Synthesis, Structure And Luminescent Properties Of Zinc-Lanthanide Hetero-Metallic Schiff-base Complexes

There is considerable interest in the chemistry of luminescent lanthanide materials due to potential application in biology, medicine and materials science. For lanthanide ions, because the f-f transitions are parity forbidden, the absorption coefficients are normally very low and the emissive rates are low. Organic ligands with strongly absorbing chromophores which transfer energy to the lanthanide can be used to overcome this drawback (antenna effect). Series of Zinc-Lanthanide hetero-metallic Schiff base complexes are designed, prepared and characterized and their photophysical properties were studied. The main contents are described as follows:Chapter one describes the latest developments in the sensitization of near-infrared luminescence by organic ligands or organic ligands-transition metal complexes and their potential application in luminescent bio-sensing, bio-imaging and luminscent materials. Furthermore, the design strategies and the research topic of the thesis are presented in the end of this chapter.Chapter two describes the synthesis, structural characterization and photoluminscent properties of series of Zinc-Lanthanides heterobimetallic complexes. Introduction of 2-furyl,2-thienyl, pyridyl or 4-(N-carbazyl)phenyl by the Stille coupling or Sonogashira coupling reaction to give novel o-Vanilin derivatives 2a-2h; Reaction of 2a～-2h with ethylenediamine lead to the Schiff-base Ligands H2Lm(m=1～7); Schiff-base Ligands H2Lm(m=1～7) react with Zinc(II) Acetate Dihydrate in Methanol to give the Zinc complexes of Schiff-base ZnLm(m=1～7); The Zinc-Lathanide heterobimetallic complexes ZnLnLm(L1-L3:Ln=Nd, Yb, Er, Tb, Eu, Gd; L7:Ln=Nd, Gd) are obtained by refluxing ZnLm(m=1-7) and Lanthanide(Ⅲ) Nitrate in Acetonitrile. The luminescence properties of the bimetallic complexes were determined and displayed metal-centre (MC) near infrared (NIR) emission coming from the Nd(Ⅲ), Er(Ⅲ) and Yb(Ⅲ) ions at room temperature, Relationship between the ligands with different functional group and the NIR emission was discussed. In Chapter 3, Asymmetric Shciff-base Liand 3a and 3b are obtained by controlling of reaction ratio of phenylenediame and o-Vanillin derivatives, their Zinc complex ZnL8, (ZnL9and ZnL10) are obtain by ’one pot, two step’reaction of 3a (or 3b) with Zn(AcO)2 and a different aldehyde sequentially; Asymmetric Schiff-base Zinc-Lanthanides heterobimetallic complexes (ZnLnL8, ZnLnL9) are obtained from refluxing of ZnL and Ln(NO3)3, Their luminescent properties are determined and the effect of various substitute to the Near-Infrared emission efficiency is discussed.In chapter 4, using Salen Schiff-base Zn(Ⅱ)-Nd(Ⅲ) bimetallic complexes as precursor, reaction with thiocyanate, cyanate, pyridine-4-caboxylate, terephthalate or Fumarate produce either macromolecules (Ⅳ-1、Ⅳ-2、Ⅳ-3、Ⅳ-4 andⅣ-8) or coordination polymers (Ⅳ-5、Ⅳ-7). The structures of the complexes are ascertained by X-ray crystallography. The relation between photoluminescent efficiency and structure are discussed.Chapter 5 shows the synthesis of a series of nonanuclear Lanthanides complexes [Ln9(μ3-O)2(μ2-OH)8(μ1-L11)8 (L12)8]·xCH3OH (Ln=Eu, Tb, Er, Gd, Yb). The complexes are characterized by Infrared spectrum, Mass spectrometer and X-ray crystal diffraction. The UV-Visible absorption, Photoluminescent and Near-Infrared emission are studied.