Azaneylylidene-based tetradentate Schiff base as a new "ON-OFF" fluorescent probe for the detection of Cu(II) ion:...

Herein we describe the synthesis of Cu²⁺ 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 Cu²⁺ ions via fluorescence quenching mechanism, which combined the character of high selectivity towards Cu²⁺ assay even in the presence of other common metal ions such as Cu²⁺, Al³⁺, Co²⁺, Ni²⁺, Mn²⁺, Zn²⁺ Pb²⁺ Cd²⁺, Fe²⁺, Hg²⁺, Mg²⁺ and Fe³⁺ (30 μM) ethanol-water (1:9 v/v) system. Upon the addition of the solution of Cu²⁺ ions to CPMB, the complexation of Cu²⁺ with CPMB leads to the immediate formation of light green color, indicating that CPMB can act as simple colorimetric sensor, particularly for Cu²⁺ in the presence of most interfering metal ions in ethanol-water medium. More interestingly, the ability of sensing behavior of CPMB for Cu²⁺ 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 Cu²⁺ with detection limit of 0.302 μM. The electronic transitions of the complex in ethanol were studied using DFT calculations.