Novel selective “on–off” fluorescence sensor based on julolidine hydrazone-Al3+ complex for Cu2+ ion: DFT study

- A hydrazone- Al 3+ complex ( T1 -Al 3+ ) enhanced sensitivity for Cu 2+ detection. - The detection limit sensing for Cu 2+ in aqueous media was estimated to be 0.62 µM. - The recognition ability of the sensors was investigated by fluorescence, 1 H NMR, MALDI-TOF MS spectroscopy and density functional theory (DFT) calculations. • A novel hydrazone-Al 3+ complex ( T1 -Al 3+ ) showed a broad linear detection range of 10-110 µM towards Cu 2+ ion. • The detection limit for Cu 2+ in aqueous systems has been determined to be 0.62 µM. • T1 exhibited anticancer efficacy against HeLa and U251 cells at around 50 µM doses using MTT assay. A hydrazone ( T1 ) was synthesized by reacting 8-hydroxyjulolidine-9-carboxaldehyde with 2-furoic hydrazide and then modified with Al 3+ ion to form a novel hydrazone Al 3+ complex ( T1 -Al 3+ ) in an aqueous solution (8% propylene glycol in 10 mM HEPES pH 5.5). The T1 -Al 3+ complex was studied as a Cu 2+ selective sensor due to its highly efficient capacibility of paramagnetic quenching. The results showed that the T1-Al 3+ complexed sensor possesses remarkable sensitivity and selectivity for Cu 2+ ion in 8% propylene glycol in 10 mM HEPES pH 5.5 as compared with other tested analytes. Notably, this sensor has a broad linear detection range of 10–110 µM for Cu 2+ ion and a detection limit level of 0.62 µM, which is lower than the Cu 2+ concentration threshold in drinking water designated by the United States Environmental Protection Agency (EPA). Additionally, it was detectable for the presence of Cu 2+ ion in mineral water and tap water samples. The selectivity of T1 -Al 3+ complexed sensor with Cu 2+ ion could be explained by the basis of computation with Gaussian software complied with the basis sets of B3LYP/6-31 G(d,p)/LANL2DZ. Furthermore, only T1 exhibited anticancer efficacy against HeLa and U251 cells with MTT assay.