Europium complexes luminescence

The red-luminescence (612 nm) europium complex is an excellent luminescer in commercial use however, the green-luminescence Tb +-cored dendrimer complex enables a simultaneous assay at another wavelength (545 nm). The latex formation was carried out by mini-emulsion radical polymerization of the monomers dissolving the Tb +-cored dendrimer complexes. The polymeriza-... 

Until very recently, studies of the use of luminescent lanthanide complexes as biological probes concentrated on the use of terbium and europium complexes. These have emission lines in the visible region of the spectrum, and have long-lived (millisecond timescale) metal-centered emission. The first examples to be studied in detail were complexes of the Lehn cryptand (complexes (20) and (26) in Figure 7),48,50,88 whose luminescence properties have also been applied to bioassay (vide infra). In this case, the europium and terbium ions both have two water molecules... 

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... 

Bender JL, Corbin PS, Fraser CL, Metcalf DH, Richardson FS, Thomas IiL, Urbas AM. Site-isolated luminescent europium complexes with polyester macroUgands metal-centered heteroarm stars and nanoscale assemblies with labile block junctions. J Am Chem Soc 2002 124 8526-8527. 

The europium complexes are highly luminescent, with quantum yields of up to 0.19 in methanol. The ligand triplet state is too low in energy to efficiently populate the terbium excited state, and no metal-centered emission is observed. 

Alteration of the chromophore by conversion of some of the bipyridyl groups to their N-oxide derivative leads to a significant improvement in the luminescence performance (88). Although the lifetimes of the europium complexes of ligands L54 and L55 were still less than a millisecond, the quantum yields of 0.15 and 0.20 respectively are significantly better. 

Fig. 5 Data acquisition cycles for ratiometric PDI using luminescent dyes (e.g., europium complexes) with decay times in the ps range...

Lowe, M. P., Parker, D., Reany, O., Aime, S., Botta, M., Castellano, G., Gianolio, E., Pagliarin, R. pH-dependent modulation of relaxivity and luminescence in macrocyclic gadolinium and europium complexes based on reversible intramolecular sulfonamide ligation, J. Am. Chem. Soc. 123 (2001), 7601... 

Due to the modifications of the electronic cloud induced by complexation, the quantum yield and the excitation spectrum are also modified. As the direct determination of the absolute quantum yield is very difficult to achieve, one usually finds in the literature quantum yield values determined by comparison to well-known standards, such as quinine sulfate. For example, some values can be found in Georges (1993) or in Klink et al. (2000) for some europium complexes but may be found also in many other papers on lanthanide luminescence. Studies on the correlations between the photophysical properties of a given type of europium complexes and the energy levels can be found in Latva et al. (1997), Klink et al. (2000). A correlation has been found between the excitation properties and the stoichiometry of various Eu(III) complexes (Choppin and Wang, 1997). Note that the changes in the excitation maximum induced by complexation usually amount to a few tenths of nanometers, which requires high resolution for detection. In the case of Eu(III), a correlation has been found between the frequency... 

Structure determinations of salts containing [R c P5W30O110]12-, R = Y, Eu, and a redetermination of the sodium derivative, showed that the central cavity also contained a water molecule coordinated to the encrypted cation (Dickman et al., 1996 Kim et al., 1999). This observation, also noted for the Ca and structures, provides an explanation for the fact that the encrypted cation does not lie in the pseudo-equatorial mirror plane of the polytungstate framework. Luminescence lifetime measurements on the europium complex have led to ambiguous conclusions regarding the number of coordinated water molecules (Soderholm et al., 1995 Lis et al., 1996). As shown in Table 9 the 31P chemical shifts are significantly affected by the acidity of the solution. Remarkably, at intermediate acidities... 

J. Jiang, N. Higashiyama, K.I. Machida, G.Y. Adachi, The luminescent properties of divalent europium complexes of crown ethers and cryptands, Coord. Chem. Rev. 170, 1-29, 1998. 

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... 

Fu L., Zhang H., Wang S., Meng Q., Yang K. and Ni J. Preparation and luminescence properties of the ternary europium complex incorporated into an inorganic/polymer matrix by a sol-gel method, J. Sol-Gel Set. Technol. 15 (1999) pp. 49-55. 

Study of these and other transitions can thus yield valuable information. Crystals of the nine-coordinate complex [Eu(tmhd)3(terpy)] contain two slightly different molecules present in the crystal, its luminescence spectrum showing a broad but imresolved Do Fo transition. In solid [Eu(tmhd)3(Me2phen)] (Ln = La, Eu, Tb, Ho), there are two different square-antiprismatic isomers in the unit cell, and in this case emissions from both isomers can be distinguished in the fluorescence spectrum of the europium complex, which shows an unusually high splitting of the Dq Fq transition. ... 

Yang, C., Fu, L.-M., Wang, Y. et al. (2004) Highly luminescent europium complex showing visible-light-... 

Figure 2.40 Crystal structure of [Eu3(L )3(H20)e]. View of the trinuclear complex (a) along and (b) perpendicular to the threefold axis [45]. (Reproduced with permission from S. Zebret, N. Dupont, G. Bemardinelli and J. Hamacek, Self-assembly of a trinuclear luminescent europium complex, Chemistry-A European Journal, 2009,15, 3355-3358. Wiley-VCH Verlag GmbH Co. KGaA.)...

Zebret, S., Dupont, N., Bernardinelli, G, and Hamacek, J. (2009) Self-assembly of a trinuclear luminescent europium complex. Chemistry — A European Journal, 15, 3355-3358. 

Figure 3.9 Structures of (a) [CeL3(phen)]2 (HL = acetic acid) and (b) [EnL3(phen)]2 (HL = 2-furancarboxylic acid) [RE, black (large balls) O, grey N, black (small balls) C, white H, omitted]. (Redrawn from the CIF files of A. Panagiotopoulos et al., Molecular structure and magnetic properties of acetato-bridged lanthanide(III) dimers, Inorganic Chemistry, 34, 4918 920, 1995 [37] and X. Li et al., Synthesis, structure and luminescence property of the ternary and quaternary europium complexes with furoic acid, Journal of Molecular Structure, 604, 65-71, 2002 [48].)...

Li, X., Jin, L., Lu, S., and Zhang, J. (2002) Synthesis, structure and luminescence property of the ternary and quaternary europium complexes with furoic acid. Journal of Molecular Structure, 604, 65-71. 

In 1990, Kido etal. [16] first reported the europium complex tris(thienyltrifluoro-acetonato) europium [Eu(TTA)3], based OLED in which the complex was molecularly dispersed in holetransporting poly(methylphenylsilane) (PMPS). Luminescence started at 12 V, and a maximum intensity of 0.3cdm at 18 V was achieved when the device was operated in continuous DC mode (biased ITO positive) with the configuration ITO/PMPS-Eu(TTA)3/PBD/Mg/Ag [PBD = 2-(4-biphenyl)-5-(4-tert-butylphenyl)-l,3,4-oxadiazole, the structure shown in Eigure 11.4, being used as the electron-transporting layer]. Since then, many Eu(III) complexes and related electroluminescent devices have been studied extensively. 

Figure 11.13 The PL spectra from CN-PPP and CN-PPP doped with 5 wt.% of the indicated Eu complexes. All of the films had the same thickness and absorbed approximately the same amount of light, so the emission spectra can be compared to each other to determine relative quantum yields [50]. (Reproduced with permission from M.D. McGehee et al., Narrow bandwidth luminescence from blends with energy transfer from semiconducting conjugated polymers to europium complexes, Advanced Materials, 1999, 11, 1349-1354. Wiley-VCH Verlag GmbH Co. KGaA.)...

McGehee, M.D., Bergstedt, T., Zhang, C., et al. (1999) Narrow bandwidth luminescence from blends with energy transfer from semiconducting conjugated polymers to europium complexes. Advanced Materials, 11, 1349-1354. 

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