FLUORESCENCE AND EXCITED-STATE ABSORPTION IN MODIFIED PIGMENTS OF BACTERIAL PHOTOSYNTHESIS - A COMPARATIVE-STUDY OF METAL-SUBSTITUTED BACTERIOCHLOROPHYLLS A

A series of transmetalated bacteriochlorophylls, where the central mag nesium has been replaced by Pd, Ni, Zn, Cd, Cu, have been investigated by linear and non-linear laser spectroscopic methods. A strong depend ence of the fluorescence on the central metal was obtained. Difference s in fluorescence lifetimes and quantum yields are caused mainly by di fferent efficiencies of intersystem crossing. Strong excited state abs orptions were found, in particular, In particular, the Pd-compound has a strong transient absorption in the 550-670 nm range. The results ar e of interest with respect to a possible oxygen-free sensitizing actio n of Pd-BPhe a for photodynamic tumor therapy.