Investigation of photochemistry for new optical data storage processes: I. Photodissociation of PhCo(III)TPP. II. Unique properties of porphyrin-core dendrimers

To demonstrate a new laser recording process based on fast photoinduced electron transfer we have synthesized three different three porphyrin chromophores, PhCo(III)TPP, PhCo(III)TECP, and PhCo(III)TPTBP, and investigated their electrochemical and electronic absorption properties. The Soret bands of PhCo(III)TECP and PhCo(III)TPTBP are red-shifted due to the steric congestion between the substituents at the porphyrin periphery compared to that for PhCo(III)TPP. The steric interactions also affect the ease of oxidation of the neutral compound of PhCo(III)TPTBP. Irradiation at the Soret band of PhCo(III)TPP and PhCo(III)TECP solution leads to the decomposition of the compounds while irradiation at thin film leads to photobleaching.; Porphyrin core dendrimers show unique properties in electronic, electrochemical, and fluorescence-quenching experiments. The higher generations, ZnG4 and ZnG5, encapsulate an electron acceptor to show high fluorescence-quenching efficiency and the porphyrin core is site isolated. Porphyrin core dendrimers show structural change from linear molecule to globular structure beyond ZnG4 as estimated from the intrinsic viscosity.