Intrinsically Switchable Electroactive Fluorophores Based on λ -Biphosphinines.

The synthesis and full characterization of a family of stable λ -biphosphinines connected in 4,4-position through a variety of π-conjugated bridges is reported. The impact of the π-bridge on the optical (absorption/emission) and redox properties was investigated using a joint experimental/theoretical approach. In contrast to the π-extended ones, the λ -biphosphinines directly connected through a C-C bond in 4,4-position display two easily accessible and reversible oxidations highlighting their multi-stage redox character. The in situ formed radical cations are studied by spectro-electrochemistry and electron paramagnetic resonance. Finally, electrochemical modulation of fluorescence (electrofluorochromism) was performed and revealed the potential of these intrinsically switchable electroactive fluorophores for further applications as switchable materials.