Ligand Based Dual Fluorescence and Phosphorescence Emission from BODIPY Platinum Complexes and Its Application to Ratiometric Singlet Oxygen Detection

Four new 4,4-difluoro-4-bora-3a,4a-diaza-s-indacen-8-yl (BODIPY) platinum(II) complexes of the type cis-/trans-Pt(BODIPY)Br(PR3)2 (R = Et or Ph) were synthesized and characterized by NMR, electronic absorption, and luminescence spectroscopy. Three of the complexes were also studied by single crystal X-ray diffraction. The absorption profiles of the four complexes feature intense HOMO → LUMO π → π* transitions with molar extinction coefficients e of ca. 50 000 M–1cm–1 at around 475 nm and vibrational progressions that are characteristic of BODIPYs. Most remarkably, most complexes exhibit dual emissions through fluorescence at ca. 490 nm and phosphorescence at ca. 650 nm that originate from Pt-perturbed BODIPY-centered 1ππ* or 3ππ* states, respectively. Electronic absorption and luminescence spectroscopy data are in good agreement with our TD-DFT calculations. While the emission of the cis-complexes is dominated by fluorescence, their trans-isomers emit predominantly through phosphorescence with a phosphore...