Selective colorimetric and ratiometric probe for Ni(ii) in quinoxaline matrix with the single crystal X-ray structure

Abstract

A quinoxaline based colorimetric nickel sensor, HQAP [2-(quinoxalin-2-ylmethyleneamine)phenol] with high selectivity and sensitivity toward Ni²⁺ ions is shown to have potential for practical use. The absorption maximum of HQAP shows a large ratiometric shift from 306 to 570 nm (ΔI = 264 nm) in the presence of Ni²⁺ ions, and the color changes from colorless to deep violet only upon addition of Ni²⁺ which is very easily observed by the naked eye (the detection limit of Ni²⁺ is as low as 4.16 μM in solution). The predicted binding mode (2 : 1) from spectral analysis and Job's plot was confirmed by the single crystal X-ray structure of the complex.