Europium complexes 1,3-diketones

Escherichia coli nitrate reductase structure, 1438 Europium complexes -diketones, 1081 dipositive oxidation state hydrated ions, 1109... 

Assays based on luminescent lanthanide ions were developed initially in the 1970s, when instrumentation became available which could distinguish long-lived luminescence from a shortlived background. Leif and co-workers reported the first attempts to use lanthanide complexes (in this case europium complexes with 1,10-phenanthroline and 7-diketonates, i.e., [Eu(phen)(diketo-nate)3]) as tags for antibodies.107 These proved kinetically unstable in the pH regime required... 

The luminescence of various chelated compounds of the rare earths is very promising because their spectral and luminescent properties help to solve a number of theoretical and applied problems. Luminescence spectra of europium complexes with selenophene /3-diketones have been studied as a function of the ligand structure. Of the spectra obtained, m-picolinoyl-2-acetoselenophene and di-selenoylmethane look most promising for obtaining induced radiation.136... 

Pettinari et al. [49] reported a Zundel ion H5OJ stabilized tetrakis(P-diketonate) europium complex, H5O J [Eu(L" )4]. The complex anion in this ion-pair complex is charge balanced by the Zundel cations H5OJ, which is stabilized by strong H bonding with the N atoms of the anionic heterocyclic ligand The crystal structure study revealed that different [Eu(L )4] ... 

Figure 11.11 Modified diketones incorporated in the europium complexes used in OLEDs.

Uekawa, M., Miyamoto, Y., Ikeda, H., et al. (1998) Synthesis and properties of europium complexes with P-diketone ligands for orgnic electroluminescent devices. Bulletin of the Chemical Society of Japan, 71,... 

Research is going on to improve the DELFIA system , because of drawbacks such as the time-consuming conversion of the non-fluorescent RE label into a luminescent complex, or the system vulnerability to contamination by RE due to the excess of the reagents ntfa and topo. An alternative is the use of a -diketone that can be covalently bonded to proteins such as 5-(4,4,4-trifluoro-l,3-dioxobutyl)-2-thiophenesulfonyl chloride (ctta) . Since the stability of the RE + complexes formed by this ligand is quite low, a large excess of RE + has to be used to shift the equilibrium to the rare-earth complex. More stable europium complexes can be obtained by the use of tetradentate fi-diketonates, such as 7a-7d, anchored on a functionalized o-terphenyl skeleton, or 8a-8c, anchored on a biperfluorobutadiene skeleton . ... 

Six types of Eu(dik)3 complexes were accurately analyzed in the absence and presence of phen, using both infusion ESI-MS and ELD. The LOD by FLD for compounds extracted with acetonitrile were 1-100 ppb. Using ESI-MS, high sensitive and prompt discrimination of luminescent europium S-diketonates can be achieved. The combination of laser samphng and ion trap MS is a powerful analytical technique for the direct analysis of complex samples. Thus, the generation of both negative and positive ions by laser desorption directly within a quadrupole ion trap was apphed to analyze complex samples such as Cr(acac)3. ... 

Fluoroimmunoassay makes use of the above behaviour. One of the common commercial methods is dissociation-enhanced fluoroimmunoassay (DELFIA). In this, a nonfluorescent Eu(III) EDTA-like complex is attached by a simple chemical reaction to an antibody or antigen, in a process called labelling. An immunoreaction is next initiated to bind the target, and then a (3-diketone and trioctylphosphine oxide (TOPO) mixture are added to the immunocomplex formed, at pH 3, to promote release of the Eu(III) from the antibody and its complexation as the strongly fluorescent complex [Eu((3-diketonate)3(TOPO)2], which is then measured by time-resolved fluorescence methods. The signal size relates to the amount of europium complexed, which in turns relates directly to the amount of the specifically formed target immunocomplex. This process is represented schematically in Figure 9.5. 

Although, a thioester-substituted p-diketone ligand was eventually chosen for the sensor, many vinyl-substituted p-diketones were found to be unsuitable for making stable europium complexes. For example, methylene substituted... 

Obviously, p-diketone ligand influences the fluorescence of europium complexes in the same order as that of samarium complexes. However, fluorescence of terbium complexes decreases in a quite different way to that of the europium and samarium complexes in chloroform solution. Moreover, the complex formed by the p-diketone ligand TTA binding Eu(III) or Sm(III) has the most intense fluorescence in europium or samarium complexes. However, Tb(TTA)3Phen emits the weakest fluorescence in terbium complexes. Here we simply show the fluorescence declining sequence, detailed discussion would be given in section 3.4-3.5. 

Sm(lll) has a similar resonance energy level as Eu(lll). The physical and chemical properties of the two ions are also similar [11]. So samarium complexes emit fluorescence in the same sequence as that of europium complexes with different p-diketone ligands. Tb(IIl) has a higher resonance energy level. The fluorescence of Tb(Ill) complexes decrease in a different way to that of Eu(lll) and Sm(lll) complexes. Tb(acac)3Phen emits the most intense fluorescence in the terbium complexes. The reason is that the triplet state of acac is 25300 cm, much higher... 

The equivalence of silyl enol ethers and ends has been used in syntheses of -halogeno-a -unsaturated ketones, /8-keto-sulphidesand 1,3-dike-tones (Scheme 94) the 1,3-diketone (39) prepared in this manner forms a europium complex of high solubility in non-polar solvents. 

Due to the paramagnetism of most of the REM ions they are used as shift reagents in NMR spectroscopy. The J-diketonates and other chelate complexes of Eu(III) are exploited most frequently [125-127]. These compounds are rather soluble in most of organic solvents and the shift of NMR signals promoted by them is not accompanied by their broadness. At the same time it should be taken into account that in some cases the europium complexes cause the intramolecular rearrangement of the studied compound [128]. 

Nockemann P, Breuer E, Driesen K et al (2004) Photostability of a highly luminescent europium p-diketonate complex in imidazolium ionic liquids. Chem Commun 4354-4356... 

In order to compare the luminescence intensities of eirropium(lll) complexes, the ratio between the area under the emission curve of the l persensitive Dq p2 and of the magnetic-dipole allowed Do Fi can be reported. This corresponds to the intensity ratio I ( Do -> F2)//( Do Fi ). These values for different europium(III) -diketonates are listed in table 7. The higher this ratio is, the more intense is the red emission of the hypersensi-... 

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