Photophysics lanthanide complexes

LANTHANIDE COMPLEXES AS PROBES BASIC PHOTOPHYSICAL PROPERTIES 917... 

Whilst there have been a number of excellent reviews on the design, synthesis, structural determination, and photophysics of luminescent lanthanide complexes (1-6), detailed information for coordination chemists on how these compounds may be used as analytes in the biochemical and biological sciences has been somewhat less readily... 

Recently, a series of derivative ligands, [L19]4-—[L23]4-, has been reported (32,62), where the acetophenone chromophore in [L18]4- is replaced by a dipyrazolylpyridine chromophore. These form lanthanide complexes that are stable in aqueous solution, and which possess very promising photophysical attributes. The europium and terbium complexes of all these ligands have long lifetimes (1.3-1.4 ms for europium and 2.3-2.8 ms for terbium) in water that are largely unchanged by solvent deuteration, indicating the effective exclusion of solvent from the primary coordination sphere. 

Photophysical studies have been conducted on a number of lanthanide complexes of calix[n]arenes, and a significant number of these are discussed in a recent review (79). The first europium and terbium calixarene complexes showed promising photophysical properties, with terbium luminescence lifetime of 1.5 ms and quantum yield of 0.20 in aqueous solution (80). 

Complexes of calixarenes with bipyridyl chromophores can be stabilized by the addition of anionic side arms, such as iminodiacetate units (85). Whilst the lanthanide complexes of ligands [L51]4- and [L52]4- are not soluble in water, their photophysical properties in... 

The first cage lanthanide complexes studied for their photophysics were the simple 2.2.1 cryptands. The lack of a strongly absorbing chromophore, and easy approach of solvent molecules meant that their luminescence properties were disappointing in comparison to many recently studied complexes. The Lehn cryptand (L53) (Scheme 6... 

Mono- and bimetallic lanthanide complexes of the tren-based macrobicyclic Schiff base ligand [L58]3- have been synthesized and structurally characterized (Fig. 15), and their photophysical properties studied (90,91). The bimetallic cryptates only form with the lanthanides from gadolinium to lutetium due to the lanthanide contraction. The triplet energy of the ligand (ca. 16,500 cm-1) is too low to populate the terbium excited state. The aqueous lifetime of the emission from the europium complex is less than 0.5 ms, due in part to the coordination of a solvent molecule in solution. A recent development is the study of d-f heterobimetallic complexes of this ligand (92) the Zn-Ln complexes show improved photophysical properties over the homobinuclear and mononuclear complexes, although only data in acetonitrile have been reported to date. 

Casnati, A. Baldini, L. Sansone, F. Ungaro, R. Armaroli, N. Pompei, D. Barigelletti, F. Synthesis, complexation and photophysics in protic solvents of lanthanide complexes of novel calix[4]arene polycarboxylic-2,2,-bipyridine mixed ligands. Supramol. Chem. 2002,14(2-3), 281-289. 

Many aza-crown macrocydic ligands [118] have been used to produce stable, well-shielded lanthanide complexes that have good photophysical properties. The aza-crown macrocydic ligand 19 has a terpyridine moiety incorporated into it to act as a sensitiser. Quantum yields of 0 = 0.18 and 0 = 0.21 were determined in water for the Eu(III) and Tb(III) complexes respectively. 19 is an... 

In this chapter, different properties of nonlinear behavior in lanthanide complexes have been overviewed, including brief examination of their optical emission and excitation spectra. A perception of the importance of photophysical relationships of molecular complexes to these phenomena has also been conveyed. 

Chauvin, A.S., Gumy, R, Matsubayashi, I., etal. (2006) Fluorinated fl-diketones for the extraction of lanthanide ions photophysical properties and hydration numbers of their Eu " complexes. European Journal of Inorganic... 

Lam, A.W.-H., Wong, W.T., Gao, S., Wen, G, and Zhang, X.-X. (2003) Synthesis, crystal structure, and photophysical and magnetic properties of dimeric and polymeric lanthanide complexes with benzoic acid and its derivatives. European Journal of Inorganic Chemistry, 149-163. 

Figure 4.21 The structure of [Lu(19)2](CH30H)(H20)] + [37]. (Reproduced with permission from C. Piguet, A.R Williams, C. Bemardine and J.C.G. Btinzli, Structural and photophysical properties of lanthanide complexes with planar aromatic tridentate nitrogen ligands as luminescent building blocks for triple-helical structures, Inorganic Chemistry, 32, 4139, 1993. 1993 American Chemical Society.)...

The preparation, characterization, aqueous stability, and photophysical properties of NIR emitting lanthanide complexes with tetradentate chelating ligands 36 and 37 were described by Raymond and coworkers [61, 62]. In aqueous solution, the chelating ligand 36 or 37 forms stable complexes with Ln(III) ions, and sensitized NIR lanthanide luminescence was detected for the complexes with Pr(III), Nd(III), Ho(III), or Yb(III) ions. For [Ln(36)2] complexes, the luminescence decay curves were biexponential due to partial hydrolysis of the complexes or alternately the presence of a slowly exchanging equilibrium mixture with a hydrated form of the complexes. For [Ho(37)2] , the NIR band due to Fs -> I transition of the Ho(III)... 

Davies, G.M., Aarons, R. J., Motson, GR., et al. (2004) Structural and near-IR photophysical smdies on ternary lanthanide complexes containing poly(pyrazolyl)borate and 1,3-diketonate Ugands. Dalton Transactions, 1136. 

Figure 13.4 Typical design principle of lanthanide complex-based chemosensors based on binding of an analyte (an) (a) directly influencing the Ln(III) luminescence, (b) influencing photophysical properties of the ligand, and (c) addition of a sensitizing analyte onto a poorly luminescent lanthanide-containing sensor [1]. (Reproduced from J.C.G. Bunzli and C. Piguet, Taking advantage of luminescent lanthanide ions, Chemical Society Reviews, 34, 1048-1077, 2005, by permission of The Royal Society of Chemistry.)...

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