The Studies On Syntheses Of New Oxime Compounds And Their Recognition Properties For Cations

How to accurately identify the metal cations in the test sample by using simple instruments or even naked eye observation is a research hotspot in environmental protection,chemical analysis and life sciences,and cationic probe molecules are the better choice for solving this problem with the advantages of low cost,easy synthesis,good selectivity,strong anti-interference ability and high sensitivity,compared with traditional detection methods?coordination titration,spectrophotometry,chemiluminescence,electrochemical analysis,chromatography,atomic spectroscopy,mass spectrometry and on-line coupling?,so the design and synthesis of cationic probe molecules are the key to efficient detection of cations.New oxime-type probe molecules are one of the common reagents for metal cation chelation because of their good coordination ability and optical,electrical,magnetic and biological activities,and Salamo-type probe molecules are a kind of organic probe molecules of bisoxime-type,with structural units of Ar-CH=NO-?CH₂?_n-ON=CH-Ar',and by changing the linked substituents-Ar or-Ar'it is possible to construct novel structures such as half Salamo-,symmetrical Salamo-,asymmetrical Salamo-and bis?Salamo?-type,etc,selectively sensitive cation-recognizing probe molecular materials owning important research significance.1.Two novel tridentate oxime-type probe molecules HL¹ and H₂L² with benzene ring as signal reporting group,phenolic hydroxyl group and thiol group as recognition groups are designed and synthesized,their structures are characterized by elemental analysis,solubility testing,¹H NMR,IR and X-ray crystal diffraction analysis techniques,and the recognition properties of HL¹ and H₂L² to 11 kinds of cations(Zn²⁺,Cd²⁺,Hg²⁺,Cu²⁺,Cr³⁺,Ni²⁺,Co²⁺,Fe²⁺,Mn²⁺,Al³⁺and Pb²⁺)in methanol solution are investigated.The colorimetric experiments show that both probes HL¹ and H₂L² can be used as the colorimetric probe for Cu²⁺ions?blue becomes grass green?.UV-visible spectroscopy analyses show that in methanol solution for Cu²⁺ions the probe molecule HL¹ has good UV-visible spectroscopy selectivity?ICT,LMCT?,strong anti-interference,and the coordination ratio of HL¹ to Cu²⁺is 1:1,the binding constant is 9.98×10¹³(mol L^-1)^-1,the minimum detection limit is 1.05×10^-6 mol L^-1,and the probe molecule HL¹ has high sensitivity to ultraviolet recognition of Cu²⁺and can be used as an ultraviolet probe for Cu²⁺.Fluorescence spectroscopy analyses reveal that the probe molecule HL¹ has good fluorescence selectivity for Zn²⁺in methanol solution,and can distinguish Zn²⁺and Cd²⁺from anti-interference,and the coordination ratio of HL¹ to Zn²⁺is 1:1,the binding constant is 7.09×10¹¹(mol L^-1)^-1,the minimum detection limit is 2.84×10-7 mol L^-1,and HL¹can be used as a fluorescent probe for Zn²⁺.The nuclear magnetic titration experiments and Gaussian?DFT density functional theory?calculations indicate that the fluorescence quenching recognition mechanism of the probe molecule HL¹ for Cu²⁺is the photoinduced electron transfer process?PET?between the recognition group of the probe molecule and the signal reporter group,and the enhanced fluorescence recognition mechanism of the probe molecule HL¹ for Zn²⁺is of its hindered PET process.2.A novel tetradentate oxime-type probe molecule H₂L³ with naphthalene ring and benzene ring as signal reporting groups,phenolic hydroxyl and thiol as recognition groups is designed and synthesized,the single crystals of Zn²⁺,Co²⁺,Ni²⁺,and Cu²⁺complexes of it are cultured by solvent evaporation methods,their structures are characterized by elemental analysis,¹H NMR,IR and X-ray crystallographic analyses,and then the colorimetric,the ultraviolet-visible and the fluorescence recognitions of the probe molecule H₂L³ to various cations(Zn²⁺,Cd²⁺,Hg²⁺,Cu²⁺,Cr³⁺,Ni²⁺,Co²⁺,Fe²⁺,Mn²⁺,Al³⁺and Pb²⁺,etc.)are carried out in alcohol solutions to investigate the effects of its recognition.The colorimetric experiments show that the probe molecule H₂L³ can highly sensitive colorimetric recognize of Cu²⁺,Co²⁺,Ni²⁺and Fe²⁺cations.The UV-visible selectivity experiments show that the probe molecule H₂L³ can be used as ultraviolet probes to recognize cations such as Cu²⁺,Ni²⁺,Co²⁺,Zn²⁺,Fe²⁺and Mn²⁺,but the interference between the cations is relatively strong,which can be pre-excluded by colorimetric methods,etc,and the UV-visible spectrums after coordination are red-shifted?the smaller band gap value?,which can be originated in the intramolecular charge transfer?ICT?and the ligand metal charge transfer transition?LMCT?.The UV-visible titration experiments show that the recognition order of the probe molecule H₂L³ to metal cations in methanol probably is Ni²⁺,Co²⁺,Cu²⁺and Zn²⁺,which may be rooted to the low energy of?3d4s?orbitals and?d-electron?of Ni²⁺,Co²⁺,Cu²⁺ions against the high energy of?4s?orbital of Zn²⁺.The fluorescence recognition solvent effect experiments show that DMSO,DMF,ethanol and methanol can be used as the solvent system for H₂L³fluorescence recognition of Zn²⁺.The fluorescence recognition selectivity experiments show that the probe molecule H₂L³ has good fluorescence selectivity to Zn²⁺in ethanol solution(distinguishing Zn²⁺from Cd²⁺ions).The fluorescence recognition cation competition experiments show that the metal cations with higher coordination ability with H₂L³ are Cu²⁺,Ni²⁺,Co²⁺,Cr³⁺,Zn²⁺and Al³⁺which are of larger interference in the fluorescence recognition process of the probe molecule H₂L³ to Zn²⁺,and the three-factor experiments with ions masking agents are preliminarily designed to eliminate those interference.The anion coordination selection and competition experiments show that NaEDTA has a fluorescence quenching effect on H₂L³-Zn²⁺,indicating that NaEDTA has a larger complexing constant for Zn²⁺,alkaline substance can enhance the fluorescence intensity of the probe molecules H₂L³and H₂L³-Zn2+,while acidic substance can be the opposite,as a result the acid and base can be used as the reversible reagents to realize the recycling of the probe.The acid-base effect of recognition experiments indicate that the probe molecule H₂L³ can recognize Zn²⁺well in a wide pH range?5.0¹0?.The fluorescence titration experiments show that the coordination ratio of probe molecule H₂L³ to Zn²⁺is 2:3,the binding constant is 2.85×10¹²(mol L^-1)^-4,and the minimum detection limit is 1.89×10^-6 mol L^-1.The fluorescence Job experiments show that H₂L³ and Zn²⁺tend to form a complex with a coordination ratio of 3:2 in the H₂L³excess ethanol solution,while in the Zn²⁺excess ethanol solution,H₂L³ and Zn²⁺tend to form a complex with the coordination ratio of 2:3.Job,nuclear magnetic experiments and Materials Studio?MS?simulation calculations show that the fluorescence detection of Zn²⁺by H₂L³ is carried out step by step,and it is speculated that the recognition mechanism may be due to the inhibition of PET process leading to fluorescence enhancement.The single crystal structure data are in good agreement with the spectral data and simulation calculations.3.Two novel pentadentate oxime-type probe molecules?H₃L⁴,H₃L⁵?are designed and synthesized with weak electron-repellent phenolic hydroxyl soft group?-OH?added focusly to the signal reporting groups,and are characterized by elemental analysis,¹H NMR,IR and other techniques.The 11 metal cations(Zn²⁺,Cd²⁺,Hg²⁺,Cu²⁺,Cr³⁺,Ni²⁺,Co²⁺,Fe²⁺,Mn²⁺,Al³⁺and Pb²⁺)are added respectively to H₃L⁴ DMF solutions and H₃L⁵ DMSO solutions successively to investigate their recognition properties.The colorimetric experiments find that the probe molecules H₃L⁴ and H₃L⁵ have colorimetric recognition for Fe²⁺,Co²⁺,Ni²⁺,Cu²⁺and Zn²⁺ions,and colorimetric probes for these cations can be developed.The ultraviolet-visible spectroscopy selectivity experiments show that the probe molecules H₃L⁴and H₃L⁵ have poor selectivity for UV-visible absorption identification of cations,the interferences between various cations are numerous,and the UV-visible absorption spectra after coordination are red-shift which may be result from the intramolecular charge transfer?ICT?and the charge transfer transition?LMCT??the smaller band gap value?.From the UV-visible titration experiments that the probe molecules H₃L⁴,H₃L⁵ and Zn²⁺are both coordinated in a ratio of 2:4 can be speculated.From the fluorescence selectivity experiments that the probe molecules H₃L⁴ and H₃L⁵ had fluorescence recognition effects on Al³⁺and Zn²⁺can be found respectively.The kinetics of the probe molecule H₃L⁴ for the fluorescence recognition of Al³⁺ions show that the coordination reaction is apparently a zero-order reaction,and the apparent reaction rate is controlled by the diffusion of the Al³⁺ions,indicating that the coordination reactions are completed instantaneously,explaining the high fluorescence cognition sensitivity of these type probes.The spectral titration experiments,the UV Job experiments and the Materials Studio?MS?simulation optimization calculations show the presence of intermediate products?[{Zn?L??CH₃COO?}]?and terminal products[{Zn?L???-OAc?Zn?OCH₂CH₃?}₂]in the coordination recognition reaction of probe molecule H₃L⁵ for Zn²⁺ions,and the presence of the gradually completed from easier to easy coordination recognition process.