Ethynyl–Boron Subphthalocyanines Displaying Efficient Cascade Energy Transfer and Large Stokes Shifts

A new class of luminescent dyes incorporates aromatic residues attached by an ethynyl link to the boron center of a subphthalocyanine (SubPc; see picture). Efficient energy transfer from energy-donor subunits to the SubPc produces very large Stokes shifts, while luminescence quantum yields are maintained. An acid-triggered “switching on” of SubPc emission occurs when a dibutylamino fragment is axially coordinated to the SubPc.