Influence of electronic effects on one- and two-photon absorption in porphyrin isomers

The one- and two-photon absorption characteristics of the Porphyrin isomers Porphycene, Corrphycene, Hemiporphycene, N-confused Porphyrin, cis- and trans-Doubly confused Porphyrins, the newly synthesised Neo-confused Porphyrin, and a set of core-substituted Porphycenes are systematically investigated using linear and quadratic density functional response theory. It is shown that, despite the one- photon spectra displaying characteristic Soret- and Q-regions, the classic Gouterman four orbital theory has limitations for the analysis of the absorptions in this series of compounds. Generated spectra for the two-photon absorptions are shown to be very sensitive to the isoelectronic changes, contrary to the one- photon spectra. This accesses a potentially powerful tool by which the two-photon absorption can be fine-tuned without large structural changes to the nature of the macrocycle.