Mesitylene based azo-coupled chromogenic tripodal receptors - a visual detection of Ag(I) in aqueous medium

A series of novel tripodal ligands 3a-d, based on a mesitylene anchor, containing aza-thioethers as donor atoms and coupled with 4-(4/3/2-nitrophenyl)azophenol or 4-(2-chlorophenyl)azophenol have been synthesized as chromogenic receptors, which are highly selective for silver(l). The complexation behavior of 3a-d with various metal ions has been evaluated by UV-vis spectrometry in dioxane/water (1:9/v:v) solution at 25 degrees C. The UV-vis spectra show that the complexation of 3a-c with Ag+ have pronounced bathochromic shifts accompanied by a unique color change in the solution from yellow to red, which is visible with the naked eye. The ligands do not show any significant change on addition of other metal ions like Li+, Na+, K+, Sr2+, Ca2+, Cd2+, Zn2+, Hg2+, Pb2+, Ni2+, and Cu2+ and thus are highly specific and selective for Ag+ in the aqueous medium. (c) 2006 Elsevier Ltd. All rights reserved.