Characterization,Spectroscopic,and Electrochemical Properties Of Salicylaldehyde Derivatives And Containing Pyrrole Ring Ligand And Ni(Ⅱ),Co(Ⅱ)and Cu(Ⅱ)Complexes

Due to its special properties,Schiff base compounds have always played an important role in the fields of medicine and pesticides.The Schiff base ligand synthesis method is widely studied in coordination chemistry because of its relatively simple,complex structure,good solubility,and stable complex formation with most metal ions.In recent years,Schiff base metal complexes have been rapidly developed,and many complexes containing Ni（II）,Co（II）,and Cu（II）metal ions exhibit good biological activity.In addition,Schiff base complexes have broad application prospects in analytical chemistry,catalysis,and functional materials.This paper designed and synthesized several novel organic ligands,and studied the interaction mechanism between these ligands and metal ions such as Ni（II）,Co（II）and Cu（II）,and discussed these The chemical nature of organic ligands.Specific research content includes:1.Firstly,the intermediate o-aminoacetophenone oxime was synthesized and reacted with 5-nitrosalicylaldehyde,3-pyrrole benzaldehyde and 2-pyrrole benzaldehyde to synthesize three organic ligands..HL¹:2-（5-nitro-2-hydroxyphenyl）-4-methyl-1,2-dihydroquinazoline 3-oxide;HL²:2-（3-prrole）-4-methyl-1,2-dihydroquinazoline 3-oxide;HL³:2-（2-prrole）-4-methyl-1,2-dihydroquinazoline 3-oxide.The composition and structure of the ligands HL¹-HL³ were determined by elemental analysis,nuclear magnetic resonance spectroscopy,and infrared characterization.2.The ligands HL¹ were reacted with Ni（CH₃COO）₂?4H₂O and Co（CH₃COO）₂?4H₂O to obtain two kinds of Ni（II）and Co（II）complexes single crystals.Ligand HL¹was used as the main ligand,phenanthroline was used as the auxiliary ligand,HL² and HL³ were the main ligands,and 2,2’-bipyridyl was used as the auxiliary ligand to react with Cu（NO₃）₂?3H₂O to obtain three kinds of Cu（II）complexes single crystal.The single crystal structures of the above five complexes were characterized by IR and X-ray single crystal diffraction.The chemical composition and spatial structure of the crystal were determined by X-ray single crystal diffractometer.The metal complexes are:Ni（II）complex 1:[2Ni（L²）₂];Co（II）complex 2:[2Co（L²）₂];Cu（II）complex 3:[Cu₂（L¹）（phen）₃（NO₃）₃]?NO₃?CH₃OH;Cu（II）complex 4:[2Cu₂（L²）（2,2’-bipyridine）（NO₃）]?（NO₃）₂?CH₃COOCH₂CH₃?H₂O and Cu（II）complex 5:[2Cu₂（L³）（2,2’-bipyridine）（NO₃）]?（NO₃）₂.The coordination configurations of the above five complexes and the supramolecular forces inside the crystals were analyzed,and their supramolecular structures were determined.3.The UV absorption,antibacterial activity of the complexes 1–4 and the fluorescence spectra of the complex 2 were analyzed and compared with the corresponding ligands;The electrochemical properties of complexes 1–4 and the electron paramagnetic resonance spectroscopy（EPR）of binuclear Cu（II）complex 4 were investigated.In addition,the electronic structure of complexes 1,2,and 4 were optimized by density functional theory （DFT）,and calculated the energy and band gap values of the highest occupied molecular orbital（HOMO）and the lowest unoccupied molecular orbital（LUMO）.The time-dependent density functional theory（TD-DFT）calculation of the adiabatic complexes 1 and 2 further clarifies the effect of electronic transition on the UV-visible absorption spectrum.The intermolecular interactions in the crystal structure of complexes 1–4 were quantified by using Hirshfeld surfaces analysis and Fingerprint plots analysis.