Synthesis,Characterization,Application And Theoretical Research Of Carboxyl Bis-schiff Base And Their Metal Complexes

Bis-Schiff base is an excellent organic ligand,which regulates the coordination sites such as O,S,N in its structure and can form different coordination modes with transition metal ions.The diversity of the structure of the Bis-Schiff base determines the universality of its application.It is of great significance to synthesize novel bis-Schiff bases and their complexes and to develop new applications.In this paper,three kinds of 17 Bis-Schiff bases and their complexes have been synthesized,which are o-carboxybenzaldehyde Bis-Schiff bases?L1^L3?and their complexes?M1^M3?,2,6-diaminopyridine Bis-Schiff base?L4^L6?and their complexes?M4^M6?,L-histidine Bis-Schiff base?L7^L8?and their complexes?M7,M7',M8?.The structure and properties of the synthesized Bis-Schiff base and their complexes were characterized by X-ray single crystal diffraction data,NMR,MS,IR,UV-Vis,fluorescence spectra and thermogravimetric analysis.The modified glassy carbon electrode was prepared by electrodeposition of o-carboxybenzaldehyde-ethylenediamine Bis-Schiff base copper complex.The modified glassy carbon electrode was characterized by cyclic voltammetry,scanning electron microscopy and AC impedance.The results showed that the complex formed a layer of polymer film on the surface of glassy carbon electrode.The electrochemical behavior of benzoic acid in modified glassy carbon electrode was studied by cyclic voltammetry.The results showed that the oxidation peak current had a good linear relationship with the concentration of benzoic acid in the range of 0.001² mmol·L^-1.the detection limit is 0.27?mol·L^-1?SNR 3?.The method has been applied to the determination of benzoic acid in practical samples with satisfactory results.A modified glassy carbon electrode was prepared by electrodeposition with2,6-diaminopyridine-o-carboxyl benzaldehyde Bis-Schiff base cobalt complexes.The electrochemical behavior of paracetamol?PR?and 4-aminophenol?4-AP?on the modified glassy carbon electrode was studied by cyclic voltammetry.The results showed that the oxidation peak?anodic peak?of 4-AP and PR was significantly higher than that of bare glassy carbon electrode.The peak potential difference was 288mV,which could detect PR and 4-AP simultaneously.PR and 4-AP were Simultaneously detected by differential pulse method.The oxidation peak current and concentration of PR and 4-AP showed a good linear relationship in the range of 5³0?mol·L^-1,the detection limit is 1.64×10^-5 mol·L^-1 and 2.39×10^-5mol·L^-1.The method has been applied to the simultaneous determination of PR and 4-AP in paracetamol tablets with satisfactory results.The results of UV-Vis diffuse reflectance spectroscopy show that the L-histidine-ethanediamine Bis-Schiff base cobalt complexes have semiconductor properties.The photocatalytic degradation effect of cobalt complex on methylene blue?MB?solution was studied by spectrophotometry.When the mass concentration of cobalt complex was 0.1mg·m L^-1 and the illumination time was 220 min,the degradation rate was 78.30%.The structure of three o-carboxybenzaldehyde Bis-Schiff bases metal complexes and2,6-diaminopyridine Bis-Schiff base metal complexes have been optimized by using density functional theory?DFT?method.The highest occupying track energy,the net charge of metal atom and other parameters are compared with the oxidation potential in cyclic voltammetry curve.The results show that the theoretical calculation is consistent with the cyclic voltammetry.The molecular frontier orbitals,total density of states?DOS?and local density of states?PDOS?of L-histidine-ethanediamine Bis-Schiff base cobalt complexes have been calculated by first principles.The results show that the cobalt complexes have semiconductor properties.The theoretical results are in good agreement with the experimental results.Based on the theoretical results,the photocatalytic degradation mechanism of methylene blue was obtained.