To further assess the effect of the functional and of the basis set on the general features of the PES we calculated the energies of triplet and singlet states at different critical point of the PES, namely Franck-Condon and S1 and T1 minima. The results are collected in ESI. Once again while the effect of the basis set appears negligible, the functional effects are more crucial. In any case the use of 6-31G basis in combination with the wB97XD exchange-correlation functional provide a coherent description.