N-benzoate-N' salicylaldehyde ethynelediamine: a new fluorescent sensor for Zn2+ ion by "off-on" mode.

Imbalance of zinc ion (Zn(2+)) in human body causes diseases like Alzheimer's and Parkinson's and therefore Zn(2+) estimation in biological fluids has diagnostic values. Fluorescence "off-on" sensors have advantages of high sensitivity and in situ application over other sensors. A new fluorescent "off-on" Zn(2+) sensor, N-benzoate-N' salicylaldehyde ethynelediamine (L), has been synthesisied. In 1:1(v/v) CH3OH:PBS (PBS = phosphate buffer solution), L shows ca. 20 times enhancement in fluorescence intensity on interaction with Zn(2+), due to snapping of photoinduced electron transfer (PET) process, which is selective over metal ions - Na(+), K(+), Ca(2+), Ni(2+), Cu(2+), Cd(2+), Hg(2+) and Pb(2+). These metal ions either individually or all together does not interfere the sensing ability of L towards Zn(2+). A 1:1 interaction between L and Zn(2+) ion with binding constant 10(4.25) has been established from spectroscopic data.