of the fullerene cages. The encaging of these molecules doesn't change the geometries of the fullerenes much, while the bond lengths of CO and H2 are shortened and the N2 is lengthened. Almost no charge transfer happened between the encaged molecules and the fullerence cages. The inclusion reaction is endothermic. H2@Cn are more stable than N2@Cn and CO@Cn, and H2@C36, N2@C36, CO@C36 are the most reactive. Our studies suggestthat the internal cage of fullerene is more inert than its external surface. No charge transfer will happen when nonmetal atoms or small molecules are encaged into fullerene due to the weak electronegativity of the internal cage.The raw arc-discharging carbon soots exhibit high reactivity towards oxidants under basic condition. Water-soluble fullerenes C6o(OH)n and C7o(OH)n were synthesized directly from the raw soots in concentrated NaOH disusing the phase transfer catalyst. The laser desorption time-of-flight mass spectrum (LD-TOF MS) and FT-IR spectra were used to characterize the products, the probable reaction mechanism was discussed.A heatronic technique was used to synthesize metal carbides, metallofullerenes were synthesized by using Kra'tschmer arc burning of metal carbides and extracted from fullerene-containing soots by a novel reactive extraction method using alkali metals as reducing agents, the resulting extracts were free of empty fullerenes and M@Cgo, M@C82 and M2@Cso were selectively enriched. Electrospray-ionization (ESI) and Matrix-assisted laser-desorption-ionization time-of-flight mass spectrometry (MALDI-TOF) analysis were used to characterize the products. These studies present a new route to isolate metallofullerenes and an ESI-MS method to characterize them.