Design, Synthesis, and Dynamics of a Green Fluorescent Protein Fluorophore Mimic with an Ultrafast Switching Function

While
rotary molecular switches based on neutral and cationic organic π-systems have been reported, structurally homologous anionic switches providing complementary properties have
not been prepared so far. Here we report the design and preparation
of a molecular switch mimicking the anionic p-HBDI
chromophore of the green fluorescent protein. The investigation of
the mechanism and dynamics of the E/Z switching function is carried out both computationally and experimentally.
The data consistently support axial rotary motion occurring on a sub-picosecond
time scale. Transient spectroscopy and trajectory simulations show
that the nonadiabatic decay process occurs in the vicinity of a conical
intersection (CInt) between a charge transfer state
and a covalent/diradical state. Comparison of our anionic p-HBDI-like switch with the previously reported cationic N-alkyl indanylidene pyrrolinium switch mimicking visual
pigments reveals that these similar systems translocate, upon vertical
excitation, a similar net charge in the same axial direction.