Synthesis and characterization of a novel lanthanum (III) complex with a di(2-picolyl)amine-based ligand endowed with fluorescent properties

In this work, 1-(1-benzyl-1H-1,2,3-triazol-4-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine (1), a ligand belonging to the DPA family, was coordinated to La(III), yielding compound La-1. The structural and spectroscopic properties of the complex were analyzed by experimental and theoretical methods. The structural characterization of La-1 was described by means of single-crystal X-ray diffraction (SC-XRD) and Hirshfeld surface analysis, allowing a detailed conformational investigation. The lowest-energy conformer obtained from DFT calculations conformationally agreed with the structure obtained by SC-XRD. 1H NMR titration studies confirmed the formation of a stable complex in solution. Ligand 1 exhibited a sensitive fluorescence enhancement and ratiometric response to La(III) ions, indicating that 1 can be considered a first step towards the design of new tools for the detection of lanthanide metal ions in environmental chemistry. • Nitrogen based heterocyclic compounds are very effective in metal coordination • The use of click reaction open the way to complex structures embedding the triazole ring • Lanthanum is the one of the most common rare earth metal used in industry • Toxicity of lanthanum requires novel approaches for its detection and removal from the environment • A combined solid/liquid state and computational approach is fundamental in understanding the properties of ligand-metal coordination