An azine based sensor for selective detection of Cu ions and its copper complex for sensing of phosphate ions in physiological conditions and in living cells.

A simple and cost effective unsymmetrical azine based Schiff base, 5-diethylamino-2-[(2-hydroxy-benzylidene)hydrazonomethyl]-phenol (1) was synthesized which selectively detect Cu ions in the presence of other competitive ions through "naked eye" in physiological conditions (EtOH-buffer (1:1, v/v, HEPES 10mM, pH=7.4)). The presence of Cu induce color change from light yellow green to yellow with the appearance of a new band at 450nm in UV-Vis spectra of Schiff base 1. The fluorescence of Schiff base 1 (10μM) was quenched completely in the presence of 2.7 equiv. of Cu ions. Sub-micromolar limit of detection (LOD=3.4×10M), efficient Stern-Volmer quenching constant (K=1.8×10Lmol) and strong binding constant (log K=5.92) has been determined with the help of fluorescence titration profile. Further, 1-Cu complex was employed for the detection of phosphate ions (PO, HPO and HPO) at micromolar concentrations in EtOH-buffer of pH7.4 based on fluorescence recovery due to the binding of Cu with phosphate ions. Solubility at low concentration in aqueous medium, longer excitation (406nm) and emission wavelength (537nm), and biocompatibility of Schiff base 1 formulates its use in live cell imaging.