Abstract: Excitation of a triad artificial photosynthetic reaction center consisting of a porphyrin (P) convalently linked to a fullerene electron acceptor (C60) and a carotenoid secondary donor (C) leads to the formation of a long-lived C+-P-C60− charge-separated state via photoinduced electron transfer. This reaction occurs in a frozen organic glass down to at least 8 K. At 77 K, charge recombination of C*+-P-C60− occurs on the &mgr;s time scale, and yields solely the carotenoid triplet state. In the presence of a small (20 mT) static magnetic field, the lifetime of the charge-separated state is increased by 50%. This is ascribed to the effect of the magnetic field on interconversion of the singlet and triplet biradicals. At zero field, the initially formed singlet biradical state is in equilibrium with the three triplet biradical sublevels, and all four states have comparable populations. Decay to the carotenoid triplet only occurs from the three triplet sublevels.

Abstract: A process of tumor identification comprising administering a carotenoporphyrin to a tumor-bearing mammalian host and irradiating the mammalian host with light whereupon the carotenoporphyrin, which has been preferentially taken up by the tumor tissue, fluoresces and permits precise identification of the location, size and shape of the tumor tissue. An improved process of synthesizing carotenoporphyrins 1-5 is also provided.

Abstract: Excitation of a triad artificial photosynthetic reaction center consisting of a porphyrin (P) convalently linked to a fullerene electron acceptor (C60) and a carotenoid secondary donor (C) leads to the formation of a long-lived C+-P-C60? charge-separated state via photoinduced electron transfer. This reaction occurs in a frozen organic glass down to at least 8 K. At 77 K, charge recombination of C*+-P-C60? occurs on the ?s time scale, and yields solely the carotenoid triplet state. In the presence of a small (20 mT) static magnetic field, the lifetime of the charge-separated state is increased by 50%. This is ascribed to the effect of the magnetic field on interconversion of the singlet and triplet biradicals. At zero field, the initially formed singlet biradical state is in equilibrium with the three triplet biradical sublevels, and all four states have comparable populations. Decay to the carotenoid triplet only occurs from the three triplet sublevels.