Development and applications of fluorescent indicators for Mg2+ and Zn2+

Article abstract of DOI:10.1021/jp110305k

In a study of the spectroscopic behavior of two Schiff base derivatives, salicylaldehyde salicylhydrazone (1) and salicylaldehyde benzoylhydrazone (2), Schiff base 1 has high selectivity for Zn²⁺ ion not only in abiotic systems but also in living cells. The ion selectivity of 1 for Zn²⁺ can be switched for Mg²⁺ by swapping the solvent from ethanol-water to DMF (N,N-dimethylformamide)-water mixtures. Imine 2 is a good fluorescent probe for Zn²⁺ in ethanol-water media. Many other ions tested, such as Li⁺, Na⁺, Al³⁺, K⁺, Ca ²⁺, Cr³⁺, Mn²⁺, Fe³⁺, Co ²⁺, Ni²⁺, Cu²⁺, Ag⁺, Cd ²⁺, Sn²⁺, Ba²⁺, Hg²⁺, and Pb ²⁺, failed to induce any spectral change in various solvents. The selectivity mechanism of 1 and 2 for metal ions is based on a combinational effect of proton transfer (ESPT), C=N isomerization, and chelation-enhanced fluorescence (CHEF). The coordination modes of the complexes were investigated.