Lanthanide complexes in solutions

The interpretation of conductance data is complicated by the labile nature of the lanthanide complexes in solution which results in ligand exchange and dissociation reactions. It is difficult to understand the nature of the complex species present in solution. A combination of conductance data and molecular weight determination may be useful in determining the coordination number and structure of the complexes in solution. However, due to the poor solubility of lanthanide complexes in suitable solvents, molecular weight data have been obtained for only a few complexes. The dissociative reactions of lanthanide complexes in solution are well illustrated by the TPPO complexes of lanthanide isothiocyanates (202). In chloroform solution, the dissociation... 

ILs are becoming useful solvenfs to investigate fhe specfroscopic behavior of both organic and inorganic lanthanide complexes in solution, especially of complexes with weakly binding ligands, which otherwise would be unable to compete with the solvent molecules for a binding site on the lanthanide ion [9]. 

There are difficulties associated with the use of ordinary electronic absorption spectra of lanthanide complexes in solution to provide detailed information regarding coordination number and geometry. However, difference spectra versus NdCl3 are reported for Nd3+-ligand (L) solutions for the 4/9/2— -4G5/2, 4G7,2 transitions (L = dipicolinate, oxydiacetate, iminodiacet-ate, malate, methyliminodiacetate and Ar,Ar -ethylenebis Af-(o-hydroxyphenyl)glycinate ). Hypersensitive behaviour was examined and transition dipole strengths were discussed in terms of the nature of the complex species present.431... 

Some salient features of the absorption spectra of lanthanide complexes in solutions.635... 

If one carboxylic acid side chain in H4DOTA is replaced by hydrogen, the resulting acid, H3DO3A, forms neutral lanthanide complexes. In solution, they are believed to have two water molecules coordinated so that the... 

Table 2 Examples of typically observed luminescence decay times for the NIR transitions in luminescent lanthanide complexes in solution...

Figure 1.1 Normalized emission spectra of luminescent lanthanide complexes in solution, illustrating the sharp emission bands and minimal overlap of lanthanide luminescence. (Reproduced with permission from S. Petoud, et al,J. Am. Chem. Soc., 2003, 125, 13324-13325. Copyright (2003) American Chemical Society and from ref. 6 with permission from John Wiley and Sons. Copyright 2005 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim.)...

Knowledge of the structural characteristics of actinide and lanthanide complexes in solution has increased significantly in the past two decades with the observation of a... 

Our colleague Minas D. Marcantonatos has pointed out that the electron transfer bands of lanthanide complexes in solution (Jprgensen, 1962c Ryan and J0rgensen, 1966 Ryan, 1969) also show quite varying intensities (though much... 

For certain transitions which have AJ < 2, AL 2, and AS = 0, the intensities are far more sensitive to complexation than for the other transitions. These have been termed hypersensitive transitions by Jdrgensen and Judd (1964). The intensities of these transitions may be up to 200 times greater than the corresponding transition in the aquo ion whereas the intensities of the other transitions are generally approximately the same as in the aquo ion. The sensitivity of these transitions to the environment has led to their use in determining the coordination number for lanthanide complexes in solution. Since the subject of hypersensitivity has been reviewed recently by Henrie et al. (1976) and is covered in ch. 24 (Solution Chemistry), the phenomenon is only mentioned briefly here. 

Bruce JI, Parker D, Lopinski S, Peacock RD. Survey of Eactors Determining the Circularly Polarized Luminescence of Macrocychc Lanthanide Complexes in Solution. Chirality 2002 14 562-567. 

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