A novel aspect of spectroscopy for porphyrinic compounds under magnetic fields.

The spectroscopies of a range of porphyrinic compounds performed under a magnetic field are reviewed, focusing on the molecular functions of the compounds. Characteristic molecular magneto-optical effects, such as the Kerr effects and magnetochiral dichroism (MChD), as well as time-resolved electron paramagnetic resonance (TREPR) are reviewed. A novel molecular magneto-optical memory is described on the basis of the results of a Kerr spectroscopic study of Si phthalocyanine coupled with a ferromagnetic substrate. The results of TREPR analyses of low-symmetry tetraazaporphyrin derivatives are discussed in order to determine the relationship between molecular symmetry and singlet oxygen yield, as knowing this relationship is essential for photodynamic therapy. Finally, the MChD of porphyrins is introduced as a new way of elucidating the asymmetry in biological systems. Further, it can lead to new asymmetric synthesis methods and form the basis for novel magneto-optical devices.