Synthesis And Properties Of Coumarin Acylhydrazone Fluorescent Probe

Compared with traditional analytical methods,fluorescent probes have become a versatile tool for analytical sensing due to their high sensitivity,fast response time,and technical simplicity,which can accurately,efficiently and conveniently detect various cations,anions and small molecules.In this paper,two intermediates diethylaminocoumarin-3-carboxyl hydrazide（B）and 5,6-benzocoumarin-3-carboxyl hydrazide（D）were designed and synthesized using coumarin as the parent material.Subsequently,three fluorescent probes ZY-1,ZY-2 and ZY-3 were obtained by condensation reaction with different aldehydes.The strong and stable fluorescence emission of the coumarin moiety and its excellent structural flexibility,together with the flexible and versatile nature of the acylhydrazone moiety,make the probes ZY-1,ZY-2and ZY-3 excellent multi-dentate chelators that can be combined with transition metals to form a variety of complexes for the detection of a range of cations,anions and small molecules in the environment.The specific content is as follows:In Chapter 2,the fluorescent probe ZY-1 was synthesized by the condensation of 7-（diethylamino）-2-oxo-2H-chromene-3-carbohydrazide and 4-（diethylamino）-2-hydroxybenzaldehyde.The structure of ZY-1 was determined by ¹H NMR,¹³CNMR and ESI-MS.When excited at 490 nm,the probe ZY-1 exhibited high selectivity towards Al³⁺with fluorescence color changed from colorless to orange and prominent fluorescence enhancement at 592 nm in DMSO/H₂O（9:1,v/v,p H=7.4,HEPES=0.2 m M）solution,and the recognition process was hardly affected by other cations.The detection limit for Al³⁺was calculated to be 3.42×10^-9 M while the association constant was determined to be 2.13×10⁴ M^-1.The binding ratio of ZY-1 to Al³⁺was obtained as 2:1 according to the Job’s plot.Subsequently,the complex ZY-1-Al³⁺was constructed for the specific recognition of H₂PO₄^-among common anions.The emission intensity of ZY-1-Al³⁺complex at 592 nm was quenched with the addition of H₂PO₄^-and the LOD was 1.1×10^-8 M.The sequential recognition characteristics of ZY-1 to Al³⁺and H₂PO₄^-had been researched through Job’s plot,¹H NMR titration,ESI-MS,cyclic experiment and UV-Vis spectra.Furthermore,the probe ZY-1 was successfully applied in detection of Al³⁺in real water samples.In Chapter 3,the fluorescent probe ZY-2 was synthesized by the condensation of 3-oxo-3H-benzo[f]chromene-2-carbohydrazideand4-（diethylamino）-2-hydroxybenzaldehyde.The structure of ZY-2 was determined by ¹H NMR,¹³CNMR and ESI-MS.The fluorescent probe ZY-2 was developed for sequential detection of Al³⁺and F^–in absolute ethanol.when Al³⁺was added,the fluorescent probe ZY-2 showed a significant fluorescent enhancement at 630 nm under excitation at 440 nm.Meanwhile,the fluorescence color of ZY-2 changed from colorless to bright red,and then the color of complex ZY-2-Al³⁺returned to colorless after the addition of F^-.The fluorescence probe ZY-2 and the complex ZY-2-Al³⁺had strong anti-interference ability to other metal ions and non-metal ions.The detection limit of fluorescent probe ZY-2 for Al³⁺was calculated to be 7.05×10^-8 M while the association constant was determined to be 1.29×10⁵ M^-1,and the LOD of complex ZY-2-Al³⁺for F^-was as low as 2.34×10^-8 M.The binding ratio of ZY-2 to Al³⁺was obtained as 1:1 according to the Job’s plot.The sequential recognition characteristics of ZY-2 to Al³⁺and F^-had been researched through Job’s plot,¹H NMR titration,ESI-MS,cyclic experiment and UV-Vis spectra.Furthermore,the probe ZY-2 was successfully applied in detection of Al³⁺and F^-in real water samples.In Chapter 4,the fluorescent probe ZY-3 was synthesized by the condensation of 3-oxo-3H-benzo[f]chromene-2-carbohydrazide and 2,4-dihydroxybenzaldehyde.The structure of ZY-3 was determined by ¹H NMR,¹³C NMR and ESI-MS.The fluorescent probe ZY-3 exhibited a highly sensitive recognition towards Al³⁺in absolute ethanol.With the addition of Al³⁺,the fluorescence intensity of ZY-3 at 567 nm dramatically enhanced under excitation at 420 nm and the fluorescence color of ZY-3 changed from colorless to yellow.The competition experiments showed that probe ZY-3 was almost free from other cations.The detection limits of fluorescent probe ZY-3 for Al³⁺was calculated to be 2.89×10^-8 M while the association constant was determined to be 1.85×10³ M^-1.The binding ratio of ZY-3 to Al³⁺was obtained as 1:1 according to the Job’s plot.Meanwhile,the complex ZY-3-Al³⁺exhibited a significant solvatofluorchromic characteristic and could be used to detect water content in organic solvents such as methanol,ethanol,n-butanol,isopropanol and acetonitrile,with the LODs were 0.013%、0.037%、0.013%、0.008%、0.072%（v/v%）,respectively.The recognition characteristics of ZY-3 to Al³⁺and H₂O had been researched through Job’s plot,¹H NMR titration,ESI-MS,and polarity experiment.Furthermore,the probe ZY-3 was successfully prepared into test paper for the detection of Al³⁺and the complex ZY-3-Al³⁺had been successfully applied to the testing of water content in organic solvents and to the testing of alcohol content in commercially available Baijius.