Multi-stimuli-responsive azomethine embedding the phenoxazine chromophore as an extra mean of tuning smart materials

Abstract

Multi-stimuli-responsive architectures incorporating photochromic molecules with light-triggered behavior are listed as “smart” materials. Pursuing to develop such materials, this study is focused on the development of a new structurally designed phenoxazine (POZ)-based dye, which was thoroughly assessed with regard to the structural, photo-optical, and electrochemical characteristics. The sensing capability of the newly developed material was first demonstrated towards transition/heavy metallic ions detection with good sensitivity in solution at the addition of only 0.2 equivalents of Cu2+, Fe3+ or Hg2+ ions. In solid state (blend film), the dye complexation was complete after 1120 s of immersion in the Cu2+ solution. The sensitivity towards hydrochloric acid was very high after the addition of only 0.2 equivalents, whilst the full dye protonation occurred after 4 s of exposure to acid vapors. The synthesized dye is also endowed with photodetection capabilities, showing important spectral changes in chloroform solution after only 10 s of exposure to light of 354 nm. None the less, this dye shows electrochromic response, with 7.4 and 4.2 s for coloring and blanching, respectively, coloration efficiency of 121 cm2/C, and switching stability and reversibility of 72% after 50 cycles. Complementary theoretical calculations by DFT were employed to validate these experimental findings. Due to these multi-stimuli-responsive functions, the developed dye may find applications in optoelectronic and biological fields.