Several metal complexes with a boron dipyrromethene (BODIPY)-functionalized N-heterocyclic carbene (NHC) ligand 4 were synthesized. The fluorescence in [(4)(SIMes)RuCl₂(ind)] complex is quenched (Φ=0.003), it is weak in [(4)PdI₂(Clpy)] (Φ=0.033), and strong in [(4)AuI] (Φ=0.70). The BODIPY-tagged complexes can experience pronounced changes in the brightness of the fluorophore upon ligand-exchange and ligand-dissociation reactions. Complexes [(4)MX(1,5-cyclooctadiene)] (M=Rh, Ir; X=Cl, I; Φ=0.008–0.016) are converted into strongly fluorescent complexes [(4)MX(CO)₂] (Φ=0.53–0.70) upon reaction with carbon monoxide. The unquenching of the Rh and Ir complexes appears to be a consequence of the decreased electron density at Rh or Ir in the carbonyl complexes. In contrast, the substitution of an iodo ligand in [(4)AuI] by an electron-rich thiolate decreases the brightness of the BODIPY fluorophore, rendering the BODIPY as a highly sensitive probe for changes in the coordination sphere of the transition metal.

A Crabtree-type Ir^I complex tagged with a fluorescent dye (bodipy) was synthesized. The oxidative addition of H₂ converts the weakly fluorescent Ir^I complex (Φ=0.038) into a highly fluorescent Ir^III species (Φ=0.51). This fluorogenic reaction can be utilized for the detection of H₂ and to probe the oxidative addition step in the catalytic hydrogenation of olefins.

Electrophilic monofluorination with Selectfluor and nucleophilic trifluoromethylation with the Ruppert–Prakesh reagent of dimethyl-, tetramethyl- and pentamethyl-substituted boron dipyrromethenes (BODIPY) are investigated. Monofluorinated dyes are synthesized with low yields (<30 %), however trifluoromethyl derivatives are obtained in moderate to high yields (≈40–90 %). All compounds are characterized by steady-state and time-resolved fluorescence spectroscopy, the photostability is investigated with fluorescence correlation spectroscopy (FCS) and total internal reflection fluorescence microscopy (TIRF). Monofluorination hardly affects the spectroscopic parameters of the unsubstituted parent compounds, but distinctly enhances the photostability, whereas trifluoromethylation leads to a hypsochromic shift by up to 17 nm in both absorption and emission, slightly enhanced intersystem crossing, and higher photostability. Further development of soft fluorination and trifluoromethylation methods is therefore highly desired.