Photochemical and photophysical behaviour of porphyrins and phthalocyanines irradiated with violet or ultraviolet light

Photochemical irradiation of porphyrins or phthalocyanines with violet or u ltraviolet light absorbed by their second or higher absorption bands popula tes their higher excited states. These higher excited states generally diss ipate very rapidly, but, competing with such rapid deactivation, often show unique behaviour different from the lowest excited states populated under visible light irradiation of the first absorption band, namely wavelength-d ependent reactions or emission. The higher excited states often exhibit cha racteristic emission and enhanced reactivity in electron transfer, energy t ransfer and so on, competing with rapid deactivation. This paper attempts t o summarize our work, perfomed particularly by means of femtosecond spectro scopy, and recent progress in this area. Copyright (C) 2001 John Wiley & So ns, Ltd.