Biomedical subjects

Fudong Wang

Publications and source records attributed to Fudong Wang.

6 recordsLinked to original sources

PubMed2006

Solution-liquid-solid growth of semiconductor nanowires.

The serendipitously discovered solution-liquid-solid (SLS) mechanism has been refined into a nearly general synthetic method for semiconductor nanowires. Purposeful control of diameters and diameter distributions is achieved. The synthesis proceeds by a solution-based catalyzed-growth mechanism in which nanometer-scale metallic droplets catalyze the decomposition of metallo-organic precursors and crystalline nanowire growth. Related growth methods proceeding by the analogous vapor-liquid-solid (VLS) and supercritical fluid-liquid-solid (SFLS) mechanisms are known, and the relative attributes of the methods are compared. In short, the VLS method is most general and appears to afford nanowires of the best crystalline quality. The SLS method appears to be advantageous for producing the smallest nanowire diameters and for variation and control of surface ligation. The SFLS method may represent an ideal compromise. Recent results for SLS growth are summarized.

Journal Article↗

PubMed2006

Lewis acid promoted preparation of isomerically pure fullerenols from fullerene peroxides C60(OOt-Bu)6 and C60(O)(OOt-Bu)6.

Fullerene mixed peroxides C60(t-BuOO)6 and C60(O)(t-BuOO)6 react with Lewis acids to form various fullerenols through the partial fragmentation of t-BuOO groups. Two monohydroxyl fullerenols with the general formula C60(OH)(t-BuOO)5 and six monohydroxyl fullerenols with the general formula C60(O)(OH)(t-BuOO)5 were prepared, which are essentially the same except the location of the OH group. An additional reaction of the monohydroxyl fullerenols gave bis- and trishydroxyl fullerenols. Single-crystal X-ray structures have been obtained for the two monohydroxyl fullerenols. Other compounds are characterized by chemical correlation and their spectroscopic data. Cuprous bromide could protect the most reactive t-BuOO group from being attacked by stronger Lewis acids. The proposed mechanism mainly involves Lewis acid induced heterolysis of the peroxo O-O bond.

Crystallography, X-Ray↗

PubMed2006

Preparation of fullerendione through oxidation of vicinal fullerendiol and intramolecular coupling of the dione to form hemiketal/ketal moieties.

[reaction: see text] Vicinal fullerendiol is oxidized to fullerendione in good yield by (diacetoxy)iodobenzene. The resulting cage-opened fullerendione reacts with oxygen nucleophiles in the presence of BF(3).Et(2)O to form fullerene hemiketal/ketal derivatives through coupling of the two carbonyl groups. Fullerene-mixed peroxide derivatives are involved in all these reactions. The compounds are characterized by spectroscopic data and single-crystal X-ray analysis.

Journal Article↗

PubMed2005

Preparation of [5,6]- and [6,6]-oxahomofullerene derivatives and their interconversion by Lewis acid assisted reactions of fullerene mixed peroxides.

[60]Fullerene mixed peroxides C60(O)(OOtBu)4 exhibit chemo- and regioselective reactions under mild conditions. The epoxy moiety is opened by ferric chloride to form vicinal hydroxy chloride C60Cl(OH)(OOtBu)4. BF3 is also effective in opening the epoxy moiety. The O-O bond of the fullerene mixed peroxide is cleaved by aluminum chloride to form both [5,6]- and [6,6]-fullerene hemiketals (oxohomo[60]fullerenes). A Hock-type rearrangement is proposed for the formation of the hemiketals, in which a fullerene C-C bond is cleaved. Lewis acids and/or visible light can initiate isomerization of the hemiketal isomers. Single-crystal X-ray analysis and theoretical calculations confirmed the results.

Journal Article↗

PubMed2005

Regiochemistry of [70]fullerene: preparation of C70(OOtBu)n (n = 2, 4, 6, 8, 10) through both equatorial and cyclopentadienyl addition modes.

[reaction: see text] tert-Butylperoxy radicals add to [70]fullerene to form a mixture of adducts C(70)(OO(t)()Bu)(n)() (n = 2, 4, 6, 8, 10). Four isomers were isolated for the bis-adduct with the two tert-butylperoxo groups attached at 1,2-, 5,6-, 7,23-, and 2,5-positions, respectively. Two isomers were isolated for the tetrakis-adduct with the tert-butylperoxo groups located along the equator in C(s)() symmetry and on the side in C(1) symmetry, respectively. Similarly, two isomers were isolated for the hexakis-adducts with a structure related to the tetrakis-adducts, one of which has the cyclopentadienyl substructure. No isomer was detected for the octakis- and decakis-adducts. The C(s)()-symmetric octakis- and C(2)-symmetric decakis-adducts have all the tert-butylperoxo groups located along the equator. The decakis-adduct is the major product under optimized conditions. The compounds were characterized by their spectroscopic data. Chemical correlation through further addition of tert-butylperoxy radicals to isolated pure derivatives confirmed the structure assignment. Mechanisms of the tert-butylperoxy radical addition to C(70) follow two pathways: equatorial addition along the belt and cyclopentadienyl addition on the side.

Cyclopentanes↗

PubMed2004

Selective preparation of oxygen-rich [60]fullerene derivatives by stepwise addition of tert-butylperoxy radical and further functionalization of the fullerene mixed peroxides.

tert-Butylperoxy radicals add to C(60) selectively to form multi-adducts C(60)(O)(m)(OO(t)Bu)(n) (m = 0, n = 2, 4, 6; m = 1, n = 0, 2, 4, 6) in moderate yields under various conditions. Visible light irradiation favors epoxide formation. High concentration of tert-butylperoxy radicals mainly produces the hexa-homoadduct C(60)(OO(t)Bu)(6) 6; low concentration and long reaction time favor the epoxy-containing C(60)(O)(OO(t)Bu)(4) 7. The reaction can be stopped at the bis-adducts with limited TBHP. A stepwise addition mechanism is discussed involving mono-, allyl-, and cyclopentadienyl C(60) radical intermediates. m-CPBA reacts with the 1,4-bis-adduct to form C(60)(O)(OO(t)Bu)(2) and C(60)(O)(3)(OO(t)Bu)(2). The C-O bond of the epoxy ring in 7 can be cleaved with HNO(3) and CF(3)COOH. Nucleophilic addition of NaOMe to 7 follows the S(N)1 and extended S(N)2' mechanism, from which four products are isolated with the general formula C(60)(O)(a)(OH)(b)(OMe)(c)(OO(t)Bu)(d). Visible light irradiation of the hexa-adduct 6 results in partial cleavage of both the C-O and O-O bonds of peroxide moieties and formation of the cage-opened compound C(60)(O)(O)(2)(OO(t)Bu)(4). All the fullerene derivatives are characterized by spectroscopic data. A single-crystal structure has been obtained for an isomer of C(60)(O)(OH)(2)(OMe)(4)(OO(t)Bu)(2).

Journal Article↗