A tetrazole-based fluorescence “turn-on” sensor for Al(iii) and Zn(ii) ions and its application in bioimaging

Abstract

A tetrazole derivative 1-[(1H-tetrazol-5-ylimino)methyl]naphthalen-2-ol (H₂L) as a fluorescent chemosensor for Al³⁺ in DMSO and Zn²⁺ in DMF was designed and synthesized. From ¹H NMR data, the Job plot and the ESI-MS spectrum, 1 : 1 stoichiometric complexation between H₂L and Al³⁺/Zn²⁺ was found in DMSO and DMF, respectively. The theoretical calculations at the level of B3LYP/6-311G** for the ground state and TD-B3LYP/6-311G** for the excited state revealed the sensing mechanism is the inhibition of excited state intramolecular proton transfer (ESIPT). And the possible fluorescent species formed in the DMSO and DMF solutions were deduced to be [Al(HL)(OH)(NO₃)(H₂O)(DMSO)] and [Zn(HL)(OH)(H₂O)(DMF)]. What's more, it is confirmed that H₂L could be used to detect Al³⁺ and Zn²⁺ in cells by bioimaging.