LONGWAVE LUMINESCENT PORPHYRIN PROBES

A set of luminescent dyes, namely the porphyrin-ketones and their zinc (II), platinum(II) and palladium(II) complexes, are described. The pro bes are derived from a partially oxidized porphyrin ring and have been studied by absorption and luminescence spectroscopy including time-re solved measurements. The metal-free porphyrin-ketones display strong a nd pH-dependent fluorescence due to a protolytic equilibrium that exis ts between the free base and the dication. The zinc(II) complexes also give strong fluorescence along with a weak long-decay emission at roo m temperature which are attributed to delayed fluorescence and phospho rescence, respectively. Platinum(II) and palladium(II) complexes exhib it room-temperature phosphorescence without any detectable fluorescenc e. Compared to existing porphyrins, the new dyes display a considerabl y longwave-shifted luminescence along with substantially improved (pho to)chemical stability. They are considered to be promising probes for very near-infrared luminescence studies, and to be particularly useful for applications such as labelling of biomolecules, pH-sensing, and d etection of quenching species such as molecular oxygen.