A new half-condensed Schiff base platform: structures and sensing of Zn and HPO ions in an aqueous medium.

A newly designed and synthesized half-condensed organic moiety 2-hydroxy-5-methyl-3-[(2-phenylamino-phenylimino)-methyl]-benzaldehyde (HL') and a ZnL complex sequentially detect Zn and HPO ions as low as 1.13 nM and1.23 μM, respectively. HL' and a dinuclear Zn(ii) complex of in situ generated L in a solution formulated as ZnL under investigation were characterized by physicochemical and spectroscopic studies along with detailed structural analyses by single-crystal X-ray crystallography. The selectivity and sensitivity of HL' towards Zn ions and of the ZnL complex towards HPO ions are based on CHEF and via displacement pathways, respectively. Dual sensing of Zn ions and HPOions in an aqueous medium via "Green-Blue-Green" emission with the reversible transformation of in situ formed HL' to HL was established by detailed electronic absorption and emission spectroscopic studies. This non-cytotoxic probe (HL', i.e. produced HL in solution) and ZnL complexes are able to monitor the subcellular distribution changes of Zn and HPO ions, respectively, by fluorescence microscopy using the human semen sample.