Boron-Dipyrromethene-Functionalized
Hemilabile Ligands as “Turn-On” Fluorescent Probes for
Coordination Changes in Weak-Link Approach Complexes
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Abstract
Herein we report
a new class of hemilabile ligands with boron-dipyrromethene (Bodipy)
fluorophores that, when complexed to Pt(II), can signal changes in
coordination mode through changes in their fluorescence. The ligands
consist of phosphino-amine or phosphino-thioether coordinating moieties
linked to the Bodipy’s meso carbon via a phenylene spacer.
Interestingly, this new class of ligands can be used to signal both
ligand displacement and chelation reactions in a fluorescence “turn-on”
fashion through the choice of weakly binding heteroatom in the hemilabile
moiety, generating up to 10-fold fluorescence intensity increases.
The Pt(II) center influences the Bodipy emission efficiency by regulating
photoinduced electron transfer between the fluorophore and its meso
substituent. The rates at which the excited Bodipy-species generate
singlet oxygen upon excitation suggest that the heavy Pt(II) center
also influences Bodipy’s emission efficiency by affecting intersystem
crossing from the Bodipy excited singlet to excited triplet states.
This signaling strategy provides a quantitative read-out for changes
in coordination mode and potentially will enable the design of new
molecular systems for sensing and signal amplification