Porphyrins may be used as dyes in solar cells. They are characterized by intense B band absorptions at about 420 nm and very weak Q-band absorptions due to the electronic structure of the porphyrin core. This distinctive optical behaviour may be satisfactorily modeled by time-dependent DFT (density functional theory) calculations. Computational chemistry may also be used to conduct accurate normal coordinate analyses. We have studied porphyrin linked to barbiturate chromophores. These compounds have a B band split into two strong bands and intense Q-bands. Resonance Raman spectroscopy of the porphyrins showed enhancement of vibrations associated with the linking moiety as well as the barbiturate group. Time-dependent DFT calculations showed that the substituents perturb the frontier MOs of the porphyrin to the extent that the HOMO-2 and the LUMO+2 are strongly involved in the low energy transitions. This deviation from the "normal" porphyrin behaviour, or the four-orbital model, causes the red-shifts and enhancement of the Q bands, and the red-shifts of the B bands. The use of such substitutents may offer a way to produce porphyrin dyes which are spectrally efficient absorbers throughout the visible region.