Tetra-Au(I) Complexes Bearing a Pyrene Tetraalkynyl Connector Behave as Fluorescence Torches

A pyrene tetraalkynyl ligand has been used for the preparation of three different tetraalkynyl Au(I) complexes. Two of these complexes display fluorescent emission in CH2Cl2 solution, with quantum yields exceeding 90%. Although the emission is mainly due to ligand-centered excited states, the presence of the metal center is key to reaching such excellent quantum yield values, providing an extra rigidity to the system and therefore, minimizing the nonradiative deactivation pathways. To the best of our knowledge, these quantum yields lie among the highest reported for metal-based luminophores in solution, a quality that makes them resemble molecular torches. Preliminary studies on healthy cheek cells show that one of the complexes is efficiently and rapidly taken up into the cell.