Radical and Redox Forms of Pyridyl Appended MB-DIPYs.

We discuss the synthesis and properties of pyridine-appended nickel(II) complex of "Manitoba dipyrromethene" (NiII(MB-DIPY)), which is stable radical at ambient conditions. The NiII(MB-DIPY), 6• shows absorption at ∼1300 nm and a g-value of ∼2.00 in EPR. The redox features of NiII(MB-DIPY) were studied by electro- and spectroelectrochemistry. The reduced form, 6-, has an intense NIR absorption and a broad spectrum in the visible region, making this compound a prospective non-fullerene acceptor for light-harvesting. The axial coordination and photophysical properties of the supramolecular dyad formed between pyridine-appended NiII(MB-DIPY) with zinc 5,10,15,20-tetrakis-(pentafluorophenyl)porphyrin (TPPF20Zn) were also studied. NiII(MB-DIPY) 6• failed to interact with TPPF20Zn. However, reduced NiII(MB-DIPY) in its anionic form, 6-, self-assembles and forms a donor-acceptor dyad with TPPF20Zn with a binding constant of Ka = 1.13 × 102 M-1 and fluorescence quenching constant of KSV = 1.31 × 103 M-1. This work represents the first report on the potential of MB-DIPYs to self-assemble and form a donor-acceptor type supramolecular dyad with TPPF20Zn. This study explored the potential of the MB-DIPYs to act as a non-fullerene acceptor in light-harvesting supramolecular donor-acceptor systems formed via non-covalent interactions.