The vibronic interactions and Jahn-Teller distortions in the mono- and trianions of annulene are discussed comparatively with those of benzene and annulene. We calculate the electronic structures, vibrational modes, and linear vibronic coupling constants of annulene as well as its deutero-form using the B3LYP method, the hybrid density functional theory method of Becke and Lee, Yang, and Parr. The lowest-frequency E2g mode of 38 cm-1 which causes deformation of the carbon ring is important compared to any other mode in causing the Jahn-Teller distortions. Such a low-frequency vibrational mode is characteristic of nanosized molecular systems, being analogous to acoustic mode of phonon in solid. We find that such a vibrational mode plays an important role in the Jahn-Teller distortions as the ring size of annulene becomes large from benzene to annulene. We also study the H/D isotope effect and find that the vibronic coupling constant of the E2g mode of 1513 cm-1 becomes larger by substituting deuteriums for hydrogens in negatively charged annulene.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry