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

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 H2PO4- results in a notable change in the visible region of spectrum (an approximately 90 nm 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- > H2PO4 >> Cl-, Br-, I-. The nature of the color change of I induced by AcO- was due to the intramolecular charge transfer (ICT) which was confirmed by X-ray crystal structure and H-1 NMR titration spectra. (c) 2009 Elsevier B.V. All rights reserved.