Synthesis, Characterization And Properties Of Complexes With Coumarin-based Amide And Schiff Base Ligands

The design and synthesis of complexes which have special optical, electrical,magnetic and antitumoral properties is the frontier of coordination chemistry. In thisdissertation, coumarin was selected as the framework because of its excellentfluorescent and antitumoral properties, and a series of amide and Schiff base ligandswere synthesized. The structures and properties of their complexes have also beeninvestigated. This thesis is divided into five parts:1. The background of this work is concisely introduced with the emphasis on thecurrent survey of coumarin-containing compounds and luminescent lanthanidecomplexes.2. A series of coumarin-based amide ligands and their complexes are prepared andcharacterized. The research shows that these ligands can form stable complexes withmetal nitrates, and conform to 1:1 metal-to-ligand complexes. The coordinationnumber of metal ion decreases from 10 to 8 accompanied with the increase in volumeof terminal groups.Six ligands were involved in this section:L¹: 2,2-(4-methyl-2-oxo-2H-chromene-6,7-diyl)bis(N,N-diethylacetamide);L²: 2,2-(4-methyl-2-oxo-2H-chromene-6,7-diyl)bis(N,N-diisopropylacetamide);L³: 2,2-(4-methyl-2-oxo-2H-chromene-6,7-diyl)bis(N,N-dibenzylacetamide);L⁴: 2,2-(4-methyl-2-oxo-2H-chromene-6,7-diyl)bis(N,N-diphenylacetamide);L⁵: 2,2-(4-methyl-2-oxo-2H-chromene-6,7-diyl)bis(N- benzyl-N-methylacetamide);L⁶: 2,2-(4-methyl-2-oxo-2H-chromene-6,7-diyl)bis(N- benzyl-N-ethylacetamide).3. The fluorescent and biological properties of the above complexes wereinvestigated. The results indicate that the different terminal groups influence thefluorescent properties of europium and terbium complexes. The antitumor resultsshow that only L⁵ and its complex have good effects.4. A new chemosensor for Fe³⁺ based on the coumarin fluorophore is designed andsynthesized. The binding properties of this ligand (L⁷: (N-(1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl)-2-oxo-2H-chromene-3-carboxamide))on metal ions was investigated in HEPES aqueous buffer (pH=7.2). The resultsshow that this new ligand can recognize Fe³⁺.5. Based on the strategy of Hg²⁺-promoted desulfurization and cyclization ofthiourea, we design and synthesize a fluorescent sensor for Hg²⁺ (L⁸:ethyl-8-((2-carbamothioylhydrazono)methyl)-7-hydroxy-2-oxo-2H-chromene-3-carbo-xylate). The binding properties of this ligand on metal ions were investigated. Theresults indicate that this ligand can selectively recognize Hg²⁺.