Synthesis, Crystal Structure Of Aromatic β-diketones And Characterization Of Eu(Ⅲ) Complexes With β-diketones

β-Diketones are well known to have two forms, that is enol and keto forms. One of the most interesting properties is the conversion between the two forms, which was termed as keto-enol tautomerism. The enol form is more stable than the keto form, and the tautomeric equilibrium can be affected by various factors such as solvent polarity, substitution groups, pH values, and UV light irradiation.β-Diketones possess a broad spectrum of useful and sometimes unique chemical properties, which makes them extremely attractive as intermediates and are used widely in the chemistry of metallocomplexes.In this paper, the property and structure of theβ-diketones complexes and the study for rare metal complexes withβ-diketone ligands have been reviewed. Fifteenβ-diketones, fifteen 1H-pyrazoles, Fifteen lanthanide binary and ternary complexes with fiveβ-diketone ligands were synthesized.1. Fifteenβ-diketones complexes were synthesized from aromatic ketone and ester by classical Claisen condensation using NaNH₂ as strong base. Their compositions and structures were characterized by means of UV, IR, ¹HNMR and MS. Fourβ-diketones complexes were characterized by X-ray single-crystal diffraction. UV results show that they are a kind of good UV-A ultraviolet absorbents in UV region from 320 to 400nm; ¹HNMR results show thatβ-diketones complexes have two forms and predominately exist in the enol form in chloroform (>90%); The X-ray crystal structure analysis revealed that fourβ-diketones complexes exist in the solid state as enol tautomers only stabilized by the stronger intramolecular hydrogen bond.2. Fifteen 1H-pyrazoles complexes were synthesized fromβ-diketones and Hydrazine monohydrate. Their compositions and structures were characterized by means of IR, ¹HNMR and MS. MS results show that 1H-pyrazoles complexes exist in dimer form for the intermolecular N-H…N hydrogen bonds.3. Fifteen lanthanide Eu(III) binary and ternary complexes, withβ-diketones, phenanthroline and bipyridine were synthesized. Their compositions and structures were characterized by means of IR, ¹HNMR, elemental analysis and TG/DTG. IR results show that theβ-diketones ligands were coordinated to the metal ions acting as enol form, the main absorption peaks of the ligands in IR spectra were red-shifted for the influence of chelating effect. Luminescence Spectroscopy of these complex results show that complexes emit red fluorescence and the fluorescence intensity of the ternary complex is better than that of the duality , but phenanthroline indicate a more efficient ligand-to-metal energy transfer than bipyridine.