Aryl Bridged 1-Hydroxypyridin-2-one: Effect of the Bridge on the Eu(III) Sensitization 'Process

The efficiency of Eu3+ luminescence by energy transfer from an antenna ligand can be strongly dependent on the metal ion coordination geometry. The geometric component of the Eu(III) sensitization has been probed using series of tetradentate 1,2-HOPO derivatives that are connected by bridges of varying length and geometry. The ligands are N,N'-(1,2-phenylene)bis(1-hydroxy-6-oxo-1,6-dihydropyridine-2-carboxamide) for the ligand (L{sup 1}), 1-hydroxy-N-(2-(1-hydroxy-6-oxo-1,6-dihydropyridine-2-carboxamido)benzyl)-6-oxo-1,6-dihydropyridine-2-carboxamide (L{sup 2}) and N,N'-(1,2-phenylenebis(methylene))bis(1-hydroxy-6-oxo-1,6-dihydropyridine-2-carboxamide) (L{sup 3}). Spectroscopic characterization of both the Gd(III) and Eu(III) metal complexes, TD-DFT analysis of model compounds and evaluation of the kinetic parameters for the europium emission were completed. Some striking differences were observed in the luminescence quantum yield by altering the bridging unit. The [Eu(L{sup 2}){sub 2}]{sup -} derivative shows efficient sensitization coupled with good metal centered emission. For [Eu(L{sup 3}){sub 2}]{sup -}, the large quenching of the luminescence quantum yield compared to [Eu(L{sup 2}){sub 2}]{sup -} is primarily a result of one inner sphere water molecule bound to the europium cation while for [Eu(L{sup 1}){sub 2}]{sup -}, the low luminescence quantum yield can be attributed to inefficient sensitization of the europium ion

Sensitization of Eu(III) luminescence by donor-phenylethynyl-functionalized DTPA and DO3A macrocycles

WOS:000281662600012International audienceThe synthesis and complexation to Eu(III) of two macrocyclic ligands functionalized donor-phenylethynyl-moieties as sensitizer is presented The two ligands based on DTPA bis-amide ([Eu(L(1))]) and DO3A ([Na][Eu(L(2))]) have been chosen because of their increased stability in water for potential applications as luminescent bioprobes for one- or two-photon excited scanning microscopy The DTPA and DO3A ligands possess oxygen or sulfur donor atoms, respectively, connected to a tnethyleneglycol (PEG) chain to ensure the water solubility. The optical properties were studied and reveal that ((Eu(L(1))1) present a lower brightness than the ([Nal[Eu(L(2))]) counterpart because of its inner sphere water molecule coordination that quenches the emission On the other hand, [NallEu(1.2)1 exhibits excellent spectroscopic properties with high quantum yield phi = 0.284, and brightness B = 10,220 M(-1)cm(-1)(defined as epsilon.phi) Unfortunately, the two-photon cross-section of this last complex was measured to be only 4 GM limiting its potential applications to linear microscopy. (C) 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved. R SU

Using the Antenna Effect as a Spectroscopic Tool; Photophysics and Solution Thermodynamics of the Model Luminescent Hydroxypyridonate Complex [EuIII(3,4,3-LI(1,2-HOPO))]-

While widely used in bioassays, the spectrofluorimetric method described here uses the antenna effect as a tool to probe the thermodynamic parameters of ligands that sensitize lanthanide luminescence. The Eu3+ coordination chemistry, solution thermodynamic stability and photophysical properties of the spermine-based hydroxypyridonate octadentate chelator 3,4,3-LI(1,2-HOPO) are reported. The complex [EuIII(3,4,3-LI(1,2-HOPO))]- luminesces with a long lifetime (805 mu s) and a quantum yield of 7.0percent in aqueous solution, at pH 7.4. These remarkable optical properties were exploited to determine the high (and proton-independent) stability of the complex (log beta 110 = 20.2(2)) and to define the influence of the ligand scaffold on the stability and photophysical properties