Vibronic interactions and superconductivity in acene anions and cations

Abstract

Vibronic interaction and its role in the occurrence of superconductivity in the monoanions and cations of benzene and acenes are studied. The vibrational frequencies and the vibronic coupling constants for benzene and acenes are computed and analyzed and electron—phonon coupling constants in the monoanions and cations are evaluated. The C–C stretching E2g mode of 1656 cm−1 affords large electron—phonon coupling constants in the monoanion and cation of benzene. The C–C stretching Ag modes of 1400–1600 cm−1 and the lowest frequency Ag mode play an important role in the electron–phonon coupling in the monoanions of acenes, while the only C–C stretching Ag modes of 1400–1600 cm−1 afford large electron–phonon coupling constants in the monocations of acenes. We estimate possible superconducting transition temperatures Tcs for the monoanions and cations of benzene and acenes. The predicted Tcs for the monocations of benzene and acenes are much lower than those for the monoanions. Possible high-temperature superconductivity in the monoanion and cation of benzene is suggested.