Dual-functional anionic electrochemical sensing of nitrite and dichromate using a glassy carbon electrode modified by a Ni(II) complex

A new nickel(II) complex, {[Ni(IDB) 2 ]SO 4 } 2 , was synthesized in aqueous DMF at 90 °C using bis(benzimidazole-2-ylmethyl)amine (IDB) as ligand for NiSO 4 ·6H 2 O. Single-crystal X-ray diffraction analysis indicated that the complex has a mononuclear structure and can self-assemble into a one-dimensional supramolecular substructure through hydrogen bonding. Hirshfeld surface analysis verified the dominant non-covalent interaction mode in the complex. Gassy carbon electrodes (Ni/GCE) modified with the complex were characterized using cyclic voltammetry, and the electrochemical detection performance for two anions [dichromate (Cr 2 O 7 2− ) and nitrite (NO 2 − )] was systematically studied using chronoamperometry. Experimental results indicate that in 0.2 m H 2 SO 4 , the Ni/GCE exhibits a linear response to Cr 2 O 7 2− in the range of 0.5 μm–4 mm, with a detection limit of 0.17 μm; in the 0.2 m phosphate buffer salin (PBS), the Ni/GCE shows a good current response to NO 2 − , with a range of 0.5 μm–4 mm and a detection limit of 0.32 μm. Furthermore, the Ni/GCE demonstrated high accuracy in real sample detection, with spiked recoveries of Cr 2 O 7 2− and NO 2 − ranging from 97.7 % to 99.3 % and 98.0 % to 99.3 %, respectively. This study opens a new door for the use of Ni(II) complexes as dual-function anion electrochemical sensors.