Synthesis of multi-branched dipyrromethene dyes with soluble diethynylphenyl links

Multi-branched dyes were prepared using a convergent step-by-step procedure. The key dibutoxydiethynylphenyl spacing units were first linked to a difluoroboradipyrromethene (yellow fluorophore) dye via the pseudo-meso position and then selectively cross-coupled to a di-(4-phenyliodo)ethynylborodiisoindolomethene (red emitter via the boron). When ethynylpyrene units were connected at the periphery to the boron of the yellow emitter, efficient cascade singlet energy transfer events occurred from the pyrene to the yellow and to the red emitters.