The magnetic circular dichroism (MCD) and absorption studies of 1,8-naphthalimide. The theoretical analysis in terms of density functional (DF) and coupled cluster (CC) theories

► First quantum chemical results for the low-energy states of 1,8-naphtalimide at the CC level. ► First theoretical interpretation of the MCD spectrum of 1,8-naphtalimide. ► Highlighting the importance of vibronic coupling in interpreting the MCD spectra.