Meso-meso-linked subporphyrin dimer

Directly meso meso linked subporphyrin dimer 5 and 7 were synthesized by Ni-mediated reductive coupling of the corresponding meso-bromosubporphyrins. Dimer 5 exhibited a largely perturbed absorption spectrum, a redshifted and enhanced fluorescence spectrum, higher oxidation potentials with a large potential difference between the first and second oxidation waves, and a long-lived large anisotropy of S1 state. Directly meso meso linked Zn^II diporphyrin was prepared by Ag^I- promoted oxidative dimerization of Zn^II porphyrin. The absorption spectrum shows a split Soret band, which can be interpreted in terms of simple exciton coupling of the two Zn^II porphyrins without significant conjugative interaction. The high-resolution electrospray ionization time-of-flight (HR ESI-TOF) mass spectrum revealed an intense borenium cation peak at m/z 817.3095. These properties have been interpreted in terms of the effective conjugative interactions of the two subporphyrin units due to the small rotational barrier of the meso meso bond.