Selective detection of Fe3+ and Congo red adsorption properties studies of Ln-complexes based on imidazopyridine carboxylic acid ligand

Abstract

Five new Ln-complexes [Ln(L)2(OH)(H2O)3]n (1 and 2) and {[Ln2(L)2(HL)2(H2O)8]Cl4·7H2O}n (3–5) [Ln = Nd (1), Sm (2), Eu (3), Ho (4), Er (5), HL = 4-(1H-imidazo[4,5-c]pyridin-2-yl)benzoic acid] were synthesized under solvothermal conditions. The single crystal X‑ray diffraction showed that Ln-complexes 1–5 were one-dimensional (1D) structures. Interestingly, the sensing experimental showed that 1–5 could be considered as promising specificity fluorescent sensor for Fe3+ ions with good reusability and high sensitivity, and the detection limits were 7.14 × 10−6, 3.21 × 10−6, 7.28 × 10−6, 6.74 × 10−6 and 7.42 × 10−6 M, respectively. Ln-complexes 1–5 exhibited excellent adsorption performance to dye Congo red (CR), and the adsorption capacities were 2792 mg·g−1, 2551 mg·g−1, 2858 mg·g−1, 2752 mg·g−1 and 2654 mg·g−1, respectively. Adsorption kinetics and adsorption isotherms showed that the adsorption of 1–5 belongs to the chemical adsorption process, the hydrogen bonding and π-π interactions between the 1–5 host and CR guest molecules resulted in high adsorption capacity.