Preparation of a 2,2′-(4-nitrophenyl)dipyrromethane copper coordination compound and its catalytic behavior for phenol hydroxylation

Ultrasensitive reversible chromophore reaction of BODIPY functions as high ratio double turn on probe

Chromophore reactions with changes to conjugation degree, especially those between the conjugated and unconjugated state, will bring a large spectral variation. To realize such a process, a meso-naked BODIPY (MNBOD) with two electron-withdrawing groups around the core is designed and synthesized. The resulting system is extremely sensitive to bases. The red, highly fluorescent solution readily becomes colorless and non-fluorescent after base addition; however, the color and fluorescence can be totally and instantly restored by addition of acid or formaldehyde. Analyses show that two identical MNBODs are connected by a C–C single bond (sp³) at the meso-position through a radical reaction that results in an unconjugated, colorless dimer complexed with bases. When the bases are consumed, the dimer immediately dissociates into the red, highly fluorescent, conjugated MNBOD monomer. With 260 nm spectral change and over 120,000 turn-on ratio, this chromophore-reaction can be utilized as a sensitive reaction-based dual-signal probe.

BODIPY dyes, though widely explored, have not been pursued as chromophore reaction based chemical probes. Here, the authors synthesize a meso-naked BODIPY core flanked with two electron-withdrawing groups, which undergoes a reversible change in conjugated structure in the presence of base and functions as a dual signal and ultrahigh turn-on ratio chemical probe.