Ferrocene-Grafted Photochromic Triads Based on a Sterically Hindered Ethene Bridge: Redox-Switchable Fluorescence and Gated Photochromism

Multifunctional switches, as well as gated photochromism, are particularly challenging. Here, a ferrocene (Fc)‐modified photochromic diarylethene (DAE) with sterically hindered ethene bridge, in which the photo‐inactive parallel conformer and photoactive antiparallel conformer are individually investigated, is reported. The photoswitchable triad system (parallel conformer p‐Fc and anti‐parallel ap‐Fc ) contains three functional parts: photochromic DAE unit, naphthalimide chromophore, and redox‐active ferrocene. Upon incorporation of ferrocene unit, the photochromic efficiency in the anti‐parallel triad conformer ap‐Fc is blocked to a great extent in the ferrocene state but distinctly enhanced in the ferrocenium state via chemical or electrochemical stimuli, thereby constructing redox‐gated photochromism. Meanwhile, the reversible redox between ferrocene and ferrocenium states can also switch “OFF/ON” the fluorescence of naphthalimide chromophore via photoinduced electron transfer pathway (PET). The fluorescence and photoisomerization in the triad system are well modulated with chemical‐ or electrochemical redox and light stimuli, which enables the specific gated photochromism and fluorescence switches work in multi‐addressable states.