A new fluorescent labeled compound of microcystin-LR with terbium cryptate was obtained by initial conjugation of microcystins-LR with aminoethanethiol followed by the reaction with the ester group of terbium cryptate. The product formation was followed by high performance liquid chromatography ( HPLC) at 238 nm and 310 nm. The presence of microcystin-LR in the labeled molecule was confirmed by enzyme linked immunosorbent assay ELISA and by protein reaction with bicinhonic acid. Luminescence spectra of cryptate and the conjugated molecule were carried through as well.

The complexes tris(4,4,4-Trifluoro-1(1-naphthyl)-1,3-butanedionate) (2,2'-bipiridyl) Ln(III), Ln(tan)(3)bipy, where Ln(III) = Eu3+ and Gd3+ have been synthesized, characterized and their photophysical properties (absorption, excitation and luminescence spectra and emission quantum yield) investigated down to 4.2 K. The Eu(tan)(3)bipy complex has its molecular structure experimentally determined using X-ray crystallography and theoretically using the SMLC/AM1 method as well as their electronic singlet and triplet states were calculated, using the INDO/S-CI method with a point charge model to represent the Eu3+ ion, where two values were adopted, + 3.0e and + 3.5e, to investigate the imperfect shielding of the 4f shells. The so calculated + 3.5e model electronic absorption spectrum and low lying triplet state energies agreed very well with the experimental ones. The emission quantum yield of the Eu3+ complex is quite low at room temperature, namely 7%, probably due to the too low lying triplet state, 19,050cm(-1), and increases by a factor of three when the temperature is lowered to 4.2 K. This strong thermal effect indicates the presence of a channel deactivating the main emitting state, what can be due to a LMCT state possibly lying in the same spectral region, as usually found in Eu3+ compounds. (c) 2005 Elsevier B.V. All rights reserved.

The chemical literature attests to the growing importance of rare-earth ions in the development of luminescent materials.1 Recently, highly luminescent europium (III) adducts with ligands such as fluorinated β-diketones and 2,2′-dipyridyl have been synthesized and suggested as promissing hight-conversion molecular devices (LCMD), as described by Lehn.2