UNSYMMETRICALLY SUBSTITUTED BENZONAPHTHOPORPHYRAZINES - A NEW CLASS OF CATIONIC PHOTOSENSITIZERS FOR THE PHOTODYNAMIC THERAPY OF CANCER

Unsymmetrical zinc(II) complexes of benzonaphthoporphyrazines 5a-12a b earing between one and eight pyridyloxy substituents are synthesized b y statistical tetramerization of -(1,1-dimethylethyl)-2,3-naphthalened icarbonitrile (1) with 4-(3-pyridyloxy)- or 4,5-bis-(3-pyridyloxy)-1,2 -benzenedicarbonitrile (2,3). Methylation of 5a-12a leads to the catio nic pyridyloxybenzonaphthoporphyrazines 5b-12b having between one to e ight positive charges, The Q-band transition in the visible spectra ex hibits a bathochromic shift from 680 to 760 mm dependent upon the numb er of annelated naphthalene rings. The singlet oxygen quantum yields o f the benzonaphthoporphyrazines determined by the dye-sensitized photo oxidation of 1,3-diphenylisobenzofurane is surprisingly high (in the r ange of zinc phthalocyanine). The photooxidative stabilities of the ph otosensitizers described quantitatively by first-order kinetics decrea se with the number of annelated naphtho groups, A linear correlation b etween the logarithm of the decomposition rate constant and the positi on of the highest occupied molecular orbital (HOMO)-level of the photo sensitizers is found. Destabilization of the HOMO leads to a decrease of the photostability. Due to their adjustable long wavelength absorpt ion, their intramolecular polarity axis and their different hydrophili c/hydrophohic character, these novel compounds may be suitable photose nsitizers for the photodynamic therapy of cancer.