Effects of the molecular structure on the electronic vertical spectrum of oxoglaucine

The vertical electronic spectrum of oxoglaucine by means of a multireference configuration interaction method (DFT/MRCI) was studied. The effect of both methyl and methoxy groups on the geometries and energetic distribution of the low-lying excited states was analyzed. The results show that, by means of the TZVP basis set, at the ground state minima of oxoglaucine, oxoglaucine without methyl and methoxy groups, the lowest excited singlet states are of n pi* (S-1) and pi pi* (S-2) type. Triplet states of pi pi* (T-1) and n pi* (T-2) type are energetically accessible from S-1. From the energetic point of view, it can be proposed that the channel for an efficient intersystem crossing 1(n pi*)->(3)(pi pi*) is plausible. Although the presence of the methyl and methoxyl groups distort the planarity of the rings system, the effect in the vertical distribution of the lowest lying singlet and triplet states can be considered as negligible.