Electronic absorption, MCD, and luminescence properties of porphyrin J-aggregates

In this paper, we have investigated electronic absorption, magnetic circular dichroism, fluorescence, and phosphorescence spectra for a protonated form of H 2 TPPS 4 ( H 4 TPPS 4 ) and the J-aggregates of H 4 TPPS 4 . The J-aggregation induces a large red-shift in the B (Soret) and Q absorption bands, while the phosphorescence peaks of H 4 TPPS 4 and its J-aggregates are almost entirely similar. The large red-shift of the B-band is quantitatively explained by the exciton interactions. Thus, the exciton interactions in the J-aggregates are proposed as a useful approach to decrease the energy splitting between the fluorescent and phosphorescent states.