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

A hydrazone (T1) was synthesized by reacting 8-hydroxyjulolidine-9-carboxaldehyde with 2-furoic hydrazide and then modified with Al3+ ion to form a novel hydrazone Al3+ complex (T1-Al3+) in an aqueous solution (8% propylene glycol in 10 mM HEPES pH 5.5). The T1-Al3+ complex was studied as a Cu2+ selective sensor due to its highly efficient capacibility of paramagnetic quenching. The results showed that the T1-Al3+ complexed sensor possesses remarkable sensitivity and selectivity for Cu2+ 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 Cu2+ ion and a detection limit level of 0.62 µM, which is lower than the Cu2+ concentration threshold in drinking water designated by the United States Environmental Protection Agency (EPA). Additionally, it was detectable for the presence of Cu2+ ion in mineral water and tap water samples. The selectivity of T1-Al3+ complexed sensor with Cu2+ 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.