ORGN 313

           Recently, there has been an increasing interest in long-range charge separations in conformationally rigid donor-bridge-acceptor systems.  Studies have shown that linear pi-conjugated polyene and polyyne spacers enhance through-bond electronic coupling between donor and acceptor.  A promising strategy to facilitate electron transfer (ET) over long distances involves the incorporation of a "molecular wire" in D-B-A systems.  Several systems in which redox centers are separated by "molecular" wires such as polyynes have exhibited efficient, long-range ET and EN.  Although the distance between the donor and acceptor in D-B-A systems is an important consideration when investigating ET and EN processes, studies of these parameters as they apply to conjugated pi systems are scarce.  In polyene-linked D-B-A systems, rotation about a single bond can lead to variations in the D-A distance as well as overall reduced conjugation within the system.  In polyyne-linked D-B-A systems, the molecular length is distributed linearly and the D-A distance is constant.  Alkynyl groups can provide full conjugation within a given D-B-A system and give geometrically well-defined systems that simplifies interpretation of physical data.

             Several new systems and their photophysical properties will be discussed. All systems will involve acetylene-derivatized fullerenes with fully conjugated porphyrin-linker-fullerene architectures.