Complexes antenna effect

Figure 2.18 Schematic representation of photophysical processes in lanthanide(III) complexes (antenna effect). A = absorption, F = fluorescence, P = phosphorescence, L = lanthanide-centred luminescence, ISC = intersystem crossing, ET = energy transfer S = singlet, T = triplet. Full vertical lines radiative transitions dotted vertical lines nonradiative transitions...

Self-assembly of aromatic dendron subunits has been tried by the design of coordination to multivalent metal cations (i.e., metal-cored dendrimer complexes). Several metal-cored dendrimer complexes have successfully exhibited luminescence by antenna effects. 

Kawa, M., and Frechet, J.M.J. (1998) Self-assembled lanthanide-cored dendrimer complexes enhancement of the luminescence properties of lanthanide ions through site-isolation and antenna effects. Chem. Mater. 10, 286-296. 

Kawa M, Takahagi T (2004) Improved antenna effect of terbium(III)-cored dendrimer complex and green-luminescent hydrogel by radical copolymerization. Chem Mater 16 2282-2286... 

Balzani V., Campagna S., Denti G. and Serroni S. (1992) Supramolecular Photochemistry Antenna Effect in Polynuclear Metal Complexes, in Kochanski E. (Ed.), Photoprocesses in Transition Metal Complexes, Biosystems and Other Molecules. Experiment and Theory, Kluwer Academic Publishers, Dordrecht, p. 233. 

Another water-soluble (3-CD (105) bearing seven naphthoyl chromophores forms very stable 1 1 complexes with a merocyanine laser dye DCM-OH [90], The energy transfer from the naphthoyl antenna chromophores to the included dye is shown to occur with 100% efficiency (antenna effect) (Scheme 3). 

When looking for R(III) determination, use can be made of the antenna effect already discussed in sect. 3.7, provided the lanthanide of interest is luminescent. The basic principle is to add a given organic ligand, which will ensure a high complexation constant with the lanthanide together with an efficient UV absorption and energy transfer to the R(III)... 

N. Sabbatini, M. Guardigli and I. Manet, Antenna effect in encapsulation complexes of lanthanide ions 69... 

As it is well known, sensitization of Ln-centered luminescence can be achieved via an intramolecular energy transfer upon excitation of organic ligands, instead of using direct excitation of the weak Lnm absorption bands. This phenomenon now called antenna effect or luminescence sensitization has first been observed in 1942 by Weissman for europium(III) complexes formed with salicylaldehyde and with /3-diketonates, more particularly benzoyl-acetonate (ba, 48a), dibenzoylmethanate (dbm, 48b) and wieta-nitrobenzoylacctonatc (47a, fig. 41) (Weissman, 1942). 

N. Sabattini, M.Guardigliandl. Manet, 1996,23,69 (antenna effect in encapsulated complexes). G.E. Buono-core and H.LiB. Marciniak, Coord. Chem. Rev., 1990, 99,55 (quenching of excited states by lanthanide ions and chelates in solution). 

FIGURE 6. The antenna effect in the luminescence of rare-earth complexes. Reproduced by permission from Reference 2, Copyright 2005 the Royal Society of Chemistry... 

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