NIR sensing of Zn(II) and subsequent dihydrogen phosphate detection by a benzothiazole functionalized ninhydrin based receptor

A benzothiazole functionalized ninhydrin based chemosensor (L-1), exhibits selective naked eye detection of biologically important zinc ions (from light yellow to orange) accompanied by a 'turn-on' fluorescence emission response in the near infra-red (NIR) region. Most importantly, Zn2+ ion induced 'turn-on' fluorescence emission is also preserved in the presence of Cd2+ and most of the other competing metal ions which clearly suggests the high sensitivity of the chemosensor towards Zn2+. The Job's plot suggests 1 : 1 binding of the L-1 with the Zn2+ ion with a detection limit of 6 nM. Detailed H-1 NMR titrations were also conducted to understand the binding behaviour of L-1 towards the Zn2+ ion. The 'L-1-Zn2+ ensemble' further shows a ratiometric response to H2PO4- among other competitive anions and nucleotides in the same experimental conditions.