Ab initio energies and geometries of symmetrical corannulenes having carbons selectively substituted by heteroatoms are reported. It is found that substitution can greatly affect the inversion barrier : pentaazocorannulene has a barrier 8 times that of corannulene, while in pentaborazacorannulene it is less than 1 kcal/mol. A very small barrier is also found for the tetraanion of corannulene. For corannulene itself, vibrational frequencies are reported for its equilibrium bowl (C-5v) and planar (D-5h) forms at the 6-31G* SCF level. All 84 vibrational frequencies of the bowl form are real. Planar corannulene has one imaginary (A(2)(")) frequency, strongly suggesting that it is the transition state for bowl-to-bowl inversion. The energies, vibrational frequencies, and moments of inertia provide estimates of the enthalpy and free energy of activation for inversion. T Delta S-double dagger is positive and ca. 12% of Delta H-f,298(degrees) at 298 K. Delta H-f,298(degrees) of corannulene is calculated to be 122.1 kcal/mol.