Hydrogen peroxide (H2O2) is responsible for numerous damages when overproduced, and its detection is crucial for a better understanding of H2O2-mediated signaling in physiological and pathological processes. For this purpose, various “off–on” small fluorescent probes relying on a boronate trigger have been prepared, and this design has also been involved in the development of H2O2-activated prodrugs or theranostic tools. However, this design suffers from slow kinetics, preventing activation by H2O2 with a short response time. Therefore, faster H2O2-reactive groups are awaited. To address this issue, we have successfully developed and characterized a prototypic borinic-based fluorescent probe containing a coumarin scaffold. We determined its in vitro kinetic constants toward H2O2-promoted oxidation. We measured 1.9 × 104m−1⋅s−1 as a second-order rate constant, which is 10,000-fold faster than its well-established boronic counterpart (1.8 m−1⋅s−1). This improved reactivity was also effective in a cellular context, rendering borinic acids an advantageous trigger for H2O2-mediated release of effectors such as fluorescent moieties.

We report the synthesis, characterization, and photophysical properties of two new cyclometalated halfsandwich iridium(III) complexes having the general formula [(η 5 -Cp*)Ir(ppy)Z]PF 6 where η 5 -Cp* = pentamethylcyclopentadienyl and ppy = 2-phenyl-pyridine as C ∧ N-chelating ligand and Z = 3-or 4-pyridyl-BODIPY (BODIPY = 4,4-difluoro-4bora-3a,4a-diaza-s-indacene dye containing a 3-or 4-pyridyl group at the meso position). The molecular structure of both complexes has been determined by X-ray crystallography. The photophysical properties of the dyads were investigated and compared to the pyridyl-BODIPY precursors. Antiproliferative studies demonstrated that one of the compounds was highly active with submicromolar IC 50 on a panel of cancer cell lines. The replacement of the chlorido ligand by the pyridyl-BODIPY increased the lipophilicity of the complexes and slowed down the hydrolysis rate, which in turn increased the cytotoxicity of the metallodrug candidate. For the first time, cell uptake of one of the dyads was monitored by living cell fluorescence imaging. Interestingly, extremely fast internalization was observed the rate of which was temperature-dependent.