A visible-light-gated donor-acceptor Stenhouse adduct chemosensor: synthesis, photochromism and naked-eye colorimetric/fluorometric sensing of Al3+ and Zn2+

In this study, a new visible-light-gated donor-acceptor Stenhouse adduct (DASA) chemosenor with a Schiff base naphthalene unit was successfully designed and synthesized. The synthesized ND-O exhibited typical and excellent negative photochromic properties in a solution. It also possessed multi-responsive photoswitchable properties under visible Eight, heat, and in the presence of metal ions. After activation by visible Eight, the purple ND-O was converted to the nearly colorless ND-O (ring-dosed form). Remarkably, this ND-O could not only be utilized as a cobrimetric chemosensor to recognize Al3+ by evident color changes in solution but also could be used as a fluorescence chemosensor to detect Zn2+ by a noticeable enhancement of the emission intensity and change in fluorescence color. The Lowest detection Limits for Al3+ and Zn2+ ions were 3.65 x 10(-7) mol L-1 and 1.00 x 10(-7) mol L-1, respectively. The binding mode of ND-C with Al3+ and Zn2+ was determined as a 1:1 coordination stoichiometry by employing fluorescence titration curves and Job's plot analysis.