Synthesis of dithiaporphyrin-based singlet-singlet energy transfer systems

The synthesis of the first alkynyl core-modified porphyrin building block, 5,10,15,20-tetrakis(4-ethynylphenyl)-21,23-dithiaporphyrin (N2S2 core), is reported. The building block was used to construct donor-appended dithiaporphyrin systems under mild palladium-coupling conditions. The porphyrin building block appended to four boron-dipyrrin units, (BDPY)(4)S2TPP, did not show any energy transfer from the BDPY unit to the central dithiaporphyrin core. However, the pentaporphyrin containing a central dithiaporphyrin sub-unit and four peripheral normal porphyrin sub-units (N-4 core) showed efficient energy transfer from the peripheral N-4 porphyrins to the central N2S2 porphyrin.