Novel push-pull based phenothiazine-benzothiazole derivatives integrated with molecular logic gate operation for reversible volatile acid detection

Abstract

• Design and synthesis of push-pull based phenothiazine benzothiazole derivatives. • Positive solvatochromism with large Stokes shifts (113-146 nm). • Naked eye colorimetric and fluorescent acid sensing behavior in solution and solid state. • Fabrication of paper strip sensors for volatile acid. • Development of INHIBIT molecular logic gate with acid and base as inputs. A series of novel push-pull based phenothiazine-benzothiazole derivatives, in which phenothiazine and benzothiazole groups act as donors and acceptors, respectively is designed and synthesized in good yields. These compounds exhibit strong fluorescence in solution and solid state. These derivatives respond to external stimuli such as solvents and acid. A positive solvatochromism with large Stokes shifts (113-146 nm) was observed. In solution state, blue shifted emission wavelengths of compounds containing electron-withdrawing aryl groups indicated reduced Intramolecular Charge Transfer (ICT). However, red shifts in solid state emission spectra of compounds with electron-withdrawing aryl groups indicated more planarity of the excited state. The naked eye detection of reversible acid/base-induced chromogenic and fluorescence switching properties were observed in both solution and the solid state upon subsequent addition of trifluoroacetic acid (TFA) and triethylamine (TEA), thereby making the synthesized derivatives efficient volatile acid-base switches. The reversible acidochromic response was further utilized for the development of inhibit (INH) molecular logic gates using TFA/ (TEA) as the chemical inputs.