Azaneylylidene-based tetradentate Schiff base as a new "ON-OFF" fluorescent probe for the detection of Cu(II) ion: Synthesis, characterization and real sample analysis.

Herein we describe the synthesis of Cu sensor, 2,2'-((1E,1'E)-((4-chloro-1,2-phenylene)bis(azaneylylidene))bis(methane-ylylidene))bis(4-bromophenol) (CPMB) and characterization using various spectral and analytical techniques. CPMB exhibited high selectivity towards Cu ions via fluorescence quenching mechanism, which combined the character of high selectivity towards Cu assay even in the presence of other common metal ions such as Cu, Al, Co, Ni, Mn, Zn Pb Cd, Fe, Hg, Mg and Fe (30 μM) ethanol-water (1:9 v/v) system. Upon the addition of the solution of Cu ions to CPMB, the complexation of Cu with CPMB leads to the immediate formation of light green color, indicating that CPMB can act as simple colorimetric sensor, particularly for Cu in the presence of most interfering metal ions in ethanol-water medium. More interestingly, the ability of sensing behavior of CPMB for Cu ion in the real water samples (tap water and lake water samples) was also investigated. Further, Job's plot confirmed that the complexation occurred in 1:1 ratio (ligand:metal). Furthermore, the fluorescence inhibiting factor showed a good linear relationship with the concentration of Cu with detection limit of 0.302 μM. The electronic transitions of the complex in ethanol were studied using DFT calculations.