Electronic circular dichroism spectrum of uridine studied by the SAC–CI method

Symmetry-adapted cluster–configuration interaction (SAC–CI) method was applied to calculate electronic CD spectrum of a nucleoside, uridine. Based on the theoretical CD and absorption spectra, the observed peaks in the experimental spectra were assigned. The excited states of uracil, the base part of uridine, were also calculated for comparison. The origin of CD rotational strength for the low-lying π–π∗ and n–π∗ excited states was analyzed. Rotational strength of the π–π∗ transition depends on the magnitude of the electric and magnetic transition dipole moments, while that of the n–π∗ originates from the angle between the two transition moments.