Fluorescence sensors for Cu2+ based on conjugated indole Schiff base

Two new conjugated Schiff bases were prepared by condensation reactions between indole derivatives and o-phenylenediamine, respectively. The structures of the synthetic compounds were characterized by IR, ¹H NMR, and elemental analysis. And the melting point determination revealed that both compounds have good thermal stability. Their fluorescence measurements indicated that both compounds in solution have excellent performance on fluorescence emission, and the intensity of fluorescence emissions was quenched sharply by adding copper (II) nitrate. And the spectral changes were examined upon addition of various metal ions, such as Cu²⁺, Cd²⁺, Co²⁺, Ni²⁺, and Zn²⁺. The results indicated that the fluorescence intensity of two compounds quenched dramatically, and the quenching efficiency of Cu²⁺ was the highest.