Syntheses and fluorescence properties of lanthanide isostructural complexes derived from aspartic acid

To protect ecosystem balance and human health, the development of fluorescent sensing materials with high sensitivity and portability has attracted wide attention in several decades. Herein, six lanthanide isostructural complexes {[Ln(μ₆-Hcaa)(H₂O)]Cl} (H₃caa = N-(4-carboxylbenzyl)-L-aspartic acid, Ln³⁺ = Ce³⁺ (1), Pr³⁺ (2), Nd³⁺ (3), Sm³⁺ (4), Eu³⁺ (5), and Tb³⁺ (6)) with optical properties based on aspartic acid derivative (H₃caa) were synthesized by the solvothermal method and characterized in detail. It is worth noting that complex 6 can not only specifically recognize Cr(VI) with very low detection limits (LODs) of 3.66 nM (Cr₂O₇^2-) & 5.35 nM (CrO₄^2-) but also selectively recognize TCs with LODs of 0.24 μM (CTC = chlortetracycline) and 0.25 μM (TC = tetracycline) based on the method of fluorescence detection. In addition, the identification of Cr(VI) and TCs by visual colorimetry may be realized through the combination of a smartphone and portable test strips. This study suggests that complex 6 is a good optical material for detecting heavy metals and antibiotic contaminants in aqueous systems and broadens the development of amino acid derivatives.