Sensitive detection of chloramphenicol and efficient adsorbent for conge red of lanthanide complexes based on lactam carboxylic acid ligands

Two lanthanide metal complexes [M(H4L)Cl(OH) (H2O)2]n [M = La (1), Ce (2)] were constructed via lactam carboxylic acid ligand (2-(5-amino-2,5-dihydro-1H-imidazole-4-yl)-4-oxo-3,4-dihydroquinazoline-7-carboxylic acid) (H5L) under solvothermal condition. Complexes 1 and 2 could sensitively, selectively and repeatedly detect chloramphenicol (CAP) through the fluorescence quenching effect with a quenching constant (Ksv) of 1.87 × 103 and 1.52 × 104 Μ−1, respectively, and the detection limit (LOD) were 1.23 × 10−6 and 2.03 × 10−7 M, respectively. Density functional theory (DFT) calculations indicate that the LUMO energy level of the CAP quenched was lower than that of the ligand, so the photoelectron energy transfer (PET) between complexes and CAP leads to fluorescence quenching. Moreover, 1 and 2 exhibited excellent adsorption performance to Congo red (CR) and adsorption capacity were 3448.3 mg g−1 and 1886.5 mg g−1, respectively. Adsorption kinetics experiments showed that this kind of adsorption belonged to chemisorption, the hydrogen bonding and π-π interactions between the complex host and CR guest molecules resulted in high adsorption capacity.