Substitutional group dependent colori/fluorimetric sensing of Mn(2+), Fe(3+) and Zn(2+) ions by simple Schiff base chemosensor.

Schiff base is one of the easiest synthesizable chemosensor and exhibit strong coordination with metal ions; the property that has been vastly exploited for metal ions sensing. Simple Schiff base chemosensors (1a-d and 2a-d) were synthesized and demonstrated substitutional group dependent colorimetric sensing of metal ions. Chemosensor without (1a, 2a) and OCH3 substitution (1b, 2b) did not show any significant colour change for metal ions. However, a highly selective colorimetric change (colourless to pink) for Mn(2+) ions (10(-6)M) was observed with diethylamine substituted 1c, 2c. Hydroxyl substitution (1d, 2d) leads to selective colorimetric sensing (colourless to orange) of Fe(3+) ions (10(-6)M). PVA thin films of 2c/2d were fabricated and demonstrated selective colorimetric sensing of Mn(2+) and Fe(3+) ions. The practical applicability of the synthesized chemosensors were also demonstrated by performing selective colorimetric sensing of Mn(2+) and Fe(3+) ions in real samples such as tap, ground, pond and river water. Effect of substitution on the fluorescence selectivity of Zn(2+) has also been investigated.