A pyrazine-containing hydrazone derivative for sequential detection of Al3+ and F−

The hydrazone sensor (1) derived from pyrazine-2-carbohydrazide and 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) was applied to the fluorescent “turn-on” detection of Al3+ in semi-aqueous solutions. The strongly emissive 1+Al3+ complex could identify F− among other tested anions. The detection limits of sensor 1 for Al3+ and F− were 0.18 and 0.20 μM, respectively, which are both much lower than the corresponding values recommended by the World Health Organization, namely, 7.41 and 79 μM. Several spectral methods, including single crystal X-ray analysis for the crystal structures of the Cu2+ and Ni2+ complexes of sensor 1, as well as the density-functional theory method, were used to elucidate the binding mode between the sensor and Al3+. 1 can also be used for a selective sensor to continuously monitor Al3+ and F− in living cells.