K. C. Khemani

Organic molecular soft ferromagnetism in a fullerene C60

The properties of an organic molecular ferromagnet [C60TDAE0.86; TDAE is tetrakis(dimethylamino)ethylene] with a Curie temperature ;Tc = 16.1 kelvin are described. The ferromagnetic state shows no remanence, and the temperature dependence of the magnetization below ;Tc does not follow the behavior expected of a conventional ferromagnet. These results are interpreted as a reflection of a three-dimensional system leading to a soft ferromagnet.

The Higher Fullerenes: Isolation and Characterization of C76, C84, C90, C94, and C70O, an Oxide of D5h-C70.

The toluene extract of the fluffy carbon material produced by resistive heating of graphite contains a variety of molecules larger than C60 and C70 in a total amount of 3 to 4% by weight. Repeated chromatography of this material on neutral alumina has led to the isolation of stable solid samples of C76, C84, C90, and C94. The characterization, which includes mass spectrometry, 13C nuclear magnetic resonance, electronic absorption (ultraviolet/visible) and vibrational (infrared) spectroscopy identifies these all-carbon molecules as higher fullerenes. In addition, C70O, a stable oxide, has been isolated that is structurally and electronically closely related to D5h-C70. This compound forms during the resistive heating process and probably has an oxygen atom inserted between two carbon atoms on the convex external surface of the C70 skeleton.

Systematic Inflation of Buckminsterfillerene C60: Synthesis of Diphenyl Fulleroids C61 to C66

The synthesis of a new family of spheroidal carbon molecules derived from the fullerenes is described. The fulleroids are produced by incremental addition of a divalent carbon equivalent that has two phenyl (Ph) rings to fullerene C60. The fulleroids Ph2C61, Ph4C62, Ph6C63, Ph8C64, Ph10C65, and Ph12C66 have been prepared and characterized.

Absorption spectra and electronic properties of alkali-metal-doped C60

Abstract Changes in optical absorption spectra of ≈ 500 A thick films of C 60 during doping with alkali metals (A = Li, Na, K, and Rb) were recorded. The stoichiometry of the potassium-doped C 60 films was monitored by simultaneous in situ measurements of electrical conductivity. The spectral changes indicate that the molecular solid behavior of C 60 bulk is preserved in the A 6 C 60 phase. Assignments for the C 60 and K 6 C 60 absorption spectra based on molecular orbitals of C 60 are discussed.

Studies of photoexcitations in C70 by optically detected magnetic resonance

Abstract Photoexcitations in C70 both as a dispersion in polystyrene (PS) glass and as films produced by evaporation, have been studied by photomodulation, photoluminescence and their respective versions of optically detected magnetic resonance. In C70: PS glass at 4 K we observed metastable triplet excitons with a distribution of lifetimes and a correlated distribution of magnetic powder patterns. In C70 films, on the other hand, in addition to triplet excitons we observed photogenerated charged excitations with spin 1 2 and a correlated photoinduced electroabsorption; we identify the charged excitations as C∓70.