Structure/energy correlation of bowl depth and inversion barrier in corannulene derivatives: Combined experimental and quantum mechanical analysis

Synthesis of a series of corannulene derivatives with varying bowl depths h as allowed for a study correlating the structure (bowl depth) and the energ y of bowl inversion. Substituents placed in the peri positions are repulsiv e and flatten the bowl, thus causing a decrease in the bowl inversion barri er. Conversely, annelation across the peri positions causes a deepening of the bowl, thus an increase in the bowl inversion barrier. Barriers between 8.7 and 17.3 kcal/mol have been measured, and their structures have been ca lculated using a variety of ab initio methods. The energy profile of an ind ividual corannulene derivative is assumed to fit a mixed quartic/quadratic function from which an empirical correlation of bowl depth and inversion ba rrier that follows a quartic function is derived. Structure/energy correlat ions of this type speak broadly of the nature of enzymatic and catalytic ac tivation of substrates.