Synthesis and cation-mediated electronic interactions of two novel classes of porphyrin-fullerene hybrids

There has been considerable interest in hybrid molecules in which C-60 is covalently linked to highly conjugated electron donor systems which absorb strongly in the visible region, such as porphyrins and phthalocyanines. Synthesis of such compounds has previously proceeded by Diels-Alder or azomethine ylide cycloaddition to C-60. Two novel methodologies allowing for the expedient elaboration of novel hybrids with tunable molecular topographies are reported. One of these involves the preparation of the first known [6,5]-open azafullerene-porphyrin hybrid. These hybrids have been fully characterized and display varying degrees of electronic intramolecular interactions between the two chromophores. Photophysical studies, and direct measurements of quantum yields for formation and quenching of O-1(2) by these hybrids are reported. In one such hybrid, a polyether linker is used to produce an allosteric effect via metal cation complexation which brings the two chromophores closer together in space. Similar data for the azafullerene hybrid is also reported. Photophysical, computational, and NMR studies provide evidence for the proposed complexation of metal ions by these hybrids.