Synthesis,Structure And Properties Of Chiral 3d/4f Metal Compounds And Metallogels

Chiral metal compound is an important branch of metal compounds,which firstly used in chiral asymmetric catalysis.In recent years,chiral metal compounds have received more and more attention from chemists,because they possess many advantages,such as flexible coordination modes,diverse coordination sites,and exhibit great potential in ferroelectric materials,nonlinear optics,magnetic materials and chiral recognition.In crystallography,chiral metal compounds crystalizing in chiral space group show great superiority and excellent prospect in constructing molecular ferroelectric.The research of metallogels is a new field in supramolecular chemistry.The synthesis of metallogel is similar to that of metal compounds.Introducing metal components into gelators provides an effective strategy to develop soft materials with advantageous properties such as:luminescence,magnetic response activity,self-healing activity,etc.A close relationship between crystallization and gelation also emerged as a major factor for the synthesis and application of metallogels,because there are metallogel–crystallization transition and crystallization–metallogel transition in responsive to multiple external stimuli.However,few studies concerns on the structural relationship and transformation mechanism between metal compounds and metallogels,because the theory is not perfect.In order to improve the potential applications of chiral metal compounds and metallogels,thirteen new compounds and four multifunctional metallogels have been synthesized by the reactions of reduced Schiff-base ligands with transition metallic or lanthanides ions in this thesis.Among of them,seven chiral metal compounds were prepared by metallogels,and one high-temperature metallogel comes from the chiral4f metal compound.Then,further researches were performed on their reasonable mechanism and applications.The main contents are as follows:1.A series of chiral Zn-MOFs（1-3）and Co-MOFs（4）were constructed through utilizing the reduced Schiff-base ligand L-HL with Zn（II）ions and Co（II）ions.The crystal structures of the compounds 1-4 were determined by X-ray crystallographic methods,and some of them were characterized by other methods,such as element analyses,IR,PXRD and so on.What’s more,dielectric property,thermal behavior and ferroelectricity were performed to further confirm the polar character of compound 4.Ferroelectric measurements reveal that compound 4 displays obvious electric hysteresis loop of ferroelectricity when test frequency are 0.1 Hz and 1 Hz at the room temperature.2.Two hydrogels were synthesized by the chiral ligands（L-L1 and D-L1）and Zn（II）ions,and their rheological properties and response characteristics（mechanical,thermal,and chemical reaction）were studied.The porous structures of the hydrogels were observed by SEM.Furthermore,a pair of chiral Zn-MOFs（compound 5 and 6）were prepared through metallogel to single crystal transformation.The structures of compound 5 and 6 were determined through X-ray single crystal diffraction analysis,which were 3D structures,and the diameter of the channel is 18?.CD spectra verify compound 5 and 6 are a pair of enantiomers.3.A multi-functional chiral metallohydrogel was constructed through using chiral ligand（S-HL）and Zn（II）ions.The as-synthesized metallohydrogel is remarkably performed as a visual sensor for the recognition of（R）-phenylglycinol and（S）-phenylglycinol.After adding（S）-phenylglycinol in the metallohydrogels,the metallohydrogel remained stable whereas gel collapsing and precipitation was observed for（R）-phenylglycinol under identical conditions.Furthermore,the metallohydrogel presents a significant capacity for adsorption and enrichment of Cr（IV）in aqueous solution,and the removal rate of Cr（VI）was almost over 90 percent.To gain insight into the gelation mechanism,scanning electron microscopy（SEM）was carried out to directly obtain the morphological details of metallohydrogel.Interestingly,compound 7 was directly synthesized by the metallohydrogel,and compounds 10-12 were synthesized by layering the metallohydrogel with solid salt.Compound 8 was successfully constructed via single-crystal to single-crystal（SC-SC）transformation.Compound 9 was directly synthesized by the coordination reaction between chiral ligand S-HL and Co（II）salt.Ferroelectric measurements reveal that Compound 8 does not exhibit hysteretic behaviour while compound 9,in contrast,displays obvious electric hysteresis loop of ferroelectricity.According to the point electric charge model,the saturation spontaneous polarization（P_s）is close to the expected value.4.Compound 13（Pr₇）was constructed through utilizing the reaction of L-H₂L and Pr（III）salt.One of the most salient feature in the crystal structure of Pr₇ is that oxygen atoms of the carbonate anion in the core of the cluster are bonded to three equatorial Pr（III）ions in a rareμ₃-?²:?²:?²-tridentate fashion.The whole framework of the cluster exists as a helical coordination compound formed from apically linked ligands and Pr（III）ions.Variable-temperature magnetic susceptibility data were collected for compound 13,showing antiferromagnetic interactions between the Pr（III）ions.Ferroelectric properties are changing with the temperatures from low temperature（-20℃and 0℃）to high temperature（20℃）.Interestingly,Pr₇ was dissolved in pyridine,followed by heating affording the immediate formation of metallogel.For the H₂O and D₂O,the metallogel showed differing response times of gel collapsing,where makes it possible to distinguish them visually.Furthermore,SEM and TEM were carried out to directly obtain the morphological details of the metallogel.