Synthesis And Spectroscopic Properties Of Functionalized Bis-β-Diketones And Their Derivatives

The past decade has witnessed torrential effort devoted to the eatensive research on β-diketonates. Normally, enolisable 1,3-diketones exist in solution or in solid phase state as keto-enol tautomers. They possess a broad spectrum of useful and sometimes unique chemical properties, which makes them extremely attractive as intermediates for synthetic organic chemists. At the same time, it is well know that β-diketonate complexes represent a typical class of metal-chelating agent, as a result of forming very stable chelate complexes with most metal ions. The importance of 1,3-diketones in synthetic organic chemistry and coordination chemistry and the related discipline is difficult to overstate. In this paper, we take bis-β-diketone ligands as the object of the research, six novel bis-β-diketone 1a–1f were synthesized useing easy acceccibility and cheap drug as materials. Moreover three series of derivatives were obtained.The main work is as follows:(1) Synthesis of bis-(β-diketones) ligands(1a–1f)The bis-(β-diketones) ligands were synthesized via the standard Claisen condensation between 3,5-diacetyl-2,6-dimethylpyridine the appropriate esters, including no aromatic methyl and aromatic substituent 1-phenyl, 2-chlorophenyl, 4-chlorophenyl, 4-fluorophenyl and 4-tert-butylphenyl groups, respectively, with potassium n-Bu OH in benzene to generate the bis-β-diketones ligands. 1H NMR results suggested that the enol is the dominant form for bis-β-diketone ligand in solution and soild. Their UV-vis absorption showed that the set of complexes 1a-1f excihit high extinction coefficients(log εmax34.65).(2) Synthesis of bis-(β-diketones) derivatives and complexesSix bis-1H-pyrazole derivatives was prepared from the corresponding bis-β-diketone as intermediate via condensation with hydrazine, the structure of them were confirmed by 1H NMR, FTIR, MS techniques and elemental analysis. According to the results of X-ray crystal analysis, crystallization of 2a contains one H2 O and one 2a molecule; Optical properties of 2a-2f in different solvents THF and CH2Cl2 have also been disscussed.(3) Synthesis of complexes based bis-(β-diketones)While, with these two bis-β-diketone(1a, 1f) as the first ligand and Bipy, Phen, PTP as the second ligand, 8 new europium(III) binary and ternary complexes were prepared; The study of the photoluminescence properties of these Eu(III) complexes showed that the complexes emited the characteristic fluorescence of Eu(III) ion, moreover the first ligand with extended conjugation and the introduction of second ligands possess better sensitization behavior to the lanthanide ions and indicate a more efficient ligand-to-metal energy transfer. Additionally, we also synthesised a set of novel difluoroboron β-diketonate derivatives by the corresponding new bis-β-diketone reaction with a slight excess of BF2·OEt2; especially, the compound 2b displayed the stronger fluorescence intensity and the highest fluorescence quantum yield(Φu = 0.94) in these boron compounds. The structure of all compounds was confirmed by 1H NMR, FTIR, MS techniques and elemental analysis.