Long-Lived Two-Photon Excited Luminescence of Water-Soluble Europium Complex: Applications in Biological Imaging Using Two-Photon Scanning Microscopy.

International audienceA new europium complex presenting good solubility and stability in water, intense emission in the red (616 nm), long luminescence lifetime, and significant two-photon absorption cross-section in the biological window has been designed and successfully used for two-photon scanning microscopy bioimaging experiments on fixed cancer cells

Meso-Ester Corroles

International audienceDedicated to Professor Mieczysław Józef Mąkosza on the occasion of his 80th birthday. Abstract: The introduction of ester groups on the 5 and 15 meso positions of corroles stabilizes them against oxidation and induces a red-shift of their absorption and emission spectra. These effects are studied through the photophysical and electrochemical characterization of up to sixteen different 5,15-diester corroles where the third meso position is free or occupied by an aryl group, a long alkyl chains or an ester moiety. The single crystal X-ray structure analysis of five 5,15-diestercorroles and Density Functional Theory (DFT) and Time Dependant Density Functional Theory (TD-DFT) calculations, show that the strong electron withdrawing character of the 5,15 ester substituents is reinforced by their π-overlapping with the macrocycle aromatic system. The crystal packings of corroles 2, 4, 6, 9 and 15 feature short distances between chromophores that are stacked into columns thanks to the low steric hindrance of meso ester groups. This close packing is partially due to intermolecular interactions involving inner hydrogen and nitrogen atoms and thereby stabilizing a single and identical corrole tautomeric form

Tricaesium tris­(pyridine-2,6-dicarboxyl­ato-κ3 O 2,N,O 6)lutetium(III) octa­hydrate

Colourless block crystals of the title compound, Cs3[Lu(dipic)3]·8H2O [dipic is dipicolinate or pyridine-2,6-dicarboxyl­ate, C7H3NO4] were synthesized by slow evaporation of the solvent. The crystal structure of this LuIII-complex, isostructural with the DyIII and EuIII complexes, was determined from a crystal twinned by inversion and consists of discrete [Lu(dipic)3]3− anions, Cs+ cations and water mol­ecules involving hydrogen bonding. The Lu atom lies on a twofold rotation axis and is coordinated by six O atoms and three N atoms of three dipicolinate ligands. One Cs atom is also on a twofold axis. The unit cell can be regarded as successive layers along the crystallographic c-axis formed by [Lu(dipic)3]3− anionic planes and [Cs+, H2O] cationic planes. In the crystal structure, although the H atoms attached to water mol­ecules could not be located, short O—O contacts clearly indicate the occurrence of an intricate hydrogen-bonded network through contacts with other water mol­ecules, Cs cations or with the O atoms of the dipicolinate ligands

A multidimensional approach to the analysis of chemical shift titration experiments in the frame of a multiple reaction scheme

International audienceWe present a method for fitting curves acquired by chemical shift titration experiments, in the frame of a three-step complexation mechanism. To that end, we have implemented a fitting procedure, based on a nonlinear least squares fitting method, that determines the best fitting curve using a “coarse grid search” approach and provides distributions for the different parameters of the complexation model that are compatible with the experimental precision. The resulting analysis protocol is first described and validated on a theoretical data set. We show its ability to converge to the true parameter values of the simulated reaction scheme and to evaluate complexation constants together with multidimensional uncertainties. Then, we apply this protocol to the study of the supramolecular interactions, in aqueous solution, between a lanthanide complex and three different model molecules, using NMR titration experiments. We show that within the uncertainty that can be evaluated from the parameter distributions generated during our analysis, the affinities between the lanthanide derivative and each model molecule can be discriminated, and we propose values for the corresponding thermodynamic constants. Copyright © 2013 John Wiley & Sons, Ltd

Guanidinium as powerful cation for the design of lanthanate tris-dipicolinate crystalline materials: Synthesis, structure and photophysical properties

International audienc

Solution-processed bulk heterojunction solar cells based on BF2-hydroxychalcone complexes

International audience2′-Hydroxychalcone derivatives featuring a triphenylamine terminal unit were synthesized in one step and behaved as effective ligands for borondifluoride coordination, enabling the straightforward generation of D-A molecules with strong absorption. Solution-processed solar cells based on these complexes and PC61BM showed a PCE of 1.13%

Exciton lifetime in donor-acceptor-donor planar dumbbell-shaped triazatruxene-thienopyrroledione derivatives

Organic semiconductor materials such as planar conjugated small molecules are of great interest to the photovoltaic community. In thin films, the exciton and charge carrier dynamics, which are crucial to photovoltaic device operation, depend in a non-trivial way on the organic molecular structure and on the molecular organization in the solid state. Recently, the exciton diffusion has been found to strongly depend on the crystalline order of the organic thin films. This work presents the study of the exciton lifetime in an innovative class of molecular semiconductors able to present different crystalline order. This family of molecules has a “dumbbell-shaped” structure based on triazatruxene units that act as a π-stacking platform. Such molecules with different side-chains have been found to self-assemble into various crystalline and liquid crystalline phases. We have studied the steady-state photoluminescence and the exciton lifetime for several triazatruxene-based derivatives with different side-chains, in solution and in thin films for different solid state phases. In solution, the fluorescence lifetime corresponds to the reference value that can be obtained without intermolecular interaction. In thin films, we measured the exciton lifetime for different molecular structures in order to correlate the exciton dynamics with the molecular stacking. The results reveal a significant increase in the exciton lifetime with the enhancement of the structural order