Two hexaazatriphenylene based selective off–on fluorescent chemsensors for cadmium(II)

Two hexaazatriphenylene (HAT) derivatives, 2,3,6,7-tetramethyl-10,11-di(pyridin-2-yl)dipyrazino[2,3-f:2ʹ,3ʹ-h]quinoxaline (1) and 2,3-dimethyl-6,7,10,11-tetra(pyridin-2-yl)dipyrazino[2,3-f:2ʹ,3ʹ-h]quinoxaline (2), were designed and synthesized. Both 1 and 2 exhibited high off–on fluorescent selectivity for Cd2+ over many other metal ions, and the detection limits were determined to be 0.6 and 5.0 μM, respectively. The stoichiometry and coordination mode of blue fluorescent 1-Cd2+ and cyan fluorescent 2-Cd2+ were determined with fluorescence titration fit, Jobʹs plot analysis, 1H NMR titration and X-ray crystallography, and the fluorescence enhancement mechanism was analyzed with density functional theory calculation.