POTENTIAL PHOTOSENSITIZERS FOR PHOTODYNAMIC THERAPY .4. PHOTOPHYSICALAND PHOTOCHEMICAL PROPERTIES OF AZAPORPHYRIN AND AZACHLORIN DERIVATIVES

The photophysical and photochemical properties of a 5-azaprotoporphyri n derivative ([5]AZPP), a zinc-15-azaporphyrin derivative (Zn-[15]AZID P) and an E-Z isomeric mixture of a 5-azachlorin derivative ([5]AZCH) were studied in various solvents. The quantum yields of fluorescence P HI(F)0, S1-T1 intersystem crossing PHI(T)0 and singlet oxygen (1DELTA( g) formation PHI(DELTA) were measured and the Stern-Volmer constants f or the quenching of the S1 states by oxygen and the rate constants of quenching of O2(1DELTA(g)) by the different azaporphyrinoid compounds were obtained. The fluorescence quantum yield (PHI(F)0 = 0.23), the st rong absorption in the red (LAMBDA(max) = 674 nm, epsilon(max) = 66 00 0 M-1 cm-1) and the high value of the quantum yield for singlet oxygen (1DELTA(g)) formation (PHI(DELTA) = 0.65) observed for [5]AZCH recomm end azachlorin derivatives as potential markers and photosensitizers f or tumour therapy.