A novel colorimetric HSO4(-) sensor in aqueous media

A novel and sensitive anion receptor 3, bearing Schiff base structure, nitrophenyl azobenzol and carboxyl groups, was developed and characterized as a single chemosensor for the recognition of HSO(4)(-) anion. The different responses of UV-vis spectra and color changes of 3 could be applied to the recognition for HSO(4)(-) over other anions such as F(-), CI(-), Br(-), I(-), AcO(-), H(2)PO(4)(-) and CIO(4)(-) by the naked eye. Furthermore, the anion binding interaction of receptor-anion was also studied using UV-vis and (1)H NMR titration which revealed that 3 displayed a remarkable binding ability for the HSO(4)(-) with an association constant K(a)=6.59×10(4) M(-1). And the detection limitation of HSO(4)(-) with the receptor 3 was 2.0×10(-6) mol L(-1) in aqueous solution. Most importantly, the qualitative detection of HSO(4)(-) using receptor 3 was attempted with test kit which was made from receptor 3.