Ion Recognition Performance Optimization And Recognition Mechanism Research Of Ferrocenyl Imidazole Disubstituted Derivatives

The ferrocene disubstituted imidazole derivatives containing nitrogen heterocycles（L1-L4）,sulfur,oxygen,and nitrogen five-membered heterocycles（L6-L8）synthesized in the early stage of the research group,in the previous test,because the test conditions are not Optimal,resulting in suboptimal test results,and these compounds are not tested under uniform test conditions,and the test results cannot be compared.According to literature research,we found that when the probe structure is determined,its ion test conditions such as solvent,probe and ion concentration,p H value,etc.will all affect the recognition selectivity and recognition signal strength,so this paper uses optics（Fluorescence emission Spectrum,UV-Visible Spectrum）,electrochemistry（cyclic voltammetry,square wave voltammetry）,to further improve the ion recognition performance of the ferrocenyl imidazole derivatives L1-L4 and L6-L8 previously synthesized by the research group optimization.In the acetonitrile solution,the probe L1 showed high fluorescence selectivity to Al³⁺and Cu²⁺,especially at low concentrations,the selectivity to Al³⁺was better;the addition of F^-made L1 show unique dual fluorescence emission peaks.Both L2 and L4 can"recognize"Cu²⁺with the naked eye through the color of the solution from light yellow to orange.The probe L4 can be used as a fluorescent"on"probe for selective recognition of H₂PO₄^-ion.The pre-formed L1-4Al³⁺and L2-4Al³⁺solutions react to Hg²⁺It exhibits a highly selective fluorescence"off";the L1-Al³⁺and L1-4Cu²⁺solutions show the presence of Br^-and I^-through fluorescence and color changes.H₂PO₄^-can cause significant cathode displacement of the electrochemical oxidation-reduction potentials of L1 and L4(L1:ΔE_1/2=-150 m V,L4:ΔE_1/2=-140 m V).On the other hand,in a water-containing test system,by adjusting the concentration of ions,L6-L8 can selectively identify Fe³⁺,Cr³⁺,and Al³⁺through the fluorescence channel.In addition,L6-L8 can all"identify"Cu²⁺with the naked eye through the color of the solution from light yellow to orange,and the probe L7 can be used as a fluorescent"on"probe for selective recognition of HSO₄^-ion.The pre-formed L6-3Fe³⁺or L7-HSO₄^-shows a highly selective fluorescence"off"to Hg²⁺.H₂PO₄^-causes significant cathode displacement of the electrochemical oxidation-reduction potential of L7 and L8,L7:ΔE_1/2=-100 m V,L8:ΔE_1/2=-170 m V.Based on the ¹H NMR titration experiment,the analysis of the recognition results and the reference to the single crystal structure[Ag₂（L1）₂（NO₃）₂]before the research group,the reasonable coordination modes of L1-L4 and L6-L8 for the recognition ions are proposed And it was found that the more stable the complex formed by the probe with a stable five-membered ring structure or strong hydrogen bond ability,the stronger the selectivity for anions and cations.