Corrole-BODIPY dyads: Synthesis, structure, and electrochemical and photophysical properties

A free-base and its Cu(III) derivative of bichromophoric meso-β linked corrole-BODIPY dyad were synthesized and structurally characterized by single crystal X-ray diffraction (XRD). Both corrole and BODIPY fragments maintained respective ground state electronic isolation despite their connection through a single bond due to a tilted orientation as observed by XRD. This was further supported by UV-vis and cyclic voltammetric studies. The Cu(III)-metalated dyad exhibits temperature-dependent paramagnetic behavior as observed in the variable temperature ¹H NMR due to the presence of a Cu(II)-corrole-π-cation radical. Importantly, the free-base exhibits complete fluorescence quenching probably due to photoinduced electron transfer to a low lying charge separated state. Interestingly, emission was regained upon addition of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) due to the deprotonation of corrole. The "turn on" fluorescence behavior and the presence of acidic NH protons were further exploited toward basic anion sensing utility.