A highly selective and sensitive colorimetric chemosensor for Fe(2+) based on fluoran dye.

A highly selective chemosensor based on fluoran dye for Fe(2+), 2'-anilino-3'-methyl-6'-dibuthylamino-N-((2'-(2''-ethylimino) methyl) naphthalen-2-ol) iso-indolin-1-one-fluoran (5), was designed and synthesized. The chemical structures of all the intermediates and the fluoran dye 5 are characterized by (1)H NMR, (13)C NMR, Ms and elemental analysis. Upon addition of Fe(2+), the fluoran dye 5 shows a new peak around 658nm in its absorption spectra, and the color of solution changed from colorless to greenish black. Whereas other ions including Mg(2+), Pb(2+), Ni(2+), Hg(2+), Cd(2+), Fe(3+), Cu(2+), Zn(2+) and Al(3+) and so on induced basically no spectral change, which constituted a Fe(2+) highly sensitive and selective colorimetric chemosensor by "naked eyes".