Synthesis of bis(phenylethynyl)arylene-linked diporphyrins designed for studies of intramolecular energy transfer

A series of donor-bridge-acceptor systems has been designed to give informa tion on how the medium between the donor and the acceptor influences the ex citation energy transfer process. The donor and the acceptor are zinc and f ree base porphyrins, respectively. The systems were obtained by a synthetic strategy that guarantees a precise state of metalation, i.e. by a building block approach in which a third chromophore is formed as the two porphyrin s are covalently linked together in a geometrically well defined structure. The porphyrins are linked by one of the three different bridge chromophore s; 9,10-bis(phenylethynyl)anthracene, or 1,4-bis(phenylethynyl)-substituted benzene or naphthalene. The different units were assembled using copper-fr ee, palladium-catalyzed cross-coupling of aryl iodides with terminal alkyne s. Reference compounds that correspond to different parts of the systems ha ve also been prepared.