Ab initio calculations at the CI (singles) level of theory were carried out
for the ground state and the singlet and triplet excited states of substit
uted free-base porphyrins. The results predict a substantial red-shift in t
he long-wavelength electronic spectra of compounds due to the push-pull sub
stitution at the pi-system of the porphyrin ring or due to the substitution
by a nitro-group. The compounds and their derivatives may be good candidat
es for deep-penetrating photodynamic therapeutic agents. (C) 2000 Elsevier
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