Study On The Synthesis And Properties Of Metal Complexes With N-containing Heterocycles As Ligands

In recent years,metal complexes of N heterocycles and their derivatives have been widely used in magnetics,energy storage,biological activity,gas adsorption,ion exchange,etc.,and thus have become active frontier hot topics.In this paper,In this paper,we choose pyrazole–3–carboxylic acid and cyano as the first ligand,2,2’–bipyridine,4,4’–bipyridine and 1,10–o–phenanthroline as the second ligand,and Cu²⁺,Ni²⁺,Fe²⁺,Co²⁺metal ions as the center,four new metal complexes were synthesized by hydrothermal method.We experimentally characterized the new complexes and explored their structure and properties.At the same time,we investigated the relationship between structure and properties of the complexes synthesized in the literature through theoretical methods.The main research contents of this thesis include the following aspects:（1）We synthesize two complexes[Cu（pca）（2,2’–bpy）H₂O]₂·2H₂O（1）and[Cu（pca）（4,4’–bpy）]_n（2）(pca²⁺=pyrazole–3–carboxylic acid anion,2,2’–bpy=2,2’–bipyridine and 4,4’–bpy=4,4’–bipyridine).Complex 1 is a binuclear metal cluster.Each Cu ion in the binuclear cluster is located in a hexacoordinate twisted octahedron geometric environment,and is connected to each other through a hydrogen bond to form a 2 D–hydrogen–bonded supramolecular layered structure.In complex 2,Cu ion has a five–coordinated environment with a tetragonal pyramidal coordination mode.In 2 as the first ligand pca^2–anion and the second ligand 4,4′–bpy simultaneously bridged the copper metal ions leading to the formation of a two–dimensional coordination polymer layer structure.Due to the change of the second ligand,the distance between the metals in complex 2 is shorter than the distance in complex 1.The antiferromagnetic interaction between metal ions increases as the distance between the molecular metals decreases.The antibacterial activity of the two complexes against four bacteria was tested,and the results showed that the biological activity of complex 1 was stronger than that of complex 2.（2）Synthesis of two complexes by hydrothermal method,[Ni（1,10–phen）₂Fe（CN）₄]_n（3）,[Fe₂（1,10–phen）₄（CN）₄Co₂（1,10–phen）₂Fe（CN）₆]_n（4）（1,10–phen=1,10–phenanthroline）.In complex 3,1,10–phenanthroline is used as a terminal group ligand,and Fe²⁺and Ni²⁺ions are alternately bridged by a cyano group to form a one–dimensional zigzag chain.In complex 4,cyano–bridged Fe²⁺ions and Co²⁺ions form a stepped shape composed of the multinuclear structural unit Fe₂（1,10–phen）₄（CN）₄Co₂（1,10–phen）₂Fe（CN）₆]chain.The transition from antiferromagnetism of complex 3 to ferromagnetism 4 can be explained by the regulating effect between the metal ion and the ligand effect.（3）The magnetic properties of complex 5 such as（bmim）₂[Cu₃（μ₃–OH）（μ–Cl）（μ–pz）₃Cl₃]（5）（bmim⁺=1–butyl 3–methylimidazole,cationic,pz^–=pyrazole anion）were studied using broken symmetry（BS）approach combined with density functional theory（DFT）.The magnetic coupling constants of the complex were calculated at five basic sets（LANL2DZ,6–31G–SVP,TZVP–SVP,SDD,6–31G）by eight density functional methods（B3P86,B3LYP,PBE,PBE0,B3PW91,BP86,BLYP,M06）.The calculation results show that the data obtained are consistent with the experimental values.Among them,the coupling constant of the complex was calculated to be–99.61 cm^–1at the level of BP86//6–31G–SVP,which is the closest to the experimental value(–98 cm^–1).This shows that the energy splitting between the occupied orbits is the cause of the antiferromagnetic coupling of the complex.