Chelates, luminescent stable

Zucchi, G. Ferrand, A.-C. Scopelliti, R. Btinzli, J.-C. G. Highly luminescent, visible-emitting lanthanide macrocyclic chelates stable in water and derived from the cyclen framework. Inorg. Chem. 2002, 41, 2459-2465. 

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)... 

It is observed that in most /3-diketones the substituents on the a-carbon are hydrogen atoms. Consequently, only very few examples of luminescent rare-earth a-substituted fi-diketonate complexes are known. The /S-diketonates are good chelating ligands forming highly stable RE + complexes. 

Covalent coupling of a lanthanide luminescent chelate to bioactive molecules such as peptides, proteins, or nucleic acids makes use of the chemically reactive groups of these molecules. The most common ones are aliphatic a- or s-amines. A typical example of s-amine is lysine, the pRa of which is 9.2 so that it reacts cleanly above pH 8 to yield stable... 

---