1-(D-Glucopyranosyl-2 '-deoxy-2 '-iminomethyl)-2-hydroxynaphthalene as chemo-sensor for Fe(3+) in aqueous HEPES buffer based on colour changes observable with the naked eye

Abstract

A new glucose-based C2-derivatized colorimetric chemo-sensor (L(1)) has been synthesized by a one-step condensation of glucosamine and 2-hydroxy-1-naphthaldehyde for the recognition of transition metal ions. Among the eleven metal ions studied, viz., Mg(2+), Ca(2+), Mn(2+), Fe(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+) Zn(2+), Cd(2+) and Hg(2+), L(1) results in visual colour change only in the presence of Fe(2+), Fe(3+) and Cu(2+) in methanol. However, in an aqueous HEPES buffer (pH 7.2) it is only the Fe(3+) that gives a distinct visual colour change even in the presence of other metal ions, up to a concentration of 280 ppb. The changes have been explained based on the complex formed, and the composition has been determined to be 2:1 between L, and Fe(3+) based on job's plot as well as ESI MS. The structure of the proposed complex has been derived based on HF/6-31G calculations. (C) 2008