Majid Keshavarz-K

Linear free energy relation of methanofullerene C61-substituents with cyclic voltammetry: Strong electron withdrawal anomaly

Abstract Methanofullerenes with cyano, nitro, and carboxyethyl substituents on C 61 were prepared and characterized. The bis(cyano) methanofullerene shows a first, irreversible, reduction peak at room temperature which is ca 160 mV more positive than the corresponding step in C 60 . We report for the first time a comparative study of electron-donating and electron-withdrawing substituents on C 61 , using the Hammett σ m , which shows that the cyano substituent appears to be more electron-withdrawing than predicted by the Hammett relation. This anomaly could be due to kinetics of a rapid follow-up reaction, periconjugation, or “conjugation” through the cyclopropane Walsh orbitals.

Isolation, structure, and electronic calculations of the heterofullerene salt K6C59N

An intercalation compound of azafullerene, K6C59N, was prepared and structurally characterized. It is isostructural with the fullerene compound K6C60, adopts a body-centered- cubic structure (lattice constant a = 11.31 angstroms), and consists of quasi-spherical monomeric (C59N)6− ions. Density functional calculations of the structural and electronic properties confirm the similarity to K6C60 but also suggest a sizable deformation, principally confined in the vicinity of the nitrogen atom, of both the molecular structure and the electron states. These results show that study of the intercalation chemistry of azafullerene promises to reveal a rich family of both n- and p-doped systems with novel conducting and magnetic properties, like their fullerene antecedents.

Near IR photoluminescence in mixed films of conjugated polymers and fullerenes

The photoinduced electron transfer between conjugated polymers and a series of functionalized fullerenes was studied. A new photoluminescence signal was observed in the near IR (∼1.4 eV). This weak IR photoluminescence does not result from direct excitation of the fullerene, but from radiative electron-hole recombination between the fullerene excited state and the polymer ground state. The intensity of this recombination luminescence depends on the electrochemical nature of the functional group; it is observed only for fullerenes with first reduction potential higher than that of C60.

Resolution and circular dichroism of an asymmetrically cage-opened [60]fullerene derivative

The enantiomers of the first cagewise inherently asymmetric C 60 derivative, i.e. N-MEM (MEM = 2-methoxyethoxymethyl) keto lactam 1, have been separated by HPLC and their chiroptical properties compared with data obtained from C 60 derivatives that are dissymmetric or asymmetric due to chiral addends.

The dielectric function of dimerised C59N

We present electron energy-loss spectroscopy studies in transmission of the electronic structure of (C59N)(2). The overall broadening observed for the pi-derived structures in the low energy-loss function of (C59N)(2) when compared to C-60 is due to the reduced symmetry of the heterofullerene. The optical gap of (C59N)(2) is about 1.4 eV, slightly smaller than that of C-60 (1.8 eV). Using a Kramers-Kronig analysis the dielectric function in the low energy region was calculated. A static dielectric function at zero energy of similar to 5.6 is found.

Heterocyclic and heteroatom derivatives of buckminsterfullerene C-60

The synthesis of hydroazafullerene and the dimer of azafullerenyl are presented. The structures of these heterofullerene molecules were characterized with the use of proton and carbon NMR as well as C-H and C-15N coupling constants.