The Studies On Synthesis And Characterization Of 8-hydroxyquinoline Aldehydes Schiff-base Ligands As Aluminium Fluorescent Sensors

Mounting evidences suggest that aluminium has severe toxicity in the central nervous system. It is found that the toxicity is higher in acid envrionment, so it is important to explore high selective fluorescence sensors for monitoring toxic Al3+in acid aqueous medium.8-hydroxyquinoline-5-carbaldehyde (HQ5A) and 8-hydroxyquinoline-7-carbaldehyde (HQ7A) were regarded as important medical intermediates and possessed excellent optical properties. Though HQ5A or HQ7A were synthesized and characterized in many papers, the reported physical and chemical parameters of the two isomers were ambiguous or even paradoxical. So it is important to provide a complete and correct characterization on HQ5A and HQ7A. In this text, HQ5A and HQ7A were synthesized by the Reimer-Tiemann reaction and separated by column chromatography. And full characterization on HQ5A and HQ7A using multiple methods, concluding NOE spectrum and X-ray single diffraction analysis determined the structures.In this text, four Al3+fluorescence sensors have been designed and synthesized. But Zn2+and Cd2+obviously interfered with HLland HL2 recognizing Al3+in neutral aqueous medium. And the interfering from Zn2+and Cd2+was eliminated thoroughly by adding 10 equivalent of H+. The interest phenomenon was studied systematically using UV-visible and Fluorescence spectroscopy. The results illustrated that HL1 and HL2 binds Al3+stronger than Zn2+and Cd2+. Then the selectivity of HL1 and HL2 in acid aqueous medium displayed highly selective and efficient for Al3+, and the enhancement of fluorescence emission as large as 36-fold and 27-fold was observed by adding 2 equivalent of Al3+to HL1 and HL2, respectively. And the detection limit at 10-7M level under weak acid aqueous conditions. Moreover, water soluble (L3) and duel emission aluminium fluorescence sensor H2L4 were prepared.