BODIPY–subporphyrin hybrids bridged by a 1,4-biphenylene or 1,4-diphenylethynylene spacer were synthesized either by the palladium-catalyzed Suzuki–Miyaura reaction or the Sonogashira reaction. Their structural and optical properties were examined with respect to the bridge and BODIPY structures. In all cases, intramolecular excitationenergy transfer from the subporphyrin core to the BODIPY peripheries is efficient. Depending on the presence or absence of β-methyl groups adjacent to the meso position of the BODIPY subunit, the fluorescence is either increased or decreased. It was also found that the electronic interaction between the subporphyrin core and the meso-(1,4-phenylene) substituents causes spectral changes for the subporphyrin part, which is not observed for porphyrin counterparts.
Intramolecular excitation energy transfer in BODIPY-appended subporphyrins was found to occur from the subporphyrin to the BODIPY part. Fluorescence from BODIPY follows the intrinsic fluorescence properties of BODIPY references. meso-Oligo(1,4-phenylene) substituents can interact electronically with the subporphyrin core to cause redshifted absorption bands and to increased fluorescence quantumyields.
