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Luminescent Bimetallic Lanthanide Bioprobes for Cellular Imaging with Excitation in the Visible‐Light Range
Author(s) -
Deiters Emmanuel,
Song Bo,
Chauvin AnneSophie,
Vandevyver Caroline D. B.,
Gumy Frédéric,
Bünzli JeanClaude G.
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200801868
Subject(s) - lanthanide , bimetallic strip , luminescence , chemistry , crystallography , ligand (biochemistry) , osmium , ion , quantum yield , excitation , europium , fluorescence , materials science , metal , optoelectronics , physics , organic chemistry , optics , quantum mechanics , catalysis , biochemistry , receptor , ruthenium
A series of homoditopic ligands H 2 L C X ( X =4–6) has been designed to self‐assemble with lanthanide ions (Ln III ), resulting in neutral bimetallic helicates of overall composition [Ln 2 (L C X ) 3 ] with the aim of testing the influence of substituents on the photophysical properties, particularly the excitation wavelength. The complex species are thermodynamically stable in water (log β 23 in the range 26–28 at pH 7.4) and display a metal‐ion environment with pseudo‐ D 3 symmetry and devoid of coordinated water molecules. The emission of Eu III , Tb III , and Yb III is sensitised to various extents, depending on the properties of the ligand donor levels. The best helicate is [Eu 2 (L C5 ) 3 ] with excitation maxima at 350 and 365 nm and a quantum yield of 9 %. The viability of cervix cancer HeLa cells is unaffected when incubated with up to 500 μm of the chelate during 24 h. The helicate permeates into the cells by endocytosis and locates into lysosomes, which co‐localise with the endoplasmatic reticulum, as demonstrated by counterstaining experiments. The relatively long excitation wavelength allows easy recording of bright luminescent images on a confocal microscope ( λ exc =405 nm). The new lanthanide bioprobe remains undissociated in the cell medium, and is amenable to facile derivatisation. Examination of data for seven Eu III and Tb III bimetallic helicates point to shortcomings in the phenomenological rules of thumb between the energy gap Δ E ( 3 ππ*– 5 D J ) and the sensitisation efficiency of the ligands.