Intrinsically switchable electroactive fluorophores based on lambda-5-phosphinine dimers

We report the synthesis and full characterization of a family of stable lambda- 5-phosphinine dimers connected through a variety of pi-conjugated bridges. The impact of the pi-bridge on the optical (absorption/emission) and redox properties is investigated using a joint experimental/theoretical approach. In contrast to the pi-extended ones, the dimers directly connected through a C-C bond 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.