SPECTROSCOPIC AND PHOTOPHYSICAL PROPERTIE S OF HYPERICIN-METAL COMPLEXES IN RELATION WITH THEIR PHOTODYNAMIC ACTIVITY

At high pH (pH > 10), proton jump is favoured, resulting in a waveleng ht increase of the absorption spectrum. The binding of a metal in the carbonyl-hydroxyl region should result in a red shift in this spectrum as well. The absorption spectra are red shifted with Al3+, Fe3+, Cu2, Gd3+ and Tb3+. The last two elements also induce red shifts in the t riplet-triplet absorption spectra, while all act as quenchers of the f irst excited singlet state. We have determined the formation constants of the hypericin-metal complexes (HYP-M2) or (HYP-M(2)) and some of t heir photophysical properties. The photosensitized generation of the s inglet oxygen has been demonstrated by a kinetic study of the oxidatio n of 1,3-diphenylisobenzofuran and the corresponding quantum yields ph i Delta have been evaluated. The hypericin-metal complexes with CU2+ a nd Gd3+ are the most attractive from the viewpoint of their applicatio n in phototherapy.