Mark S. Meier

Photo-assisted structural transition and oxygen diffusion in solid C60 films

Using Raman scattering we have observed a phototransformation of C60 films on Si(100) from a face‐centered‐cubic (fcc) phase to a second solid phase leaving the C60 molecules intact. Furthermore, photoassisted oxygen diffusion into the deep bulk is detected using alpha resonance scattering. The Raman spectrum for oxygen‐doped C60 is found to be similar to the result for oxygen‐free fcc C60, and oxygen is found to harden the film against phototransformation.

Dielectric function of solid C70 films

Using variable‐angle ellipsometry and normal incidence reflection/transmission optical techniques we have measured the dielectric function e(ω) at room temperature for solid C70 films over the photon energy range 0.5≤E≤5.3 eV. The onset of absorption across the highest‐occupied‐molecular‐orbit (HOMO)–lowest‐unoccupied‐molecular‐orbit (LUMO) gap is measured to be 1.25 eV. Furthermore, structure in the interband absorption at 2.41, 3.10, 3.50, and 4.45 eV is observed. The refractive index at zero frequency is estimated to be n(0)=1.94 as compared to the value n(0)=1.90, which we obtained for solid C60 from our previous study.

The Synthesis and Characterization of Fullerene Hydrides

The syntheses and characterization of fullerene hydrides prepared from C60 and C70 are reviewed. Methods of isolation and characterization are discussed, particularly MS and NMR, including 3He nuclear magnetic resonance spectroscopy. The higher hydrides are discussed in terms of novel structural features and their unusual spectroscopic properties.

THE ADDITION OF NITRILE OXIDES TO C60

Abstract The 1,3-dipolar cycloaddition of nitrile oxides to C60 is described. These reactions result in the formation of fullerene-fused isoxazoline heterocycles bearing a series of different substituents in 3-position. The preparation and spectroscopic characterization of these compounds are reported, as well as some investigations of the reactivity of these heterocycles. It is found that fullerene isoxazolines are less reactive than aliphatic isoxazolines.

Synthesis of hydrogenated fullerenes by zinc/acid reduction

Abstract Reduction of C 60 with zinc and acid results in the formation of C 60 H 2 , C 60 H 4 , and more highly hydrogenated fullerenes.

Tearing open nitrogen-doped multiwalled carbon nanotubes

Reductive alkylation of N-MWNTs with Li/NH3 results in fracturing of the nanotubes, ripping channels that breach the central core and generating significant new pore volume.

Muon investigations of fullerenyl radicals

Four of the five possible isomeric C70Mu radicals have been detected by transversefieldμSR in a C70 powder sample at 298 K. Their assignment is based on the results of semi-empirical MNDO calculations. There are significant changes in intensity and lineshape of the signals at low temperature. The first μSR spectrum of a fullerenyl radical in solution has been obtained.

Reactivity, spectroscopy, and structure of reduced fullerenes

Abstract Reduced fullerenes, the simplest covalent derivatives of the fullerene family of carbon allotropes, provide an excellent context for the study of the fundamental chemical reactivity of fullerenes. We have developed a general method for the formation of a number of these compounds. Using Zn(Cu) reduction, we have access to pure samples of several isomerically pure C 60 H n and C 70 H n species. We have completely assigned the 13 C NMR spectrum of C 60 H 6 and have assigned the majority of the resonances in C 60 H 2 .

Oxidation of lignin and lignin β-O-4 model compounds via activated dimethyl sulfoxide

Lignin oxidation reactions are increasingly being utilized in the field of lignin valorization. This is primarily due to the prospect of obtaining high-value aromatic products from cleavage of the Cα–Cβ bond in lignins β-O-4 linkages. In this work activated dimethyl sulfoxide reactions, namely Swern and Parikh–Doering oxidations, were performed both on lignin and on compounds modeling the β-O-4 linkage. When phenolic moieties were present in the model compounds, enol ethers were formed rather than the ketone expected from oxidation of the β-O-4 alcohol moiety. Conversely, in the absence of phenolic moieties, the β-O-4 alcohol was oxidized to a ketone. These results are interpreted in terms of enol ether formation from a quinone methide intermediate formed via deprotonation of the phenolic –OH in the initial sulfur ylide species. When applied to Kraft lignin, alcohol oxidation was observed at both the α and γ positions in lignin under both Swern and Parikh–Doering conditions, although analytical data were unable to shed light on the relative importance of enol ether versus 1,3-diketone formation (or its tautomer). These results emphasize the importance of working with realistic lignin model compounds in order to understand and develop lignin chemistry.

A comparison of the oxidation of lignin model compounds in conventional and ionic liquid solvents and application to the oxidation of lignin

The oxidation of lignin model compounds was studied in conventional solvents in parallel with oxidations in ionic liquid solvents. Catalyst systems were investigated in ionic liquid solvents to determine how reaction rates and the selectivity for benzylic carbon oxidation were affected. Oxidation rates were often lower in ionic liquids than in conventional solvents – as indicated by lower conversion in a standard reaction time – likely due, at least in part, to the higher viscosity of ionic liquids. Selectivity of the TPPFeCl/t-BuOOH catalyst system for oxidation of the benzylic C–OH versus benzylic C–H was higher in the ionic liquids tested than in conventional solvents.