| In the process of structural phase transition,the molecular motion phase transfer solid state functional materials can easily cause the abrupt change of their physical properties,such as electrical,optical,magnetic,thermal,etc.Especially switchable dielectric-ferroelectric phase transition functional materials have important application value in electronic communications,data storage,optical sensing and laser devices and other frontier fields.Chain-like amino acids,due to their molecular flexibility,are easy to form multi-component supramolecular cations with spatial writhing,swinging and rotation through complex hydrogen bond interactions with crown ether molecules.The structural elements of small molecular metal complexes have good regulatory properties,and are easy to fill the hydrogen-bonding supramolecular system to form a new self-assembly system of one-dimensional chain,two-dimensional layer and three-dimensional network.The motion of the frame is often accompanied by a reversible phase transition,causing multifunctional properties such as dielectric,ferroelectric,piezoelectric,optics and magnetism.In the paper,18-crown-6 was used as the main body,with amino acids with different chain lengths[Glycine,?-Alanine,DL-Alanine,4-aminobutyric acid,L-Aspartic acid,and L-Isoleucine]as guest molecules respectively.A variety of transition metal complexes were introduced to design and synthesize 9kinds of crown ether amino acid-transition metal complexes that have not been reported in the literature:(Gly)(18-crown-6)(Zn Cl2OH2)(1)?(Gly)2+(18-crown-6)2(Mn Cl4)2-(2)?(Gly)2+(18-crown-6)2(Co Cl4)2-(3)?(?-Ala)(18-crown-6)(Zn Cl2OH2)(4)?(?-Ala)4+(18-crown-6)2(Mn Cl4)22-(5)?(DL-Ala)+(18-crown-6)2(Fe Cl4)-(6)?(GABA)+(H3O)+(18-crown-6)(Zn Cl4)2-(H2O)(7)?(L-Asp)+(18-crown-6)(Fe Cl4)-(8)?(L-Ile)+(18-crown-6)3(Fe Cl4)-(H2O)2(9).The structure and properties of the above materials were analyzed and studied by means of variable temperature infrared spectrum,X-ray single crystal diffraction,thermogravimetric analysis,dielectric constant test,ferroelectric test and other analysis methods.Glycine-crown ether cations in compound 1-3 occur oscillate dynamically in one dimensional chain and three dimensional network structures.Compounds 1 and 3 have obvious abnormal dielectric peaks near240-260 K and exhibit relatively perfect hysteresis loops,which belongs to good ferroelectric functional materials.Compound 2 has a step-like dielectric response near 220 K and 250 K,which is a reversible step-like switching dielectric material.The amino acid cations in compound 4-6 interacts with the metal complexes by hydrogen bondings,forming a one-dimensional chain(5)two-dimensional layer(6)three-dimensional network frame(4)structure.Reversible dielectric anomaly peaks were produced near240-280 K in all three compounds by frame deformation.Among them,compound 4(Ps=0.18?C/cm2)showed ferroelectric properties similar to classical Rochelle salts(Ps=0.20?C/cm2).The long chain amino acids of compound 7-9 have obvious dynamic oscillations in supramolecular structure.This causes obvious phase transfer in space group,DSC,variable temperature XRD,etc and generates reversible dielectric anomalies.All three compounds belong to novel hydrogen-bonding dielectric-ferroelectric materials. |
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