Strong excitonic coupling in photosynthetic systems is believed to enable efficient light absorption and quantitative charge separation, motivating the development of artificial multi-chromophore arrays with equally strong or even stronger...

A series of 3,5-bis(hetero)arylethenyl-substituted BODIPY derivatives has been prepared in Knoevenagel-type condensation of alkyl-substituted BODIPY with corresponding aldehydes.2-Pyrrolylethenyl-substituted derivatives feature near-IR emission (lem > 700 nm), with high fluorescence quantum yield. Both, emission maxima and fluorescence quantum yields are relatively insensitive to solvent polarity, contrary to corresponding near-IR emitting 4-(N,Ndimethylaminophenyl)ethenyl derivatives. Alkylation at the N-pyrrolic position of ethenyl substituent allows for installation of hydrophilic PEG group and afforded amphiphilic BODIPY derivatives. Overall, 2-pyrrolylethenyl-substituted BODIPY appears to be versatile fluorophores with potential application in near-IR imaging.

Targeted near-infrared (NIR) fluorescence probes are playing a significant role in biomedical imaging because NIR penetrates deeper into tissues and is associated with reduced autofluorescence compared to visible light fluorescence probes. Long-wavelength emitting 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) is an attractive platform for synthesizing NIR fluorophores because of its high photostability, high molar absorption coefficient, and sharp absorption and emission spectra. However, its lipophilicity hampers the conjugation chemistry necessary to add targeting moieties. In this study, we synthesized a novel NIR BODIPY derivative, NMP14. Substitutions of ethylene-bridged pyrrole units at the 3- or 5-position of the parent BODIPY chromophore result in a red shift of more than 200 nm. However, NMP14 cannot be conjugated to antibodies because of its hydrophobicity. Therefore, we synthesized NMP13 by adding short poly­(ethylene glycol) to NMP14 and successfully conjugated NMP13 to cetuximab and trastuzumab. In vitro microscopic studies showed that NMP13 conjugated antibodies were activated after internalization and lysosomal processing, which means that NMP13 acts as an activatable probe only turning on after cellular internalization. After the administration of NMP13 conjugated antibodies, mice tumors were detected with high tumor to background ratios for a long period. These results suggest that NMP13 has potential as an activatable fluorescence probe for further clinical applications.

In photosynthetic light‐harvesting complexes, strong interaction between chromophores enables efficient absorption of solar radiation and has been suggested to enable ultrafast energy funneling to the reaction center. To examine whether similar effects can be realized in synthetic systems, and to determine the mechanisms of energy transfer, we synthesized and characterized a series of bioinspired arrays containing strongly‐coupled BODIPY dimer as energy donors and chlorin derivatives as energy acceptors. The BODIPY dimer feature broad absorption in the range of 500 – 600 nm, complementing the chlorin absorption to provide absorption across the entire visible spectrum. Ultrafast (~10 ps) energy transfer was observed from photoexcited BODIPY dyads to chlorin subunits. Surprisingly, the energy‐transfer rate is nearly independent of the position where the BODIPY dimer is attached to the chlorin and of the type of connecting linker. In addition, the energy‐transfer rate from BODIPY dimers to chlorin is slower than the corresponding rate in arrays containing BODIPY monomers. The lower rate, corresponding to less efficient through‐bond transfer, is most likely due to weaker electronic coupling between the ground state of the chlorin acceptor and the delocalized electronic state of the BODIPY dimer, compared to the localized state of a BODIPY monomer.