The crystal structures, spectrometric, photodynamic properties and bioimaging of β-β linked Bodipy oligomers

A series of β-β directly linked Bodipy oligomers (D1, D2, D3 and T1) based on different monomers are synthesized and the crystal structures, photophysical properties, singlet oxygen (1O2) generation abilities, bioimaging and phototoxicity are investigated. Single-crystal X-ray analyses of D1 and D2 indicate the distorted orthogonal conformation of two linked Bodipy planes. In comparison with the meso-β analogues, the β-β dimers exhibit red-shifted spectroscopy bands, strong fluorescent emission but modest 1O2 quantum yields due to the distorted orthogonal structures and electron interaction, which is demonstrated by single-crystal analysis, spectroscopy measurements and quantum calculations. The fluorescence imaging and cytotoxicity assay results indicate that the unsubstituted D1 and D2 with excellent bioimaging performance alongside with obvious phototoxicity are promising candidates in the fields of cell imaging and photodynamic therapy.