Assembly,Structure And Ferroelectric Property Of Chiral 3d Metal Complexes

Chiral metal complexes,due to possessing chiral properties,exhibit great potential in ferroelectric materials,chiral recognition,nonlinear optics and asymmetric catalysis.In crystallography,polar point group is an essential condition to obtain ferroelectric.Chiral metal complexes crystalizing in chiral space group show great superiority and excellent prospect in constructing ferroelectric.In this thesis,eight chiral 3d metal complexes were synthesized by assembling chiral Schiff-base ligands and transition metal ions.Meanwhile,crystal structures and ferroelectricity were mainly researched.The main contents are as follows:Firstly,four complexes were synthesized through solvent volatilization utilizing a pair of chiral Schiff-base ligand(L/D-H₂L,H₂L=（R/S,E）-2-（（（1-hydroxy-3-phen-ylpropan-2-yl）imino）methyl-6-methoxyphenol）and CuCl₂?2H₂O and CuBr₂,respectively.(The formula are[Cu₄(L^2-)₂（HL^-）₂（MeOH）₂]²⁺?2Cl^-for complex 1 and 2,and[Cu₄(L^2-)₂（HL^-）₂（H₂O）（MeOH）]²⁺?2Br^-for complex 3 and 4).CD spectra verify complex 1 and 2,complex 3 and 4 are a pair of enantiomers,respectively.Single crystal analysis indicate that both complex 1 and 3 belong to chiral space group P2₁,and exhibit[Cu₄O₄]configuration including free halogen anions（Cl^-and Br^-,respectively）.What’s more,both complex 1 and 3 present obvious hysteresis loop,while ferroelectric properties are different.It is extremely rare that halogen anions have an effect on ferroelectricity in metal complex ferroelectrics.Secondly,a chiral 3D Cd-MOF（complex 5,Cd₄（R-H₂L）₄（Hina）₄）with porous structure was constructed using a chiral Schiff-base ligand（R-H₃L,R-H₃L=（S,E）-3-（（2-hydroxy-3-methoxy-benzylidene）amino）propane-1,2-diol）,auxiliary ligand（Hina=isonicotinic acid）and Cd（NO₃）₂?4H₂O by solvent thermal method.Nevertheless,complex5doesn’tshowferroelectricity.Intriguingly,（CH₃）₂NH?HCl@Cd-MOF obtained by post synthesized modification exhibits apparent ferroelectricity under the frequency of 1 KHz.The work achieved the change of ferroelectric properties from nothing to exhibiting great ferroelectric properties at high frequency.Thirdly,a 1D chain zinc-based complex 6（Zn（R-H₂L）₂）was synthesized by the coordination reaction using a chiral Schiff-base ligand（R-H₃L）and ZnBr₂,aiming to research ferroelectric behavior of thin films.Complex 6 exhibits ferroelectric properties in single crystal,thin pellet and thin film.It is important to achieve device for ferroelectrics that thin film can display ferroelectric properties.It will provide a certain reference for further research ferroelectric films.Finally,a pair of chiral trinuclear nickel-based complexes（7 and 8,Ni₃[（L-HL）₂（H₂O）₂（benzoate）₂]?2EtOH and Ni₃[（D-HL）₂（H₂O）₂（benzoate）₂]?2EtOH）were assembled by a couple of chiral Schiff-base ligand L/D-H₃L(H₃L=（2R/S）-3-Hydroxy-2-（（（E）2-hydroxy-3-methoxy-benzylidene）-amino]-butanoic acid）,Ni（ClO₄）₂?6H₂O and sodium benzoate as the bridging ligand through solvent volatilization method.Magnetic susceptibility studies illustrate that complex 7 and 8show ferromagnetic interactions between the Ni（II）centers within the trinuclear units,while antiferromagnetic interactions among inter-trinuclear units.Unfortunately,it was found that complex 7 didn’t show obvious ferroelectricty.