A simple colorimetric sensor for biologically important anions based on intramolecular charge transfer (ICT)

Abstract

A sensitive colorimetric sensor (1) based on 4,5-dinitrobenzene-1,2-diamine was designed and synthesized. Binding of anions such as AcO(-), F(-) and H(2)PO(4)(-) results in a notable change in the visible region of spectrum (an approximately 90nm red shift), which can be detected by the 'naked-eye'. Furthermore, the binding ability was evaluated by UV-vis titration experiments as following: AcO(-)>F(-)>H(2)PO(4)(-)>>Cl(-), Br(-), I(-). The nature of the color change of 1 induced by AcO(-) was due to the intramolecular charge transfer (ICT) which was confirmed by X-ray crystal structure and (1)H NMR titration spectra.