Synthesis of 21-thia and 21-oxaporphyrin building blocks and boron–dipyrrin appended systems

A series of 21-thia and 21-oxaporphyrin building blocks bearing iodo-, ethynyl-and aldehyde functional groups were synthesized and characterized. These porphyrins are ideal building blocks for the construction of unsymmetrical porphyrin arrays containing two dissimilar porphyrin cores. The building blocks were used to construct boron–dipyrrin appended core-modified porphyrin systems under mild palladium coupling conditions. A preliminary steady state fluorescence measurements suggested that boron–dipyrrin unit transfers the energy to both 21-oxaporphyrin and 21-thiaporphyrin and the efficiency depends on the orientation of the boron–dipyrrin units and the core structure of the porphyrin.