An ICT-guided ratiometric naphthalene–benzothiazole-based probe for the detection of cyanide with real-time applications in human breast cancer cells

Abstract

A methoxynaphthalene benzothiazole conjugate (MNBTZ) armed with CC vinylic double bonds was synthesized and utilized for the selective detection of CN⁻ ions. The probe showed yellow fluorescence due to ICT from the methoxynaphthalene moiety to benzothiazole, which instantly changed to light purple upon the nucleophilic addition of CN⁻ to the vinylic double bond, inhibiting ICT due to the break-in conjugation. The effectiveness of the probe was proved by this brilliant ratiometric fluorescence change, which was achieved selectively as observed by experiments with competing anions. ¹H NMR titrations and DFT calculations support this mechanism. A low detection limit of 2.1(±0.0022) × 10⁻⁸ M along with good fluorescence color change on solid TLC plates and human breast cancer cells makes it amenable to CN⁻ sensing.