Synthesis,structures And Properties Of Amino Acid Hydroxamic Acid And Schiff Base Metal Complexes

Amino acid hydroxamic acid and amino acid Schiff base ligands have multiple coordinated N and O atoms to coordinate easily with metal ions to form metal complexes with diverse structure.It has been found that these complexes show different and unique properties in ion recognition,biological activity,catalysis,magnetic properties as well as in other aspects.We have synthesized three ligands,which is histidine hydroxamic acid,3-aminobutyric acid hydroxamic acid and o-vanillin 3-aminobutyric acid Schiff base.Fourteen compounds were obtained through the reaction of Schiff base ligand and metal salts,and their structures have been characterized through various scientific and technological methods.The main work is listed as follows:1.Three compounds were synthesized by the reactions of histidine hydroxamic acid(Hisha)ligand with Zn salts,Ni salts to obtain 3 metal compounds:[Zn₄(hisha)₄(bpy)₂]·5H₂O(1),[Ni₄(hisha)₄(py)₄]·8H₂O(2),[Ni₄(hisha)₄(bpy)₂]·6H₂O(3).They are composed of four deprotonated histidine hydroxamic acids as a tetradentate ligand and four metal ions.The results of magnetic studies show that there is a significant antiferromagnetic coupling interaction between metal ions in the temperature range of2-300K.Complex 3 does not show frequency dependence under an external DC magnetic field of 2000 Oe.2.3-aminobutyric acid hydroxamic acid ligand(H₂butyrat)reaction with different salts to obtain eight 3d-4f complexes:{Er[Cu₄(butyrat)₄]₂}·3Cl·Me OH·26H₂O(4),{Yb[Cu₄(butyrat)₄]₂}·3Cl·Me OH·26H₂O(5),{Ho[Cu₄(Butyrat)₄]₂}·3Cl·Me OH·22H₂O(6),{Dy Cu₄[(butyrat)₄]₂(N₃)}·2Br·14Me OH·3H₂O(7),{Na₂Er[Cu₈(Butyrat)₈](NO₃)₂}·NO₃·2Cl(8),{Na₂Tm[Cu₄(Butyrat)₄]₂(N₃)(H₂O)₇}·4Cl(9),{Na₂Eu[Cu₄(butyrat)₄]₂}·5Cl·2Me OH·4Me CN·6H₂O(10),{Gd[Cu₄(butyrat)₄]₂(H₂O)₂}·3Cl·2Me OH·6H₂O(11).Complexes 4-11 have similar structures.The whole complex presents a unique sandwich configuration.A cyclic core is formed through four Cu²⁺cations and four deprotonated bidentate ligands with the[Cu-N-O]repeating units to exhibit a 12-MC-4 structural motif and each face is comprised by a 12-MC-4 unit.For complexes 4-11,each Cu²⁺cation is almost located in the centers of the N₂O₂pocket formed by the deprotonated polydentate ligand.Plane distance of compounds 4-11 between the upper and lower[12-MC_Cu-4]planes are 3.552(?),3.617(?),3.616(?),3.601(?),3.551(?),3.619(?),3.612(?)and 3.659(?),respectively.The study of magnetic properties shows that the continuous decrease of the?_MT value in the temperature range of 2-300 K indicates that the significant antiferromagnetic interaction between the metal ions of complexes 4-7.With the presence of an external DC magnetic field,magnetic susceptibilities of compounds 4 and 6 exhibited temperature dependence.Complexes 5 and7 exhibited obvious temperature-dependent imaginary magnetic susceptibility signals at a dc field of 2000 Oe and 1000 Oe,respectively and the maximum peak of imaginary magnetic susceptibility signal were observed,indicating the occurrence of single-molecule magnet behavior.It is worth noting that Cu-Yb compounds with single-molecule magnet behavior have not been seen in previous studies.3.We synthesized 3-aminobutyric acid vanillin Schiff base and reacted with metal salts to acquire 3 complexes:[Co₇(van-butyrine)₃(OAc)(N₃)₄(OH)₃(OMe)₇]·5H₂O·3Me OH(12),[Co₄(van-butyrine)₂(N₃)₄(OMe)₄(H₂O)₂](13),[Na₂Ni₅(van-butyrine)₄(N₃)₂(OMe)₂(Et OH)₂(H₂O)₂](14).For complex 12,with the decrease of temperature,the value of?_MT first decreased and then rapidly increased to11.01 cm³K mol^-1at 8 K,and then the value of?_MT decreased rapidly to 9.04 cm³K mol^-1at 1.8 K for complex 12.The rapid decrease of the?_MT value represents the presence of antiferromagnetic exchange interactions.The results of magnetic studies show that the complex 12 has a slow magnetic relaxation phenomenon at a dc field of 2000 Oe...