Study On The Recognition Function Of Salamo-Type Fluorescence Sensors And Its Polynuclear Nickel(Ⅱ) Complex

Salen is a class of compound commonly used in coordination chemistry and homogeneous catalysis,but its shortcomings have been slowly revealed with the research work on salen-type compounds,which are prone to hydrolysis and exchange reactions and show limitations in many reactions.To address this issue,a new class of salamo-type compound with a-C=N-O-group was obtained by modifying the salen-type compound.Due to the introduction of highly electronegative oxygen atoms to the nitrogen atom of the imine,the salamo-type ligand is much more stable compared to the Salen-type ligand and is neither prone to exchange reactions nor to hydrolysis reactions.Similarly,salamo-type ligands,like salen ligands,can also be coordinated with metal ions to obtain metal complexes with various structures and properties,and salamo-type ligands and their diverse complexes are playing an increasingly important role in ion detection,coordination chemistry,spectroscopy,catalysis and other disciplines.In this thesis,three fluorescent chemosensors HL¹,H4L² and H4L³ were designed and synthesized,and their recognition performance and mechanism were investigated by means of fluorescence spectroscopy and theoretical calculations.In addition,novel Ni（Ⅱ）complex of H₄L³ was obtained and characterized by X-ray single crystal diffraction,IR and some other experimental methods.1.A fluorescent chemosensor HL¹ was synthesized,which contains a pyridine group and thus forms a novel N₃O ligand cavity.The fluorescence chemosensor HL¹exhibits efficient selective recognition of Cu²⁺and relatively excellent anti-interference ability.The mechanism of Cu²⁺recognition by HL¹ was investigated by means of titration experiments,Job’s working curve and density functional theory（DFT）.2.A fluorescent chemosensor H4L² was designed and synthesized,which was structurally innovative by introducing salicylaldehyde molecule on one side,shaped like a unilateral arm.This single-armed sensor can achieve the detection of Al³⁺in DMF-water solution,and the addition of Al³⁺makes the sensor solution exhibit strong yellow-green fluorescence under 365 nm UV lamp.The mechanism of Al³⁺recognition by H4L² was also investigated by means of titration experiments,Job’s working curve,and density functional theory（DFT）.3.A novel double-armed salamo-based fluorescent sensor H4L³ was designed,which is an improvement of the explored single-armed fluorescent sensor H4L² by introducing two symmetric salicylaldehyde molecules using a simple one-pot reaction with a relatively simple reaction process.The sensor was able to achieve recognition of both tryptophan and Al³⁺efficiently and selentively.The recognition mechanisms of the H4L³ were analyzed and studied by mass spectrometry,DFT calculation results and some other experimental tests.4.The structurally novel L³-Ni（II）complex was obtained by the coordination of the double-armed salamo-type ligand H4L³ and Ni（II）atoms.The structure of the Ni（II）complex was determined by the characterization methods such as ¹H NMR,elemental analysis,and X-ray single-crystal diffraction.The Ni（II）complex is formed by the ligand H4L³ and the Ni（II）atoms at a ratio of 1:3 coordination pattern.One of the Ni（II）atom enters the upper N₂O₂ cavity,while the other two Ni（II）atoms are coordinated by bridging with the acetate moieties at the positions of the two salicylaldehyde arms,respectively,which is quite novel structure.The Ni（II）complex were also characterized by infrared spectroscopy,UV-vis spectroscopy,and density functional theory（DFT）calculations as well as Hirshfeld surface analysis.