A simple pyridine-based colorimetric chemosensor for highly sensitive and selective mercury(II) detection with the naked eye

Two easily-prepared pyridine-based derivatives of (Z)-2-(4-amino-phenyl)-3-(pyridine-4-yl)acrylonitrile (I)and (Z)-2-phenyl-3-(pyridin-4-yl)acrylonitrile (II) were designed, synthesised and characterised. Due to the formation of a complex with Hg2+, hence leading to an enhanced ICT effect, I exhibits a visible colour change from light yellow to orange, rendering it suitable for use as a naked-eye sensor for rapid detection of Hg2+ in an aqueous ethanol solution. When mixed with Hg2+, I interacts with Hg2+ in a2:1 (Y1-Hg2+) stoichiometry via a coordination bond with an association constant of 7.7 × 108 M−2 (R2 = 0.96). The present probe I exhibits excellent reproducibility, reversibility, sensitivity and selectivity with the presence of low concentration of Hg2+ (1.74 × 10−10 M).