Vibrationally resolved absorption and emission spectral shapes of one 5-carbohelicene derivative: A theoretical study

Abstract In this work, we present a theoretical study on the vibrationally resolved absorption (ABS) and emission (EMI) spectra of a methoxy-substituted 5-carbohelicene (MeO-HeliIm). To analyze the optical properties of MeO-HeliIm from theoretical perspective, herein, we adopt different computational methods and theoretical models, accounting for Franck-Condon (FC), Herzberg-Teller (HT), temperature effects and Duschinsky mixing. Therefore, time-independent (TI) and time-dependent (TD) approaches have been used to compute the vibronic spectra, Adiabatic Hessian (AH) and Vertical Hessian (VH) models have been applied to build the PESs, HTi and HTf have been compared to check the accuracy of linear approximation of dipole moment. The different methods and models present with similar results, all in nice agreement with the experiment. This confirms the reliability and accuracy of our theory and results. We show that the temperature effect leads to a reduced resolution and a broader spectral width. FC plays a dominant role in reproducing the spectral shape, relative height of different bands and spectral width. However, HT causes a broader spectral width to EMI. Detailed analysis by comparing among the results obtained by AH, Adiabatic Shift and Frequencies (ASF), and Adiabatic Shift (AS) models, we find that the slight overestimation of Duschinsky enlarges the spectral width.