Fluorescent Probes Of Metal Ions Based On Quinoline Derivatives: Design, Synthesis And Properties

Most of quinoline derivatives are good chromophore and bioactivators which can act as medical intermediate. For the alkalescence of quinoline derivatives, more derivatives can be got by reacting with electrophile and nucleopilic reagent.Quinoline derivatives are the compounds with rigid structure, coordination sites and water solubility, with which metal binding can enhance the fluorescence, and thus have been widely used in fluorescence detection and imaging of metal ions.Metal ions play very important roles in environment and biological process.However, excess concentrations of ions, especially heavy metal ions, can make great hazards to human health and environment. For example, mercury is a severe neurotoxin and long-term exposure to high levels of mercury can cause damage of the brain, nervous system, immune system and the endocrine system. Therefore, it’s very important to detect metal ions efficiently. In recent years, fluorescence probes are popular to detect metal ions for their low cost, good selectivity, simplification, high sensitivity, and speediness.In this work, two quinoline-based fluorescent probes L1 and L2 for detecting metal ions are designed and synthesized. Their structures and detection mechanisms are confirmed by many analysis methods. Fluorescent probe L1 is water-soluble,which can detect Cd²⁺ by fluorescence-enhanced and detect Hg²⁺ by fluorescence-quenched in 100% aqueous medium. Experimental analysis and TD-DFT calculations show the different mechanisms of CHEF-based for L1-Cd²⁺ and PET-based for L1-Hg²⁺. The detection abilities of L1 for both Cd²⁺ and Hg²⁺ are keeping valid in a wide pH range of 5.0–12.0. And the reversible binding features of probe L1 toward Cd²⁺ and Hg²⁺ imply that this probe can be a useful chemical tool to monitor Cd²⁺ and Hg²⁺ in biological system and environmental systems. Probe L2 is Schiff-based fluorescent probe which based on quinoline and acridine derivatives. L2 shows high selectivity toward Fe³⁺ by fluorescence-enhanced in H2O:DMF of 122:3.The detection of L2 for Fe³⁺ is transient, reversible and the detection limit is low. The fluorescent probe L2 is insensitive to pH and has potential application in environmentand organisms.