BODIPY Substrates for Probing Reactions of Double Bonds

BODIPY Substrates for Probing Reactions of Double Bonds 

BODIPY dyes were subjected to modifications in their meso position as the previous fluorescein dyes. Aromatic moieties at this position are perpendicular to the molecular plane but, nevertheless, affect the fluorescence properties of the core [99]. Subtle manipulation of the redox potential can be also read out by changes of the fluorescence lifetime as exemplified in a substrate for phosphoester cleavage [100]. Depending on of the redox properties of the substituents, fluorescence can be turned on and off [101]. When the electrochemical potential of the substituent is altered during a reaction, a fluorogenic probe for this particular reaction is tailored. This was exploited for studying interfacial electron transfer [61]. More applications appear feasible. 

As a first approach, we studied the epoxidation of the exocychc double bond of 1 by weto-chloroperbenzoic acid (mCPBA) in dichloromethane. IR spectra provided evidence for a fluorescent epoxide [94]. Eater on, surface-catalyzed epoxidation was ascribed to the formation of further fluorescent BODIPY derivatives [54]. The bimolecular rate constant had been determined beforehand, and pointed to the concentration range of mCPBA for maintaining useful pseudo-first-order kinetics. Immobilization turned out to be a major issue because, while the oxidizing species should have free access to the double bond, the translational mobility of the substrate must be widely suppressed. Introduction of a further terminal double bond permitted subsequent immobilization on polymeric sihcone [102-104]. 

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