Studies On Synthesis, Characterization And Luminescence Properties Of Rare Earth Complexes With Multi-Amide Ligands

The luminescence properties of rare earth complexes have always attracted much attention for their uses in light-converting devices, fluorescence probes and electroluminescent devices. Studies have shown that the efficient energy transfer from ligand to center ions is the key factor to achieve rare earth characteristic luminescence. Amide ligands have the advantage in simple synthesis, adjustable structure and changeable sensitive conjugate groups, which make their complexes indicated good luminescence properties. In order to investigate the coordinating properties of different ligands with rare earth ions, and the influence of different conjugate groups of the ligands to their rare earth complexes luminescence properties, this dissertation reported the synthesis and characterization of series of multi-amide ligands L^1-12 which combined with different flexibility of framework and size of terminal group, and their rare earth complexes. The luminescence properties of the complexes have also been investigated.The dissertation includes following five chapters:1. A brief review of concepts of supramolecular and photoluminescent rare earth complexes for its luminescence principle, influence factors, investigation progress and application were summarized.2. Four series of different flexible framework of novel ligands L^1-4 using N, N-diethyl-carbamoyl as terminal groups and 24 rare earth nitrate complexes have been synthesized and characterized. From the crystal structure, it shows that the flexibility of ligands directly influence the structure of complexes. The eight dinuclear rare earth picrates complexes of ligand L¹ have also been prepared. The structures of complexes can be affected remarkably by the counter anions. Based on crystal diffraction analysis, hydrogen bonds,π…πstacking interactions in building novel supramolecular have been studied.Four ligands were involved in this chapter:L¹: N,N'-1,2-ethanediyl-bis{2'-[(N, N-diethyl-carbamoyl)-methoxy]-benzamide}L²: N,N'-1,3-propanediyl-bis{2'-[(N, N-diethyl-carbamoyl)-methoxy]-benzamide}L³: N,N'-1,4-butanediyl-bis{2'-[(N, N-diethyl-carbamoyl)-methoxy]-benzamide}L⁴: N,N'-1,6-hexanediyl-bis{2'-[(N, N-diethyl-carbamoyl)-methoxy]-benzamide}3. Five series of different flexible framework of novel ligands L^5-9 using N,N-di(n-propyl)-carbamoyl as terminal groups and 27 rare earth nitrate complexes have been synthesized and characterized. From the obtained data, it shows that the flexibility of ligands directly influence the structure of complexes, and the radii of the rare earth ions also can influence the structure of complexes with ligand L⁹Five ligands were involved in this chapter:L⁵: N,N'-1,2-ethanediyl-bis(2'-{[N,N-di(n-propyl)-carbamoyl]-methoxy}-benzamide)L⁶:N,N'-1,3-propanediyl-bis(2'-{[N,N-di(n-propyl)-carbamoyl]-methoxy}-benzamide)L⁷: N,N'-1,4-butanediyl-bis(2'-{[N,N-di(n-propyl)-carbamoyl]-methoxy}-benzamide)L⁸: N,N'-1,6-hexanediyl-bis(2'-{[N,N-di(n-propyl)-carbamoyl]-methoxy}-benzamide)L⁹: 2,5-bis{2'-[N,N-di(n-propyl)-carbamoyl-methoxy)-phenyl]}-1,3,4-oxadiazole4. Three series of different flexible framework of novel ligands L^10-12 using N-benzyl- carbamoyl as terminal groups and their 18 rare earth nitrate complexes have been synthesized and characterized, 1D zigzag coordination polymer of rare earth complexe with ligand L¹² can be synthesized by changing the terminal group.Three ligands were involved in this chapter:L¹⁰: N,N'-1,3-propanediyl-bis[2'-(benzyl-carbamoyl-methoxy)-benzamide]L¹¹: N,N' -1,6-hexanediyl-bis[2 '-(benzamide-carbamoyl-methoxy)-benzarnide]L¹²: 2,5-bis[2'-(benzyl-carbamoyl-methoxy)-phenyl]-1,3,4-oxadiazole5. Photoluminescence studies of europium and terbium complexes show:(1) The luminescence properties of rare earth ions were sensitized by ligands which have the conjugate groups like benzamide, N, N-diethyl-carbamoyl, N, N-di(n-propyl)-carbamoyl, N-benzyl-carbamoyl, phenoxy, 2, 5-dibenzene-1, 3, 4-oxadiazole. Among these groups, benzamide and 2, 5-dibenzene-1, 3,4-oxadiazole display the better sensitive function.(2) While the ligands have same terminal groups and different flexible framework, the dinuclear rare earth nitrate complexes display higher intense emission than the mononuclear complexes. When the ligands have same framework, the luminescence intension of europium nitrate complexes was similar, but the terbium nitrate complexes' was changed due to the different energy transfer efficiency.(3) The energy level of the ligands L^1-12 triplet state was determinated from the phosphorescence spectrum of Gd complexes. The ligands are shown to be efficient sensitizer, particular for Tb.(4) The different coordination anions such as nitrate and picrate anions influence the lowest triplet-state energy of the ligand, and then influence the luminescence intension of europium and terbium complexes. The solvent factors influencing the fluorescent intensities are also discussed.