Rexford D. Sherwood

Bio: Rexford D. Sherwood is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 444 citations.

Synthesis and characterization of C60O, the first fullerene epoxide

Abstract: The isolation of C{sub 60} in preparatively useful quantities has stimulated intensive efforts to generate and characterize functional derivatives. Many reactions of C{sub 60} furnish complex, inseparable mixtures of products, and only a few discrete, monofunctional congeners have been described to date. We now report that photooxidation of C{sub 60} in benzene furnishes a single monooxide, C{sub 60}O, as the sole isolable product. Moreover, we have obtained the same species as a byproduct of the synthesis of C{sub 60}. Spectroscopic analysis strongly supports the epoxide structure. It is demonstrated that C{sub 60}O is efficiently converted to C{sub 60} in a 91% yield during chromatography of neutral alumina. The widespread use of alumina for purification of the fullerenes may explain why the fullerene oxide was not isolated before.

Chemistry of the fullerenes: the manifestation of strain in a class of continuous aromatic molecules.

Abstract: Within the wr-orbital axis vector theory, the total rehybridization required for closure of the fullerenes is approximately conserved. This result allows the development of a structure-based index of strain in the fullerenes, and it is estimated that about 80 percent of the heat of formation of the carbon atoms in C60 may be attributed to a combination of v strain and steric inhibition of resonance. Application of this analysis to the geometries of structurally characterized organometallic derivatives of C60 and C70 shows that the reactivity exhibited by the fullerenes may be attributed to the relief of a combination of local and global strain energy. C60 is of ambiguous aromatic character with anomalous magnetic properties but with the reactivity of a continuous aromatic molecule, moderated only by the tremendous strain inherent in the spheroidal structure.

The Chemistry of Fullerenes

Abstract: Initially envisaged as rather unreactive, aromatic-like molecules, the fullerenes instead undergo a wide variety of reactions characteristic of alkenes. The many derivatives of C60, and the few of C70, that have now been reported offer new directions for organic chemistry.

Covalent Fullerene Chemistry

Abstract: The covalent functionalization of C 60 has developed vigorously over the past 5 years. Several methods are now available for the formation of C 60 monoadducts. Regioselective formation of multiple adducts has allowed study of the changes in chemical and physical properties that occur when the conjugated fullerene chromophore is reduced during an increase in functionalization. The systematic development of covalent fullerene chemistry provides an unprecedented diversity of tailor-made three-dimensional building blocks for technologically interesting materials.

New Phases of C60 Synthesized at High Pressure

Abstract: The fullerene C60 can be converted into two different structures by high pressure and temperature. They are metastable and revert to pristine C60 on reheating to 300°C at ambient pressure. For synthesis temperatures between 300° and 400°C and pressures of 5 gigapascals, a nominal face-centered-cubic structure is produced with a lattice parameter ao = 13.6 angstroms. When treated at 500° to 800°C at the same pressure, C60 transforms into a rhombohedral structure with hexagonal lattice parameters of ao = 9.22 angstroms and co = 24.6 angstroms. The intermolecular distance is small enough that a chemical bond can form, in accord with the reduced solubility of the pressure-induced phases. Infrared, Raman, and nuclear magnetic resonance studies show a drastic reduction of icosahedral symmetry, as might occur if the C60 molecules are linked.

Donor‐Linked Fullerenes: Photoinduced electron transfer and its potential application

Abstract: Redox-active fullerenes can be covalently bound to a variety of donors; their photophysical properties have been investigated. Their photochemical processes, including electron transfer and energy transfer, are varied, depending on the donor, linkage between the donor and C 60 , and solvent. Regardless of the solvent and linkage, the charge-separated state is produced efficiently in zinc porphyrin-C 60 systems, showing that C 60 is a good electron acceptor. The most intriguing characteristic of C 60 in electron transfer is that C 60 accelerates photoinduced charge separation and retards charge recombination in the dark. The long-lived charge-transfer state of the C 60 -porphyrin dyad was successfully converted to photocurrent using a self-assembled monolayer technique. These findings will provide a new strategy for the design and synthesis of artificial photosynthethic systems and photoactive materials using C 60 as a building block.