A luminescence molecular switch via modulation of PET and ICT processes in DCM system

A novel versatile dicyanomethylene-4H-pyran (DCM) based derivative bearing ferrocenyl group (DCM-N-Fc) is designed as modulator to construct off-on logic operation. The optical properties of DCM-N-Fc are characterized by absorption and steady-state fluorescence technique, showing that the fluorescence from DCM chromophore via intramolecular charge transfer (ICT) is strongly quenched by photoinduced electron transfer (PET) process from ferrocene moiety. In contrast with the references (DCM-N and DCM-Fc), the fluorescence of DCM-N-Fc can be triggered by oxidizing ferrocenyl unit either chemically or electrochemically, exhibiting a characteristic emission modulation at around 610 nm with an electrofluorochromic behavior. Furthermore, the free energy and the fluorescence lifetime in the PET path verify the thermodynamic feasibility. Cyclic voltammetry, absorption spectroscopy, time-resolved fluorescence as well as DFT calculation have been used to elaborate the manipulation via both PET and ICT processes.