Europium -complexes

A dye molecule has one or more absorption bands in the visible region of the electromagnetic spectrum (approximately 350-700 nm). After absorbing photons, the electronically excited molecules transfer to a more stable (triplet) state, which eventually emits photons (fluoresces) at a longer wavelength (composing three-level system.) The delay allows an inverted population to build up. Sometimes there are more than three levels. For example, the europium complex (Figure 18.15) has a four-level system. 

Two typical dye molecules. The europium complex (a) transfers absorbed light to excited-state levels of the complexed Eu , from which lasing occurs. The perylene molecule (b) converts incident radiation into a triplet state, which decays slowly and so allows lasing to occur. 

Europium, tris(2,2,6,6-tetramethyl-3,5-heptanedione-quinuclidine)-stereochemistry, 1, 81 Europium complexes... 

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... 

J Kido, K Nagai, Y Okamoto, and T Skotheim, Electroluminescence from polysilane film doped with europium complex, Chem. Lett., 20 1267-1270, 1991. 

Another example of efficient Forster energy transfer in Eu3+ complexes of fluorene copolymers (similar to the alternating copolymers described in Scheme 2.49) was demonstrated by Huang and coworkers [414] for random copolymers. They synthesized copolymers 336 with a different ratio between the fluorene and the benzene units in the backbone and converted them into europium complexes 337 (Scheme 2.50) [414]. The complexes 337 were capable of both blue and red emission under UV excitation. In solution, blue emission was the dominant mode. However, the blue emission was significantly reduced or completely suppressed in the solid state and nearly monochromatic (fwhm 4 nm) red emission at 613 nm was observed. 

It is well-known that rare-earth complexes such as europium complexes emit sharp spectral bands due to electronic transitions between inner d and f orbitals of the central rare-earth... 

J. Fang and D. Ma, Efficient red organic light-emitting devices based on a europium complex, Appl. Phys. Lett., 83 4041 1043 (2003). 

T Sano, M Fujita, T Fujii, Y Hamada, K Shibata, and K Kuroki, Novel europium complex for electroluminescent devices with sharp red emission, Jpn. J. Appl. Phys., 34(Part 1) 1883-1887,1995. 

The dipole moment measurement of scandium and europium complexes in solution showed the complexes to be planar. In the solid state, the values of metal atoms are squeezed out of... 

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