Electronic structure studies of fullerenes and their derivatives

Relative energies of C₆₀F_N fluorofullerenes are reproduced well at the B3LYP/6-311G** level of theory employed in conjunction with isodesmic trans-fluorination reactions. Overestimation of steric repulsions among non-bonded atoms is evident for species with larger values of N. The MNDO method is found to be less suitable for studies of fluorofullerene thermochemistry. The gas-phase standard enthalpy of formation of the C ₆₀F₁₈ species is predicted to lie between −360 and −300 kcal/mol.; Accurate standard enthalpies of formation of 115 IPR fullerenes with 60–180 carbon atoms were derived from energies of isodesmic reactions computed at the B3LYP/6-31G* level of theory. The calculated values of $DHof$ are reproduced within 3 kcal/mol by a simple scheme based upon counts of 30 distinct structural motifs composed of hexagons together with their first and second neighborhoods. The inclusion of a global curvature term and the low computational cost of the scheme make it ideal for rapid prescreening for large and small thermodynamically viable IPR fullerenes.; Endohedral 3He chemical shifts were computed at the GIAO-SCF/3-21G level of theory using B3LYP/6-31G* optimized geometries for all C₆₀–C ₈₆ IPR fullerenes with non-vanishing HOMO-LUMO gap and one non-classical C₇₂(C_2ν) isomer. The experimental 3He NMR signals are reproduced reasonably well in cases where assignments are unambiguous. New assignments are proposed for one C₈₂ isomer and one C₈₆ isomer. The calculated endohedral chemical shifts suggested reassignment of the NMR resonances for two C₇₈ isomers.; Standard enthalpies of formation, ionization potentials, electron affnities, and band gaps of finite-length [5,5] armchair and [9,0] zigzag single-walled carbon nanotubes (SWNTs) capped with C30 hemisphere have been computed at the B3LYP/6-311G* level of theory. Properties of SWNTs are found to depend strongly on the tube length and on the relative orientation of the caps. The oscillatory size dependence of the properties of finite-length tubes suggested that an infinite-length [5,5] armchair SWNT is a metal. An infinite-length [9,0] zigzag SWNT is predicted to be a semiconductor rather than a metal. The present results underscore the slow convergence of SWNT properties with respect to the tube length and uncover small but significant radial distortions along the long axes of SWNTs.