Luminescence diketone ligands

However, the lanthanide p-diketonates shown in scheme 4 cannot be used as labels, since there is no active binding group on the p-diketonate ligands and these complexes are not very stable with stability constants in the order of 103-106 only, therefore the complexes dissociate in highly diluted solutions and the luminescence intensity decreases. Recently, three chloro-sulfonylated tetradentate p-diketones were synthesized by Yuan and Matsumoto (1996,1997) and Yuan et al. (1998a, 1998b) (scheme 5). They differ from other p-diketones, because the emission intensity of their Eu3+ complexes is not weakened by the presence of the sulfonyl... 

Bis(P-diketones) ligands, were proved to be efficient motifs or structural elements for selfassembling highly luminescent metallo-supramolecular lanthanide complexes [53-59] and representative examples (H2L" ) are shown in Figure 2.8. Special attention has also been paid to the use of enantiomerically pure bis-P-diketones ofH2L " [58]. H2L ° in Figure 2.8 was shown to have the ability to form d-f-d molecular magnetic materials [60]. 

Figure 2.38 Molecular model of the [Eu2(L )3] complex [53a]. (Reprinted with permission from A.R Bassett, S.W. Magennis, RB. Glover et al., Highly luminescent, triple- and quadruple-stranded, dinuclear Eu, Nd, and Sm(III) lanthanide complexes based on bis-diketonate ligands, Journal of the American Chemical Society, 126, 9413-9424, 2004. 2004 American Chemical Society.)...

Figure 2.43 (a) [Lns] clusters, hydrogen atoms have been removed for clarity (b) view of the cluster where ligands have been removed for clarity [77]. (Reproduced from S. Petit, F. Baril-Robert, G. Pilet, C. Reber and D. Luneau, Luminescence spectroscopy of europium(III) and terbium(III) penta-, octa-and nonanuclear clusters with fS-diketonate ligands, Dalton Transactions, 34, 6809-6815, 2009, by permission of the Royal Society of Chemistry.)... 

Shiga, T., Ohba, M., and Okawa, H. (2004) A series of trinuclear Cu Ln Cu complexes derived from 2,6-di(acetoacetyl)pyridine synthesis, structure, and magnetism. Inorganic Chemistry, 43, 4435 446. Albrecht, M., Schmid, S., Dehn, S., et al. (2007) Diastereoselective formation of luminescent dinuclear lan-thanide(III) helicates with enantiomerically pure tartaric acid derived bis(P-diketonate) ligands. New Journal of Chemistry, 31, 1755-1762. 

Petit, S., Baril-Robert, F., Pilet, G, etal (2009) Luminescence spectroscopy of europium(lll) and terbium(lll) penta-, octa- and nonanuclear clusters widi -diketonate ligands. Dalton Transactions, 6809—6815. 

The fluorescence properties of several europium and samarium ) -diketonates have been measured and assignments of the transitions made. Rare-earth element hexafluoroacetylacetonates with amino-acids have also been reported to fluoresce. The luminescence of the heptafluoroheptane-2,4-dione complexes of Sm, Eu, and Tb has been measured in dilute ethanol at pH8 and 610nm mixed-ligand complexes with 1,10-phenanthroline exhibited an enhanced luminescence. Photolysis of the Tb chelate of 2,2,6,6-tetramethylheptane-3,5-dione has been examined at 311 nm in various alcohols, and loss of one -diketone ligand found to be the primary photochemical step. A linear correlation was demonstrated between the quantum yield of dissociation of the complex and the formation constant of the complex-alcohol adduct. 

The use of these cations have been extended in the two photon absorption field. A carbazole (3-diketone ligand (HL = 4,4,4-trifluoro-l-(9-butylcarbazole-3-yl)-l,3-butanedione) has been used to prepare two novel luminescent six-coordinated metal complexes of Cd(ii), Zn(ii). The experimental results, supported by time-dependent density functional theory (TD-DFT) calculations, indicate that the complexation of the ligands with metal ion extends the electronic delocalization in the coordination compounds, leading to enhanced two-photon absorption." ... 

It would be worthwhile to follow up and optimize the capability of LLCs entrapped in polymer matrices for the indication of humidity in the gas phase. This approach seems promising since it was shown that the luminescence of EuCls included in a dehydrated Nafion membrane is quenched in the course of adsorption of water vapor [108]. A series of p-diketonate complexes of Eu " (28 A-C in Scheme 5) embedded in Nafion membranes were also evaluated for their responses to relative humidity [109]. There still remains some analytical work to be done because astonishingly it depends on the type of p-diketonate ligand whether the luminescence is suppressed or enhanced in presence of water. 

Bis(/3-diketones) ligands were proved to be efficient motifs or structural elements for self-assembling highly luminescent metallo-supramolecular lanthanide complexes, and representative ones are shown in Fignre 7. 

Lanthanide /3-diketonates are complexes of /3-diketone ligands (1,3-diketones) with lanthanide ions. These complexes are the most popular and the most intensively investigated luminescent lanthanide coordination compounds (see P-Diketonate). Three main types of lanthanide(III) /3-diketonate complexes have to be considered fra complexes, Lewis base adducts of the tris complexes (ternary lanthanide /3-diketonates), and tetrakis complexes. Most Eu +/3-diketonate complexes show an intense visible luminescence, but many /3-diketonates are not good ligands to sensitize the luminescence of Tb + ions. NIR luminescence can be... 

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