A theoretical study on the molecular and electronic structure of heteroaromatic bowl-shaped molecules

Geometries, inversion barriers, local aromaticities and vertical excitation energies of four heteroaromatic coronenes including (triphenylenotri)-pyrrole, (-)-furan, (-)-phosphole and (-)-thiophene were computed using MO and DET methods, and compared with those of coronene and corannulene. The barriers to bowl-to-bowl inversion amount to 297, 183 and 8 kJ/mol for O-, N- and S-forms, respectively, thus the recently synthetized thiophene derivative is a floppy bowl-shaped species. The P-derivative exhibits an almost planar form. NICS values point out that the bowl-shaped molecules have similar local aromaticity in the six-membered rings but differ in those of the five membered rings. The excitation energies were evaluated using the DFT-RPA method. (C) 2001 Elsevier Science B.V. All rights reserved.