Lanthanide Complexes Based on Rigid Benzimidazole Carboxylic Acid Ligand: Sensing of Nitrobenzene, Fe(III) Ions, and Adsorption of Dyes

Five new lanthanide complexes {[Sm(H 2 L )(H 2 O) 4 (Cl)]⋅H 2 O⋅Cl} n ( 1 ), {[Eu(H 2 L )(H 2 O) 4 Cl]⋅Cl} n ( 2 ), {[La(H 2 L )(H 2 O) 4 Cl]⋅Cl} n ( 3 ), {[Pr(H 2 L )(H 2 O) 4 Cl]⋅Cl} n ( 4 ), {[Ce(H 2 L )(H 2 O) 4 Cl]⋅Cl} n ( 5 ) (H 3 L = 2‐hydroxy‐5‐(5‐(hydroxy‐λ 2 ‐methoxy)‐1 H ‐benzo[d]imidazole‐5‐carboxylic acid) were successfully synthesized under solvothermal method. 1 exhibits a two‐dimensional (2D) network structure, whereas 2–5 feature one‐dimensional (1D) chain structure. The fluorescence investigations demonstrated that 1–5 could be the fluorescent sensor for nitrobenzene (NB) and Fe(III) ions with high selectivity, sensitivity, and low detection limits. Furthermore, 1–5 displayed the good adsorption to anionic dye Congo red (CR), and the adsorption capacities were 140.5, 206.5, 212.5, 111.5, and 211.5 mg·g −1 , respectively.