Pyrromethene Dialkynyl Borane Complexes for “Cascatelle” Energy Transfer and Protein Labeling

All aglow: A new class of highly luminescent dyes is built by the attachment of a pyrene fragment to the boron center of a boradiazaindacene moiety through an ethynyl unit (see scheme). Very efficient energy transfer from the pyrene to the indacene center produces virtual large Stokes shifts, which are maintained, along with strong luminescence (Φ=32–45 %) when the dyes are attached to proteins such as bovine serum albumin.