First Principles Studies of the Vibrationally Resolved Magnetic Circular Dichroism Spectra of Biphenylene

We present density-functional response theory calculations of the one-photon absorption and magnetic circular dichroism spectral bandshapes of biphenylene. The effects from the surrounding solvent environment and molecular vibrations have been included. The solvent is described by the Polarizable Continuum Model (PCM), while the vibrational structures of the spectra have been computed including both Franck-Condon and Herzberg-Teller contributions in the vibronic model. This is the first study of vibronic effects on magnetic circular dichroism spectra including non-Franck-Condon contributions. A detailed comparison with experimental data has been performed, revealing that the B3LYP functional in combination with PCM gives the best agreement with experimental data. Our calculations indicate that nonadiabatic vibronic coupling may play a role, and even small computational inaccuracies might cause significant changes in the calculated HT term, which raises concerns about the inclusion of HT contributions in the calculations of vibronic MCD in systems that have close-lying excited states.